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Phng php ph hp th nguyn t ngdng phn tch tch tn d kim loi nngtrong thc phm

TS: L Th Hng HoTrung tm KN-VSATTP

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QU THNH PHT TRIN PH NGUYN T

1950 1960 1970 1980 1990

ph pht x

hp th nguyn t

nguyn t hunh quang

ICPS

year

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Khong nng phn tch

ICP-MS

pht xAAS ngn

laAAS khng ngn la

1 ppt 1 ppb 1 ppm 0.1% 100%

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E2

E1e-

hn

E = E2 - E1

= hn

l = hc/ (E2 - E1 )

E2 = trng thi kch thch

E1 = trng thi c bnh = hng s Planckn = Spectral frequency

Hp th nguyn t

l = c / v

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H thngAAS

Ngun sng

gng

MONOCHROMATOR

DETECTORGhi nhn tn

hiu

Nguyn tho

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H thngAAS

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H thngAAS(1) ngun bc x (n catot rng)

Ngun sng

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Ngun pht bc x n sc

Phi l cc tia bc x nhy i vi nguyn t cn phn tch,chm tia sng phi c cng n nh, lp li c trong ccln o khc nhau trong cng iu kin v phi iu chnh c c cng cn thit trong mi php o (bng dng in lmvic ca HCL).

Ngun pht tia bc x to c chm bc x thun khit, chbao gm mt s vch nhy c trng ca nguyn t phn tch.Ph nn ca n phi khng ng k.

Chm tia pht x n sc do ngun cung cp phi c cng

cao. Nhng li phi bn vng theo thi gian v phi khng bcc yu t vt l khc nhiu lon, t b nh hng bi cc daong ca iu kin lm vic. Ngoi ra, khng qu t v khngqu phc tp khi s dng.

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n Catot rng

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N PHNG IN KHNG IN CC

Ngunbc x mnh hn n catot rnggp 10 ln

sdng cho As, Se, Te, Hg, Pb nhngnguyn t km nhyvin catot rng.

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(2) Nguyn t ho

nguyn t ho

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Nguyn t ho

L qu trnh ho hi v nguyn t ho chtphn tch thnh nguyn t t do

Dung dich

Phun kh

Son kh Nguyn

t t doNhit

Ngn la

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Cc dng nguyn t ho

(1)Ngn la

(2) Khng ngn la- L graphit AAS (GFA)

- hydride vapor generator (HVG)

- mercury vapor unit (MVU)

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Ngn la

Ngn la l s oxi ho c kt hp bi khng kh,NO2, Ar, H2, acetylene.

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Qutrnh nguyn t ho trong ngn la

Dung dch

Ho hi

Bay hi

Son kh ho

Son kh

Nguyn t hoNguyn t t do

Nguyn tc bit

Ion cbit

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Qutrnh nguyn t ho khngngn la

(1) L graphite AAS (GFA)

(2) Hydride vapor generator (HVG)

(3) Mercury vapor unit (MVU)

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L graphite AAS

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Qutrnh nguyn t ho trong l

Chuyn

Dung dch muDung dch

sy

Bt kh

Nguyen t ho

Vapor

Nguyn tc bit

Ion cbit

Free atoms

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Cc bc thay i nhit trong l

Lm kh

Tro ho

Nguyn t ho

Nhit(oC)

Thi gian (s)Outer gas (Ar)

Inner gas (Ar)

Inner gas (O2)0 20 35 50 54

Lm sch

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Cc loi cuvet nguyn t ho mu

Than ch

Pyrolytic

Platform

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Graphite Furnace Tubes

L bm mu

Cuvet graphite

L bm mu

Cuvet pyrolytic

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Cuvet Platform

im bm mu

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Qutrnh nguyn t ho khngngn la

(1) Graphite furnace

(2) Hydride vapor generator (HVG)

(3) Mercury vapor unit (MVU)

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Hydrid ho (HVG)

Se, As, Sn, Sb, Te

Bi

Ho hi Hydride

Nguyn t ho

Ngn la Nhit

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Hydrid ho (HVG)

BH4- + 3H2O + H

+ H3BO3 + 4H2

3BH4- + 3H + + 4H3AsO3 4AsH3 + 3H2O + 3H3BO3

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Hydrid ho (HVG)

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Flameless AAS

(1) Graphite furnace AAS (GFA)

(2) Hydride vapor generator (HVG)

(3) Mercury vapor unit (MVU)

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Ho hi lnh (MVU)

Ion thu ngn trong dung dch c kh

bi SnCl2to thnh nguyn tthu ngn ckhnng bay hinhit phng.

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B ho hi thu ngn (MVU)

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Mercury Vapor Unit (MVU)

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Detector - Photomultivlier

L mt loi dng c quang hc dng thu nhn v phthin tn hiu quang hc theo hiu ng quang in ca n.Trc y thu nhn ngi ta dng knh nh hay

phim nh, sau l t bo quang in. l cc dng cc in vi nhy km.

Vi s pht trin ca khoa hc v k thut, ngy nay ngita ch to ra c nhiu loi detector quang hc c thkhuch i tn hiu o c ln c triu ln. l cc ngnhn quang in.

Nhn quang in kiu ng l mt loi dng c thu nhn

tn hiu quang hc c tnh cht vn nng, n c nhy v chn lc cao. Vng ph hot ng ca cc detector kiuny thng l t 190 900 nm, c khi n 1100 nm. H skhuch i thng n 106, i khi n 107.

C t h h

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Cc yu t gy nh hng n qutrnh o hp th nguyn t

nh hng ca nng axt v loi axttrong dung dch mu:Nng axt lmthay i nht ca dung dch, do aniongc axt quyt nh. Cc axt cng kh bayhi thng cng lm gim cng vchph. Cc axt d bay hi gy nh hng t.

Axt lm gim hp th theo th t HCl