XÁC ĐỊNH HÀM LƯỢNG CÁC NGUYÊN TỐ ĐỘC HẠI Pb, Hg, Cd, As TRONG MỘT SỐ LOÀI RAU Ở VÙNG TRỒNG RAU ĐÀ LẠT

8/12/2019 XC NH HM LNG CC NGUYN T C HI Pb, Hg, Cd, As TRONG MT S LOI RAU VNG TRNG RAU LT

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BGIO DC V O TOTRNG I HC VINH

NGUYN KIM NGN

XC NH HM LNG CC NGUYN TC

HI Pb, Hg, Cd, As TRONG MT SLOI RAU

VNG TRNG RAU LT

Chuyn ngnh: ha v cM s: 60.44.01.13

LUN VN THC SHA HC

Ngi hng dn khoa hc: TS. Nguyn Quc Thng

Vinh, 2012

www.daykemquynhon.ucoz.com

www.facebook.com/daykem.quynhon


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LI CM NTi xin chn thnh by t lng cm n su sc ca mnh ti TS.

Nguyn Quc Thng Ngi tn tnh hng dn, ng vin v gip ti trong sut qu trnh hc tp nghin cu v thc hin lun vn.

Ti xin trn trng cm n cc thy c khoa Ha ng gp nhng kin qu bu ca mnh, cc thy, cc c k thut vin ph trch phng thnghim to mi iu kin tt nht cho vic nghin cu v hon thnh lunvn.

Qua y ti cng xin cm n Ban Gim hiu, Ban lnh o Khoa Ha,Khoa Sau i hc Trngi hc Vinh to mi iu kin thun li choti hon thnh lun vn ny.

Ti xin cm n gia nh, bn b cng vi cc ng nghip v tt cnhng ngi nhit tnh gip , ng vin v to mi iu kin thun linht ti hon thnh tt lun vn.

Tuy nhin, trong lun vn skhng trnh c nhng khuyt im vthiu st nn ti rt mong qu thy c v cc bn gp hon thin hnlun vn v tch ly kinh nghim cho cng tc nghin cu sau ny.

Xin chn thnh cm n!

Vinh, Thng 09 nm 2012

Nguyn Kim Ngn




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MC LCLi cm n ........................................................................................................ 2Mc lc .............................................................................................................. 3Danh mc bng ................................................................................................. 3Danh mc hnh .................................................................................................. 5

Mu .............................................................................................................. 6Chng 1: TNG QUAN .............................................................................. 9

1.1. Gii thiu chung vrau xanh .................................................................. 91.2. Gii thiu v Lt v rau Lt ...................................................... 111.3. Gii thiu vkim loi nng .................................................................. 151.4. Vai tr, chc nng sinh ha v snhim c Pb, Hg, Cd, As ............ 231.5 Cc phng php nghin cu ............................................................... 321.6. Phng php xl mu phn tch xc nh Pb, Hg, Cd, As ............... 40

CHNG 2 THC NGHIM ....................................................................... 44

2.1. Dng cv ha cht ............................................................................. 442.2 . Ly mu v xl mu .......................................................................... 472.3. Pha cc dung dch cn cho nghin cu ................................................. 502.4. Qui trnh thc nghim ........................................................................... 512.5. Xl cc sliu tkt quo c ..................................................... 55

CHNG 3: KT QUV THO LUN .................................................. 563.1. Kt quxc nh hm lng Pb, Cd trong mu rau v trong nc tibng phng php cc ph.......................................................................... 563.2. Kt quxc nh ng thi hm lng Pb, Cd, Hg, As trong mu rau

v trong nc ti bng phng php phhp thnguyn tAAS .......... 593.3. Kt quxc nh ng thi hm lng Pb, Cd, Hg, As trong mu rauv trong nc ti bng phng php quang phplasma ghp ni khi phICP-MS ........................................................................................................ 603.4. So snh kt quphn tch vi gii hn an ton ca kim loi nng ...... 613.5. Mi lin hgia kim loi nng trong nc ti v trong rau .............. 63

TI LIU THAM KHO ............................................................................... 66PHLC ........................................................................................................ 69




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DANH MC BNG

Bng 1.1 Ti lng mt scht gy nhim ra bin ca mt shthngsng ................................................................................................................. 21

Bng 1.2 Ti lng cht gy nhim ra bin Hi Phng Qung Ninh . 22Bng 1.3 So snh khnng pht hin ca cc kthut phn tch (ppb) ......... 38Bng 2.1 Vtr ly mu v k hiu mu .......................................................... 47Bng 2.2 Tlkhi lng ca mt sloi rau trc v sau khi sy kh. ...... 49Bng 2.3 Qui trnh xl mu trn my vi sng Anton Paar Multiwave 300053Bng 2.4 iu kin o mu trn my phhp thu nguyn tngn laShimadzu AAS 6300 cho hai nguyn tCd, Pb ............................................. 53Bng 2.5 iu kin o trn my bng phng php HVG-AAS cho nguyn tAs .................................................................................................................... 53

Bng 2.6 iu kin o trn my bng phng php MVU-AAScho nguyn tHg .................................................................................................................... 54Bng 2.7 Thng so trn ICP-MS 7500 Series Agilent ............................... 54Bng 3.1 Kt quxc nh hm lng ch bng phng php cc ph......... 56Bng 3.2 Kt quxc nh hm lng cadimi bng phng php cc ph... 56Bng 3.3 Kt quxc nh hm lng ch bng phng php AAS .............. 59Bng 3.4 Kt quxc nh hm lng cadimi bng phng php AAS ........ 59Bng 3.5 Kt quxc nh hm lng thy ngn bng phng php AAS ... 60Bng 3.6 Kt quxc nh hm lng asen bng phng php AAS ........... 60Bng 3.7 Kt quxc nh hm lng ch bng phng php ICP MS ...... 60Bng 3.8 Kt quxc nh hm lng cadimi bng phng php ICP MS 61

Bng 3.9 Kt quxc nh hm lng thy ngn bng phng php ICP MS ................................................................................................................... 61Bng 3.10 Kt quxc nh hm lng asen bng phng php ICP MS . 61Bng 3.11 So snh kt quphn tch vi gii hn an ton ca kim loi nng:

Pb, Cd, Hg, As trong thc phm ..................................................................... 62Bng 3.12 So snh kt quphn tch vi gii hn an ton ca kim loi nng:

Pb, Cd, Hg, As trong nc ti rau ................................................................ 62




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DANH MC HNH

Hnh 1.1 Bn phn bdin tch canh tc rau cc loi ti cc phng xthnh ph Lt ............................................................................................ 14

Hnh 1.2. Kim loi ch ..................................................................................... 23Hnh 1.3. Kim loi cadimi ............................................................................... 23

Hnh 2.1: My o cc ph797 Computrace................................................... 44Hnh 2.2: Hthng my quang phhp thnguyn tAA 6300................ 46Hnh 2.3: Hthng Agilent 7500 Series ICP-MS........................................... 46Hnh 2.4 Rung sp l .................................................................................... 48Hnh 2.5 Rung bp ci .................................................................................. 48Hnh 2.6 Rung hnh ty ................................................................................ 48Hnh 3.1ng cong cc phmu nc Lt........................................... 56Hnh 3.2ng cong cc phmu trng nc Lt................................. 57Hnh 3.3: ng cong cc phmu sp lxanh.......................................... 57Hnh 3.4ng cong cc phmu bp ci................................................... 58Hnh 3.5ng cong cc phmu hnh ty................................................. 58Hnh 3.6 ng cong cc ph mu trng rau.............................................. 59




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MU1. L do chn ti:

Ngy nay vic bo vmi trng v an ton thc phm l vn quantrng i vi mi quc gia. Trong i sng, rau xanh lun l ngun thc

phm cn thit v quan trng. Hin nay do nhiu nguyn nhn khc nhau m

chyu l vic sdng phn bn ho hc, thuc bo vthc vt, thuc tr

su, dit c, cht thi ca cc nh my, khu cng nghip dn n s

nhim ngun t, ngun nc v bu kh quyn. Do rau xanh c th b

nhim m

t s

kim loi nng nh

Se, Pb, Hg, As, Cd, Sn, Mn, Cu, Zn... v cc

vi sinh vt gy bnh. Nu con ngi sdng phi sbngc c thgy ra

nhng cn bnh him ngho nhung thsdn n tvong.

Hin nay, Lt l ni cung cp rau xanh ln v c uy tn trn c

nc. Vn ang c t ra l lm thno c c rau xanh an ton

(rau sch)?

Nhvy vic iu tra, nh gi cht lng rau sch trnn v cng cp

thit. Mt trong cc chtiu dng nh gi an ton thc phm ni chung

v rau sch ni ring l hm lng cc kim loi nng. Do , vic phn tch

tm ra hm lng cc kim loi nng trong rau xanh vng trng rau

Lt sgp phn kim sot c cht lng rau sch theo tiu chun rau sch

ang c p dng Vit Nam.

V vy, chng ti chn ti: Xc nh hm lng cc nguyn t

c hi Pb, Hg, Cd, As trong mt s loi rau vng trng rau

Lt lm ni dung nghin cu cho ti lun vn cao hc thc sca

mnh.

2. Mc ch nghin cu:

Xc nh c hm lngcc nguyn tc hi Pb, Hg, Cd, As trong

mt sloi rau xanh, trong nc ti rau v nh gi hin trng nhim bi




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cc kim loi ny trong rau xanh, trong nc ti rau mt svng trng rau

Lt.

3. Nhim vnghin cu:

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

sau:

3.1. Xc nh cc nguyn tkim loi nng nhPb, Hg, Cd, As trong

nuc ti, trong rau xanh vng trng rau Lt cung cp cho thnh

phHCh Minh

3.2. So snh kt quphn tch c vi gii hn an ton ca kim loi

nng trong thc phm.

3.3. nh gi mi quan hgia thnh phn kim loi nng trong nc

ti v trong rau xanh.

3.4. Rt ra kt lun v c nhng khuyn co cn thit.

ti ny c t ra l cn thit v Lt l ngun cung cp rau

ln cho Thnh phHCh Minh v cnc hu nhquanh nm. Xc

nh mt schtiu vcht lng rau rt quan trng, lm cho ngi tiu

dng yn tm, m rng vng sn xut, nu c du hiu nhim th c

khuyn co n ngi sn xut, ngi tiu dng v cc c quan chc

nng c bin php gim thiu.

4. i tng phm vi nghin cu:

Ly mu rau vng trng rau Lt.

Xc nh ng thi hm lng Pb, Hg, Cd, As trong mt smu rau v

trong nc ti bng cc phng php khc nhau.

So snh kt quphn tch vi gii hn an ton ca kim loi nng: Pb,

Hg, Cd, As trong thc phm.

Xt nh hng gia hm lng kim loi trong nc ti rauv trong

rau.

5. Phng php nghin cu:




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C nhiu phng php xc nh hm lng cc kim loi, ty thuc

vo hm lng cht phn tch m c thsdng cc phng php khc nhau:

phng php phn tch thtch, phng php phn tch trng lng, phng

php in ha, phng php phn tch cng c (phng php kch hot

ntron, phng php phpht xnguyn tAES, phng php phhp th

nguyn tAAS)

Trong lun vn ny, chng ti chyu sdng cc phng php sau:

1. Phng php cc ph

2. Phng php AAS

3. Phng php ICP-MS

6. Githuyt khoa hc:

Cc kim loi nng c chn kho st l Pb, Hg, Cd, As. Chng c

nh gi l cc nguyn tc dng vt (Gover, 1996) v c thgy ngc

tc thi hoc nh hng lu di n sinh vt v con ngi.

NI DUNG




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Chng 1: TNG QUAN

1.1. Gii thiu chung vrau xanh:[10, 13, 28]

Cc loi rau nc ta rt phong ph. Nhn chung ta c th chia rau

thnh nhiu nhm: nhm rau n l nh rau ci, rau mung, rau x lch, rau

cn... nhm rcnhc rt, cci, csu ho, cu...nhm cho qunhc

chua, da chut... nhm hnh gm cc loi hnh, ti. Trong n ung hng

ngy rau c vai tr c bit quan trng. Rau xanh nm trong nhm thc phm,

cung cp vitamin v mui khong. Rau cn quan trng ch n cung cp

cht x. Cht xkhng dtiu ho hp thc, khng cung cp nng lng,

n to ra cht thi ln trong rut, lm tng nhu ng rut, chng to bn. y

l iu rt quan trng trong vic trnh hp thc hi cho cth. Nu phn

lu trong rut do thiu cht xcng tng tlung thtiu ho, i trng, gy

xva ng mch. Ngoi ra, cht xcn thc y shp thca cthi

vi ba nhm thc n m, bo, ng. Rau cn l ngun cht st quan trng.

St trong rau c cthhp thtt hn. Cc loi rau, u, x lch l ngun

cung cp mangan tt. Tm li, rau xanh c vai tr quan trng trong dinhdng, trong ba n hng ngy ca chng ta khng ththiu c. Ngy nay

c sc khe tt trn bn n ca mi gia nh lun hng gim lng tht c

v tng cng lng rau xanh. iu quan trng l phi m bo rau sch,

khng c vi khun gy bnh v cc ho cht c nguy him.

1. 1. 1. Rau sch:

Rau sch l rau khng b nhim bi cc tc nhn sinh hc, ho hc,

vt l vt qua gii hn cho php v khng gy nguy hi ti sc kho cho

ngi tiu dng.

nhim sinh hc: nhim vi khun, vi rt, k sinh trng.

nhim ho hc: nhim kim loi nng, ho cht bo vthc vt, ph

gia bo qun.




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1.1.2. Mt stiu ch rau an ton

1.1.2.1.nh ngha

Trong qu trnh gieo trng , c sn phm rau an ton nht thit phi

p dng cc bin php k thut v s dng mt s nguyn liu nh nc,phn bn, thuc phng tr su bnh. Trong cc nguyn liu ny, k ct

trng u c cha cc nguyn tgy nhim rau v t nhiu u li mt s

dlng trn rau sau khi thu hoch.Trong thc thin nay hu nhkhng th

c sn phm ca rau sch vi ngha hon ton khng c yu tc hi. Tuy

vy nhng yu tny thc schgy c khi chng li mt dlng nht

nh no trn rau, di mc dlng ny th khng c hi, mc dlngti a khng gy hi cho ngi c thchp nhn c gi l mc dlng

cho php (hoc ngng dlng gii hn). Nhvy nhng sn phm rau ti

(bao gm cc loi rau n l, c, thn, hoa, qu) c cht lng ng nhc

tnh ca chng, mc nhim cc cht c hi v cc vi sinh vt gy hi

khng vt qu ch tiu cho php, m bo an ton cho ngi tiu dng v

nui trng c coi l rau m bo an ton vsinh thc phm, gi tt l rauan ton (theo BNng nghip v Pht trin Nng thn).

1.1.2. 2. Cc yu tgy nhim cho rau

C nhiu yu tlm rau b nhim, song quan trng nht l cc yu tsau:

Dlng thuc bo vthc vt

Dlng nitrat (NO3-)

Sinh vt gy bnh. Dlng kim loi nng

S nhim rau do dlng kim loi nng:

Cc kim loi nng nh asen (As), ch (Pb), thy ngn (Hg), cadimi

(Cd), km (Zn), thic (Sn), .... nu vt qua mc cho php l nhng cht c

hi cho c th, hn ch spht trin ca tbo v hot ng ca mu, gy

thiu mu, bin ng thn nhit, ri lon tiu ha ...




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Nguyn nhn

- Trong thuc bo vthc vt (BVTV) v phn bn NPK c cha mt

skim loi nng trong qu trnh ti tiu , cc kim loi nng ny bra

tri xung ao h,sng rch, thm nhp vo mch nc ngm gy

nhim ngun nc ti rau.

- Ngun nc thi ca thnh phv cc khu cng nghip cha nhiu

kim loi nng chuyn trc tip vo rau ti.

Bin php khc phc:

- Khng trng rau trong khu vc c cht thi ca nh my , cc khu vc

t b nhim do qu trnh sn xut trc gy ra.

- Khng ti rau bng ngun nc c nc thi ca cc nh my cng

nghip. Nhng yu t trn l nguyn nhn ch yu lm cho rau b

nhim , nh hng n sc khe con ngi , trong phbin nht l

thuc BVTV v vi sinh vt gy bnh . V vy yu cu cn thit l phi

gieo trng thno c c nhng sn phm rau khng b nhim ,

tc rau an ton i vi tt cmi ngi .

1.2. Gii thiu v Lt v rau Lt [13, 23]

1.2.1. Thng tin chung vthnh ph Lt

1.2.1.1. Din tch, dn s, lao ng

Thnh ph Lt thuc tnh Lm ng. Nm trn cao nguyn Lang

Biang nn Lt c cao 1.520m so vi mt nc bin. Vpha Bc,

Lt gip vi huyn Lc Dng, vpha ng v ng Nam gip vi huyn

n Dng, v pha Ty v Ty Nam gip vi hai huyn Lm H v c

Trng.

Do cao trung bnh 1.520 m v c bao quanh bi nhng dy ni

cao, nn tuy trong vng nhit i gi ma, kh hu Lt mang nhng nt

ring ca vng cao. Lt c c mt kh hu mt m, dchu ca vng n




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i vi nhit trung bnh trong ngy thp nht l 15oC v cao nht l 24oC.

Mc d c hai ma: ma ma tthng 4 n thng 11 v ma nng tthng

12 n thng 3 nm sau nhng quanh nm Lt u c nng. Cc iu kin

kh hu ny cho php Lt sn xut cc loi rau c, hoa v cc tri cy

c sn

Theo Nin gim thng k tnh Lm ng, tng din tch t tnhin

ca Tp Lt l 39.106 ha. Do rng, i hoang chim vi din tch ln nn

t dnh cho nng nghip Lt khng nhiu, chkhong 10.000 ha,chia

ra t chuyn nng nghip 5.300 ha, t xen canh 4.678 ha. t sn xut nng

nghip chia lm 2 nhm chnh: nhm feralit vng chim tlcao, nhngph tthp n trung bnh, tuy nhin lng ln dtiu v mt snguyn t

vi lng thch hp cho cy rau, hoa v cy n qu. Nhm cn li l feralit nu

trn bazan c ph cao hn, thch hp cho vic canh tc loi rau c c.

iu kin giao thng tng i thun li mrng giao lu kinh tvi cc

vng trng im kinh tpha Nam, cc tnh Duyn hi min Trung v Ty

Nguyn.

Tnm 1990 n nay, dn sthnh ph Lt tng kh nhanh. Nm

2004 Lt c 188. 467 ngi vi 96% l ngi Kinh. Trong , dn s

sng khu vc thnh thl 88.94%, sng cc khu vc nng thn l 11,06%,

mt dn sl 480 ngi/km2. Mt bng dn tr trong nhng nm gn y

c nng ln ng knhng vn cn c khong cch nht nh gia cdn

sng khu vc thnh thv nng thn.

Lao ng x hi tng nhanh, nht l lao ng nng nghip ph thng

(chim 38,5%). Lao ng c tay nghcha c o to theo quy chun v

cng cha c iu kin hot ng do Lt cha c nhng khu cng

nghip ln.




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1.2.1.2. Nng nghip: Tnh hnh hin ti & phng hng pht trin

Hin nay ngnh nng nghip Lt vn cn thu ht 38.5% lao ng x

hi. Sn xut nng nghip trn lnh vc trng trt ang pht trin vdin tch,

tng v, tng nng sut v cht lng nng sn. Hng nm, ngnh nngnghip Lt cung ng cho thtrng tiu dng (chyu Tp.HCh Minh

v cc tnh pha Nam) khong 200.000 tn rau cc loi, trn 300 triu cnh

hoa. Lnh vc chn nui pht trin chm.

Thnh ph ang thc hin cc chng trnh chuyn i c cu cy

trng, vt nui nhm tng cng tnh a dng ca sn phm nng nghip, p

ng cho nhu cu ca thtrng tiu dng trong nc theo hng cht lng

cao v tng bc to lp thtrng xut khu nng sn.

V c cu ngnh nng nghip Lm ng - Lt, trng trt ang

chim ttrng lnhn chn nui v dch v. Trong nghtrng rau v hoa

ang l thmnh ca a phng ni ring v cnc ni chung vi tc

pht trin bnh qun trong 5 nm l 9.1%/nm

Ti lt c hn 20.000 cs sn xut, hnng dn tham gia trng

rau, trong c 13 n vng k v cp giy chng nhn rau an ton, tp

trung nhiu nht phng 7,5,8,11, x Xun Trng, x Xun Th(xem

bn sau)




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Hnh 1.1 Bn phn bdin tch canh tc rau cc loi ti cc phng x thnhph Lt

Nhng loi rau quchnh trng Lt gm:

- Rau n l (l bp ci, ci tho, x lch, ci ngt, sp lxanh, cn ty,

b xi)

- Rau n c(khoai ty, hnh ty, cdn, su ho, c rt, cci trng)

- Rau an qu(c chua, c tm, u c ve v.v.)

1.2.2 Gii thiu vnghtrng rau Lt Lt khng chl mt thnh phdu lch ni ting ca Vit Nam m

l vng trng rau ni ting ca cnc.

Nm trong vng nhit i gi ma, chu nh hng ca cao nn

Lt c nn kh hu ca vng n i. Mc d vi din tch khng ln (42.400




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ha) nhng c u i bi thin nhin, nhc c im kh hu ca vng n

i m Lt c thsn xut c nhng loi rau qun i quanh nm.

Nghtrng rau Lt c tlu v pht trin mnh trong nhng

nm cui ca thp k30. Rau Lt ngon, b, mang hng vc th carau n i. Nhng loi rau cao cp hin nay nhb xi (spinach), x lch,

khoai ty hng, lxanh, trng, ci bp x.. i vo cc ba n thng thng

khng chca ngi dn Lt m cn cdn ca thnh phHCh Minh,

cc tnh min Ty Nam B, cc tnh min Trung v ccc nc ln cn.

Ni n rau Lt l ni n huyn n Dng, c Trng v thnh

ph Lt, tng sn lng rau ca 3 vng l ny khong 250.000 tn, chim

30% rau qucnc. Ngun li do rau trng t Lt khng chl ngun

li nhun ng kv gii quyt vic lm cho phn ln lao ng ca Tp.

Lt m ctnh Lm ng, gp mt phn ln thc y stng trng vkinh

tchung ca tnh trong vng 10 nm qua.

1.3. Gii thiu vkim loi nng [11, 18, 20, 25, 26, 30]Mt skim loi nng rt cn thit cho cthsng v con ngi. Chng

l cc nguyn tvi lng khng th thiu, smt cn bng cc ny c nh

hng trc tip ti sc khe ca con ngi. St gip nga bnh thiu mu,

km l tc nhn quan trng trong hn 100 loi enzyme. Trn nhn ca cc l

thuc vitamin, thuc bxung khong cht thng c Cr, Cu, Fe, Zn, Mn, Mg

chng c hm lng thp v c bit n nhlng vt. Lng nhcc kim

loi ny c trong khu phn n ca con ngi v chng l thnh phn quan

trng trong cc phn tsinh hc nhhemoglobin, hp cht sinh ha cn thit

khc. Nhng nu cthhp thu mt lng ln cc kim loi ny, chng c th

gy ri lon qu trnh sinh l, gy c cho cthhoc lm mt tnh nng ca

cc kim loi khc.




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Kim loi nng c c tnhl cc kim loi c ttrng t nht ln gp 5

ln t trng ca nc. Chng l cc kim loi bn (khng tham gia vo qu

trnh sinh ha trong c th) v c tnh tch t sinh hc (chuyn tip trong

chui thc n v i vo cthngi). Cc kim loi ny bao gm: Hg, Ni, Pb,

As, Cd, Pt, Cu, Cr, Mn.Cc kim loi nng khi xm nhp vo cthsinh vt

gy c tnh.

1.3.1. Ngun gc xut hin v sdi chuyn cc kim loi nng

1.3.1.1. Trong nc

Kim loi nng tn ti trong mi trng nc tnhiu ngun khc nhau

nh: Nc thi tcc khu cng nghip v nc thi sinh hot, giao thng, yt, sn xut nng nghip (phn bn, thuc tr su), khai thc khong sn,

cng nghmkim loi.

Ngun nc mt b nhim kim loi nng s ko theo nhim mi

trng t, nhim ngun nc ngm, nhim khng kh.

1.3.1.2. Trong t

Ngun gc xut hin cc kim loi nng trong t l do: cht thi cng

nghip, knghpin, hot ng khai thc khong sn, ckh, giao thng, cht

thi sinh hot v phn bn, cc ho cht dng trong cc ngnh cng nghip.

Vit Nam tnh hnh nhim t bi kim loi nng nhn chung khng

ph bin. Tuy nhin trng hp cc b gn khu cng nghip, c bit

nhng lng ngh ti chkim loi, tnh trng nhim kim loi nng din ra

kh trm trng.

1.3.1.3. Trong khng kh

Kim loi nng tn dtrong khng kh do cc ngun sau:

Cng nghip luyn kim, ckh thi ra nhiu khi bi kim loi, khi thi

do dng nhin liu ho thch, ho cht c hi trong qu trnh luyn gang,

thp, nhit luyn kim loi.




17/77

17

Kh thi cc nh my luyn kim thng c nht cao 300 4000C

nn ddng c phn tn ra nu kt hp c vi ng khi cao.

1.3.2. Tc hi ca kim loi nng

Kim loi nng xm nhp vo c th mt phn bo thi, mt phnc gili trong cth. Cc kim loi nng l ngun cht c nguy him i

vi hsinh thi t, chui thc n v con ngi. Nhng kim loi nng c tnh

c cao nguy him l Thungn (Hg), Cadimi (Cd), Ch (Pb), Niken (Ni).

Cc kim loi nng c tnh c mnh l Asen (As), Crm (Cr), Km (Zn),

Thic (Sn), ng (Cu).

Cc kim loi nng nu tn ti dtrong thc phm vi hm lng qucao sgy tc hi cho sc khongi tiu dng. Biu hin trc ht l ng

c mn tnh.

- i vi ngi:

Gy c hi cp tnh, th dthungn (Hg) hay asen (As) vi liu cao

c thgy ngc cht ngi ngay.

Gy c hi mn tnh hoc tch luth dch (Pb) vi liu lng nhhng ngy, lin tc, sau mt thi gian sgy nhim c ch, rt kh cha, cc

kim loi khc gy si thn.

- i vi thc n:

Lm hhng thc n, th dchcn cho lng vt ng skch thch

qu trnh oxi ho v toxi ho ca du m.

Lm gim gi trdinh dng ca thc phm, th dchcn cho lng

vt kim loi nng cng kch thch sphn huvitamin C, vitamin B1

1.3.3. Sxm nhp ca kim loi nng vo cthsinh vt

Kim loi nng c thxm nhp vo cthngi v sinh vt thng qua

ba con ng sau:

- H hp




18/77

18

Khng kh c cthsng ht vo c nhng cht nhim khng ch

dng kh m cn dng lng, bi rn c khnng bay hi. Cc cht c sau

khi c hp thqua mng nhy slan toi vo mu, gy ngc.

Cc cht c dng rn hay lng, llng trong khng kh nhsng

m, khi vi ht nh hn 1 micron c th vo phi. Bi kh c c kch

thc phn tt 1 5 micron i vo cc phqun hay phnang. Ton bph

nang c din tch rt ln vi mt mng li mao mch dy c gip cht c

khuch tn nhanh vo mu, khng qua gan v khng c gii c nh theo

ng tiu ho m i ngay qua tim i n cc phtng, c bit hthn kinh

trung ng. Do , cht c xm nhp qua ng h hp tc ng gy c

nhanh v rt nguy him.

- Tiu ho

Thc n v nc ung bnhim bn khng m bo qui tc an ton v

sinh thc phm hay bn thn thc n v nc ung c cha kim loi nn kim

loi nng dxm nhp vo c thsinh vt v gy bnh. Chc mt sc

cht i vo no, cn li c cht chyu i qua gan, thn, qua sa m, tuyn

mhi v tuyn sinh dc.

- Tip xc

Da c vai tr bo vchng tc ng ca yu tho hc, vt l v sinh

hc. Do mt syu tnhy cm vi lp mdi da nn kim loi nng c th

i qua da, vo htun hon chung ca cth. Nhim c qua da cng xy ra

ddng nu da btn thng vmt chc (chn thng), l hc (bng), cc

cht ho hc (cc cht kch thch v n da, gy bng). Nu nhim qua nimmc cng nguy him hn v nim mc c mt mao mch dy.

Khi cc cht c hoc cht li vo cththng qua mt hoc nhiu

ng trn, chng si vo mu. Sau chng c thbo thi ra khi c

thbng mt schuyn ho sang mt thkhc hoc bi tit qua gan, thn (cc

cht c tan c trong nc), qua phi (cc cht c c tnh bay hi cao).

Cc cht c khng bi tit ra c th tn lu, tch lu trong cc m, cc c




19/77

19

quan ni tng ri gy cc bnh nguy him nhung thhoc cc bnh t bin

vgan hoc di truyn.

1.1.4. Tnh hnh nhim kim loi nng trn thgii v Vit Nam

1.1.4.1. Tnh hnh nhim kim loi nng trn thgii[10, 11, 27, 32]

Tnh trng nhim kim loi nng thng gp cc khu cng nghip,

cc thnh ph ln, khu vc hot ng nng nghip v khu vc khai thc

khong sn. Tcc ngun pht thi cc kim loi nng i vo mi trng t,

nc, khng kh gy nhim mi trng, nh hng n sc khe, i sng

sinh vt v tn km chi ph khc phc, xl.

Hin nay, tnh trng nhim Pb, Cd, Zn, Cu cng nh cc kim loinng khc din ra nhiu ni, tcc nc pht trin n cc nc ang pht

trin, tuy nhin mc trm trng thng xy ra cc bti mt skhu vc.

Hot ng cng nghip c bit l cng nghip khai khong, sdng thuc

bo vthc vt, sdng phn bn, giao thng, ttnhin a vo mi

trng mt lng ln kim loi nng.

Nm 1953 Nht Bn, mt nh my sn xut ha cht thi metylthy ngn ra vnh Minamata, thng qua con ng thc phm gy ra cc

triu chng bnh thn kinh v c bit n nhl bnh "Minamata". tnh

Creuse (Php) t nm 1905 1955 hot ng khai thc vng thi ra

550.000 tn cianua v thungn gy nhim nng cho mt vng rng ln v

nc sng Tardes. Irc, t b nhim metyl thungn t thuc bo v

thc vt lm hn 6.000 ngi nhim c v 88 ngi cht. dng muiv c, thy ngn gy nn cc ri lon thn kinh cho cng nhn lm m

(nn) trong cng nghip lm mca H Lan v trnn ni ting vi cm t

"mad as a hatter".

mt svng trn thgii nhi Loan, Nam M, Banglades... nng

ca asen trong nc ngm kh cao. C dn sinh sng v s dng nc

ngm cc vng c nng asen cao thng bmc cc bnh nhbnh sng




20/77

20

ha, tng hc tda ... Phi nhim mc nng cao hn c thdn n hu

qunghim trng nhbhoi tu ngn tay, ngn chn, bnh "blackfoot",

ung th...

Ti Thin Tn (Trung Quc), ni sn xut hn mt na lng ch cho

Trung Quc, do cng nghthp v qun l km nn mt lng ln ch v cc

kim loi nng c hi khc tmv qu trnh khai thc chbin pht tn

vo mi trng cao gp 24 ln tiu chun cho php gy nh hng nghim

trng cho khong 140.000 ngi.

Sukinda (n ), ni c mt trong nhng mCrom lthin ln nht

th gii, 60% nc ung y b nhim Cr+6 mc cao gp hai ln tiu

chun quc t. Theo c tnh ca mt nhm y tn , 84,75% s ngi

cht khu mny u lin quan n cc bnh do crom gy ra. Vapi mt

thnh phkhc ca n , theo iu tra cho thy hm lng thy ngn trong

nc ngm ca thnh phcao hn 96 ln so vi tiu chun an ton ca T

chc Y t thgii (WHO), cc kim loi nng bpht tn vo khng kh v

nhim vo cc sn phm ca a phng, sngi c nguy cnh hng ln

n 71.000 ngi . thnh ph La Oraya mt thnh ph m ca Peru,

99% s tr em c hm lng ch nhim vo trong mu vt qu mc cho

php, theo kho st nm 1999, hm lng Pb, Cu, Zn y cao gp 3 ln so

vi gii hn cho php v chng stn ti trong t ca thnh phny hng

thkna. [theo thng k nm 2006 ca tchc nghin cu mi trng quc

tVin Blacksmith].

1.3.4.2. Tnh hnh nhim kim loi nng Vit Nam [1, 3, 20]

Vit Nam l nc ang pht trin, qu trnh cng nghip ha, th

ha gia tng, cng vi n l tnh trng nhim kim loi nng ngy cng trm

trng. Cc khu vc nhim kim loi nng cao ti Vit Nam tp trung ti cc

thnh ph ln, khu cng nghip pht trin hay ti cc khu vc lng ngh

truyn thng.




21/77

21

nhim Asen ti Vit Nam thng phn b rng v l mt trong

nhng quc gia nhim Asen cao trn thgii. Tnm 1995 2000, nhiu

nghin cu cho thy nng Asen trong cc mu nc kho st thng

lu sng M, Sn La, Ph Th, Bc Giang, Hng Yn, Nam nh, Thanh

Ho, H Ni u vt tiu chun cho php nc sinh hot quc tv Vit

Nam.

Ngoi ra, tnh trng nhim kim loi nng cadimi v ch cng gia tng

nhanh chng, mc nhim nghim trng nht vn l cc thnh ph ln,

cc khu dn c, khu cng nghip, cc lng ngh truyn thng Ti huyn

ng Anh, H Ni hm lng cadimi, ch trong t v nc ca khu vc

trng rau u vt tiu chun cho php.

Nm 2004 ti huyn Tn Tr(Long An), hm lng cadimi trong nc

t 2 8 mg/l gp 40 60 ln tiu chun cho php, ch t0,7 - 2,7 mg/l gp 7

- 27 ln tiu chun cho php.

t khu vc xung quanh nh my Pin Vn in v nh my phn ln

Vn in (H Ni) c hm lng kim loi nng l: ch 17,44 2047 ppm;

ng 12,85 49,69 ppm; mangan 172,78 2018,05 ppm; km 25,190

243,477 pmm.

Mt skhu vc bin c biu hin nhim kim loi nng, Theo s

liu nm 2000 ca cc trm quan trc bin, cc trm tch chyu b nhim

bi cc kim loi nng nh: asen, cadimi, ng, km v thy ngn.

Bng 1.1: Ti lng mt scht gy nhim ra bin ca mt shthng sng

Hthng sngThng s(n vtn/nm)

Cu Pb Zn As Hg Cd

Thi Bnh 4101 154 3352 120 17 164

Hng 2817 730 2015 448 11 18

Hn 37 15 79

Thu Bn 62 16 192




22/77

22

Si Gn -ng Nai 102 2921 26

M Kng 1825 190 12775 982 13 128

Cnc 1418

4

2063 21739 2407 133 1082

(Ngun: Chng trnh Nghin cu bin cp nh nc KT.03.07)

Bng 1.2 : Ti lng cht gy nhim ra bin Hi Phng Qung Ninh

Cht gy nhim (n vtn/nm)

Cu Pb Zn Hg As Cd

65,29 45,12 840,73 5,13 45,89 9,44

(Ngun: Bo co hin trng mi trng Vit Nam 2003, Phm Vn Ninh)

Vn nhim kim loi nng trong thc phm l vn cn c

quan tm v kim loi nng chyu xm nhp vo c thcon ngi qua con

ng tch lu sinh hc. Theo kt qu phn tch vo thng 4 nm 2004 ti

thn Bng B, x Hong Lit, huyn Thanh Tr, H Ni qua cc mu rau dng

phn tch nh: mng ti, hnh, ci xanh, mung cn, ngi cu, mung

nc th hm lng cc kim loi nng nhCu, Zn, Pb, Cd, Hg, As l cao sovi tiu chun ca WHO. thnh ph H Ch Minh nhiu h thng knh

rch, ao mng phi hng chu mt cch lu di cc cht thi c hi t

hng ngn nh my, c s sn xut trn a bn. in hnh nhnm 2008,

Nh my bt ngt Vedan bpht hin vic nc thi cha xl ra sng

ThVi gy nhim nghim trng ngun nc v thit hi nng ncho

ngi dn trong khu vc bcquan nh nc xl.Nhng cng trnh nghin cu gn y ca mt s nh khoa hc cho

thy rau bn cc chtrong thnh phHCh Minh, nhiu loi nhim kim

loi nng c bit ch c hm lng cao hn mc cho php 30 ln. Theo

nghin cu ca Ph gio s tin s Bi Cch Tuyn (i hc Nng Lm

TP.HCM) hm lng km trong cc mu rau mung qun Bnh Chnh cao

gp 30 ln mc cho php.




23/77

23

Cc dn liu trn cho thy tnh hnh nhim kim loi nng trn thgii

v Vit Nam v ang gy nh hng rt ln n sc kho, cht lng cuc

sng ca con ngi. Mc d tnh trng nhim kim loi nng nc ta tuy

cha mc phbin v trm trng, song mt svng nht l cc vng gn

khu cng nghip c du hiu nhim kim loi nng cc b. V vy vic

nghin cu cng cnhm nng cao hiu qunh gi nhim kim loi nng

l vn c ngha thc tin nhm quan trc v kim sot cc nh hng ca

n n i sng con ngi v mi trng.

1.4. Vai tr, chc nng sinh ha v snhim c Pb, Hg, Cd, As [1, 2, 9,10, 11, 17, 20, 22, 24, 29]

1.4.1. Vai tr, chc nng sinh ha v snhim c Pb [1, 17, 22]

1.4.1.1 . Slc vch

Trlng trong thin nhin ca ch l khong 1,6.10-3% khi lng v

tri t ng vi khong 1,6.10-4% tng snguyn t ca v tri t, tc l

nguyn t t ph bin. Ch c 18 ng v trong c 4 ng v bn:208Pb

(52,3%),207

Pb (22,6 %),206

Pb (23,6%),204Pb (1,48%). Ch tn ti trng thi oxi

ho 0, +2, +4 trong mui ch ho tr2

l bn v hay gp nht. C khong 170

khong vt ca ch ch yu l: Galen

(PbS), Cerndute (PbCO3), Anglesite

(PbSO4) v pyromorphite [Pb5Cl(PO4)3]. Hnh 1.2. Kim loi ch

Trong kh quyn ch tng i giu hn so vi kim loi khc. Ngun

chnh ca ch phn tn trong khng kh xut pht tqu trnh t chy cc

nhin liu xng cha ch. Ch c trn thm di dng Pb(CH3)4 v

Pb(C2H5)4cng vi cc cht lm sch 1,2-icloetan v 1,2-ibrometan.




24/77

24

Ch l mt kim loi mm, nng, c hi v c thto hnh. Ch c mu

trng xanh khi mi ct nhng bt u xn mu thnh xm khi tip xc vi

khng kh.

1.4.1.2 . ng dng ca ch- Ch c dng lm tm in cc trong cquy, dy cp in, u n

v cc ng dn trong cng nghip ha hc.

- Ch c sdng nhcht nhum trng trong sn, thnh phn mu

trong trng men.

- Ch hp thtt tia phng xv tia rnghen nn c dng lm

nhng tm bo vphng xht nhn.

1.4.1.3. Tc dng sinh ha ca ch

Tc dng sinh ha chyu ca Pb l tc dng ca n n stng hp

mu dn n sph vhng cu. Ch c chmt senzym quan trng ca

qu trnh tng hp mu do s tch ly ca cc hp cht trung gian ca qu

trnh trao i cht. Mt phn quan trng ca tng hp mu l do schuyn

ha delta amino levunilicaxit (ALAdehydrase). Ch c ch ALA dehydrase enzym, do giai on tip theo to thnh porpho biliogen khng

thxy ra. Kt qul ph hy qu trnh tng hp hemoglobin cng nhcc

sc th hp khc cn thit trong mu nhcytochromes.

Cui cng, ch cn tr vic s dng oxi v glucoza sn sinh nng

lng trong qu trnh sng. Scn trny c thtm thy khi nng cn

trong mu nm khong 0,3 ppm. cc nng cao hn c th gy hintng thiu mu (thiu hemoglobin) nu hm lng ch trong mu khong

0,5 0,8 ppm gy ra sri lon chc nng thn v ph hy no.

Xng l ni tng tr, tch tch ca cth. Sau phn ch ny c th

tng tc cng vi photphat trong xng v thhin tnh c hi khi truyn

vo m mm ca c th. Ch nhim vo c th qua da, ng tiu ha, h

hp. Nhim ch c thdn n v sinh, sy thai, mc phi cc ri lon vthn




25/77

25

kinh, thiu mu, au u, sng khp, chng mt. trem, chsIQ skhng

cao, i khi c nhng biu hin ri lon hnh vi. Do ch tch ly dn trong c

thmt cch chm chp nn nhng triu chng skhng c nhn bit kp

thi.

1.4.1.4 .c tnh ca ch

Trong sn xut cng nghip th Pb c vai tr quan trng, nhng i vi c

thth cha chng minh c Pb c vai tr tch cc g. Song c tnh ca Pb

v cc hp cht ca n i vi c thngi v ng vt th qu r. Khng

kh, nc v thc phm b nhim Pb u rt nguy him cho mi ngi, nht

l tr em ang pht trin v ng vt. Ch c tc dng m tnh ln s phttrin ca bno trem, Pb c chmi hot ng ca cc enzym, khng ch

no m cn cc bphn to mu, n l tc nhn ph hy hng cu.

Khi hm lng Pb trong mu khong 0,3 ppm th n ngn cn qu trnh s

dng oxi oxi ha glucoza to ra nng lng cho qu trnh sng, do lm

cho cthmt mi. nng cao hn (>0,8 ppm) c thgy nn thiu mu

do thiu hemoglobin. Hm lng ch trong mu nm trong khong ( >0,5 0,8 ppm) gy ra sri lon chc nng ca thn v ph hy no. Xng l ni

tng tr, tch tch trong cth, ch tng tc vi photphat trong xng

ri truyn vo cc m mm ca cthv thhin c tnh ca n.

V thtt nht l trnh nhng ni c Pb bt k dng no, ng thi trong

dinh dng ch dng loi thc phm c hm lng Pb di quy nh cho

php v c Ca v Mg hn chtc ng ca Pb. V d chng ta khngmun th cng lun c mt lng Pb rt nhnht nh vn thm nhp vo c

thca chng ta qua ng n ung v ht th. V thnn ung sa, n nhiu

rau xanh, cc loi thc phm v ung giu vitamin B1 v vitamin C th c

li cho vic chng li v hn chnh hng ca Pb i vi cth.




26/77

26

Cc cht c dng gii c ch l EDTA, 2,3- dimercaptopropanol,

penicillamin., do chng to vi Pb cc phc chelat bn v c o thi

ra ngoi qua nc tiu.

1.4.2. Vai tr, chc nng sinh ha v snhim c Cd [1, 2, 9, 11]

1.4.2.1. Slc vCadimi

Cadimi chim khong 5.10-5% khi

lng v tri t ng vi 7.10-6 % tng s

nguyn t. Cadimi l nguyn t km ph

bin. Cadimi c 19 ng v, 8 trong s l

bn nh 114Cd (28,86%), 113Cd (12,26%),112Cd (24,07%), 111Cd (12,7%), 110Cd (12,39%)

v 100Cd. Cadimi thng c trong cc khong Hnh 1.3. Kim loi cadimivt cha km v l sn phm phqu trnh sn xut km, ng v ch. Th d,

khong vt cha cadimi l grenokit (CdS), thng tn ti lng nh trong

qung km l: blen km (ZnS), v calamin (ZnCO3) c cha khong 3%

cadimi, hoc trong qung thy ngn l xinaba thn sa (HgS). Cadimi cn tnti trong qung a kim vi ch v ng.

1.4.2.2. ng dng ca Cadimi

Cadimi c pht hin ln u tin vo nm 1817 bi Friedrich

Stromeyer (1778-1838) v mi c sdng rng ri thkXX. Vic sn

xut Cadimi trn thgii tng t11.000 tn trong nm 1960 ln n 19.000

tn nm 1985.- Khong cadimi sn xut ra c sdng trong cc loi pin (c

bit l Ni Cd ) v phn ln trong cng nghip.

- Cadimi c sdng chyu trong cc cht mu, lp sn ph, cc

cht mkim loi ( mv t, my bay v tu bin).




27/77

27

- Cadimi c sdng chto hp kim, lm cht n nh trong plastic,

lm in cc c quy kim. Hp kim Cu Cd dng lm thanh iu chnh trong

l phn ng ht nhn.

- Ngoi ra Cadimi cn c mt trong phn bn v mt sthuc trsu

bi c tnh dit nm v cn trng.

1.4.2.3. Tc dng sinh ha ca cadimi

Sau khi xm nhp vo cth, cadimi c gn vo trong cc m di

dng mt hp cht vi mt protein c chn lc v c trng lng phn tthp

nhng giu nhm tiol (-SH) l metalothionein. Metalothionein thng c

61 axit amin trong c 20 axit amin cystein v khng c axit amin thm.Chnh s tng hp nn hp cht metalothionein ny c kch thch khi c

mt ca cadimi. Metalothionein tp trung nhiu nht gan v thn, ni m

cadimi thng tch ly ( khong 50 60 % lng cadimi trong cth).

SH S

{Enzim} + Cd2+ {Enzim} Cd + 2H+

SH S

Lc u, cadimi c tr trong gan ni thng din ra s tng hp

metalothionein; sau n c vn chuyn dn n thn nhprotein ny.

y cadimi sc girt lu bi v thi gian bn hy ca chng bphn

ny c thvt qua 17 nm nhng i tng bnhin trung bnh. Slu tr

ny c thc hin mt cch c chn lc vthng thn. Da vo kt qu

nhn c ngi v ng vt sau khi cht cho thy nng ti hn ca

cadimi trong thn l 200 ppm (200gcadimi/ 1g m ti). Nu vt qu gi

trny sxut hin "chng bi tit ra phc protein - cadimi" c c trng

bng sxut hin protein phn tlng thp ( 30000) trong nc tiu cng

nh bi vic tng s thanh thi ca 2microglobulin ca protein lin kt

retinol (RBP). Bnh thn c bit ny l trng hp c bit vmt m hc,




28/77

28

bi lmt bnh ng m li chgy tc hi mt cch c chn lc n duy

nht ci ng u gn.

1.4.2.4. c tnh ca cadimi [24, 29]

Cadmi l nguyn trt c. Gii hn ti a cho php ca cadmi:Trong nc : 0,01 mg/l (hay 10ppb),

Trong khng kh : 0,001 mg/m3,

Trong thc phm : 0,001- 0,5 mg/kg.

Trong tnhin cadmi thng c tm thy trong cc khong vt c

cha km. Nhim c cadmi gy nn chng bnh gin xng. nng cao,

cadmi gy au thn, thiu mu v ph hutuxng.

Phn ln cadimi thm nhp vo cthcon ngi c gili thn v

c o thi, cn mt phn t (khong 1%) c gili trong thn, do cadmi

lin kt vi protein to thnh metallotionein c thn. Phn cn li c gi

li trong cthv dn dn c tch lucng vi tui tc. Khi lng cadmi

c tch tr ln, n c th thchion Zn2+

trong cc enzim quan trng vgy ra ri lon tiu ho v cc chng bnh ri lon chc nng thn, thiu mu,

tng huyt p, ph hutusng, gy ung th.

1.4.3. Vai tr, chc nng sinh ha v snhim c asen

1.4.3.1. Slc vAsen

Asen c k hiu ha hc l As, c shiu nguyn tZ = 33, thuc

nhm VA, chu k4 trong bng hthng tun hon. Chim 1.10-4 % tng s

nguyn ttrong vnguyn ttrong vtri t. Trng thi oxi ha ca asen

l +3, +5. Asen kim loi c mu trng bc, dn in, dn nhit nhng gin,

dnghin thnh bt, tan trong CS2

As c khi lng nguyn tl 74,92 vC, khi lng ring 5,72 g/cm3

nhit nng chy 8170C, nhit si 6100C




29/77

29

1.4.3.2. Chc nng sinh ha v c tnh Asen [1, 2, 9, 11, 22]

Vmt ho hc As l mt kim, vmt sinh hc As nm trong danh

mc cc ho cht c hi cn c kim sot. As c xp cng hng vi cc

kim loi nng, As l cht c c thgy nn 19 bnh khc nhau trong c

ung thda v phi, bng quang, rut. Cc triu chng cin ca nhim c

As l sm mu da, tng sng ha v ung th, tc ng n hthn kinh ngoi

bin v nh hng xu n sc khe nhchng to chng gan, bnh i tho

ng, cao huyt p, bnh tim, vim cung phi, cc bnh v ng h

hp. As dng v c c c tnh cao gp nhiu ln As dng hu c,

trong cc hp cht c cha As th hp cht cha As (III) c tnh cao hn

As (V), tuy nhin trong cthAs (V) c thbkhvAs (III) As3+tc ng

vo nhm - SH ca cc enzim do vy c chhot ng ca men.

SH ------ O S

{enzim} + As - O = {enzim} As+= O + 2OH-

SH ------ O S

Men pyruvate ehydrogenaz trong chu trnh axit citric to phc vi As3+ngn

cn vic to thnh ATP :O- HS CH2 S CH2

- O As + CH2 O = As+ CH2

O- HS CH S CH

(CH2)4 (CH2)4

C = O C = O

prtin prtinAcid dihydrolipoic - prtin Phc Prtin As3+ (mt hot

tnh)

i vi cy trng: Arsenic c nhiu ngi bit n do tnh c ca

mt shp cht c trong n. Shp thAs ca nhiu cy trng trn t lin

khng qu ln, thm ch t trng tng i nhiu As, cy trng thng

khng c cha lng As gy nguy him. As khc hn vi mt skim loi




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nng bnh thng v a scc hp cht As hu ct c hn cc As v c.

Lng As trong cc cy c thn c thng rt t. Sc mt ca As trong

t nh hng n sthay i pH, khi c tAs tng ln khin t trng tr

nn chua hn, nng pH < 5 khi c skt hp gia cc loi nguyn tkhc

nhau nhFe, Al.

Cht c nh hng tAs lm gim t ngt s chuyn ng trong

nc hay lm i mu ca l ko theo scht l cy, ht ging th ngng pht

trin. Cy u v nhng cy hu (Fabaceae) rt nhy cm i vi c t

As.

1.4.4. Vai tr, chc nng sinh ha v snhim c thy ngn1.4.4.1. Slc v thy ngn

Thy ngn c k hiu ha hc l Hg (tn latinh l hydragyrum) sth

t 80 chu k 6 nhm IIB trong h thng tun hon c s oxi ha +1, +2.

Khi lng nguyn tl 200,59 vC. Thion ha 10,43 eV cao nht trong

cc nguyn tnhm d, nhit nng chy -38,830C, nhit si 356,730C,

khi lng ring 13,55 g/cm3

, m in 2,0. nhit thng, thy ngnl cht lng.

Thy ngn l kim loi mu trng xm.. Cc hp cht ca thy ngn

km bn so vi hp cht cc nguyn t cng nhm, nhng phc cht ca

thy ngn vi cc phi tNH3, CN-, X-li bn hn. Cc dn xut ca thy

ngn u rt c. thy ngn dto hp kim, cc hp kim ca thy ngn gi

l hn hng, phn ln hn hng thlng hoc nho.

1.4.4.2. ng dng ca thy ngn v cc hp cht ca thy ngn

- Thy ngn kim loi dng lm in cc trong my o cc ph, lm

nhit kthy ngn

- HgO dng iu chcc hp cht khc ca thy ngn, chsn v

tu bin, thuc mv pin thy ngn. Pin thy ngn gm c cc m lm bng




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31

hn hng km, cc dng l bt nho ca HgO trn vi than v cht in li l

bt nho ca ZnO trn vi KOH. Trong pin xy ra phn ng:

Zn + HgO ZnO + Hg

Pin c lm dng cc dng cho my nghe, ng heo tay

- Nhng phc cht ca Hg (II) dng trong ha phn tch nhK2[HgI4]

v (NH4)2[Hg(SCN)4]

- Hg2Cl2dng lm in cc calomen l mt in cc so snh phbin

1.4.4.3. c tnh ca Thy ngn

Nhim c cp tnh: Khi tip xc vi Hg nhit cao, khng gian

kn gy ho, kh th, tim p nhanh, nu liu lng Hg tng dn thnhit cthtng, chong vng, nn ma, hn m, tc ngc, mt sngi

da tm ti, rt. Qu trnh kh thc thko di n vi tun.

Ngc cp tnh do n ung phi mt lng ln Hg. Ngc cp tnh

c thl bngt, hn m. V d: Nm 1952, mt ngi lng Irc c 1450

ngi cht do n phi la m ging do Lin hp quc vin tr, do la m

ging c phun tm CH3Hg+chng nm.

Nhim c mn tnh: Khi tip xc vi Hg trong mt thi gian di.

Nhim c hthn kinh, thn, chyu do Hg hu cv mt sHg v c.

Triu trng sm nht ca nhim c Hg l lng, da xanh ti, n kh tiu,

hay au u, c thkm theo vim li, chy nc bt, sau rng rng, mn,

thng, v c vt en rng, gy tthng da.

Triu trng in hnh ca nhim c mn tnh Hg biu hin thn kinh:

lit, run, lit m mt, mi, li, cnh tay, bn chn... Ngi nhim c kh c

khnng iu khin vn ng, cch din t thay i, ni kh, bt u cu

ni kh khn, ni lp. i vi trem khi bnhim c Hg th thn kinh phn

lp, thiu nng tr tu.




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Metyl thy ngn (CH3)Hg+: nh hng chnh n hthn kinh

trung ng, ngoi ra n cn gy ra cc ri lon vtiu ho v tnh hng ti

thn. Trong mi trng nc, metyl thy ngn l dng c nht, n lm phn

lit nhim sc thv ngn cn qu trnh phn chia tbo.

1.5 Cc phng php nghin cu [6, 7, 8, 12, 14, 21, 25, 31]

Hin nay c rt nhiu phng php khc nhau xc nh ch, thy

ngn, asen, cadimi cc phng php ha hc nhphn tch khi lng, phn

tch thtch. Cc phng php in ho nhphng php cc ph, phng

php von ampe ha tan. Cc phng php phn tch cng cnhphphn

tUV VIS, phpht xnguyn t(AES), phhp thnguyn tngn la(F-AAS) v khng ngn la (GF-AAS), phng php ICP MS, phng

php kch hot ht ntron... mi phng php c u v nhc im ring .

Trong phm vi ti ny chng ti chn ba phng php nghin cu chnh l

phng php cc ph, phng php ph hp th nguyn t, phng php

quang phplasma ghp ni khi phICP-MS.Sau y l mt sphng

php xc nh Ch, Thy ngn, Asen, Cadimi.

1.5.1. Phng php cc ph

Phng php ny da trn vic ng dng sphn cc nng sinh ra

trong qu trnh in phn trn in cc c bmt nh. Da vo ng cong

biu din sph thuc ca sbin i cng dng trong qu trnh in

phn vo thin t vo, c thxc nh nh tnh v nh lng vi cht

cn phn tch vi chnh xc kh cao. ng biu din cng dng ti

thi im xy ra skhion cn phn tch bgy t ngt pha trn to nn

ng gi l sng cph. Da vo vtr ca sng c thxc nh thnh

phn nh tnh ca cht in ly, da vo chiu cao ca sng c thxc nh

hm lng ca ion bkh. Phng php ny c khnng xc nh hn hp

cc kim loi cha trong cc mu kthut vi hm lng khong 0,001% vi

chnh xc trung bnh n 1%.




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1.5.1.1. Csca phng php cc ph

Phng php cc phl nhm cc phng php phn tch da vo vic

nghin cu ng cong Von Ampe hay cn gi l ng cong phn cc, l

ng cong biu din sphthuc ca cng dng in vo thkhi tin

hnh in phn dung dch phn tch. Qu trnh in phn c thc hin trong

bnh in phn c bit, trong c mt in cc c din tch bmt b hn

din tch bmt kia nhiu ln. in cc c din tch bmt b hn gi l vi

in cc. Qu trnh kh ( hoc oxi ha) cc ion chyu xy ra trn vi in

cc. vng cong phn cc, ngi ta lin tc theo di v o cng

dng in chy qua mch khi tng dn in tht vo hai cc ca bnh in

phn v xy dng ththeo hta I E, ( I l cng dng in chy

qua mch, E l in tht vo hai cc ca bnh in phn). ng cong

mang tn ng cong Von Ampe.

* Phng trnh InkovitchNgi ta tm thy mi lin quan gia cng dng gii hn Idvi

nng ion kim loi CMv cc i lng khc. Mi quan hc m tbng

phng trnh Inkovitch

Id= 605ZD1/2m2/3t1/6CM (1)

Trong : Id: Cng dng khuch tn gii hn ( A).

Z l in tch ion kim loi

D l hskhuch tn c thnguyn (cm2.s-1)

m l khi lng git thy ngn chy ra tmao qun (g/s)t l thi gian to git thy ngn (s)

Trong cc i lng c trong phng trnh (1), hskhuch tn D kh

xc nh bng thc nghim v cng t khi tm thy trong cc stay.

Trong phn tch cc ph m v t thng c gi l c trng mao

qun, c thxc nh bng quan st thc nghim.




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Trong thc tD, m, t c thc duy tr khng thay i trong iu

kin thc nghim nn (1) c thvit di dng :

Id= K.CM (2)

Tphng trnh (2) ta thy cng dng gii hn Idphthuc tuyntnh vo nng cht nghin cu v (2) l cscho phn tch cc phnh

lng.

1.5.1.2. Quy trnh ca phng php cc ph

phn tch mt cht no bng phng php cc ph, trc ht cn

chuyn n vo dung dch. Sau to mi trng cn thit v tch cc chtngn cn sxc nh cc ph.

iu bt tin nht i vi phng php cc ph l trong dung dch

phn tch c cc cht c thkhgn vi thkhca nguyn tcn xc nh

hoc c ththp hn oxi ha tan trong dung dch, chng sngn cn php xc

nh. tch cc cht ngn cn, ngi ta sdng cc phn ng kt ta, to

phc, oxi ha kh, tch sc k ...

Qu trnh phn tch cc phgm cc bc cthsau :

Bc 1: Cho dung dch phn tch vo bnh in phn.

Bc 2: Sc kh H2hoc N2nguyn cht vo dung dch bnh in phn

trong vng 10 pht loi troxi ha tan trong dung dch. V oxi cng cho

sng kh catot lm nh hng n sng kh ca cht phn tch. Nu dung

dch phn tch c mi trng axit yu hoc l kim th c thloi troxi ha

tan bng Na2S2O3tinh khit.

Bc 3: Cho cht nn thch hp vo.

Bc 4: Cho 2 cht hot ng bmt ( nhgielatin hoc metyl hay

aga-aga) gim s chnh lch sc cng bmt git thy ngn c li cho

phn tch. Cthgim c cc i loi 1 v cc i loi 2 trn ng cc

ph.




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Sau tin hnh ghi cc ph.

1.5.2 Phng php phhp thnguyn t: AAS [ 5, 19, 21]

1.5.2.1. Nguyn tc ca phng php AAS

Nguyn tc : Khi nguyn ttn ti tdo thkh v trng thi nng

lng cbn, th nguyn tkhng thu hay khng pht ra nng lng. Tc l

nguyn ttrng thi cbn. Song, nu chiu vo m hi nguyn ttdo

mt chm tia sng n sc c bc sng ph hp, trng vi bc sng vch

phpht xc trng ca nguyn tphn tch, chng shp thtia sng

sinh ra mt loi ph ca nguyn t. Ph ny c gi l ph hp th ca

nguyn t. Vi hai kthut nguyn tha, nn chng ta cng c hai php o

tng ng. l php o phhp thnguyn ttrong ngn la (F- AAS c

nhy c0,1 ppm) v php o phhp thnguyn tkhng ngn la (GF

AAS c nhy cao hn kthut ngn la 50- 1000 ln, c0,1- 1 ppb).

Csca phn tch nh lng theo AAS l da vo mi quan hgia

cng vch phv nng nguyn tcn phn tch theo biu thc:

A = a.Cx

C 2 phng php nh lng theo php o AAS l: phng php

ng chun v phng php thm tiu chun.

Thc tcho thy phng php phhp thnguyn tc nhiu u vit

nh:

nhy, chnh xc cao, lng mu tiu th t, tc phn tch

nhanh. Vi u im ny, AAS c th gii dng lm phng php tiuchun xc nh lng nhv lng vt cc kim loi trong nhiu i tng

khc nhau.

Php o phAAS c thphn tch c lng vt ca hu ht cc kim

loi v cnhng hp cht hu chay anion khng c phhp thnguyn t.

N c sdng rng ri trong cc ngnh : a cht,cng nghip ha hc, ha

du, y hc, sinh hc, dc phm...




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* Php o phc ngn la (F-AAS):

K thut F-AAS dng nng lng nhit ca ngn la n kh ho

hi v nguyn t ho mu phn tch. Do mi qu trnh xy ra trong khi

nguyn tho mu phthuc vo c trng v tnh cht ca ngn la n kh

nhng ch yu l nhit ngn la. y l yu t quyt nh hiu sut

nguyn tho mu phn tch, mi yu tnh hng n nhit ngn la

n kh u nh hng n kt quca phng php phn tch.

* Php o phkhng ngn la:

Gm: l graphit, b to hyrua (hydride vapor generator HVG), b

ha hi lnh phn tch thy ngn (MVU).

K thut khng ngn la ra i sau k thut c ngn la nhng

c pht trin rt nhanh, n nng cao nhy ca php xc nh ln gp

hng trm ln so vi kthut F-AAS. Mu phn tch bng kthut ny khng

cn lm giu sbv lng mu tiu tn t.

Kthut nguyn tha khng ngn la l qu trnh nguyn tho tc

khc trong thi gian rt ngn nh nng lng nhit ca dng in c cng

sut ln v trong mi trng kh tr(Argon). Qu trnh nguyn tho xy ra

theo cc giai on ktip nhau: sy kh, tro ho luyn mu, nguyn tho

o ph hp th nguyn t v cui cng l lm sch cuvet. Nhit trong

cuvet graphit l yu tquyt nh mi din bin ca qu trnh nguyn tho

mu.

1.5.2.2 Nhng u - nhc im ca php o

Cng nhcc phng php phn tch khc, phng php phn tch ph

hp thnguyn tcng c nhng u, nhc im nht nh l:

u im:

y l php o c nhy cao v chn lc tng i cao. Gn 60

nguyn tho hc c thxc nh bng phng php ny vi nhy t1.10-

4 1.10- 5 %.




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c bit, nu sdng kthut nguyn tho khng ngn la th c th

t ti nhy n.10- 7 %. Chnh v c nhy cao nn phng php phn

tch ny c sdng rt rng ri trong nhiu lnh vc xc nh lng

vt cc kim loi. Mt u im ln ca php o l: trong nhiu trng hp

khng phi lm giu nguyn tcn xc nh trc khi phn tch. Do , tn t

mu, t thi gian cng nhho cht tinh khit lm giu mu. Trnh c

s nhim bn khi x l mu qua cc giai on phc tp. c bit, phng

php ny cho php phn tch hng lot mu vi thi gian ngn, kt quphn

tch li rt n nh, sai snh.

Nhc im: Tuy nhin, bn cnh nhng u im php o AAS cng

c nhc im l ch cho bit thnh phn nguyn t ca cht trong mu

phn tch m khng chra trng thi lin kt ca nguyn ttrong mu.

1.5.3. Phng php quang phplasma ghp ni khi ph(ICP MS) [6,7, 31]

Kthut ICP MS l mt trong nhng kthut phn tch hin i c

khnng phn tch trn 60 nguyn ttrong bng h thng tun hon vi

nhy cao. Kthut ny c nghin cu v pht trin mnh trong nhng nm

gn y. Chnh v c nhng u im vt tri hn hn cc phng php phn

tch trc nn k thut ny c nghin cu v ng dng rt rng ri

trong nhiu i tng khc nhau, c bit l trong lnh vc phn tch vt v

siu vt, phc vnghin cu vt liu bn dn, vt liu ht nhn, mu a cht,

nng nghip, sinh hc, mi trng.

im mnh ca phng php ny l c thphn tch ng thi nhiu

nguyn t kim loi trong mt mu, c th phn tch nh lng, bn nh

lng. Ngoi ra k thut ny cn c thphn tch xc nh cc ng vca

mt nguyn ttrong cng mt i tng mu. V vy n c sdng mnh

mtrong phn tch, nh gi mc phi nhim c tkim loi trong nhiu

i tng sinh hc v mi trng.




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Hai phng php phn tch ICP ph bin hin nay l phng php

quang phpht xPlasma (ICP-AES) v ICP MS. u im ca hai phng

php ny so vi cc phng php thng thng khc l s dng ngun

plasma c th to ra nhit t 5000-100000C . Vi nhit ny c th

nguyn tha hon ton cc nguyn tcc nguyn tcn phn tch. So vi

ICP-AES th kthut ICP-MS c khnng phn tch tt hn bi v n c th

phn tch chnh xc cc ion khc nhau, xc nh cc ng vtrong mu da

trn gi tr t lM/z v c tnh ton theo cc ng chun c lp. Hiu

quphn tch ca ICP-MS so vi cc kthut phn tch khc nhquang ph

hp thnguyn t(AAS), ICP-OES, c nhiu nh khoa hc nghin

cu. Bng 1.4 cho thy khnng pht hin ca ICP-MS hn so vi cc k

thut khc.

Bng 1.3: So snh khnng pht hin ca cc kthut phn tch (ppb)STT Nguyn t ICP-MS ICP-AES F-AAS GFA-AAS

1 As < 0,050 < 20 < 500 < 1

2 Al < 0,010 < 3,0 < 50 < 0,5

3 Ba < 0,005 < 0,2 < 50 < 1,5

4 Be < 0,050 < 0,5 < 5 < 0,05

5 Bi < 0,005 < 20 < 100 < 1

6 Cd < 0.010 < 3,0 < 5 < 0,03

7 Ce < 0.005 < 15 < 200000 KPH

8 Co < 0,005 < 10 < 10 < 0,5

9 Cr < 0,005 < 10 < 10 < 0,1510 Cu < 0,010 < 5,0 < 5 < 0,5

11 Gd < 0,005 < 5,0 < 4000 KPH

12 Ho < 0,005 < 1,0 < 80 KPH

13 In < 0,010 < 30 < 80 < 0,5

14 La < 0,005 < 0,05 < 4000 KPH

15 Li < 0,020 < 1 < 5 < 0,5




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39

16 Mn < 0,005 < 0,5 < 5 < 0,06

17 Ni < 0,005 < 10 < 20 < 0,5

18 Pb < 0,005 < 20 < 20 < 0,5

19 Se < 0,10 < 50 < 1000 < 1

20 Tl < 0,010 < 30 < 40 < 1,5

21 U < 0,010 < 30 < 100000 KPH

22 Y < 0,005 < 0,5 < 500 KPH

23 Zn < 0,02 < 1,0 < 2 < 0,01

(KPH: khng pht hin c)

*Phng php ICP-MS c u im

- Phn tch nhanh v ng thi nhiu nguyn t- Gii hn pht hin thp thch hp phn tch lng vt v siu vt

- Khnng phn tch nh lng v bn nh lng

- C thphn tch v a ra y thng tin vcc ng vca mt

nguyn ttrong mt mu.

*Nhc im ca phng php

Kt quphn tch thng bnh hng bi cc kh: Argon, O2, H2vcc axit dng chun bmu v nhit cao chng bphn ng vi cc

nguyn ttrong mu to ra cc oxit, cc ht ion c cng khi lng vi

cc nguyn tcn phn tch. Tuy nhin nh hng ny c thc loi b

da vo cc kthut phn tch ca ICP-MS v la chn ng vthch hp

phn tch.

*Nguyn tc chung ca phng phpMu phn hy ti dng ng nht bng cc phng php phn hy mu

thch hp, sau c a vo phn tch trn thit bICP-MS. Mu dng

ng nht c sol ha thnh sol kh v a ti tm ngn la ICP, y xy

ra qu trnh nguyn tha v ion ha. Cc ion kim loi c thu nhn qua h

thng phn gii phtheo skhi (tskhi lng /in tch ion m/z) v c




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thu nhn cc tn hiu qua bnhn quang in. Pic phhoc sht thu nhn

c lu gitrong my tnh.

*Cc yu tnh hng n php o ICP-MS

- Nng mui nh hng t0,1 0,4%.

- ng vca cc nguyn tkhc nhau c skhi trng nhau. Skt

hp gia cc nguyn tto ra mt phn tmi c skhi trng vi skhi

ca nguyn tcn phn tch.

- Cc nguyn tkhi ion ha bc 1 hoc bc 2 scho cc skhi khc

nhau trng vi skhi ca nguyn tcn phn tch.

- nh hng ca mu phn tch trc.

*Phm vi ng dng ca phng php ICP-MS

Vit Nam, thit b ICP-MS c lp t v sdng trong mt s

vin nghin cu nhVin xhim, Vin nghin cu a cht-khong sn, Vin

cng nghmi trng, Khoa Ha hc-i hc khoa hc tnhin H Ni,..

Do c khnng phn tch hng lot cc nguyn tkim loi cng mt

lc vi nhy v chnh xc cao, nn ICP-MS c ng dng trong nhiu

ngnh nghkhc nhau nhcng nghluyn kim, chto my, a cht, lnh

vc mi trng,

1.6. Phng php xl mu phn tch xc nh Pb, Hg, Cd, As [10, 15,16, 26]

xc nh hm lng Pb, Hg, Cd, As trong rau xanh, trc ht ta

phi tin hnh xl mu nhm chuyn cc nguyn tcn xc nh c trong

mu ttrng thi ban u (dng rn) vdng dung dch. y l cng vic rtquan trng v c thdn n nhng sai lch c trong kt quphn tch do s

nhim bn hay lm mt cht phn tch nu thc hin khng tt. Hin nay c

nhiu k thut x l mu phn tch, vi i tng rau xanh th hai k thut

dng ph mu gm k thut tro ha t bng axit c hoc axit mnh

(phng php xl t) v kthut tro ha kh (phng php tro ha kh).




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1.6.1. Phng php xl t (bng axit c oxi ha mnh)

Nguyn tc ca phng php l dng axit c c tnh oxi ha mnh

nh(HNO3, HClO4), hay hn hp caxit c c tnh oxi ha mnh(HNO3

+ H2O

2)

phn h

y h

t cc ch

t h

u c

ca m

u trong bnh Kendan,

chuyn cc kim loi dng hu cvdng cc ion trong dung dch mui v

c. Vic phn hy c ththc hin trong hng kn (p sut cao), hay trong

hm(p sut thng). Lng axit thng phi dng gp t10- 15 ln lng

mu, ty thuc mi loi mu v cu trc vt l ha hc ca n. Thi gian

phn hy mu trong cc hm, bnh Kendan, ng nghim, cc thng t

vi gin vi chc gi, cng ty loi mu, bn cht ca cc cht, cn nu

trong l vi sng hkn th chcn vi chc pht. Thng khi phn hy xong

phi ui ht axit dtrc khi nh mc v tin hnh o ph.

u nhc im ca kthut ny l

- Khng mt mt skim loi nhPb, Fe, Zn, Cu

- Thi gian phn hulu, thng l t10 -12 gi.

- Tn nhiu axit tinh khit, axit dnhiu, phi ui axit sau khi

xl.

- Dgy nhim bn, nu cc ho cht khng c sch cao.

- Phi ui axit dlu, c khi kh khn khng ht c. ng

thi khi un ui axit lu li gy ra snhim bn hay bn mt

mu.

1.6.2. Phng php xl khNguyn tc: i vi cc mu hu c trc ht phi c xay nghin

thnh bt, va hay thhuyn ph. Sau dng nhit ha tro mu, t chy

cht hu cv a cc kim loi vdng oxit hay mui ca chng. Cthl:

Cn ly mt lng mu nht nh (5 -10 g) vo chn nung. Nung cht mu

nhit thch hp, t chy ht cc cht hu c, v ly b v ccn li

c

a cc mu l cc oxit, cc mu

isau

ha tan b thu

c trong axit v




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c nh HCl (1/1), HNO3 (1/2) chuyn cc kim loi v dng ion trong

dung dch.Quyt nh dng tro ha y l nhit nung v thi gian nung

(nhit tro ha v thi gian tro ha) v cc cht phgia thm vo mu khi

nung. Nhit tro ha cc cht hu c thng c chn thch hp trong

khong 400- 5500C, ty theo mi loi mu v cht cn phn tch.

Sdng phng php ny c nhng u nhc im nh:

- Tro ha trit c mu, ht cc cht hu c.

- n gin, dthc hin, qu trnh xl khng lu nhphng php

v cha t.

- Khng tn nhiu axit tinh khit cao, v khng c axit d.

- Hn chc snhim bn do dng t ha cht.

- Mu dung dch thu c sch sv trong.

- Nhng hay bmt mt snguyn tphn tch (Pb, Zn, Cu, Cd), nu

khng dng cht bo vv cht chy.

1.6.3. Phng php xl kh- t kt hp:

Nguyn tc: k thut ny l mu c nung trong chn hay cc nungmu. Trc tin ngi ta xl t sbtrong cc hay chn nung bng mt

lng nhaxit v cht phgia ph vsbcu trc ban u ca cc hp

cht mu, v to iu kin gimt snguyn tc thbay hi khi nung. Sau

mi em nung nhit thch hp. V vy lng axit chbng 1/4 hay 1/3

lng cn dng cho xl t, lng axit tinh khit cao stn t hn. Sau

em nung snhanh hn v qu trnh xl strit hn xl t v hn chc smt i mt skim loi khi nung. Do tn dng c trit u

im ca chai kthut xl t v kh v lm gim bt c cc ho cht

tinh khit cao, dung dch thu c trong v sch hn khi tro ho t.

u im ca kthut v cho mu kh - t kt hp

- Hn chc smt i ca mt scht phn tch.

- Stro ho l trit , sau khi ho tan tro sc dung dch mu.




43/77

43

- Khng phi dng nhiu axit tinh khit cao.

- Thi gian xl tro ho nhanh hn tro ho t.

- Khng phi ui axit dlu nn hn chc snhim bn do mi

trng.

- Ph hp cho nhiu loi mu khc nhau xc nh kim loi.

- Khng cn trang bphc tp nhl vi sng t tin.

1.6.4. Phng php xl mu nc:

i vi cc kim loi c thho tan tt trong axit nhZn, Cd, Cu . . .

sau khi ly mu cn axit ho ngay vi 3 5 ml dung dch HNO3/1lt H2O

trnh hp phkim loi ln bnh PE. Sau ly 100ml mu vo cc hoc bnhtam gic, thm vo 1ml HCl c c tinh khit cao lm bay hi trn bp

cch thy n gn cn kh, php thn HCl c c thc hin 2 ln, sau

ha tan b kh trong mt lng nc ct v em xc nh kim loi bng

phng php tng ng. Axit ho mu ti pH 2 nu cn thit mu trong

thi gian lu, nu mu c do c cht hu c l lng th c th lc sau

nh mc bng HNO3 0,03N n 50ml. i vi mu nc c cht d phnhy th cn dng HNO3c phn hy thay cho HCl c trn. Nu mu

nc c cht hu ckh phn hy th cn cho thm HClO4,HCl hoc H2SO4

c.




44/77

44

CHNG 2 THC NGHIM

2.1. Dng cv ha cht

2.1.1. Dng c

2.1.1.1. My o cc ph797 computrace (Metrohm Thy S).

Hnh 2.1: My o cc ph797 Computrace

Vic o v ghi kt qu c thc hin trn my o cc ph 797

Computrace do hng Metrohm (Thy S) sn xut.

Hin cc

Gm ba in cc:

* in cc lm vic (WE): in cc git thungn treo (HDME), lgit thy ngn c kch thc nh, ng knh 0,05-0,07mm, treo trn mt

mao qun, in cc ny c u im: Qu thca hidro ln ( Mi trng axit

- 1,2V cn mi trng trung tnh hay kim - 1,5V).Trn bmt in cc xy

ra qu trnh lm giu v ho tan cht cn phn tch.

* in cc so snh (RE): Ag AgCl KCl 3M in cc lun c

bo qun trong dung dch KCl bo ho.* in cc phtr(AE): in cc Pt

- Bnh in phnDung tch 50 ml, c chto tthy tinh thch anh. Np bnh c gn

cc in cc, ng dn kh tr(Ar hoc N2) nhm ui oxi ha tan trong dung

dch o v c mt motor nhgn vi que khuy khuy trn u dung dch




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45

o. Bnh in phn bao gm cc bphn: np gi y, bnh o, in cc lm

vic, in cc so snh, in cc ph tr, ng dn kh v que khuy.

- My vi tnh

Dng iu khin thit b, o, ghi v xl kt qu. Mi thng so

u c nhp t bn phm. Khi khng o, my tnh c th thc hin mi

chc nng khc ca mt my vi tnh c nhn thng thng.

- My in

My in HP Lazer Jet 1150 dng in cc d liu kt qu, thng s

php o, thao tc tin hnh php o, ghi ch, ng chun sau khi o, ghi

xong.

- Bbin i ADC-DAC v cc rle phi hpBbin i DAC 12 bit tc pht 3 s phi hp vi bbin i DAC

8 bit tc pht l lm cho bc nhy thc ththay i t0,224 mV n

2,24 mV. V vy tn hiu trn trong php o I - E.

B bin i ADC 100 s nhanh o cc tn hiu phn hi (ca

dng hoc th) trong cc php o in ho.

My khuy ba g, my sc kh ... c kt hp vi rle lm qu trnho c hon ton tng, chnh xc v lp cao c bit vi cc quy

trnh o phc tp nht nhcc phxung vi phn nhphi hp stripping.

- Phn mm 797 Computrace Application 2.0c lp trnh iu khin h thng, lu tr cc php o, qun l

thng so, xl hnh nh ph(thay i phng i, hslm trn, thay

i chmu, ng nt ph,...).

2.1.1.2. My o AAS, hthng chthkt qu: my tnh, my in,

H thng my quang ph hp th nguyn t AA 6300 ca hng

Shimadzu.




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46

Hnh 2.2: Hthng my quang phhp thnguyn tAA 6300

2.1.1.3. My Agilent 7500 Series ICP-MS

Hnh 2.3: Hthng Agilent 7500 Series ICP-MS

2.1.2. Thit bv dng ckhc

- My tnh xl sliu trn phn mm Excel.-Cn phn tch chnh xc 10-4g, cn kthut.

-My o pH.

-L nung, tsy.

-Bp in, my khuy tgia nhit.

-Tha thy tinh, a thy tinh, ng ht ha cht.

-Pipet 5 ml, 10 ml.

-ng ong 50 ml.

-Cc thy tinh 50 ml, 100 ml, 500 ml.

-Bnh nh mc 25 ml, 50 ml, 100 ml, 250 ml, 500 ml, 1000 ml.

-Phu thy tinh.

-Giy lc.




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47

-Dao inox.

-Chu thy tinh.

-Bt s, chn s, chy s, ci s.

-Kp g

Cc dng cthy tinh u c ra sch bng dung dch HNO3v hn

hp ra K2Cr2O7v H2SO4c sau trng li nhiu ln bng nc ct 2 ln.

2.1.3. Ha chtCc dung dch gc Pb2+1000 ppm, Cd2+1000 ppm HNO3 c, HCl c,

HClO4, H2O2, Mg(NO3)2, nc ct hai ln.

Cc ha cht

c pha ch dng trong qu trnh th nghi

m, HNO

3

10%, HCl 2N, H2O230%, Mg(NO3)210%

2.2 . Ly mu v xl mu

2.2.1. Ly muCc mu rau c ly ti cc a im khc nhau thnh ph Lt.

Cc mu sau khi ly c ghi km theo cc thng tin vvtr ly mu, thi

gian v loi mu.

Bng 2.1: Vtr ly mu v k hiu mu

Vtr ly mu Tn mu K hiu mu Ngy ly mu

Phng 7 Sp lxanh M1 06/06/2012

Phng 5 Bp ci M2 06/06/2012

Phng 8 Hnh ty M3 06/06/2012

Phng 8(nc h)

Nc ti rau M4 06/06/2012

Phng 5(nc ging)

Phng 7(nc ging)

Mi mu rau c ly nhiu im trn cng mt vn rau:




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Hnh 2.4 Rung sp l

- Mu 1 c ly rung thp, khu ny nc ti l nc ging c

bm vo, khu vn rau ny khng c hnc ti bn cnh.

Hnh 2.5 Rung bp ci

- Mu 2 c ly rung cao ti nc ti ging bm.

Hnh 2.6 Rung hnh ty

- Mu 3 c ly rung cnh nh , ti nc h




49/77

49

- Mu nc ti nhng im trn trn li ng trong chai nha PE,

sau khi ly mu, axit ho ngay bng 3 - 5 ml HNO3m c cho 1 lt nc

trnh hp phkim loi ln bnh PE.

2.2.2. Xl mu

2.2.2.1. Xl sbv bo qun mu

Mu rau sau khi c ly cc a im trn c ng trong ti nilon

sch, ghi nhn v a vphng th nghim. Ra sch t bm trn rau, b

phn gi, chgili phn n c, dng dao lm bng thp khng gv tht

gtrng li bng nc ct mt vi ln. ro nc, cn trng lng ti ri

sy khong 50-600C cho n kh. Chuyn mu rau kh vo bnh ht mngui, em cn li xc nh trng lng kh, ri nghin mu ti mn.

Sau mu c ng trong lkn trnh m mc. Tt ccc lng rau

u c dn nhn ghi r: tn mu, loi rau, thi gian, a im ly mu.

Bng 2.2: Tlkhi lng ca mt sloi rau trc v sau khi sy kh.

Mu Loi rau Khi lng sau v

trc khi sy (g)

Hskh/ti

(%)M1 Sp lxanh 96,02/1000 9,602M2 Bp ci 37,03/1000 3,703M3 Hnh ty 45,11/1000 4,511

2.2.2.2. Xl mu

i vi mu rau: Vic xc nh Cd, Pb, Hg, As ta c thdng phng

php xl mu kh, phng php xl mu t hoc phng php kh t

kt hp. Chng ti chn phng php v cha t xl mu chun bcho php o cc ph. Mu c xl trong hmiu kin thng bng

HNO365% v H2O230%.

Nguyn tc ca phng php l: Dng mt axit c c tnh oxi ho

mnh, hay hn hp cc axit c c tnh oxi ho mnh, hay mt axit c tnh oxi

ho mnh v mt axit khng c tnh oxi ho nh(HNO3+ HCl), hay (HF +

HClO4),

phn hu

ht cc ch

t h

u c

c

a mu trong bnh ken

an,




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50

chuyn ht cc kim loi dng hu cvdng cc ion trong dung dch mui

v c. Vic phn hu c th thc hin trong hng kn p sut cao (l vi

sng) hay hm(p sut thng). Lng axit thng dng phi gp t10

15 ln lng mu, thi gian t10 12 ginn khi phn huxong phi ui

ht axit d. Sphn hy mu l do hai tc nhn ng thi xy ra l : nng

lng nhit, axit c.

Mu c xl nhsau:Cn 5 gam mu kh nghin thnh bt mn cho vo bnh Kendal, cho

tip 70 - 75ml HNO3c (65%) vo trong bnh, sau thm tip 5ml H2O2

(30%) vo bnh, y bnh bng phu lc c ui di. un mu phn tch

1800C 2000C trong 10 n 12 gin khi ht khi nu, axit d thu c

mui m trng.

Mu trng: cho vo 70 - 75ml axit HNO3c v 5ml H2O2un cho

n khi cn hon ton

nh mc tt cmui m v mu trng thnh 25ml bng HNO310%

i vi mu nc: cho100ml mu nc vo bnh tam gic, thm vo

1ml HCl c c tinh khit cao lm bay hi trn bp cch thy n gn cn

kh, php thn HCl c c thc hin n khi khi c mui m, sau

nh mc b kh bng dung dch HCl 2N v em xc nh kim loi bng

phng php tng ng.

2.3. Pha cc dung dch cn cho nghin cu

2.3.1. Pha cc dung dch cho php o cc ph- Pha chdung dch Pb2+

Ly 0,1 ml dung dch Pb2+1000 ppm cho vo bnh nh mc 50 ml ri

nh mc bng nc ct n vch thu c dung dch Pb2+2 ppm.

Cc dung dch Pb2+c nng 0,1 ppm, 0,3 ppm, 1 ppm ... c pha

long tdung dch Pb2+2 ppm.

- Pha chdung dch Cd2+




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51

Ly 0,1 ml dung dch Cd2+1000 ppm cho vo bnh nh mc 50 ml ri

nh mc bng nc ct n vch thu c dung dch Cd2+2 ppm.

Cc dung dch Cd2+c nng 0,1 ppm, 0,3 ppm, 1 ppm ... c pha

long tdung dch Cd2+2 ppm.

2.3.2. Pha chdung dch khc

- Pha chdung dch Mg(NO3)210%

Cn chnh xc 10 gam Mg(NO3)2, sau thm vo 90 ml nc ct hailn thu c dung dch Mg(NO3)210%.

- Pha chdung dch HNO310 %

Ly chnh xc 16,9 ml dung dch HNO3c 65% (d = 1,4 g/ml) cho vobnh nh mc 100 ml c cha sn 50 ml nc ct hai ln sau cho t t

nc ct n vch mc.

- Pha chdung dch HCl 2N

Ly chnh xc 16,5 ml dung dch HCl c 37% (d = 1,19 g/ml) cho vo

bnh nh mc 100ml cha sn 50ml nc ct hai ln sau cho ttnc

ct n vch mc.

2.4. Qui trnh thc nghim

2.4.1. Xc nh hm lng Pb, Cd trong mt smu rau v trong nc

ti bng phng php cc phthc hin ti i Hc Vinh.

Qu trnh phn tch cc phgm cc bc cthsau :

- Bc 1: Cho dung dch phn tch vo bnh in phn.- Bc 2: Sc kh H2 hoc N2 nguyn cht vo dung dch bnh in

phn trong vng 10 pht loi troxi ha tan trong dung dch. V oxi

cng cho sng khcatot lm nh hng n sng kh ca cht phn

tch. Nu dung dch phn tch c mi trng axit yu hoc l kim th

c thloi troxi ha tan bng Na2S2O3tinh khit.

- Bc 3: Cho cht nn thch hp vo.




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- Bc 4: Cho 2 cht hot ng bmt (nhgielatin hoc metyl hay

aga-aga) gim schnh lch sc cng bmt git thy ngn c li

cho phn tch. C thgim c cc i loi 1 v cc i loi 2 trn

ng cc ph. Sau tin hnh ghi cc ph.

iu kin chung xc nh hm lng Pb, Cd trong mt smu rau v trong

nc ti bng phng php cc ph:

- in cc lm vic l git treo thy ngn HMDE.

- in cc so snh l in cc Ag AgCl.

- in cc ph trPt.

- Phng php phn tch: phng php thm chun.

- Sln thm: 2.

- Cgit: 4.

- Tc khuy: 2000 rpm.

- Qut tht-1,2V n - 0,7V.

- Bin xung: 0,05V.

- Thi gian mi bc th: 0,04s.

- Bc th: 0,0006V.

- Tc qut th: 0,15V.

- Thi gian sc kh: 300s.

- Thi gian sc kh cho mi ln thm dung dch chun: 30s.

- Thi gian din phn: 60s.

- Thi gian vn bng: 5s

2.4.2. Xc nh ng thi hm lng Pb, Hg, Cd, As trong mu rau v

trong nc ti bng phng php quang phhp thnguyn t(AAS)

Gi mu c sy kh vo phng phn tch trung tm i hc khoa

hc tnhin thnh phHCh Minh. Mu c ph bng phng php v c

ha t trong hkn




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53

Bng 2.3 Qui trnh xl mu trn my vi sng Anton Paar Multiwave 3000

Thng skthut

Khi lng mu (g) 1Thuc thoxy ha 10 ml HNO3v 2 ml H2O230%Nng lng vi sng(W) 600Thi gian chiu vi sng (pht) 10 (Ramp) & 20 (Hold)p sut (bar) 20Nhit (oC) 200

Bng 2.4iu kin o mu trn my phhp thu nguyn tngn la ShimadzuAAS 6300 cho hai nguyn tCd, Pb

Thng skthut Cd Pb

Cng n (mA) 8 12 10Bc sng (nm) 228.8 217.0 283.3Brng khe (nm) 0.7 0.7 0.7Hiu chnh nn D2 D2 D2Chiu cao u t (mm) 7 7 7Gc nghing u t ( ) 0 0 0Tc kh nguyn liu axetylen(L/pht)

1.8 2.0 2.0

Kh btr Khng kh Khng kh Khng kh

iu kin o trn my bng phng php HVG-AAS cho nguyn tAsbng kthut hidruaMu c v cho trong l ph mu vi sng c t chng trnh theo

tng i tng, As (V) c khvAs (III) v phn ng vi natri bohidrua

to thnh hp cht hydrua arsen (AsH3), hp cht ny c dn ti cuvet

chT nguyn tha v o phhp thca As

Bng 2.5iu kin o trn my bng phng php HVG-AAS cho nguyn tAs

Nguyn t AsThuc thha hi 0.2 % (w/v) NaBH4 trong HCl

3MNgun sng n sc n phng in phi in cc

(EDL)Cng n (mA) 379

Bc sng (nm) 193.7




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Khe 0.7 HNhit nguyn tha(C)

892 2

Kh mang Argon

iu kin o trn my bng phng php MVU-AAS cho nguyn tHgXc nh hm lng thy ngn bng kthut ho hi lnh

Mu c v cho trong l ph mu vi sng c t chng trnh theo

tng i tng. Hg(II) c chuyn vHg(0) bng SnCl2v hi thy ngn

bay ln c a ti hthng quang phhp thnguyn to ph.

Bng 2.6iu kin o trn my bng phng php MVU-AAScho nguyn tHg

Nguyn t HgThuc thha hi 10 % (w/v) SnCl2trong 20 % HClNgun sng n sc n cathod rng thy ngn (HCL)Cng n (mA) 15Bc sng (nm) 253.7Khe 0.7 HNhit nguyn tha(C)

50 2

Kh mang Argon

2.4.3. Xc nh tng svi lng Pb, Hg, Cd, As trong mu rau v trong

nc ti bng phng php quang phplasma ghp ni khi ph

Gi mu c sy kh vo phng phn tch trung tm i hc Khoahc tnhin thnh phHCh Minh.

Bng 2.7 Thng so trn ICP-MS 7500 Series Agilent

Thng skthutRF power (W) 1500Ion lenses Extrac 1: 5.3 V

Etract 2 : -100.0VCarries gas 0.9 L/phtMakeup gas 0.28 L/phtReaction cell He gas 4.0 mL/phtDetector Discriminator: 8.0 mV




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Analog HV: 1740 VPulse HV: 1060 V

Ion Cd Pb As Hg114 208 75 202

2.5. Xl cc sliu tkt quo c

Xl sliu tkt quo cc ph: Mu c v cha t5g mu

kh vthnh mui m v nh mc thnh 25ml dung dch mang o cc ph,

tkt qucc pho c ta tnh hm lng kim loi nng trong 1kg mu

kh, ri dng hskh ti (bng 2.2) tnh hm lng kim loi trn 1kg mu

ti.Xl cc kt quo bng phng php AAS v ICP MS: tkt qu

c c (ph lc 1) dng h s kh ti tnh hm lng kim loi trn 1kg

mu ti.

So snh kt quphn tch mu rau vi gii hn an ton ca kim loi

nng: Pb, Cd, Hg, As trong thc phm theo qui nh gii hn ti a nhim

sinh hc v ha hc trong thc phm ca by t(Ban hnh km Quyt nhs46 /2007/Q-BYT ngy 19 thng 12 nm 2007 ca Btrng BY t).

So snh kt qu phn tch mu nc theo cht lng nc dng cho

thuli (mg/l), TCVN 6773 2000 (BKH v CNMT, 2002 ).




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Cd, Pb trong mau nuoc Da Lat

Kim Ngan CH18 Vo co

-0.80 -0.70 -0.60 -0.50 -0.40 -0.30 -0.20

U (V)

0

20.0n

40.0n

60.0n

80.0n

100n

I(A)

Cd

Pb

CHNG 3: KT QUV THO LUN

3.1. Kt quxc nh hm lng Pb, Cd trong mu rau v trong nc ti

bng phng php cc ph

3.1.1. Kt quxc nh hm lng ch

Bng 3.1 Kt quxc nh hm lng ch bng phng php cc pha im ly mu Tn mu Hm lng Pb (mg/kg ti)

Phng 7 Sp lxanh 0,036Phng 5 Bp ci 0,014Phng 8 Hnh ty 0,042Nc ti rau Nc 3,75.10-3

3.1.2. Kt quxc nh hm lng cadimi

Bng 3.2 Kt quxc nh hm lng cadimi bng phng php cc ph

a im ly mu Tn mu Hm lng Cd (mg/kgt

i)Phng 7 Sp lxanh 6,743.10-3Phng 5 Bp ci 0,543.103Phng 8 Hnh ty 9,938.10- Nc ti rau Nc 0,581.10-3

3.1.3. Cc ng cong cc phthu c khi xc nh ng thi hm

lngPb, Cd trong mu trng v trong mu thc nghim

Hnh 3.1ngcong cc phmunc Lt




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Cd, Pb trong mau trang nuocKim Ngan CH18 Vo co

-0.80 -0.70 -0.60 -0.50 -0.40 -0.30 -0.20

U (V)

0

20.0n

40.0n

60.0n

80.0n

I(A)

Cd

Pb

Cd, Pb trong mau Sup lo Da LatKim Ngan CH18 Vo co

-0.80 -0.70 -0.60 -0.50 -0.40 -0.30 -0.20

U (V)

10.0n

20.0n

30.0n

40.0n

50.0n

I(A)

Pb

Cd

Final results +/- Res. dev. % Comments----------------------------------- ------------------ -------------------Cd: Cadmium = 7.309 ug/L 0.386 5.277Pb: Lead = 0.481 mg/L 0.017 3.486

Hnh 3.2ng congcc phmu trngnc Lt


Hnh 3.3: ng congcc phmu sp lxanh




58/77

58

Cd, Pb trong mau Bap Cai Da LatKim Ngan CH18 Vo co

-0.80 -0.70 -0.60 -0.50 -0.40 -0.30 -0.20

U (V)

0

50.0n

100n

150n

200n

I

(A)

Cd

Pb

Cd, Pb trong mau Hanh Tay Da LatKim Ngan CH18 Vo co

-0.80 -0.70 -0.60 -0.50 -0.40 -0.30 -0.20

U (V)

0

20.0n

40.0n

60.0n

80.0n

100n

120n

I(A)

Pb

Cd

Final results +/- Res. dev. % CommentsCd: Cadmium = 2.809 ug/L 0.718 8.547Pb: Lead = 0.126 mg/L 0.006 4.404

Hnh 3.4ng cong cc

phmu bp ci


Hnh 3.5ng cong ccphmu hnh ty

Final results +/- Res. dev. % Comments




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Cd, Pb trong mau Trang RauKim Ngan CH18 Vo co

-0.80 -0.70 -0.60 -0.50 -0.40 -0.30 -0.20

U (V)

0

25.0n

50.0n

75.0n

100n

125n

150n

I(A)

Pb

Cd

Cd: Cadmium = 4.406 ug/L 0.756 17.156Pb: Lead = 0.299

mg/L 0.007 2.396

Hnh 3.6 ng cong ccph mu trng rau

Final results +/- Res. dev. % Comments----------------------------------- ------------------ -------------------Cd: Cadmium = --- ug/L No result foundPb: Lead = 0.111 mg/L 0.004 3.966

3.2. Kt quxc nh ng thi hm lng Pb, Cd, Hg, As trong mu rau

vtrong nc ti bng phng php phhp thnguyn tAAS


Bng 3.3 Kt quxc nh hm lng ch bng phng php AAS

a im ly mu Tn mu Hm lng Pb (mg/kg ti)Phng 7 Sp lxanh 0,030Phng 5 Bp ci 0,029Phng 8 Hnh ty 0,042

Nc ti rau Nc < 0,05


Bng 3.4 Kt quxc nh hm lng cadimi bng phng php AAS

a im ly mu Tn mu Hm lng Cd mu ti(mg/kg)

Phng 7 Sp lxanh 0,011Phng 5 Bp ci 9,628.10-3

Phng 8 Hnh ty 7,082.10-3




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Nc ti rau Nc < 0,04

3.2.3. Kt quxc nh hm lng thy ngn

Bng 3.5 Kt quxc nh hm lng thy ngn bng phng php AAS

a im ly mu Tn mu Hm lng Hg mu ti(mg/kg)

Phng 7 Sp lxanh KPHPhng 5 Bp ci KPHPhng 8 Hnh ty KPHNc ti rau Nc KPH

3.2.4. Kt quxc nh hm lng asen

Bng 3.6 Kt quxc nh hm lng asen bng phng php AAS

a im ly mu Tn mu Hm lng As mu ti(mg/kg)

Phng 7 Sp lxanh KPHPhng 5 Bp ci KPHPhng 8 Hnh ty KPHNc ti rau Nc 2,23.10-3

3.3. Kt quxc nh ng thi hm lng Pb, Cd, Hg, As trong mu rauv trong nc ti bng phng php quang ph plasma ghp ni khi

phICP-MS


Bng 3.7 Kt quxc nh hm lng ch bng phng php ICP MS

a im ly mu Tn mu Hm lng Pb mu ti(mg/kg)

Phng 7 Sp lxanh 0,029Phng 5 Bp ci 0,028Phng 8 Hnh ty 0,042Nc ti rau Nc 0,019




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Bng 3.8 Kt quxc nh hm lng cadimi bng phng php ICP MS

a im ly mu Tn mu Hm lng Cd mu ti(mg/kg)

Phng 7 Sp lxanh 9,698.10-3

Phng 5 Bp ci 9,295.10-3Phng 8 Hnh ty 6,631.10- Nc ti rau Nc 0,015

3.3.3. Kt quxc nh hm lng thy ngnBng 3.9 Kt quxc nh hm lng thy ngn bng phng php ICP MS

a im ly mu Tn mu Hm lng Hg mu ti(mg/kg)

Phng 7 Sp lxanh KPHPhng 5 Bp ci KPHPhng 8 Hnh ty KPHNc ti rau Nc KPH

3.3.4. Kt quxc nh hm lng asen

Bng 3.10 Kt quxc nh hm lng asen bng phng php ICP MSa im ly mu Tn mu Hm lng As mu ti

(mg/kg)Phng 7 Sp lxanh KPHPhng 5 Bp ci KPHPhng 8 Hnh ty KPHNc ti rau Nc 2,43.103

3.4. So snh kt quphn tch vi gii hn an ton ca kim loi nng

3.4.1. So snh kt quphn tch vi gii hn an ton ca kim loi nng:

Pb, Cd, Hg, As trong thc phm

Qua cc phng php phn tch thc hin chpht hin hai kim loi

ch v cadimi c trong cc mu rau, cn hai kim loi thy ngn v asen khng

tm thy. Chng ti so snh kt quphn tch c vi gii hn an ton kim

loi nng trong th

c ph

m theo qui

nh gi

i h

n t

i

a nhim sinh h

c v




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ha hc trong thc phm (Ban hnh km Quyt nh s46 /2007/Q-BYT

ngy 19 thng 12 nm 2007 ca Btrng BY t)nhsau:

Bng 3.11 So snh kt quphn tch vi gii hn an ton ca kim loi nng: Pb,Cd, Hg, As trong thc phm

Tn mu

Kt quphn tchch (Pb)bng cc phngphp (mg/kg)

Gii hn antonchtrong

thc phm(mg/kg)Cc ph AAS ICP - MS

Sp lxanh 0,036 0,030 0,029 0,1Bp ci 0,014 0,029 0,028 0,3Hnh ty 0,042 0,042 0,042 0,1

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XÁC ĐỊNH HÀM LƯỢNG CÁC NGUYÊN TỐ ĐỘC HẠI Pb, Hg, Cd, As TRONG MỘT SỐ LOÀI RAU Ở VÙNG TRỒNG RAU ĐÀ LẠT