Phng php ph hp th nguyn t ng dng phn tch tch tn d kim loi nng trong thc phmTS: L Th Hng HoTrung tm KN-VSATTP

QU THNH PHT TRIN PH NGUYN Tph pht xhp th nguyn tnguyn t hunh quangICPSyear

Khong nng phn tch ICP-MSpht x AAS ngn laAAS khng ngn la1 ppt 1 ppb 1 ppm 0.1% 100%

E2E1e-hnE2 = trng thi kch thch E1 = trng thi c bnh = hng s Planckn = Spectral frequency Hp th nguyn tl = c / v

H thng AASNgun snggngMONOCHROMATORDETECTORGhi nhn tn hiuNguyn t ho

H thng AAS

H thng AAS (1) ngun bc x (n catot rng)Ngun sng

Ngun pht bc x n scPhi 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 cc ln o khc nhau trong cng iu kin v phi iu chnh c c cng cn thit trong mi php o (bng dng in lm vic ca HCL).Ngun pht tia bc x to c chm bc x thun khit, ch bao 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 b cc yu t vt l khc nhiu lon, t b nh hng bi cc dao ng ca iu kin lm vic. Ngoi ra, khng qu t v khng qu phc tp khi s dng.

n Catot rng

N PHNG IN KHNG IN CCNgun bc x mnh hn n catot rng gp 10 ln

s dng cho As, Se, Te, Hg, Pb nhng nguyn t km nhy vi n catot rng.

(2) Nguyn t ho nguyn t ho

Nguyn t hoL qu trnh ho hi v nguyn t ho cht phn tch thnh nguyn t t doPhun khSon khNguyn t t doNhitNgn la

Cc dng nguyn t ho(1) Ngn la(2) Khng ngn la - L graphit AAS (GFA) - hydride vapor generator (HVG) - mercury vapor unit (MVU)

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

Qu trnh nguyn t ho trong ngn la Dung dchHo hiBay hiSon kh hoSon khNguyn t hoNguyn t t doNguyn t c bitIon c bit

Qu trnh nguyn t ho khng ngn la(1) L graphite AAS (GFA)(2) Hydride vapor generator (HVG)(3) Mercury vapor unit (MVU)

L graphite AAS

Qu trnh nguyn t ho trong lChuynDung dch muDung dchsyBt khNguyen t hoVapor Nguyn t c bitIon c bitFree atoms

Cc bc thay i nhit trong l Lm khTro hoNguyn t hoNhit (oC)Thi gian (s)Outer gas (Ar)Inner gas (Ar)Inner gas (O2)020355054Lm sch

Cc loi cuvet nguyn t ho muThan ch

Pyrolytic

Platform

Graphite Furnace TubesCuvet graphite Cuvet pyrolytic

Cuvet Platform

Qu trnh nguyn t ho khng ngn la(1) Graphite furnace(2) Hydride vapor generator (HVG)(3) Mercury vapor unit (MVU)

Hydrid ho (HVG)

Hydrid ho (HVG)

Hydrid ho (HVG)

Flameless AAS(1) Graphite furnace AAS (GFA)(2) Hydride vapor generator (HVG)(3) Mercury vapor unit (MVU)

Ho hi lnh (MVU) Ion thu ngn trong dung dch c kh bi SnCl2 to thnh nguyn t thu ngn c kh nng bay hi nhit phng.

B ho hi thu ngn (MVU)

Mercury Vapor Unit (MVU)

Detector - Photomultivlier L mt loi dng c quang hc dng thu nhn v pht hin 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 c c in vi nhy km. Vi s pht trin ca khoa hc v k thut, ngy nay ngi ta ch to ra c nhiu loi detector quang hc c th khuch i tn hiu o c ln c triu ln. l cc ng nhn 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 kiu ny thng l t 190 900 nm, c khi n 1100 nm. H s khuch i thng n 106, i khi n 107.

Cc yu t gy nh hng n qu trnh o hp th nguyn t nh hng ca nng axt v loi axt trong dung dch mu: Nng axt lm thay i nht ca dung dch, do anion gc axt quyt nh. Cc axt cng kh bay hi thng cng lm gim cng vch ph. Cc axt d bay hi gy nh hng t. Axt lm gim hp th theo th t HCl < HNO3 < H2SO4 < H3PO4 < HF. (HCl, HNO3 1%)

Cc yu t gy nh hng n qu trnh o hp th nguyn t nh hng ca cc cationTrong dung dch phn tch, ngoi nguyn t cn xc nh cn cha nhiu cation l. nh hng ca cc cation c th c hiu ng dng, hiu ng m hoc va c hiu ng dng va c hiu ng m cc nng khc nhau. loi tr nh hng ca cc cation s dng mt s bin php sau:* Chn iu kin x l mu ph hp loi cc nguyn t l ra khi dung dch phn tch* Chn cc thng s my o thch hp* Chn iu kin th nghim v iu kin nguyn t ho mu thch hp* Thm vo mu cht ph gia ph hp loi tr nh hng ca cc cation nh: LaCl3, SrCl3, AlCl3.

Cc yu t gy nh hng n qu trnh o hp th nguyn t nh hng ca cc anionnh hng ca cc anion v c bn cng tng t nh nh hng ca cc loi axt. Ch c 2 anion ClO4- v CH3COO- l gy hiu ng dng, cn cc anion khc gy hiu ng m theo th t Cl- < NO3- < CO32- < PO43- < F-. nh hng ca cc anion khng ln nh cc cation, nn loi tr nh hng ca cc anion ta ch cn trong mi php o phi cho nng ca cc anion trong mu phn tch v trong mu chun nh nhau l c.Php phn tch o ph hp th nguyn t cn b nh hng ca mt lot yu t khc na nh: Thnh phn nn ca mu, dung mi hu c, nht v sc cng b mt ca dung dch mu, s ion ho, s kch thch ph pht x, s chen ln ca vch ph, s hp th ca nn, thu c kt qu tt, khi lm th nghim phi khng ch dung dch phn tch v dung dch chun phi c tin hnh trong cng iu kin v tin hnh o vi cc thng s ti u hon ton nh nhau.

Nhng u im v nhc im ca php o AAS u im D nhy v chn lc cao. Gn 60 nguyn t ho hc c th xc nh bng phng php ny vi nhy t 10-4 n 10-5%. c bit nu s dng k thut nguyn t ho khng ngn la th c th t n nhy 10-7%. Chnh v c nhy cao nn phng php phn tch ny c s dng rng ri trong nhiu lnh vc xc nh lng vt cc kim loi. c bit l trong phn tch cc nguyn t vi lng trong cc i tng mu y hc, sinh hc, nng nghip, kim tra cc ha cht c tinh khit cao.ng thi cng do c nhy cao nn trong nhiu trng hp khng cn phi lm giu kim loi cn xc nh trc khi phn tch. Do tn t nguyn liu mu, tn t thi gian khng cn phi dng nhiu ho cht tinh khit cao khi lm giu mu. Mt khc cng trnh c s nhim bn khi x l qua cc giai on phc tp. cng l mt u im ln ca php o ph hp th nguyn t.Cc ng tc thc hin nh nhng. Cc kt qu phn tch c th ghi li trn bng giy hay gin lu gi li sau ny. ng thi vi cc trang thit b hin nay ta c th xc nh ng thi hay lin tip nhiu nguyn t trong mt mu. Cc kt qu phn tch li rt n nh, sai s nh. Trong nhiu trng hp sai s khng qu 15% vi vng nng c 1 - 2 ppm. Hn na bng s ghp ni vi my tnh c nhn v cc phn mm thch hp qu trnh o v x l kt qu s nhanh v d dng, lu li ng chun cho cc ln sau.

Nhng u im v nhc im ca php o AAS Nhc imMt khc cng chnh php o c nhy cao, cho nn s nhim bn rt c ngha i vi kt qu phn tch hm lng vt. V th mi trng phng th nghim phi khng c bi. Cc dng c ha cht dng trong php o phi c tinh khit cao. cng l mt kh khn khi ng dng phng php phn tch ny. Mt khc cng v php o c nhy cao nn cc trang thit b l kh tinh vi v phc tp. Do cn phi c k s c trnh cao bo dng v chm sc. Cn cn b lm phn tch cng c thnh tho vn hnh my. Nhng yu t ny c th khc phc c qua cng tc chun b v o to cn b.Nhc im chnh ca phng php phn tch ny l ch cho ta bit thnh phn nguyn t ca cht trong mu phn tch m khng ch ra trng thi lin kt ca nguyn t trong mu. V th n ch l phng php phn tch thnh phn ho hc ca nguyn t m thi.

Mt s quy trnh ng dng phng php ph hp th nguyn t phn tch kim loi nng trong thc phm

Xc nh asen bng k thut hydrua Mu c v c ho trong l ph mu vi sng c t chng trnh theo tng i tng, As (V) c kh v As (III) v phn ng vi natri bohidrua to thnh hp cht hydrua arsen (AsH3), hp cht ny c dn ti cuvet ch T nguyn t ha v o ph hp th ca As

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Xc nh asen bng k thuat l graphit Mu c v c ho trong l ph mu vi sng c t chng trnh theo tng i tng. Xc nh hm lng arsen trong dung dch to thnh bng o ph hp th nguyn t l graphit.

iu kin o my

Xc nh hm lng selen bng k thut hydrid (AAS-HVG) Mu c v c ha trong l vi sng theo tng i tng, cc ion Se(IV) v Se(VI) phn ng vi Natri bohidrua trong mi trng axt sinh ra hp cht Selen hydrua (SeH4 v SeH6), v hp cht ny c dn vo cuvet nguyn t ho thnh Se v o ph hp th ca Se (php o HVG-AAS) .

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Xc nh selen bng k thut l graphit Mu c v c ho trong l ph mu vi sng c t chng trnh theo tng i tng. Xc nh hm lng selen trong dung dch to thnh bng o ph hp th nguyn t l graphit

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Xc nh hm lng thy ngn bng k thut ho hi lnh Mu c v c ho trong l ph mu vi sng c t chng trnh theo tng i tng. Hg(II) c chuyn v Hg(0) bng SnCl2 v hi thy ngn bay ln c a ti h thng quang ph hp th nguyn t o ph

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