''' Phuong phap trac quang
Theo Ciic lac gia trong tai lieu [66] , cd the xac dinh idl (1) trong nude lieu bang phuang phap trac quang vdi thude thii tao mau la telramethylbenzidinẹ Ca sd ciia phuang phap nay nhu sau: loai trú cac lap chat irong nude lieu bfmg ciich cho nude tieu chiiy qua cot cd chiia cacbon hoiit tfnh, sau đ axit hda dung dich nude lieu (pH: 4) bang dung dich dem citrat, them vao telramethylbenzidine (2,5 mM), chill nay se tiic dung vdi T de liio thanh mot phiic chat mau xanh luc, do Iruc licp
mat do quang dung dich ciia phiic đ d budc sdng (k) 646 nm. Cd the diing mgl sd
amin tham khiic lam chat Uio phiic mau nhu: o va p-phenylendiamine, benzidine, nhuiig diui xuitl ciia benzidinẹ Bang phuang phap nay cd the xac dinh ndng do idt trong nude lieu khoiing 6 ^100 pg/dl. Vdi dieu kien trong dung dich nghien ciiu khong cd Uip chat huu ca, GHPH ciia phuang phap nay diU deii 0,2pgr/dl.
"^"^ Phuong phap chiet trdc quang [34], [46]
Phuang phap nay dua tren nguyen tac: oxi hda I" trong dung dich thanh IO3 bang nude brom, loiii bd lugng brdm du bang axit fomic. Trong moi trudng axit iixelic (pH: 4,5H-5,5), IO"^ se oxi hda KI Ihanh I2, va I2 oxi hda leucocrystal violet
(CH[Cf,H4'^(CH3)2].0 thanh diing crystal violet, chiet crystal violet bang clorofom rdi do mat do quang ciia dich chiet d budc sdng 588 nm. Dinh luiU Bia luycii tfnh trong khoiing ndng do tii" 0,8 -^8,0 jagl'/dl, vdi he sd hap thu plmn lii gam s va do nhay theo Siindell Mn lugt la l,01x 10^' 1 moí'. cm"' va 0,00012pg c m ' l Tac giii trong lai lieu tren da dung phuang phiip nay de xac dinh idt trong nude bien.
Ciing cd the xac dinh idt bang phuang phap trac quiing hoiic chiet trdc quang vdi viec oxi hda I" thanh I2, cho I2 liic dung vdi hd linh bgt se tao thanh phiic mau xiinh tfm cd hap thu cue diii d budc sdng 590 nm, bang phuang phap nay cd ihe xiic dinh idl trong dung dich d ndng do khoang 1,0 j-igl'/dl. Phuang phap iiiiy dugc sií dung de xac dinh idt trong mudi an [34], [46].
:!;:i:=i= Phuong phiip quang plid phat xa nguyen tii plasma (ICP-AES) va phd khdi plasma (ICP-MS)
Theo phuang phap ICP-AES, mSu dugc bam true tiep vao ngudn kfch thfch plasma (ICP) cd nhiet do khoang 6000"C, d nhiet do đ thanh phan ciia mau bi nguyen tii" hda hoan loan va phiil ra cac biic xa cd budc sdng xac dinh. Do cudng do ciia biic xa dac trung cho nguyen td can phan tfch de suy ra ndng do nguyen id can phan ifch. Vdi phuang phap ICP-MS, mSu cQng dugc bam true liep vao ngudn ICP va sau khi da bi ion hda, cac đng ion dugc dua vao he phan lich khdi lugng de Uich Ciic ion dua vao ly sd m/z ciia chiing (m va z la khdi lugng va hda tri ciia ion). Sau đ cac đng ion dugc dua vao budng detecia va dugc chuyen ihanh tfn hieu dien. Do Idn ciia tin hieu thu dugc lií delecta la thong tin de dinh lugng.
Tac gia [110] da sií dung phuang phap ICP-MS de dinh lugng idl Irong nude lieu, vdi khoang tuyen tfnh [0,1-rlO pgl'/dl]. Mac dij thiet bi ICP-MS dat
lien va kl thuat van hanh phiic tap, tuy nhien klii so sanh phuang phap ICP-MS vdi nam phudng phiip kliiic hien dang dugc sií dung de djnh lugng idt tren the gidi, Sandia L May va cong su cho ling cung nhu phuang phap NAA, phuang phap ICP-MS dugc xem la phuong phap "chuan vang" de xac dinh lugng v6'l va sieu vet idt [92].