Nghiên cứu xác định hàm lượng selen và mangan trong một số loài nấm Linh chi lấy từ vườn Quốc gia Pù Mát - Nghệ An bằng phương pháp quang phổ

8/12/2019 Nghin cu xc nh hm lng selen v mangan trong mt s loi nm Linh chi ly t vn Quc gia P Mt - N

1/97

BGIO DC V O TO

TRNG I HC VINH

TRN THTHY VN

NGHIN CU XCNH HM LNG SELENV MANGAN TRONG MT SLOI NM LINH CHI

LY TVN QUC GIA P MT - NGHAN

BNG PHNG PHP QUANG PH

HP THNGUYN T(AAS)

LUN VN THC SHA HC

NGHAN - 2013

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2/97

BGIO DC V O TO

TRNG I HC VINH

TRN THTHY VN

NGHIN CU XCNH HM LNG SELEN

V MANGAN TRONG MT SLOI NM LINH CHILY TVN QUC GIA P MT - NGHAN

BNG PHNG PHP QUANG PH

HP THNGUYN T(AAS)

LUN VN THC SHA HC

Chuyn ngnh: Ha phn tch

M s: 60.44.29

Ngi hng dn khoa hc:

TS. INH THTRNG GIANG

NGHAN - 2013

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3/97

LI CM N

hon thnh c lun vn ny em xin by t lng bit n su scn ging vin, Tin sinh ThTrng Giang giao ti cng nhht

lng hng dn, chbo tn tnh truyn t kin thc, kinh nghim qu bu

cho em trong sut qu trnh thc hin.

Em xin chn thnh cm n cc thy, c gio trong tbmn ha Phn

tch, cc thy, c gio hng dn phng th nghim thuc khoa Ha hc,

Trung tm phn tch chuyn giao An Ton Thc phm Mi trng - Trng

i hc Vinh to mi iu kin gip em trong qu trnh thc hin lunvn.

Cui cng, em xin gi li cm n su sc ti bm, anh, ch, em v

bn b quan tm, ng vin em hon thnh lun vn tt nghip ca mnh.

Vinh, thng 10 nm 2013.

Hc vin

Trn ThThy Vn

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4/97

MC LC

Trang

MU .......................................................................................................1

Chng 1. TNG QUAN.............................................................................3

1.1. Slc vloi Nm...........................................................................3

1.1.1. Gii thiu vNm ..............................................................................3

1.1.2. Phn loi Nm....................................................................................3

1.1.3. Nm Linh chi...................................................................................... 4

1.2. Tng quan vnguyn tSelen v nguyn tMangan......................... 6

1.2.1. Tng quan vnguyn t Selen............................................................61.2.2. Tng quan vnguyn tMangan......................................................17

1.3. Cc phng php phn tch Selen, Mangan ...................................... 24

1.3.1. Cc phng php phn tch Selen.....................................................24

1.3.2. Cc phng php phn tch Mangan................................................. 30

1.4. Phng php quang phhp thnguyn t ......................................34

1.4.1. Sxut hin phhp thnguyn t[4] ..............................................34

1.4.2. Cc giai on ca qu trnh nguyn tha mu[4]

.............................35 1.4.3. Hthng nguyn tha mu phn tch [4] .........................................36

1.4.4. Cc yu tnh hng v phng php loi trca php o AAS[4].......42

1.4.5 . Cu to my quang phhp thnguyn t .......................................46

1.4.6 . Cc phng php nh lng ca phhp thnguyn t[4]..............50

1.4.7. u nhc im ca phng php quang phhp thnguyn t..........54

1.5. Cc phng php xl mu phn tch..............................................55

1.5.1. Phng php xl mu t (bng axit c oxi ha mnh) ............... 551.5.2. Phng php xl mu kh.............................................................56

1.5.3. Phng php xl mu kh t kt hp .......................................... 56

Chng 2. NI DUNG V PHNG PHP THC NGHIM ...........58

2.1. Thit b, dng c, ha cht................................................................58WWW FA

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2.1.1. Thit b .............................................................................................58

2.1.2. Trang thit bphtr........................................................................58

2.1.3. Dng c, ha cht.............................................................................59

2.2. Phng php nghin cu ..................................................................60

2.2.1. Phng php chun bdung dch htrphn tch ............................60

2.2.2. Phng php chun b cc dung dch Se(IV) dng chy k

thut HG-AAS v GF-AAS. .............................................................60

2.2.3. Phng php chun b cc dung dch Mangan dng chy k

thut F- AAS .................................................................................... 62

2.2.4. Phng php chun bmu phn tch ...............................................632.2.5. Cc ni dung nghin cu thc nghim..............................................64

Chng 3. KT QUTHC NGHIM V BIN LUN......................66

3.1. Kho st cc iu kin th nghim trn my AAS-6800.................... 66

3.1.1. Chn bc sng thch hp................................................................66

3.1.2. La chn rng ca khe sng......................................................... 66

3.1.3. Kho st cng sut n catot rng.....................................................67

3.1.4. Kho st thi gian nguyn tha......................................................673.1.5. Kho st tc dn kh axetylen ......................................................67

3.2. Tng hp cc thng so cho cc php nh lng selen v mangan...... 68

3.3. Xy dng ng chun Se bng kthut HG -AAS v GF-AAS.......... 70

3.3.1. Nguyn tc ca phng php HG-AAS phn tch Selen................... 70

3.3.2. Xy dng ng chun thhin mi tng quan tuyn tnh gia

nng Se (IV) v hp thquang sdng kthut HG-AAS.....71

3.3.3. Xy dng ng chun thhin mi tng quan tuyn tnh gianng Se(IV) v hp thquang sdng kthut GF-AAS.......73

3.3.4. Xy dng ng chun thhin mi tng quan tuyn tnh gia

nng Mn(II) v hp thquang sdng kthut F-AAS. ........ 74WWW FA

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3.4. Xc nh hm lng Selen v Mangan trong cc mu nm Linh

chi bng phng php quang phhp thnguyn t. .......................76

3.5. So snh kt qu nh lng i din hm lng Mangan trong mt

smu nm Linh chi bng hai phng php F-AAS v ICP-MS. ........ 78

KT LUN.................................................................................................80

TI LIU THAM KHO..........................................................................81

PHLC

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7/97

DANH MC CC K HIU, CHVIT TT

AAS Quang phhp thnguyn tAbS hp thquang

APHA Hip hi bo vsc khe cng ng M

CSV Phng php Von-Ampe ha tan

EPA Hip hi bo vmi trng M

F-AAS Quang phhp thnguyn tkthut ngn la

FIA Kthut bm mu dng chy

GF-AAS Quang phhp thnguyn tkthut graphitGPX Enzim glutathione peroxidase

HCL n catot rng

HG-AAS Quang phhp thnguyn tkthut hidrua ha

HMDE in cc git treo thy ngn

ICP-AES Quang phpht xplasma cao tn cm ng

ICP-MS Phkhi lng plasma cao tn cm ng

KK Khng kh

TCVN Tiu chun Vit Nam

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DANH MC BNG, S, HNH V

Trang

Hnh v:

Hnh 1.1: Cc loi nm Linh chi.............................................................. 6

Hnh 1.2: Mt sdng tn ti ca Mangan ............................................ 23

Hnh 1.3: thchun ca phng php ng chun ......................... 51

Hnh 1.4: thchun ca phng php thm tiu chun..................... 53

Hnh 2.1: My phn tch quang phhp thnguyn tAAS-6800........ 58

Hnh 3.1: ng chun th hin mi tng quan tuyn tnh gianng Se (IV) v hp th quang s dng k thut

HG-AAS................................................................................ 72

Hnh 3.2: ng chun thhin mi tng quan tuyn tnh gia nng

Se(IV) v hp thquang sdng kthut GF-AAS......... 74

Hnh 3.3: ng chun th hin mi tng quan tuyn tnh gia

nng Mn v hp thquang sdng kthut F-AAS.... 75

Bng:

Bng 1.2: Mt stiu chun xc nh Mn theo phng php AAS........ 30

Bng 1.3: Quan hgia nhit v loi kh t..................................... 38

Bng 1.4: Thnh phn kh v nhit ngn la ..................................... 38

Bng 1.5: Dy chun ca phng php thm chun............................... 52

Bng 3.1: Kt qukho st rng khe sng cho php o Selen vi

nng Se(IV) l 4 ppb......................................................... 66

Bng 3.2: Kt qukho st rng khe sng cho php o Mangan

vi nng Mn(II) l 0,2ppm................................................ 66

Bng 3.3: Kt qunghin cu tc dn kh C2H2cho php o Se

bng kthut HG-AAS.......................................................... 68WWW FA

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Bng 3.4: Kt qunghin cu tc dn kh C2H2cho php o Mn

bng kthut F-AAS ............................................................. 68

Bng 3.5: Cc thng so ti u nh lng Se theo k thutHG-AAS ............................................................................... 69

Bng 3.6: Cc thng so ti u nh lng Se theo k thut

GF-AAS ................................................................................ 69

Bng 3.7: Cc thng so ti u nh lng Mn theo kthut

F-AAS................................................................................... 70

Bng 3.8 : Sthay i hp thquang (AbS) theo nng Se(IV)

sdng kthut HG-AAS..................................................... 72Bng 3.9: Sthay i hp thquang theo nng Se(IV) sdng

kthut GF-AAS................................................................... 73

Bng 3.10: Sthay i hp thquang theo nng Mn(II) sdng

kthut F-AAS...................................................................... 75

Bng 3.11: Tn loi v k hiu cc mu nm Linh chi............................. 76

Bng 3.12: Kt qu xc nh hm lng Se trong mt s mu nm

Linh chi bng kthut HG-AAS............................................ 77

Bng 3.13: Kt quxc nh hm lng Mn trong mt smu nm

Linh chi bng kthut F-AAS ............................................... 78

Bng 3.14: Kt qunh lng Mn trong 5 mu nm Linh chi bng

hai phng php F-AAS v ICP-MS ..................................... 79

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10/97

1

MU

Nm linh chi l mt dc liu m con ngi txa xa bit dng lmthuc. Cc chphm tnm linh chi c dng h triu trnhiu

bnh nh: Bnh gan, tit niu, tim mch, ung thTrong thnh phn ha hc

ca nm Linh chi cha hm lng cc nguyn tvi lng tng i nhSe,

Mn, K, Ca, Fe l nhng nguyn tvi lng thit yu ca cth.

Selen c vai tr tch cc lm tng khnng min dch ca c th, l

nguyn tbo m cho qu trnh tng hp collagen, bo m ston vn ca

c, hng cu, keratin v thy tinh th. nhng ngi c hm lng selentrong mu thp, nguy cung thtuyn tin lit cao gp 4-5 ln so vi ngi

bnh thng. c bit, selen y mnh qu trnh tng hp coenzim, l mt

cht chng oxy ha c kh nng ph hy cc lipopeoxit v lm trung ha

nhng cht gy hi cho tbo.

Mangan hot ha mt vi enzyme v c th can thip vo sc ch

trong mt vi tbo chuyn ng ca canxi. N ng vai tr khng r rng

trong scn bng ng mu v qu trnh tng hp cholesterol cng nhtin

trnh hnh thnh bxng.

Selen, mangan tham gia vo khu phn n ca con ngi chyu thng

qua ng thc n v nc ung. V vy, kim sot hm lng selen,

mangan a vo c thi hi phi c phng php chnh xc v c tin

cy cao. Trn thgii ngi ta dng nhiu phng php khc nhau nh:

Phng php Phng php chun , phng php sc k lng hiu nng

cao, phng php ICP-MS hay quang phhp thnguyn t.

Hin nay phng php quang phhp thnguyn tdng cc kthut

Hidrua ha, graphit cacbon xc nh Se v kthut ngn la xc nh

Mn c sdng phbin. N p ng c cc yu cu i vi vic xcWWW FA

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11/97

2

nh chnh xc cc nguyn t vi lng trong cc i tng sinh hc, dc

phm, thc phm. Xut pht t nhng l do trn chng ti chn ti

Nghin cu xc nh hm lng selen v mangan trong mt sloi nmLinh chi ly tvn Quc gia P Mt - NghAn bng phng php quang

phhp thnguyn t(AAS)lm lun vn tt nghip ca mnh.

Mc tiu:Xc nh c hm lng selen v mangan c trong mt s

loi nm Linh chi bng phng php quang phhp thnguyn t.

thc hin ti ny, chng ti tp trung gii quyt cc nhim vsau:

- Nghin cu thit b, dng cha cht;

- Nghin cu kho st cc iu kin ti u trn my o AAS-6800.- Nghin cu xy dng ng chun ca selen bng k thut o HG-

AAS v GF-AAS v tm khong tuyn tnh.

- Nghin cu xy dng ng chun ca mangan bng kthut F-AAS

v tm khong tuyn tnh

- Xc nh hm lng Se trong mt sloi nm Linh chi bng phng

php quang phhp thnguyn tsdng kthut HG-AAS v GF-AAS.

- Xc nh hm lng Mn trong mt sloi nm Linh chi bng phng

php quang phhp thdng k thut F-AAS vso snh vi phng php

ICP-MS

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3

Chng 1

TNG QUAN

1.1. Slc vNm

1.1.1. Gii thiu vNm

Nm l mt gii ring bit rt ln vi khong 1,5 triu loi (chng

sau cn trng: 10 triu loi vslng loi) trong m tc 69.000 loi

sng khp ni trn tri t, bao gm nm men, nm mc v cc loi nm ln.

Sdnm c xp vo gii ring m khng c xp vo gii thc

vt hay ng vt v Nm c nhiu c im khc thc vt nh:- Khng c lc lp, khng c sc tquang hp nn khng thtng

to cc cht hu ccho cthkhc nhthc vt.

- Khng c sphn ha cquan thnh thn, r, l, hoa.

- Phn ln nm khng cha xenlulozo trong vch t bo m ch yu

bng Chitin v glucan. Chitin l cht gp ng vt nhiu hn thc vt, ch

yu nhm gip xc v cn trng, to thnh lp vhoc cnh cng cho cc

loi ny.

- Nm dtrng di dng glycozen, thay v tinh bt nhthc vt.

Nm cng khng c xp vo gii ng vt v:

- Nm sinh sn chyu bng bo t (hu tnh hay v tnh) ging ht

phn ca thc vt.

- S dinh dng ca Nm lin quan n h si nm. Nm ly cc

cht dinh dng thng qua mng tbo ca snm (tng tnhcch

rthc vt)

1.1.2. Phn loi Nm

Gii Nm c chia lm 4 gii ph:

-Gii phnm nhy - GymnomycetoidaWWW FA

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4

-Gii phnm to - phycomycetoida

-Gii phestomycetoida

-Gii phnm tht - Eumycetoida1.1.3. Nm Linh chi

1.1.3.1. Gii thiu vNm Linh chi

Nm Linh chi (Lingzhi mushroom) c tn khoa hc l Ganoderma

Lucidum, thuc hNm Lim. Nm Linh chi cn c nhng tn khc nhTin

tho, Nm trng th, Vn nin nhung.

Nm Linh chi l mt dc liu m con ngi txa xa bit dng

lm thuc. Trong "Thn nng bn tho" xp Linh chi vo loi siu thngphm hn c nhn sm; trong "Bn tho cng mc" coi Linh chi l loi

thuc qu, c tc dng bo can (bo vgan), gii c, cng tm, kin no

(b c), tiu m, li niu, ch v (b d dy); gn y cc nh khoa

hc Trung Quc v Nht pht hin nm linh chi cn c tc dng phng v

chng ung th, chng lo ha lm tng tui th.

C nhiu cng trnh nghin cu trn th gii nh danh c cc

hot cht v xc nh tc dng dc l ca nm Linh chi nh: Germanium,

acid ganoderic, acid ganodermic, acid oleic, ganodosteron, ganoderans,

adenosin, beta-D-glucan. Cc nh khoa hc Vit Nam tm thy trong nm

Linh chi c cha 21 nguyn tvi lng cn thit cho svn hnh v chuyn

ha ca cthnh: ng, st, kali, maga, natri, canxi.

Theo y hc ctruyn, nm linh chi c vnht, tnh m, c tc dng t

bcng trng, bcan ch, an thn, tng tr nh

Germanium gip tbo hp thoxy tt hn; polysaccharit lm tng s

min dch trong cth, lm mnh gan, dit tbo ung th; acid ganodermic

chng d ng, chng vim v theo cc kt qu nghin cu th hm lng

germanium trong nm Linh chi cao hn trong nhn sm n 5-8 ln.WWW FA

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5

1.1.3.2.c im hnh thi

Linh chi thuc loi nm ln v rt a dng vchng loi. Tkhi xc

lp thnh mt chi mng l ganoderma karst (1881) n nay c hn 200 loic ghi nhn, ring Ganoderma lucidum c 400 loi.

Nm Linh chi xut hin nhiu vo ma ma trn thn cy hoc gc cy.

Vit Nam nm Linh chi c gi l nm Lim c pht hin nhiu min

Bc bi Patoui llard N.T (1890 n 1928).

Nm Linh chi gm 2 phn: cung nm v m nm. Cung nm di

hoc ngn, nh bn c hnh trng knh 0,5 - 3cm. Cung nm t phn

nhnh, i khi c un khc cong. Lp v cung mu , nu , nu en,bng khng c lng, phsut ln bmt tri nm. mnm khi non c hnh

trng ln dn c hnh qut. Trn bmt mc vn gch tm nhn bng nh

lng vecni. M nm c ng knh 2-15cm, dy 0,8 - 1,2 cm, phn nh

cung thng gln hoc hi lm. Khi nm n tui trng thnh th tn bo

ttc mu nu sm.

1.1.3.3. Cc loi nm Linh chi v cng dng ca n

- Thanh chi (xanh): vtoan bnh. Gip cho sng mt, gip cho an thn ,

bcan kh, nhn th, dng lu sthy thn thnhnhng v thoi mi.

- Xch chi (): c vng, ch tm kh, chv, tng tr tu.

- Hc chi (en): ch thn kh, khin cho u c sn khoi v tinh tng.

- Tchi (tm ): bo thn, lm cng gn ct, ch tinh, da ti p.

- Bch chi (trng): ch phkh, lm tr nhdai.

- Hong chi (vng): ch t kh, trung ha, an thn.

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6

-

Hnh 1.1: Cc loi nm Linh chi

1.1.3.4. Thnh phn ha hc ca nm Linh chi

Cc phn tch ca G-Bing Len chng minh cc thnh phn ha hc

c tng qut ca Nm Linh chi nhsau:

- Nc : 12 - 13 %

- Xenlulozo : 54 - 56 %

- Lingnine : 13 - 14 %

- Lipit: 1,9 - 2,0 %

- Monosaccarit : 4,5 - 5%- Poly Saccarit: 1,0 - 1,2 %

- Sterol (ergosterol, egosterol peroxide) 0,14 - 0,16 %

- Thnh phn K, Zn, Ca, Mn, Se, Ta, khong thit yu, vitamin

T nhng nm 1980 n nay cc phng php hin i: UV-VIS, IR

(hng ngoi), phkkhi lng- sc k kh (GC-MS), phcng hng tht

nhn c bit l sc k lng hiu nng cao (HPLC) cng ICP-MS xc nh

gn 100 hp cht v dn xut trong nm Linh chi.1.2. Tng quan vnguyn tSelen v nguyn tMangan

1.2.1. Tng quan vnguyn tSelen

Se c tm thy tng i mun - 1817 bi nh Bc hc Baron Jons

Jakob Berzerlius - Thy in - tnh cht ca Se rt ging vi lu hunh (S)WWW FA

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7

v Telu (Te), v hm lng ca n khng phbin trong thin nhin (6.10-

5%). Se v Te c tch ra tb thi tch ly bphn ht bi ca nh my

sn xut axit H2SO4, n c t tn l Selen (mt trng) tng nhvTelu (tri t). Se chyu nm dng tp cht trong cc khong vt sunfua

(PbS, CuFeS). Se c trong thnh phn bi khi ca cc mPyrite (FeS2),

trong st thin thch, c bit tnham thch ni la.

1.2.1.1. Tnh cht vt l v cc hng svt l ca Selen [8]

Selen l mt nguyn tha hc phi kim loi, k hiu l Se, thuc chu

k4, stht34, phn nhm chnh nhm VI trong bng hthng tun hon

Mendeleev, cu trc lp vin t[Ar] 3d10

4s2

4p4

, khi lng phn t78,96vC. in tch ht nhn l 34, snotron l 45.

- Bn knh nguyn t(pm): 215

- di cc lien kt ha hc:

+ Lin kt cng ha tr: 117

+ Lin kt Van der Waals: 200

+ Lin kt kim loi: 140

- m in theo thang Pauling: 2,55

- Nng lng ion ha (kJ/mol):

I1=940,9, I2=2044, I3=2974

I4= 4144, I5=6590, I6=7883

- Nng lng cc ni n (kJ/mol):

Se-F Se-Cl Se-Br Se-I Se-Se

0,285 0,192 0,151 0,151 0,3326

Soxi ha: -2, +4, +6, trong soxi ha +6 l bn nht.

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8

Bng 1.1: Cc dng th hnh ca Se v tnh cht vt l

Thng s Dng I Dng II Dng III

Mu sc Xm nh kim v nh hnhDng tinh th lc gic Lng trn Thy tinh en

Trng lng c trng 4,81 4,50 4,26

Nhit nng chy (0C) 217 170-180 60-80

Nhit si (0C) 634,9 634,8 634,8

tan trong nc

(g/100ml)Khng tan Khng tan Khng tan

tan trong H2SO4

(g/100ml)Tan Tan _

tan trong CHCl3

(g/100ml)Tan _ _

tan trong CS2

(g/100ml)Tan t _ Tan

tan trong Benzen

(g/100ml) _ _ tan

Se xm l dng hnh th bn nht, n c xy dng t cc mch

ziczc Se bn xon song song vi nhau. dng th hnh ny c tnh cht

trung gian gia dng th hnh khng kim loi v kim loi. Do Se xm l

cht bn dn. dn in ca n tng ln t ngt (khong 1000 ln) khi

c chiu sng.

Se c xy dng tcc phn tSe8, do n cng tng tnhSn l cht cch in.

1.2.1.2. Tnh cht ha hc ca Selen [8]

Mc oxi ha chnh ca Se l -2, +4, +6. Se l mt nguyn tthhin c

2 khuynh hng, tnh oxi ha v tnh khtrong tnh khquan trng hn.WWW FA

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9

1/ Tnh oxi ha

Se + 2e-Se2- E0= - 0,92V

Thoxi ha khca Se/Se

2-

= -0,92V, nn Se l cht oxi ha yu. Nchng vai tr oxi ha khi phn ng vi cc kim loi v mt sphi kim m

in hn, phn ng chxy ra khi bt nng:

Fe + Se FeSe

Se + H2 t0 H2Se

H2Se l mt cht kh khng mu, dchy v c mi c trng rt kh

chu. Khi ha tan H2Se vo nc th dung dch ca n sc tnh axit yu.

2/ Tnh khKhi phn ng vi cc phi kim c m in ln th Se thhin tnh kh:

Se + Cl2 Se2Cl2+ 2e-

Se chy vi ngn la mu xanh cho ra selenium dioxit SeO2. SeO2tc

dng vi nc to ra axit H2SeO3l mt axit yu, mui ca n tc dng vi

kim loi kim gi l selenit SeO32-

Se + O2 SeO2

SeO2+ H2O H2SeO3

H2SeO3+ 4H++ 4e- Se + 3H2O

ioxit Selen - SeO2tc dng vi ozon cho ra selenium trioxide - SeO3,

cht ny phn ng mnh lit vi nc cho ra Selenit axit H2SeO4. Axit

Selenic rt ging H2SO4vkhnng to hidrat ha mnh, mnh ca axit

v tnh cht ca mui. Khi kt tinh tdung dch, n c th tch ra tdng

hidrat H2SeO4.H2O, ngoi ra ngi ta cng thy tn ti cc dng hidrat sau:

H2SeO4.2H2O, H2SeO4.4H2O, H2SeO4.6H2O. Axit Selenic cho hai loi mui

HSeO4- v SeO4

2-.

SeO2+ O3 3SeO3

SeO3+ H2O H2SeO4WWW FA

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H2SeO4l cht oxi ha mnh nhng thng xy ra chm.

SeO42-+ 4H++ 2e H2O + H2O

Se khng boxi ha bi cc axit c tnh oxi ha mnh ngoi traxitH2SO4v HNO3

Se + 4HNO3SeO2 + 4NO2+ 2H2O

Se + 2H2SO4SeO2 + 2SO2+ 2H2O

3/ Phn ng dphn

Phn ng dphn kh xy ra do tnh khng kim loi ca Se rt km.

Tuy nhin Se cng bdphn khi un nng vi dung dch kim.

3Se + 6KOH K2SeO3+ 2K2Se + 3H2,O4/ Mt shp cht ca Selen cc soxi ha khc nhau

a) Hp cht ca Selen c soxi ha (-2)

Do c cu hnh in t4s24p4lp vngoi cng nn Se c khuynh

hng to cc hp cht trong c soxi ha -2. Qu trnh Se + 2e Se2-

cn cung cp nhit nn ion tn ti trong mng tinh thvi cc hp cht kim

loi hot ng. Trong a scc hp cht ca Se2-, lin kt mng tnh cng

ha tr.

Hp cht H2Se l mt kh c hn H2S (H2Se phn hy r rt 1500C),

c mi c trng v l mt cht khmnh, c thchy c trong khng kh:

H2Se + 1/2O2Se + H2O (thiu oxi)

H2Se + 3/2O2Se + H2O (doxi)

H2Se tan trong nc to dung dch nc ca H2Se, mt axit yu 2 nc,

to ra 2 loi mui tng ng - hydro selenua v selenua. Cc Selenua kim loi

t tan trSelenua kim loi kim , kim th. Hydro slenua tan nhiu hn.

H2Se c tan va phi trong nc, tan trong cc dung mi hu c

ln hn. H2Se cn c iu chqua 2 phn ng sau:

* Thy phn Selenit nhm (Al2Se3):WWW FA

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Al2Se3+ 6H2O 3H2Se + 2Al(OH)3

* Phn ng ca axit HCl long vi Selenit st FeSe:

FeSe + 2 HCl H2Se + FeCl2H2Se c thkt ta nhiu ion kim loi nng, to thnh cc mui Selenit

t tan nhM2Se, MHSe.

b) Hp cht ca Se c soxi ha (+4)

Hp cht ca Se (+4) rt quan trng trong ha phn tch. Trng thi oxi

ha +4 ca Se th hin cc oxit SeO2, tetrahalogenua Sehal4, oxit

dihalogenua SeOhal2, cng nh cc phc anion kiu [SeO3]2-, [Se(OH)6]

2-,

[Sehal6]2-

.SeO2 l mt cht mu trng, thng hoa 315

0C, tan trong nc to

thnh H2SeO3(axit Seleno), l mt axit yu. H2SeO3tch ra c dng t

do, l mt cht mu trng bnt vn trong khng kh do mt nc.

H2SeO3+ H2O HSeO3-+ H3O

+ k1=2,37.10-3

HSeO3- + H2O SeO3

2-+ H3O+ k2=4,80.10

-9

c) Hp cht ca Selen c soxi ha (+6)

Se (+6) to cc hp cht nh: SeO3, SeF6, H2SeO4,...c cu trc v

tnh cht tng tnhcc hp cht ca lu hunh. SeO3mu trng, c

bit n trng thi thy tinh v aming. SeO3 c tc dng mnh lit vi

nc to thnh axit selenic H2SeO4, l cht tinh th mu trng. Cng nh

H2SO4 n ht nc rt mnh, dung dch nc ca n l axit mnh c

mnh gn bng H2SO4.

SeO42-+ 4H++ 2e H2SeO3+ H2O E

0=1,15V

Hn hp H2SeO4v HCl l cht oxi ha rt mnh do H2SeO4oxi ha

HCl to thnh Cl0nguyn t(Cl2):

H2SeO4+ 2HCl H2SeO3+ Cl2+ H2O

Phn ng ny dng khSe(VI) thnh Se(IV).WWW FA

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5/ Hp cht ca Selen vi Nit

Phn ng gia SeCl4vi NH3to ra hp cht tetraselenium tetranitrit - Se4N4

12SeCl4+ 64NH

3 3Se

4N

4+ 48NH

4Cl +2N

2

Se4N4l cht rt hot ng, dnkhi ch xt nhhoc un 2000C.

6/ Hp cht hu cca Selen

Hp cht hu cca Se c cha cc ni C-Se v slng cc ni thay

i t selenol n gin nh axit RSeH, selenit-RSeOH, organyl selenium

halide - Rsehal, diorganyl selenide - R2Se v R2Se2 cho n cc phn ttrong

sinh hc nhselenoaminoacide, selenocytenin, selenoprotein, selenopeptitde,

selenomethiomin7/iu chSelen

Oxi ha b thi v bn in phn bphn ht bi ca nh my sn

xut axits H2SO4, SeO2c tch ring v cho khvi SO2theo phn ng:

SeO2+ SO2 Se + 2SO3

1.2.1.3. ng dng ca Selen

- Se c ng dng kh rng ri trong cc ngnh cng nghip. Se xm

c tnh bn dn, di tc dng ca nh sng, dn in ca Se tng lnmnh, do Se xm c sdng trong tbo quang in. Se cn sdng

trong my in k ca kthut in nhanh. Selenua km, cadimi v nhiu kim

loi khc c tnh bn dn. Se cn c sdng trong cc ngnh cng nghip

sn xut nha, sn, men, gm, xng du, luyn kim

+ Cht xc tc trong in phn ng

+ To mu nu trong thy tinh, gm s

+ Trong lu ha cao su tng sc chu mi mn ca cao su.+ Cht n nh trong qu trnh lc du.

- Ngi ta xc nh c nhng vi lng Se trong vng mc ca mt

ngi, ng vt v chim. Trong vng mc ca i Bng (loi c thgic rt

tinh) cha mt hm lng Se ln gp trm ln vng mc ca ngi.WWW FA

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13

1.2.1.4.c tnh ca Selen

Tnh c ca Se c bit n tlu, c bit l trn sc vt n c. i

vi con ngi, theo cc bo co th ngng c ca Se l 1000g/ngy.1/ Ngc Se cp tnh c cc biu hin khc nhau nh: ho, bun nn,

nn, au u, tn thng mi, da v mt.

2/ Ngc mn tnh ko theo bun nn, nn ma, cc bnh ngoi da,

tn hi n da, rng v tc, hi thc mi ti.

1.2.1.5. Selen trong tnhin

Se phn brng khp trong t, nc v khng kh, ng vt, thc vt

nhng ni chung n hin din nng thp (


23/97

14

dimethylselenide -(CH3)Se v dimethyl diselenide - (CH3)Se2nhhot ng

ca cc vi khun. Cc qu trnh methyl ha ny c xem nhl nhng giai

on loi bc cht, bi v hp cht hnh thnh ca qu trnh methyl ha tc hn.

Theo nhng cng trnh nghin cu gn y Lin X, Mphn Se ha

tan c trong nc chim 0,3-20% tng sSe cha trong t. Phn Se ha

tan cha cc selenate, selenite v cc hp cht hu cca Se.

Trong thc vt, Selen thng tp trung cc cy hu, C ph, ti ta,

to, l, ngcc, cci trng, ci bp, la m, cy ba kch v mt vi loi nm.

c bit, trn thgii c nhng cy c h s tp trung Se (Kp) rt ln, nhcy Moringa reticulata Benth (hC ph), cy Neptunia amplexicaulis Benth

(hu) v nhiu cy thuc ging Astragalus. Cy Moringa reticulata Benth

c khnng c bit, d cho mc trn vng t ngho Se vi hm lng trong

t nhhn 0,01 ppm, th hm lng Se trong cy vn t ti 1141 ppm trong

cy kh. Cy trinh npht trin rt mnh trn vng t giu selen vi Kp t

ti 4000 ppm. Tuy nhin, n cng pht trin trn cc vng t ngho Selen vi

Kp cao hn cc loi cy khc trong vng trong khong 400-500 ppm. Hm

lng Se trong mt s cy c Vit Nam trung bnh khong 0,072 mg/kg.

Hm lng cao nht ti nay c pht hin trong cy trinh n(cy xu h) l

30,7-201,1 mg/kg.

Mt scy ngcc khc cng c khnng tp trung Se nhng khng

bng la m, i mch, kiu mch. Cc loi u c hm lng Se khng ln

nhcc loi ngcc. Cc loi rau thng c hm lng Se thp. Se trong cc

loi cy mc vng m thp nhla thng c hm lng Se thp.

1.2.1.6. Vai tr sinh hc ca selen

Ging nha snguyn tvi lng khc, Se l nguyn tkhng th

thiu cho ssng v c tnh hai mt, va tch cc, va tiu cc. nng WWW FA

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15

va phi, Se c vai tr tch cc lm tng khnng min dch ca cth, l

nguyn tbo m cho qu trnh tng hp collagen, bo m ston vn ca

c, hng cu, keratin v thy tinh th. nhng ngi c hm lng Se trongmu thp, nguy cung thtuyn tin lit cao gp 4-5 ln so vi ngi bnh

thng. c bit, Se y mnh qu trnh tng hp coenzim, l mt cht chng

oxy ha c khnng ph hy cc lipopeoxit v lm trung ha nhng cht gy

hi cho tbo.

Cc loi vitamin rt cn thit cho cth, tuy nhin, nu thiu Se, cth

khng th tng hp c nhiu loi vitamin hoc tc dng ca cc vitamin

cng bgim i ng k. Vitamin E v Se c tc dng tng hln nhau vtng cng tc dng nu sdng kt hp, do vy, nu thiu Se, th cths

khng tng hp lng vitamin C cn thit.

Se c vai tr lm tng khnng min dch ca cth, do n l cht xc

tc cho qu trnh tng hp cc globulin min dch, lm tng min dch tbo,

m bo chc nng tiu ha lipit ca tuyn ty, tham gia iu khin svn

chuyn ion qua mng tbo. Se c tc dng bo vmng tbo chng li cc

hin tng oxy ha, ngn cn sto thnh cc lipopeoxit, do , c tc dng

lm chm qu trnh lo ha v chng li stn hi ca htim mch. Cho ti

nay, nhiu nghin cu chng minh, thiu Se sgy nn nhiu bnh tt i

vi ng vt. C th k ti mt s bnh nh bnh Keshan, bnh c trng,

bnh kashin-beck, ung th, ri lon ni tit, v.v..

Mt svai tr sinh hc ca Se c cc nh bc hc tm ra nhsau:

- Se c khnng chng ung th: Cthng vt c v v chim cn Se

hot ha enzim glutathione peroxidase (GPX) gp phn phc hi cc mng

tbo bhhi, bo vcc protein ca m tbo, enzyme bi cc tc nhn

oxi ha (hydrogen peroxidase v organic peroxidase) c trong qu trnh vn

ng ca cth. Ngi dng 200g/ngy, tc l gp 3 ln mc tiu thcaWWW FA

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16

ngi bnh thng slm gim tlung thtuyn tin lit, phi v rut kt

trng v cng c xem l nguyn tthit yu bo vgan, l mt trong nhng

tc nhn ko di tui thcho cc nn nhn bnhim HIV.- Thiu Se cng lm tng ngng tp tiu cu ca mu v bin i mtrong

thnh ng mch, m l hai cchchnh dn n bnh xva ng mch.

Nhchng ta bit cc nh khoa hc lm r vai tr ca Se trong vic iu tr

tim Trung Quc (hi chng Keshan) v mt shin tng bnh l quan st

c Ty u. Trong phn ln cc trng hp ny, bsung Se tht sem li

kt qu rt khquan. Bnh Keshan c m t ln u tin Trung Quc trn

trm nm trc y v c quan tm nhiu trong nhng thp kgn y khingi ta xc nh c nguyn nhn gy bnh l do cththiu ht Se. Ngi

mc bnh Keshan ch yu tp trung nhng vng c hm lng Se trong t

thp. Nghin cu gn y chra rng, cc thng sa ha ng vai tr quan trng

i vi din phn bca bnh Keshan. t c nng axit cao, giu vt cht hu

cv cc keo oxit st ng vai tr quan trng cnh Se trong t, lm gim kh

nng hp thu Se ca cy lng thc v dn n sthiu ht Se trong khu phn n

hng ngy ca cdn khu vc ng bng Trung Quc. Trong ngcc trng cc

vng pht trin bnh Keshan, hm lng Se thng di mc 0,01 ppm. Kt

qutng tquan st thy khu vc Transbaikalia, Nam Siberia. , lng Se

thiu ht trong khu phn n hng ngy dn n bnh Keshan v bnh ctrng

trong cng ng dn ca phng. Nhvy, cc vng c sthiu ht Se trong

mi trng tnhin, nu khng bsung Se vo khu phn n hng ngy, th s

dn n thiu ht Se lu di trong cth, hu qul dn ctrong vng c thmc

mt trong cc bnh va nu.

-Se c khnng lm cht khc. N c khnng lin kt vi kim

loi nng nhHg, Pbv o thi cc kim loi nng ra ng nc tiu. Se

cn bo vcthkhi cc tc hi ca Cd, Pb, Cu, Ag, Pt, AsWWW FA

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-Se cn phi hp vi GPX v vitamin E cng cc axit bo khng no

lm lng mu v dphn trong cc phn ng hmin dch

-Se ng vai tr l cht cm ng trong tng hp Hem (cu thnhhemolobin).

-i vi vt nui: Khi hp thkhng Se th sc vt schm pht

trin, sinh sn t, nu thiu ht nghim trng ssinh bnh white muscle (c

trng).Bnh c trng hay cn gi l bnh lon dng c, l mt trong cc

bnh rt phbin i vi gia sc n ccn non. Nguyn nhn chnh l do

trong khu phn n thiu Se. Khi cthbthiu Se lu di, hthng cbtn

thng di dng thoi ha hoi t, c bit l c tim v km theo londng cgan, do vy gia sc thng bt t. T thc tny, vic nh

gi tltrssinh bmc cc bnh tim mch cc vng thiu ht Se l iu

nn lm. Bi l, Se c mi lin quan cht chvi hot ng ca tim, c bit

trong giai on u i ca tr.

-Mt nghin cu Phn lan gii thiu tc dng ca vic t hp

Selen - vitamin E trong vic chng li hin tng lo ha.

Chnh nhng tc dng sinh hc ni trn nh du mt giai on

chuyn tip quan trng trong lch sY hc v dinh dng vi khong bo v

sc khe con ngi. Pht hin ra vai tr ca Se trong vic chng li cc gc

tdo, khin n trthnh mt ngi sao mi ca nhu cu bsung vi khong

mc cho php.

1.2.2. Tng quan vnguyn tmangan

Mangan l nguyn t kim loi chuyn tip ng v tr th 25 thuc

phn nhm VIIB trong bng hthng tun hon. Cu hnh electron nguyn t

l 1 s22s22p63s23p63d5 4s2.v lp 3d ny cha bo ha nn c mc nng

lng cao. Nu mt i in t lp ngoi cng, n c th to c nhng

hp cht c trng thi oxi ho t2 n 7.WWW FA

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1.2.2.1. Tnh cht vt l

Mangan l kim loi mu trng xm, ging st. N l kim loi cng v

rt gin, kh nng chy, nhng li bxi ha ddng. Mangan kim loi ch

c ttnh sau khi qua xl c bit. Kim loi mangan v cc ion phbin

ca n c tnh cht thun t

1.2.2.2. Mangan kim loi (mc oxi ha 0)

c trng ca Mangan kim loi l tnh khmnh.

nhit cao, nht l khi dng bt, Mangan dtc dng vi cc phi

kim. V d, tc dng vi O2to ra Mn3O4, vi Cl2to ra MnCl2v tc dng

vi S to ra MnS

Mangan bn vi nc, kckhi un nng v chc phn ng chm khi

dng bt mn:

Mn + 2H2OMn(OH)2 + H2

Mangan tan ddng trong cc dung dch axit v to thnh mui Mn(II).

1.2.2.3.5 Hp cht ca mangan

1/ Hp cht ca Mn(II)

Sphi tr c trng ca Mn(II) l 6 ng vi dng lai ho sp

3

d

2

vi sphn blin kt 8 mt. Cc hp cht Mn(II) u c tnh thun tv u c 5

electron c thn.

Hp cht oxit ca Mn(II) l MnO, c tnh bazo, tan ddng trong axit

to thnh mui Mn(II) trong dtan nht l MnCl2, MnSO4, Mn(NO3)2.

Cc mui Mn(II) trong mi trng kim dto thnh Mn(OH)2vi tch

stan l 7.10-15.

Mn2+

+ 2H2O + 2NH3 Mn(OH)2+ 2NH4+

Khi NH4

+ dv un nng dung dch sc phn ng

Mn(OH)2+ 2NH4+Mn2++ 2NH3+ 2H2O

p dng phn ng ny c thtch v xc nh ring tng kim loi

trong hp kim cha Mn, Fe, Ba. Mu c phn hy bng HCl, sau dngWWW FA

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dung dch H2SO4long kt ta Ba dng BaSO4, thm NH4Cl vo dung dch

v cho ttdung dch NH3n khi metyl da cam chuyn mu th Fe(III) kt

ta dng Fe(OH)3. Nc lc chcha Mn(II).

Lng Mn(II) trong dung dch cha Fe(III), Cr(III), Mn(II) c tch

bng bt ZnO d. Ban u dng H2SO4phn hy mu, sau dng dung dch

NH3trung ha lng axit d. Cho dbt ZnO vo bnh, Fe(III) v Cr(III) s

i vo kt ta nn Mn(II) nm trong nc lc.

ZnO + H2OZn2++ 2OH

Cr3++ 3OH-Cr(OH)3

Fe3+

+ 3OH-

Fe(OH)3Mn(II) l cht oxi ha yu, phi dng phng php in phn hoc cht

khmnh nhAl mi c thchuyn Mn(II) vMn(0).

Mn(II) th hin tnh kh mnh. Trong mi trng kim, Mn(II) tc

dng vi cc cht oxi ha nh(O2, Cl2, H2O2,...) to thnh MnO2.

Mn2+- 2e + 2H2OMnO2+ 4H+

C th tch Mn(II) ra khi cc kim loi kim th v magie bng

thioaxetamit hoc tch khi st bng KClO3 (chuyn Mn(II) vMnO2)Trong mi trng axit, Mn(II) boxi ha bng cc cht oxi ha mnh

nhPbO2, NaBiO3, KIO4, (NH4)2S2O8 to thnh MnO4-.

Mn(II) c thkt hp vi cc cht v c(nhcyanua) v cc cht hu

c(nhetilendiamin, oxalat, EDTA) to thnh cc phc bn.

2/ Hp cht ca Mn(III)

Hp cht ca Mn(III) l hp cht t bn v c tnh oxi ha kh.

Mn(III) oxit c cng thc phn tMn2O3. Mn2O3khi tc dng vi axitlong to ra MnO2v mui Mn(II). Nhng khi tc dng vi axit c to thnh

mui ca Mn(III) .

a s cc mui Mn(III) bn nht trong mi trng kim, khng bn

trong dung dch nc, dbphn hy thnh mui Mn(II) v MnO2.WWW FA

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Mui Mn(III) dkt hp vi cc anion ca axit to thnh phc cht bn

nhK3(Mn(CN)6), K3(Mn(C2O4)3.3H2O, K(Mn(EDTA).3H2O

3/ Hp cht ca Mn(IV), Mn(V)Oxit ca Mn(IV) l MnO2. y l hp cht bn nht ca Mn. Khi un

nng, MnO2tan trong axit v kim nhmt oxit lng tnh.

Cc mui ca Mn(IV) rt km bn trong nc v dung dch axit, d

phn hy thnh Mn(II).

MnO2va c tnh oxi ho, va c tnh kh.

Tnh oxi ha: MnO2trong mi trng axit to thnh mui Mn(II)

MnO2+ 4HClMnCl2+ Cl2+ 2H2OTnh kh: MnO2 trong mi trng kim mnh to thnh hp cht ca

Mn(V).

2MnO2+ 6KOHcK3MnO4+ K3[Mn(OH)6]

Cc tetra halogenua ca Mn(IV) km bn trong nc, dkt hp vi

halogenua kim loi kim to nn nhng phc cht c mu vng v bn hn

nh: M[MnX5] v M2[MnX6] (trong M = K, Rb, NH4v X = F, Cl).

4/ Hp cht ca Mn(VI)

Mn(VI) khng tn ti dng oxit MnO3m chthy trong ion MnO42-.

Mn(VI) chbn trong dung dch kim mnh, trong dung dch trung tnh hoc

kim yu dbthy phn:

3MnO42-+ 2H2O2MnO4

-+ MnO2+ 4OH-

Mui manganat ny l cht oxi ho mnh, phn ng vi nhiu cht kh

trong dung dch tng t nhpermanganat. Nhng vi cht oxi ho mnhhn th n li thhin tnh kh. Tuy nhin iu ny rt t xy ra:

2K2MnO4+ Cl22KMnO4+ 2KCl

Ion MnO42-theo thuyt trng tinh thc xem l phc cht ca kim

loi chuyn tip.WWW FA

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5/ Hp cht ca Mn( VII)

Mn(VII) khng tn ti dng oxit Mn2O7m chthy trong ion MnO4-.

Mui MnO4-

u dtan trong nc.KMnO4l cht oxi ha mnh, c thoxi ha nhiu cht hu choc v

c. Ty thuc axit ca mi trng m MnO4- s b kh n Mn(II),

Mn(IV) hoc Mn(VI). Trong mi trng axit mnh:

MnO4-+ 5e + 8H+Mn2++ 4H2O.E

0 = 1,51 V

Trong mi trng axit yu, bazo yu hoc trung tnh:

MnO4-+ 3e + 2H2O MnO2+ 4OH

-.E0= 1,23 V

Trong mi trng kim:

MnO4-+ 1e MnO4

2-(xanh l cy) E0= 0,56 V

Ion MnO4-theo thuyt trng tinh thc xem l phc cht ca kim

loi chuyn tip.

1.2.2.4. ng dng ca mangan

Mangan c vai tr quan trng trong sn xut st thp v c tc dng kh

lu hunh, khoxi, v mang nhng c tnh ca hp kim. Luyn thp, v c

luyn st, sdng nhiu mangan nht (chim khong 85-90% tng nhu cu).

Trong nhng mc ch khc, mangan l thnh phn ch yu trong vic sn

xut thp khng rvi chi ph thp, v c trong hp kim nhm. N cn c

thm vo du ha gim ting nlc xc cho ng c.

Mangan ddioxxit c s dng trong pin kh hoc lm cht xc tc.

Mangan c dng ty mu thy tinh (loi bmu xanh lc do st to ra)

hoc to mu tm cho thy tinh.Mangan xt l mt cht nhum mu nu, dng ch to sn, v l

thnh phn ca mu nu en tnhin. Kali pemanganat l cht xi ha mnh,

dng lm cht ty u trong ha hc v y khoa. Photphat ha mangan l

phng php chng rv n mn cho thp. N thng hay c dng snWWW FA

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xut tin xu. Nhng loi tin xu duy nht c s dng mangan l ng xu

niken "thi chin" ("Wartime" nickel) tnm 1942 n 1945, v ng xu la

Sacagawea (tnm 2000 n nay). Trnh ng dng mangan Hoa Kvnkhng c nhiu thay i. Hin nay, khng c gii php cng nghthc tno

c th thay thmangan bng cht liu khc hay sdng cc trm tch trong

nc hoc cc cng nghlm giu khc gim hon ton sphthuc ca

Hoa Kvo cc quc gia khc i vi qung mangan.

Trong nhng ng dng nh, km hoc vanai c ththay thc cho

phng php phot phat ha mangan.

Cc hp cht mangan c s dng lm cht to mu v nhummu cho gm v thy tinh. Mu nu ca gm i khi da vo cc hp cht

mangan. Trong ngnh cng nghip thy tinh, cc hp cht mangan c dng

cho 2 hiu ng. Mangan(III) phn ng vi st(II) to ra mu lc m trong

thy tinh bng cch to ra st(III) t mu hn v mu hng nht ca

mangan(II) kt hp vi mu cn li ca st (III).

1.2.2.5. Mangan trong tnhin

Mangan chim khong 0,1% trongv Trit, ng hng th 12 v

mc phbin ca cc nguyn ty. t cha 7-9000 ppm mangan vi

hm lng trung bnh 440 ppm.

Nc Bin chcha 10ppm mangan v trong kh quyn l 0,01 g/m3.

Mangan c mt chyu trong pyrolusit (MnO2), Braunit (Mn2+Mn3+6)(SiO2),

psilomelan (Ba,H2O)2Mn5O10v t hn trong Rhodochrosit (MnCO3).

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Qung mangan

Mangan oxit tp hp dng cnh cy trn mt vi, Solnhofen, c.

Qung Psilomelan

Hnh 1.2: Mt sdng tn ti ca Mangan

Qung mangan quan trng nht l pyrolusit (MnO2). Cc qung quan

trng khc thng c sphn blin quan n cc qung st. Cc ngun trn

t lin ln nhng phn bkhng ng u. Khong 80% ngun ti nguynmangan c bit trn thgii c tm thy Nam Phi, cc mmangan

khc Ukraina, c, n , Trung Quc, Gabon v Brasil. Nm 1978, ngi ta

tnh c 500 t tn mangan y bin. Nhng n lc tm phng php c

hiu qukinh t thu hi mangan ny bb lng trong thp nin 1970.WWW FA

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Mangan c khai thc Nam Phi, c, Trung Quc, Brasil, Gabon, Ukraine,

n , Ghana v Kazakhstan. Ngun nhp khu ca Hoa K(1998-2001) t:

1/ Qung mangan: Gabon, 70%; Nam Phi, 10%; c, 9%; Mexico, 5%;v ngun khc, 6%.

2/ Ferromangan: Nam Phi, 47%; Php, 22%; Mexico, 8%; c, 8%; v

ngun khc, 15%. Mangan cha trong cc ngun nhp khu gm: Nam Phi,

31%; Gabon, 21%; c, 13%; Mexico, 8%; v ngun khc, 27%. Vsn xut

ferromangan, qung mangan c trn vi qung st v cacbon, sau kh

hoc trong l cao hoc trong l in hquang. Ferromangan c to ra c

hm lng mangan t30 n 80%. Mangan tinh khit c dng sn xutcc hp kim khng cha st, c sn xut bng cch cho qung mangan

c ngm chit vi axit sunfuric v tip theo l xl bng in trit.

1.2.2.6. Vai tr sinh hc ca Mangan

Mangan l nguyn tng vai tr thit yu trong tt cdng sng. Cc

lp enzyme c cc ng yu tmangan rt rng bao gm oxidoreductases,

transferases, hydrolases,lyases, isomerases, ligases, lectins, v integrins.

Polypeptitde cha mangan c thl arginase, diphtheria toxin, v superoxide

dismutase.

1.3. Cc phng php phn tch Selen, Mangan

1.3.1. Cc phng php phn tch Selen

1.3.1.1. Phng php phn tch khi lng[4]

c im ca nhm phng php ny l l nh hng ca mt sion

kim loi c thgy nhim bn, gy sai sng k. Ngy nay phng php

phn tch trng lng t c s dng, n c thay th bng cc phng

php cng ccho chnh xc cao v n gin hn.

Ngi ta c thto nhiu dng kt ta nhSe, SeO2, piazoSeolTuy

vy i vi phng php trng lng, vic kt ta tch ra dng SeWWW FA

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nguyn tl ng tin cy nht. lm kt ta Se ngi ta thng hay s

dng cc cht nhSO2, hydrazin, hydroxyamin, Na, SnCl2xc nh vi

lng Se trong cht hu c, ngi ta chuyn n vdng Selenit bng chtkho st trong bom vn nng cha Na2O2 sau kh Selenit v cn n

di dng kim loi.

Phng php in phn nh lng Se c bt u ch ngin cu

vo nhng nm 1960, nhsdng cp in cc Cu-Pt. Khi Se c tch

ra dng Cu2Se l dng khng bht m v khng b thay i khi nung n

nhit 1300C. Sai sca phng php ny l 0,3%. Phng php ny c

ng dng xc nh SeO2trong kthut.1.3.1.2. Phng php phn tch thtch [4]

Phng php chun c bn xc nh Se+4 l chun iot. Do

phng php nhy nn cn tch trit cc nguyn tnh hng n php

xc nh. Chthdng cho php chun c thl chthha hc hoc ch

thin ha. Php chun da trn vic dng KI khH2SeO3:

SeO22-+ 6H++ 4I-Se + 2I2+ 3H2O

I2 sinh ra c chun bng Na2S2O3vi chthhtinh bt

2Na2S2O3+ I2Na2S4O6+ 2NaI

Phng php ny xc nh c n 50 mg Se.

1.2.1.3. Phng php phn tch trc quang[24], [29], [46]

Nguyn tc ca phng php ny l da trn khnng to phc mu

ca cht phn tch vi mt thuc thno . o hp thca phc mu ta

c thbit c nng cht phn tch.

Phng php thng dng xc nh Se+4da trn phn ng to mu

ca Se+4 vi cc o-diamin thm. Thuc th hay c s dng nht l

3,3diaminobenzidin. Trong mi trng axit thuc th ny to phc vi Se

cho ra phc piazoseol c mu vng. o hp thtrong pha nc 490nmWWW FA

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(hay sau khi chit bng toluene 420nm). Khong tun theo nh lut Lamber-

Beer l 0,25g/ml n 2,5 g/ml.

Cng c th xc nh Se bng phn ng to phc ca Se

+4

vi 2,3-diaminonaphtalen pH=1, sau phc c chit vo dung mi cyclohexan

v o hunh quang 520nm sau khi kch thch 380nm (cc dung dch m

nng Se qu nh th Se c lm giu bng phn ng to phc vi

aminopyrolidin dithiocacbamat pH=4,2 v sau c gii chit bng

HNO3. Phng php cho php xc nh nng Se cnanomet.

1.3.1.4. Phng php in ha[18]

Phng php cc ph ni chung nhy ch t c 10-4

- 10-5

M.Cng dng ph thuc thin phn trong dung dch v thin cc.

Ngi ta tin hnh in phn v o cng dng vi mt dy dung dch

chun bit trc nng . Da vo thxc nh c nng cht phn

tch khi bit cng dng. Gi tr thna sng cho bit thnh phn nh

tnh, chiu cao sng cho bit thnh phn nh lng ca cht phn tch.

Nm 1986 G.E. Batley sdng phng php cphxung vi phn xc

nh Se trong nc thi. Tc gidng nn HCl, pH=2, pic -0,6V (so vi

in cc Ag/AgCl) c dng nh lng. Nc thi c loi btp cht

th bng cch di qua ct C18 sep-pak sau dng nha chelex 100 loi

blng vt cc kim loi. Khong nng tuyn tnh ca phng php l 2-

100 g/l

c bit phng php Von-Ampe ha tan, nhlm giu cht phn tch

ln bmt in cc bng phn ng khhay oxi ha kt ta cht sau ha tan

sn phm kt ta v ghi tn hiu ha tan m cc phng php in ha ha tan

c nhy cao, cng trnh ca Wang.J v Jianmin.L sdng CSV trn nn

0,1M H2SO4+ 10 g/l Rh3+. in phn lm giu - 0,2V. Phng php daWW

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trn phn ng tch ly v sau khlp Rh2Se3trn in cc HMDE. Gii hn

pht hin ca phng php l 0,5g/l khi thi gian in phn l 3 pht.

1.3.1.5. Phng php phpht xnguyn t

[13], [18], [43]

Khi nguyn t trng thi hi, mt ngun nng lng thch hp nh

nhit, in..kch thch m hi nguyn t pht ra, sau thu phn ly

ton bphpht xnh gi thnh phn mu phn tch. C thdng ph

pht xphn tch inh tnh, nh lng. y l phng php hin i cho

nhy v chnh xc rt cao n ty thuc vo cc thit bkhc nhau, cho

php xc nh lng vt nguyn tm khng cn lm giu v mt u im

c trng ca phng php l cho php phn tch hng lot cc nguyn t.c bit phng php ICP-AES ra i tng nhy ln rt nhiu, lc ny

nng lng nhit ca ngun kch thch c quyt nh bi dng in cm

ng trong cun tcm, nng lng cao tn ca my pht HF. V vy nhit

plasma rt n nh dn n php o c n nh cao hn rt nhiu so vi

ngun hquang in hay tia la in.

Vic xc nh lng Se bng phng php quang phpht xnguyn

tda trn ba vch c trng ca Se l 196,1nm, 204nm v 206,3 nm. Khi

dng cc ngun nng lng l ngn la hquang hoc tia in nhy php

xc nh cht cmg/l. Khi dng ngun nng lng l plasma cao tn cm

ng ICP gii hn pht hin t 0,14 mg/l. Gn y k thut to hp cht

Hyrua c s dng rng ri khi phn tch cc hp cht d to hp cht

Hydrua nhAs, Se, HgNguyn tc ca phng php l sdng cc cht

kh mnh trong mi trng axit kh cc hp cht phn tch thnh cc

hydrua sau phn ly chng thnh nguyn ttdo v dn vo bung o ph.

Khi sdng kthut ny vi my AES, Pretorius v cng s t c gii

hn pht hin l 3g/ml v Pruzkowska 0,3 g/ml. Mc d gii hn ny l kh

nhnhng hthp hn gii hn pht hin th qu trnh lm giu trc lWWW FA

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cn thit. Thomson v cng s lm giu bng phn ng ng kt ta vi

lantanhidroxit khi gii hn pht hin l 0,06 g/ml, Wang sdng kthut

bay hi cho gii hn pht hin l 0,5g/ml.

1.3.1.6. Phng php sc k [38]

K.W. Michell xc nh Se+4trong nc bin bng phng php sc k kh

(GC) s dng detector cng kt in t (ECD). Se c kt ta cng vi

Fe(OH)3pH=5 sau kt ta c ha tan bng HCl v chuyn Se vdng 5-

nitropiazoSeol, phc ny c chit bng toluene sau dn vo ct sc k.

Gii hn pht hin l 5ng/l. chnh xc 6% mc 0,025g/l. Donald Creamer

xc nh Se trong vt liu sinh hc bng sc k khi phsdng detector cpion sau khi chuyn Se vdng 5-nitropiazoSeol (ng phn 80Se v 82Se)

1.3.1.7. Phng php kch hot ntron[28]

75Se c bn thi gian sng di nht (120 ngy) v c sdng nhl

mt nguyn tnh du trong cc th nghim cng nhtrong vic xc nh Se

bng phng php phn tch kch hot notron. Hai ng vc thi gian sng

tng i ngn l 77Se (bn thi gian 17,5 giy) v 81Se (18,6 pht) cng c

s dng trong phn tch kch hot notoron (Heath, 1969-1970; Alcino vKowald 1973).

Khi xc nh Se theo phng php kch hot phng x, Se c chuyn

vcc ng vphng x, ngun nng lng bn ph mu thng l chm

notron nhit. ng v75Se thng c sdng v ta c thtch hon ton

cc tp cht hot ng khc nhhm lng thp ca 75Se. Tuy nhin do thi

gian bn hy qu ln nn hin nay ngi ta sdng ng vc thi gian sng

ngn hn nh77Se, t1/2=17,4 giy, 81Se, t1/2=18,6 pht.nhy php xc nhphng php ny t c 0,01g.

1.3.1.8. Phng php phkhi lng plasma cm ng (ICP-MS)[36]

Sdng phng php phkhi kt hp plasma cm ng cc tc gi

xc nh c Se trong l c chua. Gii hn pht hin Se: 14-18 ng/g.WWW FA

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1.3.1.9. Phng php hunh quang Rnghen[42]

Phng php hunh quang Rghen xc nh theo vch K. Khi tin

hnh xc nh trn my Philips vi ng W, Mo v LiF, cht chun ngoi lkeo Cu-Se. nhy php xc nh t c0,3 g/5g mu. tng nhy, Se

c tch ra dng nguyn t dng cht kh l 4,5 diamin - tiopyrramidin

trong etanol hay HCl 5Nv NaI. Nguyn tSe sau c kt ta trn mt

mng lc, gii hn pht hin t c l 140ng/g mu.

Se cng c xc nh trc tip khi c mt Sb, Zn, As, Ge, Cu trn

my o phhunh quang vi anot W (20mA, 50kV) v tinh thLiF. nhy

php xc nh l 1g.1.3.1.10 .Phng php hunh quang nguyn t[33]

Ngoi ra Thomson nghin cu xc nh As, Se, Sb, Te vi cht kh

NaBH4pha trong NaOH nng 0,5%, kh hidrua sinh ra c dn trc tip

vo ng cuvet Pyrex c treo vo mt ci gi, gii hn pht hin ca phng

php l 0,06 n 0,1 ng/ml.

1.3.1.11. Phng php ng hc xc tc[34]

Phng php da trn hiu ng xc tc ca Se trong phn ng ca

xanhmetylen (MB) vi Na2S. Sphthuc ca thi gian hon thnh phn

ng t-1tlvi nng Se+4trong khong 2,5-30 ng/ml Se.

1.3.1.12. Phng php in di mao qun vng [32]

Phng php ny kt hp vi vic lm giu bng kthut khuch i

vng,xc nh c n 25ng/ml Se+4.

1.3.1.13. Phng php quang phhp thnguyn t[27],[44],[45]

Phng php quang phhp thnguyn txc nh Se bng nhiu k

thut ha hi nguyn tha. Dng ngun nng lng l ngn la v khng

kh th nhy ca php xc nh l 1 g/ml theo vch 196,1 nm, cn khi

dng ngn la axetilen - khng kh th nhy l 0,25 g/ml. Kthut nguynWWW FA

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tha khng ngn la xc nh Se trong mu v serum,gii hn pht hin l

0,8 g/ml, cn khi ni vi ct Cellex lm giu th gii hn pht hin tng

ng l 2,1 v 2,4 ng/ml.Phng php hp thnguyn tsdng k thut hidrua ha phn

tch As, Se tng nhy ln mt cch vt bc cvi g/l.

Phng php quang phhp thnguyn tcng chnh l phng php

chng ti sdng phn tch hm lng Selen trong nm Linh chi ti lun

vn ny.

1.3.2. Cc phng php phn tch Mangan

1.3.2.1. Phng php phhp thnguyn tMangan c nhiu vch phc trng nhng thng sdng ba vch c

bc sng sau: 1=279,5 nm, 2 =279,8 nm v 3=280,1 nm.[3]

C thxc nh Mangan bng phng php quang phhp thnguyn t

(AAS) vi kthut ngn la v kthut khng ngn la. chuyn nguyn t

cn phn tch vdng nguyn t, phng php ngn la sdng hn hp axetilen

v khng kh, phng php khng ngn la sdng dng in cao tn.[3]

Gii hn ca cc phng php ny c trnh by trong Bng 1.3 theo

cc tiu chun thgii nhEPA (Hip hi bo vmi trng M), APHA

(Hip hi bo vsc khe cng ng M).

Bng 1.2: Mt stiu chun xc nh Mn theo phng php AAS

Tiu chun Phng php Khong xc nh Mn

EPA 243.1 AAS vi kthut ngn la 0,1 - 3 mg/l

EPA 243.2 AAS vi kthut khng ngn la 1 - 30 g/lAPHA 3500-Mn AAS vi kthut khng ngn la 1 - 30 g/l

Nh bng trn, gii hn xc nh ca Mn theo phng php khng

ngn la nhhn nhiu so vi phng php ngn la.WWW FA

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xc nh Mn trong cc mu mu, huyt thanh hay ch, thc phm

bng phng php AAS, u phi xl mu, chit bng dung mi.

Vic xc nh lng vt Mn trong ch c Choary nghin cu bngphhp thngn la (khng kh - axetilen l hn hp chy) = 253,7nm.

Mu c xl bng cch sy kh 80oC ri chit bng dung mi, xl cn

b vi HCl v chit thm vi ln na, sau un nng vi hn hp H2SO4v

HNO3[20]

Furono xc nh Mn trong huyt thanh v mu bng phng php

phhp thnguyn t1=279,5 nm. Mu c xl bng CH3COONH4

iu chnh n pH = 8 ri chit bng benzylxantogenat trong MIBK. Gii hnxc nh l 0,45 - 1,90 g/g [25]

1.3.2.2. Phng php trc quang

Phng php trc quang da vo o mu ca hp cht Mn.

C thxc nh Mn dng Mn(II) v dng Mn(VII). Soxi ha cc

hp cht ca Mn thnh MnO4- bng cc thuc th nhbismutat, periodat,

persunfat v o hp th ca MnO4- bc sng 528nm c coi l

phng php tiu chun trong mt khong thi gian di. Ti Vit Nam cng

sdng phng php ny nhtiu chun TCVN 4578 - 1988. Mangan

cc mc oxy ha khc nhau (chyu dng Mn(II)) c thxc nh theo

phng php ny bng cch oxy ha thnh Mn(VII) bng cc cht oxy ha

mnh nh (NH4)2S2O8 (Ag+ lm xc tc), NaBiO3, KIO4, trong mi

trng HNO3, H2SO4). Lng ln cc cht hu c, ion c mu, Cl-cn tr

php xc nh. nh hng ca Cl- c loi tr bng cch kt ta vi

AgNO3hoc bay hi vi H2SO4c. nh hng ca Fe3+ c loi trbng

cch to phc vi H3PO4v dung dch o quang tin hnh hai ln loi tr

nh hng ca nhng ion mu khc. Phng php ny thch hp phn tch

Mn hm lng mg/l.[2]WWW FA

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1.3.2.2. Phng php ng hc xc tc

1/ Nguyn tc

Phng php ny c nhy v chn lc cao, thng dng phn tch vi lng m khng cn phi tch loi cc nguyn t cn hoc

lm giu.

Phng php s dng h phn ng ch th oxi ha cht mu hu c

trong mi trng kim hoc axit. Mn(II) sxc tc lm tng tc phn ng

oxi ha lm cht hu cbgim mu. Theo di sgim mu tlvi nng

xc tc Mn(II).

2/ Cc phn ng chththng dng xc nh Mn(II)Trong dung dch, Mangan trng thi Mn2+ c khnng xc tc cho

nhiu phn ng gia KIO4hoc H2O2vi cc cht hu choc v c.

Theo bi bo tng hp v cc phng php trc quang xc nh

Mangan ca cc tc giBarry Chriswell, Guy Rauchle v Mark Pascoe [16], t

nhng nm 1990 trvtrc, phng php ng hc xc tc xc nh Mn

rt pht trin. c rt nhiu nh nghin cu tm ra cc cht hu cc mu

(cht chth) khc nhau vi mc ch nng cao nhy v khnng chn lc

ca phng php.

Tnm 1990 trli y, phng php ng hc xc tc vn pht trin

mnh. Cc cht oxi ha nhKIO4v H2O2vn tip tc c p dng. Ngoi

ra cn sdng thm cc cht oxi ha khc nhO2, KMnO4 .

t c nhy cao (gii hn pht hin thp), cc phn ng oxi

ha thng tin hnh nhit cao (ln hn 50oC). Bozhanov v Alexandrov

p dng phng php ng hc xc tc xc nh Mn trong tinh du hoa

hng vi khong xc nh l 0,05 - 2,5 g/l. Phng php ny s dng h

phn ng oxi ha diphenylamin-4 azobenzen-4-sunfonic axit bng KIO4,

cht hot ha l phen- v tin hnh 80oC.WWW FA

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Qin Wei v cc cng s tm ra cht hu cdahlia violet c thxc

nh Mn(II) trong mi trng huyn ph. Tc gisdng cht hot ng b

mt Tween-20 tng tan nhng vn t c nhy cao vi gii hnpht hin l 3,75.10-2g/l. Phng php ny c p dng phn tch Mn

trong thc phm[37].

Nm 1991, Gomez v cc cng s p dng h phn ng H2O2v

Tiron trong mi trng axit, cht hot ha l phen- xc nh Mn(II) nhit

25oC. Khong tuyn tnh ca phng php l 1 - 200 g/l. Phng php

ny p dng cho phn tch nc, bia v ru[23].

H phn ng oxi ha Rhodamin B bng KIO4 trong mi trng axityu, vi cht hot ha l phen- xc nh Mn(II) trong l ch[39] v hp

kim[47] . Vi h phn ng ny, gii hn pht hin Mn(II) rt nh, khong

0,02g/l.

Vo nhng nm cui thk20, u thk21, nhiu phng php ng

hc xc tc sdng k thut FIA nng cao nhy v chnh xc.

Phng php ny cho php kim sot c lng thuc thv nhit , thi

gian n nh c chnh xc. Hny ddng tng ha v tc phn tch

nhanh, 1 gic thxc nh c 30 - 60 mu.

S.Nakano v cc cng s p dng kthut FIA xc nh Mn(II)

xc tc cho phn ng oxi ha 2,2-azinobis(3-etylbenzothiazolin-6-sunfonic

axit) bng KIO4. Phn ng ny c hot ha bng phen-. Phng php ny

cho php xc nh Mn(II) trong nc sng, hvi khong xc nh l 0,05 - 1

g/l

[40]

.H phn ng oxi ha N,N-bis(2-hydroxy-3-sunfopropyl)tolidin bng

KIO4 vi Mn(II) xc tc, cht hot ha l 2,2bipyridin cho php xc nh

Mn(II) trong nc sng, h. Phng php ny s dng k thut FIA vi

khong xc nh Mn(II) l 0,02 - 3 g/l.WWW FA

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Ling Su v cc cng s p dng phng php ng hc xc tc

xc nh Mn(II) trong nc t nhin. Phng php ny sdng k thut

FIA, thuc th hu c l 4,4-bis(dimetylamino)-diphenylmetan, cht oxiha l KIO4, cht hot ha l NTA. Phng php cho gii hn pht hin l

0,073 g/l.

1.3.2.3. Phng php so mu chun bng dung dch kali

pemanganat 0,01N

Nguyn tc: Dng kali pesunfat v cht xc tc l ion Ag+ trong mi

trng axit oxy ha Mn2+n MnO4-. Kt quc xc nh trn my o

mu hoc so mu chun bng dung dch kali pemanganat 0,01N. Phngphp ny dng xc nh hm lng Mn trong nc.

Yu t cn tr: Ion clo (Cl-) gy cn trxc nh, loi bc bng

cch thm dung dch bc nitrat, lc bta sloi c Cl-. Nu c nhiu cht

hu c, loi b bng cch v cha, loi tr bng cch thm vi git axit

photphoric. Cc cht c mu khc c loi trbng cch dng mu trng.

1.4. Phng php quang phhp thnguyn t

1.4.1. Sxut hin phhp thnguyn t[3]

Nh chng ta bit vt cht c cu to bi cc nguyn t v

nguyn tl phn cbn nhnht cn gic tnh cht ca cc nguyn t

ha hc. Trong iu kin bnh thng nguyn tkhng thu v khng pht ra

nng lng di dng cc bc x. Lc ny nguyn ttn ti cc trng thi

c bn. l trng thi bn vng v ngho nng lng nht. Nhng khi

nguyn t trng thi hi tdo, nu chng ta chiu mt chm tia sng c

nhng bc sng (tn s) xc nh vo m hi nguyn t, th cc nguyn

ttdo shp thcc tia bc xc bc sng nht nh ng ng vi

bc sng bc xm c thpht ra c trong qu trnh pht xca n. Lc

ny nguyn tnhn nng lng ca cc tia bc xchiu vo n v n chuynWWW FA

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ln trng thi kch thch c nng lng cao hn trng thi cbn. l tnh

cht c trng ca nguyn t trng thi hi. Qu trnh c gi l qu

trnh hp thnng lng ca nguyn ttdo trng thi hi v to ra ph

nguyn t. Phsinh ra trong qu trnh ny c gi l phhp thnguyn t.

1.4.2. Cc giai on ca qu trnh nguyn tha mu[3]

1.4.2.1. Sy kh mu

thc hin qu trnh sy tt, i vi mi mt loi mu cn phi tin

hnh nghin cu, pht hin v chn nhit v thi gian sy cho ph hp.

Nhit v thi gian sy kh ca mi loi ph thuc vo bn cht ca cc

cht trong mu v dung mi ha tan n. Thc nghim cho thy rng, a scc mu v c trong dung mi nc nm trong khang t100- 1500C trong

thi gian t25-40 giy.

1.4.2.2. Tro ha luyn mu

y l giai an thhai ca qu trnh nguyn tha mu. Mc ch l

tro ha t chy) cc hp cht hu cv mn c trong mu sau khi sy

kh, ng thi nung luyn mt nhit thun li cho giai on nguyn tha

tip theo t hiu sut cao v n nh, tro ha mu tt v nhit thphn nhit gii hn th php o lun cho kt qun nh v mi nguyn t

u c mt nhit tro ha luyn mu gii hn trong php o ETA-AAS.

1.4.2.3. Nguyn tha

y l giai on cui cng ca qu trnh nguyn tha mu, nhng li

l giai on quyt nh cng ca vch ph. Song n li bnh hng bi

hai giai on trn. Giai on ny c thc hin trong thi gian rt ngn,

thng thng 3 n 6 giy, rt t khi n 8 n 10 giy.Nhng tc o nhit li l rt ln t ngay tc khc n nhit

nguyn tha v thc hin php o cng vch ph. Tc tng nhit

thng t1800-2500oC/ giy, thng thng ngi ta sdng tc ti a,

nguyn tha ca mt nguyn trt khc nhauWWW FA

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ng thi mi nguyn tcng c mt nhit nguyn tha gii hn

Ta ca n. Nhit Ta ny ph thuc vo bn cht ca mi nguyn t v

cng phthuc trong mc nht nh vo trng thi v thnh phn ca mum n tn ti, nht l cht nn ca mu nguyn tha v cng vch ph

ca cc nguyn t.

1.4.2.4. Ti u ha cc iu kin cho php o khng ngn la mu.

- C thvi php o ETA-AAS bao gm nhng iu kin nguyn t

ha mu:

+ Thi gian, nhit un nng cuvet ca cc giai on sy mu, tro

ha luyn mu v nguyn tha o cng vch ph.+ Kh mi trng cho qu trnh nguyn tha mu (tc , loi hi)

+ Cng sut, tc t nng cuvet graphit nguyn tha mu.

+ iu kin lm sch cuvet graphit.

+ Lng mu v cch a vo cuvet nguyn tha cho php o.

Cht nn ca mu phn tch v cc mu chun cn phi c pha ch

v chun cho ng nht. Mi trng axit v loi axit pha chmu v lm mi

trng cho dung dch mu chun v mu phn tch.

- Cc yu tnh hng sau y cng c xem xt.

+ Cc nh hng vph

+ Cc nh hng vvt l

+ Cc nh hng ha hc ca cc cation v anion c trong mu.

+ Vnh hng ca thnh phn nn ca mu.

1.4.3. Hthng nguyn tha mu phn tch [3]

H thng ny to ra nhit thch hp v n nh nguyn tha

nguyn tthnh trng thi hi ri rc. C hai loi kthut nguyn tha mu

l k thut nguyn t ha bng ngn la n kh Flame-AAS v k thut

nguyn tha khng ngn la.WWW FA

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Bng 1.3: Quan hgia nhit v loi kh t

Kh oxi ha Kh nhin liu Tll/pht Nhit 0C

Khng kh Propan 6/1,4 2200Khng kh Axetylen 4,2/1,2 2450

Khng kh Hydro 4/3 2050

Oxy Axetylen 1/1 3000

N2O Axetylen 2/1,8 2900

Bng 1.4: Thnh phn kh v nhit ngn la

Kh oxi ha Kh nhin liu Tl Nhit 0

CKhng kh Axetylen 4,2/0,7 1800

Khng kh Axetylen 4,2/0,9 2000





c im k thut ca ngn la n kh: Nhit l mt thng sc

trng cho ngn la n kh. Nhit ca mt loi n kh phthuc rt nhiu

vo bn cht thnh phn ca cht kh c t chy to ra ngn la. Ngha

l ng vi mt hn hp kh chy ngn la sc mt nhit xc nh v khi

thnh phn kh thay i th nhit ca ngn la cng bthay i. Ngoi yu

ttrn tc dn ca hn hp kh vo n t chy cng nh hng n

nhit ca ngn la v qua m nh hng n cng vch phhp th.

Xt vcu to ngn la n gm 3 phn chnh:

- Phn ti ca ngn la: Phn ny h hp kh c trn u v t

nng cng vi cc ht sol kh (thaerosol) ca mu phn tch. Phn ny cWWW FA

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nhit thp (700-1200 0C). Dung mi ha tan mu sc bay hi trong

phn ny v mu c sy nng.

- Phn trung tm ngn la: Phn ny c nhit cao thng khng cmu hoc c mu xanh nht. Trong phn ny hn hp kh c t chy tt

nht v khng c phn ng thcp. V thtrong php o phhp thnguyn

tngi ta phi a mu vo phn ny nguyn tha v thc hin php o.

- Phn vv ui ngn la: Vng ny c nhit thp, ngn la c

mu vng v thng xy ra cc phn ng thcp khng c li cho php phn

tch quang phhp th.

Chnh v l do trn m mi php phn tch cn phi kho st v chniu kin ph hp nhthnh phn, tc dn kh chy to ra ngn la.

1.4.3.2. Kthut nguyn tha khng ngn la ETA-AAS

Phng php hp th nguyn t khng ngn la ra i sau hp th

nguyn tbng ngn la, n nng cao nhy ln gp hng trm n hng

nghn ln hp th ngn la tuy nhin i vi phng php hp th khng

ngn la n nh km hn v nh hng ca phnn thng ln.

K thut nguyn t ha khng ngn la gm hai loi chnh l l

graphite v hydrua. K thut l graphite cho php xc nh nhanh, ng,

chnh xc mc ppb. Kthut hydrua cho php xc nh mt snguyn tc

kh nng to kh hydrua, ddng nguyn tha nhit thp, php xc

nh nhanh, ng chnh xc mc ppb.

1/ Kthut l graphite (GF-AAS)

Nguyn tc ca k thut nguyn tha khng ngn la l dng nng

lng ca dng in cng sut ln hay nng lng ca dng cao tn cm ng

nguyn t ha gn nh tc khc mu cha cht phn tch trong cuvet

graphite v trong mi trng kh trAr to ra cc nguyn ttdo trng

thi hi c khnng hp thbc xn sc to ra phnguyn tca n.WWW FA

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Mu cha nguyn tcn xc nh c a vo l graphite bng bht

mu tng hoc bng tay vi thtch rt nht20l - 50l. Qu trnh phn

tch nguyn t trong l graphite bng phng php ny xy ra theo 4 giaion ktip nhau trong thi gian tng st60-80 giy. Cc giai on l:

Sy kh mu: Lm cho dung mi ha tan mu bay hi nhnhng v

hon ton nhng khng lm bn mu mt mu.

Tro ha mu: Nhm mc ch t chy cc hp cht hu cv mn c

trong mu sau khi sy kh. Mi nguyn tu c mt nhit tro ha mu

cho n trong php o GF-AAS. Nhit tro ha gii hn ca mi nguyn t

l khc nhau. N phthuc vo bn cht ca mi nguyn tv phthuc vodng hp cht m nguyn t tn ti cng nhnn mu.

Nguyn tha: Thc hin nguyn tha mu trong thi gian rt ngn

thng thng 3 n 6 giy, nhng tc tng nhit li rt ln c

18000C/giy n 25000C/giy. Mi nguyn tu c nhit nguyn tha

gii hn cho php n trong php o GF-AAS. Nhit ny phthuc vo bn

cht ca mi nguyn tv cng phu thuc vo dng hp cht m nguyn t

tn ti v thnh phn nn ca mu. Nn tin hnh nguyn tha nhit

khng c ln hn nhit ti hn v chn thi gian nguyn tha sao cho

peak cng vch phnhn.

Lm sch cuvet: Thc hin nhit trn 27000C bc hi tt ccc

cht cn li trong l, chun bcho ln phn tch mu tip theo.

Kh Argon tinh khit 99,999% c dng lm mi trng cho qu trnh

nguyn tha.

Cc nguyn tHg, Cd, Pb, As, Se u c nhit ha hi thp. V vy

nu tro ha cng nhnguyn tha nhit cao th xy ra smt mt ng

k cc nguyn t phn tch. khc phc, ngi ta s dng cht modifier

trong phn tch cc nguyn tbng phng php GF-AAS.WWW FA

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Cc cht modifier to vi nguyn tcht phn tch hp cht bn nhit

nn cho php tro ha v nguyn tha nhit cao hn lm tng nhy

ca phng php.Pd l cht c tc dng modifier rt mnh cho vic xc nh hu ht cc

nguyn tphn tch. Pd loi trc nhiu ha hc ni chung cng nhcho

php tin hnh nguyn tha nhit cao m khng bhao ht cht phn

tch. Trong qu trnh nguyn tha, hp kim Pd - kim loi bay hi mt cch

t ngt v hon ton gip n nh tn hiu hp thu ca kim loi. Ngoi ra

mi nguyn tcn c thsdng cc cht modifier khc nhau ty theo yu

cu ca hng sn xut hoc khi c snhiu r.i vi GF-AAS, phn ln cc trng hp i hi phi hiu chnh nn,

ngoi trtrng hp >450 nm. Mt trong cc kthut hiu chnh cn thit

do matrix l hiu chnh nn da vo hiu ng Zeeman.

Mu phn tch ca phng php ny c thkhng cn lm giu mc

sbv lng mu tiu tn t.

2/ Kthut hydrua ha (HG-AAS)

Nm 1955 ng Walsh gii thiu phng php hp thnguyn tsau

phng php ny c sdng rt phbin cc phng th nghim

trn ton thgii. Tuy nhin ban u vic xc nh nguyn tbng hp th

nguyn tcn gp nhiu kh khn trong vic m ha dung dch mu nht l

i vi cc nguyn tAs,Se, Sb, Temt khc bc sng hp thca cc

nguyn tny li nm xa vng tngoi (nhhn 230nm) ti shp th

nn l ln khi sdng ngn la thng thng. V dkhi sdng ngn la l

hn hp kh axetylen/khng kh bc sng hp thca As l 193,7nm ti

cng hp thcht 62%. Spht trin ca kthut nguyn tha hp

thnguyn tbng graphite th trnh c cc kh khn ca hp thnguyn

tbng ngn la. Tuy vy vic sdng cc thit bny gp mt svn WWW FA

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khc nh: Ti bc sng ngn skhuch tn cc ht gy ra snhiu nn ln,

bn cnh i vi nguyn tdbay hi nhAs, Se c thbmt trong qu

trnh nguyn tha nn php o km n nh.Nm 1969 Holak sdng k thut to hydrua kt hp vi hp th

nguyn t. ng dng hn hp kim loi v axit (km v axit clohidric) thc

hin phn ng, km v axit HCl c ng trong ng nghim c nit lng,

trc tin ng nghim c lm nng ln ri dn dung dch c cha As i

qua, khi As sinh ra c dn vo ngn la khng kh-axetylen trong mi

trng nito. Bng phng php ny khc phc c ng knhc im ca

sm ha, nng cao c nhy. Cht khdng cho phn ng to hydrual hydro mi sinh. Cng c thsdng thic II clorua hoc KI l cht kh, v

sau ngi ta sdng Natri tetrahdruaborat (NaBH4) c nhiu thun tin hn.

Kh hidrua c y ra khi dung dch chuyn n bung nguyn t

ha nhdng kh mang l kh tr (Argon, Nithoc Heli). C hai k thut

tch hidrua chuyn vo bung nguyn tha l: Hgin on v Hlin tc.

Bng kthut hydrua ha nhy ca phng php tng ln nhiu ln

so vi kthut m ha dung dch thng thng. Dng nng lng l ngn la

v khng kh th nhy php xc nh l 1g/ml theo vch 196,1 nm, nu

dng ngn la l axetylen-khng kh th nhy l 0,25 g/ml vi Selen.

Phng php hp thnguyn tsdng kthut hydrua ha phn

tch Se tng nhy ln mt cch vt bc cvi g/l.

1.4.4. Cc yu tnh hng v phng php loi trca php o AAS[4]

1.4.4.1. Cc yu tvphnh hng n php o AAS

1/ Shp thnn

Vch phc chn o nm trong vng khkin th yu tny th

hin r rng. Cn trong vng tngoi th nh hng ny t xut hin. loi

trphnn ngy nay ngi ta lp thm vo my quang phhp thnguyn tWWW FA

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hthng bchnh. Trong hthng ny ngi ta dng nW (W: habit lamp)

cho vng khkin.

2/ Schen ln vch phYu tny thng thy khi cc nguyn tthba trong mu phn tch c

nng ln v l nguyn tcsca mu. loi trschen ln vch ph

ca cc nguyn tkhc cn phi nghin cu v chn nhng vch phn tch ph

hp. Nu bng cch ny m khng loi trc nh hng ny th bt buc phi

tch bbt nguyn t c vch ph chen ln ra khi mu phn tch trong mt

chng mc nht nh, cc vch chen ln khng xut hin na.

3/ Shp thca cc ht rnCc ht ny hoc hp th hoc chn ng i ca chm sng tn

HCL chiu vo mi trng hp th. Yu tny c gi l shp thgi.

iu ny gy sai scho kt quo cng vch ph. loi trshp th

ny cn chn ng chiu cao ca n nguyn tha mu v chn thnh phn

hn hp khng kh chy ph hp.

1.4.4.2. Nhm cc yu tvt l nh hng n php o AAS [4]

1/nht v sc cng bmt ca dung dch mu

loi trnh hng ny chng ta c thdng cc bin php sau:

o v xc nh theo phng php thm chun; pha long mu bng mt

dung mi hay mt nn ph hp; thm vo mu chun mt cht chun c

nng ln; dng bm y mu vi mt tc xc nh m chng

ta mong mun.

2/ Hiu ng lu li

Khi nguyn tha mu o cng vch ph th mt lng nh

ca nguyn tphn tch khng bchuyn ha chng c lu li trn bmt

cuvet v cthtch tli qua mt sln nguyn tha mu. Nhng n mt

ln no th chng li bnguyn tha theo v o to ra snguyn ttWWW FA

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do ca nguyn tphn tch tng t ngt khng theo nng ca n trong

mu. Ngha l lm tng cng ca vch phv lm sai kt quphn tch.

Cch khc phc l lm sch cuvet sau mi ln nguyn tha mu, lm bay

hi ht cc cht cn li trong cuvet.

3/ Sion ha

loi trsion ha ca mt nguyn tphn tch c thsdng cc bin

php sau: Chn cc iu kin nguyn tha c nhit thp, m trong iu kin

nguyn tphn tch hu nhkhng bion ha; Thm vo mu phn tch mt

cht m cho sion ha l cc mui halogen ca cc kim loi kim c thion

ha thp hn thion ha ca nguyn tphn tch vi mt nng ln ph hp.Nhvy trong iu kin nguyn tphn tch skhng bion ha na.

4/ Skch thch phpht x

Yu tny xut hin thng lm gim nng ca cc nguyn ttrung

ha c khnng hp thbc xtrong mi trng hp th. V vy: Chn nhit

nguyn tha mu thp ph hp m ti nhit skch thch phpht

xl khng ng khoc khng xy ra i vi nguyn tphn tch; thm vo

mu cc cht m hn chspht xca nguyn tphn tch, chnh lcc mui halogen ca cc kim loi kim, c thkch thch phpht x thp

hn thkch thch phpht xca nguyn tphn tch.

1.4.4.3. Nhm cc yu tha hc nh hng n php o AAS

Trong php o phhp thnguyn tcc nh hng ha hc cng rt

a dng v phc tp.

Cc nh hng ha hc c thsp xp theo cc loi sau y:

1/ Nng axit v loi axit trong dung dch mu

Cc axit cng kh bay hi thng lm gim n cng vch ph.

Cc axit dbay hi gy nh hng nh. Ni chung cc axit lm gim cng

vch ph theo th t : HClO4 < HCl < HNO3< H2SO4 < H3PO4< HF.

Ngha l axit HClO4, HCl, HNO3gy nh hng nhnht trong vng nng WWW FA

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nh. Chnh v thtrong thc tphn tch ca php o phhp thnguyn t

ngi ta thng dng mi trng l axit HCl hay HNO31 hay 2% . V ny

nh hng ca 2 axit ny l khng ng k.

2/nh hng ca cc cation

Cc cation c thlm tng, c thlm gim cng c thkhng gy nh

hng g n cng vch ph ca nguyn t phn tch. loi trnh

hng ca cc cation chng ta c th s dng cc bin php sau y hoc

ring bit hoc thp chng li vi nhau. l chn iu kin xl mu ph

hp loi trcc yu tnh hng ra khi dung dch mu phn tch o

ph, chn cc thng s ca my o thch hp v thm vo mu phn tchnhng cht phgia ph hp loi trnh hng

3/nh hng ca cc anion

Ni chung cc anion ca cc axit d bay hi thng lm gim t n

cng vch ph. Cn gicho nng cc anion trong mu phn tch v

mu chun l nhnhau v mt gi trnht nh khng i. Mt khc khng

nn chn axit H2SO4lm mi trng ca mu cho php o AAS m chnn

chn HCl hay HNO3nng di 2%.4/ Thnh phn nn ca mu

Yu tnh hng ny ngi ta quen gi l matrix effect. Nhng khng

phi lc no cng xut hin m thng chthy trong mt strng hp nht

nh. Thng thng l cc mu cha cc nguyn tnn dng cc hp

cht bn nhit, kh bay hi v kh nguyn tha.

5/nh hng ca dung mi hu c

Sc mt ca dung mi hu cthng lm tng cng vch phhp thnguyn tca nhiu nguyn tln nhiu ln. y l mt bin php

tng nhy ca ca phng php phn tch ny.

1.4.4.4. Cc yu tvthng smy o

Chn cc thng sca my o bao gm:WWW FA

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- Chn bc sng nh sng ti thch hp vi nguyn tcn xc nh.

Ngun nh sng n sc phi c cng n nh, lp li c trong cc ln

o khc nhau trong cng iu kin v phi iu chnh c c cng

cn thit trong mi php o.

- Cng dng in lm vic ca n ca tt rng (HCL): Nn chn

cng dng nm trong vng 60% n 80% so vi cng dng cc i

ghi trn n HCL. Khi cn nhy cao th chn cn di cn khi cn n

nh cao th chn cn trn.

- Khe o: Khe o c nh hng n nhy v vng tuyn tnh ca

php o, do cn phi chn khe o c gi trph hp nht cho php o nhlng cn xc nh theo bc sng chn.

- Thi gian o: Yu tny phthuc vo c trng kthut ca my

o v ca kthut nguyn tha mu.

-Xc nh vng tuyn tnh ca A theo C ti cc bc sng o chn.

C xc nh c vng ny th mi c thxc nh cc mu u ph hp vi

khong tuyn tnh, bi v cc kt quthu c khi o vng tuyn tnh bao

gicng c chnh xc cao.-Lng mu: l tc dn mu, lng mu bm vo.

-Bchnh nn khi o: Nu nn ca phc nh hng n php o th

phi c bchnh nn loi trcc nh hng , nu khng nh hng th

khng cn thit.

-Hnhn quang in nhn tn hiu AAS: Phi iu chnh nm GAIN

kim ch thang nng lng nm trong vng 70-100 l vng lm vic ph

hp ca thnui nhn quang in cho my o phhp th.1.4.5 .Cu to my quang phhp thnguyn t

1.4.5.1. Ngun bc x

Mun thc hin c php o phhp thnguyn tngi ta cn phi

c mt ngun pht tia bc xn sc (tia pht xcng hng) ca nguyn tWWW FA

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cn phn tch chiu qua mi trng hp th. Hin nay trong php o ph

hp thnguyn t, ngi ta chtu dng ba ngun pht tia bc xn sc.

l:

+ n catot rng (HCl- Hollow Cathode Lamp)

+ n phng in khng in cc (EDL- Electrodeless Discharge Lamp)

+ n pht phlin tc c bin diu (D2-Lamp, W- Lamp)

+ Cc loi ngun n sc khc

1/n catot rng (HCL)

n pht tia bc xn sc c dng sm nht v phbin nht trong

php o S l n cactot rng ( HCL). n ny chpht ra nhng tia pht xnhy cunguyn tkim loi lm catot rng. Cc vch pht xnhy ca mt

nguyn t, thng l cc vch cng hng. V thn catot rng cng c th

c gi l ngun pht tia bc xcng hng.

Khi n lm vic, catot c nung , gia catot v anot xy ra s

phng in lin tc . Do sphng in m mt sphn tkh bion ha.

Cc ion va c sinh ra stn cng vo catot lm bmt catot nng v

mt skim loi trn bmt kim loi bha hi v n trthnh nhng nguyn

tkim loi tdo.

Khi di tc dng ca nhit trong n HCL ang c t nng

, cc nguyn tkim loi ny bkch thch v pht ra phpht xca n.

chnh l phvch ca chnh kim loi lm catot rng.

2/n phng in khng in cc (EDL)

Loi n ny cng nhn HCL u c nhim vcung cp chm tia

pht xc trng ca nguyn tphn tch, c bit l cc kim, th n ADL

cho nhy cao hn, n nh hn n HCL.

Vcu to, n EDL thc cht cng c mt ng phng in trong mi

trng kh km c cha nguyn tcn phn tch vi mt nng nht nhWWW FA

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ph hp to ra c chm tia pht xchbao gm mt svch phnhy

c trng ca nguyn tphn tch. n EDL cng gm cc bphn:

Thn n: Mt ng thch anh chu nhit, di 18-15cm, ng knh

56cm. Mt u ca EDL cng c ca sS, ca scho chm tia sng i qua

cng phi trong sut vi chm sng .

Ngoi ng thch anh l cun cm bng ng. Cun cm c cng sut t

400-800 W ty loi n ca tng nguyn t, v c ni vi ngun nng

lng cao tn HF ph hp nui cho n EDL lm vic. Ngoi cng l v

t chu nhit.

Cht trong n: l vi miligam kim loi hay mui kim loi dbay hica nguyn tphn tch , lm sao khi ton bcht ha hi bo m cho p

sut hi ca kim loi trong n iu kin nhit t 550-800 0C l

khong t1- 1,5mmHg.

Cht ny thay cho catot trong n HCL, n l ngun cung cp chm tia

pht xca nguyn tphn tch, khi chng bkch thch, trong qu trnh n

EDL hot ng.

Kh trong n: Trong n EDL cng phi ht ht khng kh v np thayvo l mt kh trAl, He hay Nitc p sut thp, vi mmHg khi u

cho slm vic ca n EDL.

Ngun nui n lm vic: Ngun nng lng cao tn nui n EDL

lm vic c ch to theo hai tn s. tn ssng ngn 450 MHz v tn s

sng radio 27,12 MHz, c cng sut di 1kW.

Ngoi u im vnhy v gii hn pht hin, n EDL ca cc

kim hay bn kim thng c bn cao hn n HCL. ng thi vng tuyntnh ca php o mt nguyn tkhi dng n EDL thng rng hn so vi

vic dng n HCL.

Ngoi n catot rng v n phng in khng in cc, ngi ta cng

chto ra c nhiu loi n pht tia bc xn sc ca cc nguyn t,WWW FA

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nhn catot rng nhit cao (trnh entisity cmiss ion lamp - HIEL), n

gradient nhit (controlled temperature- gradient lamp - CTGL), n phng

in c chiu sng cao (glow -discharge lamp -GDL). Cc loi n ny c

u im hn loi n HCL mt cht vnhy, vvng tuyn tnh, vgii

hn pht hin. nhng cc n loi ny li kh chto v t tin, mt khc li

km bn vng. V thn t c dng v khng c bn ngoi thtrng,

chyu chc dng trong nghin cu l thuyt vph.

3/n pht phlin tc c bin iu

Trong khong vi nm v y, mt loi ngun pht x ph lin tc

cng c dng lm ngun pht bc xcng hng cho php o AAS. ln hydrogen nng (D2- lamp), cc n xenon p sut cao (Xe-lamp), cc n

hot ca kim loi W. l cc loi n pht phlin tc trong vng tngoi

v vng kh kin (UV-VIS). Cc tc gi Fassel, Ivanop, Gibson, Mc G,

Winerfordner l nhng ngi u tin nghin cu v sdng cc loi n

ny lm ngun pht bc xcng hng cho php o AAS.

Ngun pht phlin tc c u im l dchto, rtin v c bn

tng i cao, v chcn mt n c ththc hin mt php o AAS ivi nhiu nguyn ttrong mt vng phUV hay VIS. Do n rt u vit

i vi cc my phhp thnhiu knh v xc nh ng thi hay lin tip

nhiu nguyn ttrong cng mt mu phn tch, m khng phi thay n HCL

cho vic o phmi nguyn t.

4/ Cc loi ngun n sc khc

Ngoi ba loi ngun pht bc xn sc chyu c trnh by

trn, trong php o phhp thnguyn t, ngi ta cng sdng mt vi loi

ngun pht tia bc xn sc khc na nhn cactot rng c di cao,

ng pht xc bit, tia laze. Nhng nhng loi ny chyu dng trong ngin

cu l thuyt vt l.WWW FA

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1.4.5.2. Hthng nguyn tha mu

* Hthng nguyn tha mu bng ngn la gm hai phn chnh:

+ Bung aerosol ha (Neulizer system), to thsi kh mu.

+ n nguyn tha mu(burner head).

Kh to ra ngn la nguyn tha mu thng hay c dng l hn hp

ca hai cht kh (mt cht oxi ha v mt cht chy), v dnhhn hp khng kh

nn vi axetilen hay kh NO2vi kh axetilen hay khng kh v propan.

* Hthng nguyn tha khng ngn la gm ba phn chnh l:

+ Cuvet graphit hay thuyn ta cha mu, nguyn tha.

+ Ngun nng lng nung cuvet hay thuyn ta.+ B iu khin thc hin vic nguyn t ha mu theo cc giai

on ca mt chng trnh ph hp.

1.4.5.3. Hthng n sc my quang phhp thnguyn t

Hthng n sc chnh l hthng thu, phn li, chn v pht hin

vch phhp thcn phi o. Trong php o phhp thnguyn ththng

n sc ny l mt my quang phc phn gii tng i cao c th l

my mt chm tia hay hai chm tia. Cu to ca n gm 3 phn chnh:+ Htrc chun: Dng trc chun chm tia sng vo.

+ Hthng tn sc(phn li): Dng phn li chm sng a sc thnh

n sc.

+ Hbung ti (bung nh) hi t: Dng hi tcc tia cng bc

sng li.

1.4.6 .Cc phng php nh lng ca phhp thnguyn t[3]

Phng php quang phhp th nguyn t l phng php xc nhnng hay hm lng ca mt hay nhiu nguyn t trong cng mt mu

phn tch bng cch o hp thbc xbi nguyn ttdo ca nguyn t

c ha hi tmu phn tch. Vic nh lng c tin hnh bc

sng ca mt trong nhng vch hp thca nguyn tcn xc nh.WWW FA

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xc nh nng (hm lng) ca mt nguyn t trong mu phn

tch ngi ta thng thc hin theo cc phng php sau y:

Phng php ng chunPhng php thm tiu chun

Phng php thkhng i

Phng php dng mt mu chun

1.4.6.1. Phng php thchun (ng chun)

Nguyn tc ca phng php ny l da vo phng trnh cbn ca

php o A= K.C v mt dy mu u (t nht l ba mu u) dng mt

ng chun v sau nhng chun ny v gi trAxxc nh nngCxca nguyn tcn phn tch trong mu o ph, ri t tnh c nng

ca n trong mu phn tch.

Cch tin hnh: Chun bmt dy mu u (thng thng l 5 mu) c

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