Tiiu ban Sinh thdi, Mdi tnr&ng vd qudn ly Bien II3
SU'DVNG CHAT CAI BIEN HOA HOC VA KY THUAT TIEM MAU NHIEU L A N T R O N G QUANG PHO HAP THU NGUYEN TU*
L 6 GRAPHiTXAC DINH MOT SO NGUYENTO KIM LOAI TRONG NirOC BIEN
Nguygn Binh Thuat'. Biii Minh Ly', Vo Mai Nhu Hieu', Nguyen Thj Cim Binh^
(l)Vi?n Nghien cim va U"ng dung cong nghe Nha Trang, 02 Hung Vuong - Nha Trang (2) Hpc vien Hai quan Nha Trang, 30 Trin Phii - Nha Trang
Email: [email protected] Tom tk
Dd thiet Igp cdc thong so tdi uu cho qud trinh n^yen tu hda v&i Ap thuat tiem mdu nhiiu Idn kit hgp sir dung chdt cdi biin ddi hoa hgc vd he thdng hi?u chinh nin de xac djnh true tiep hdm lugng cdc kim logi di bay hai nhu Cd vd Hg trong cdc mdu nu&c biin bdng phuong phap quang phd hdp thif nguyen tu Id graphit (ETAAS). Anh huahg cua nhieu nin do cdc mudi v6 ca trong nu&c biin la rdt quan trgng dd gidm ddng ki khi six dung hdn hgp chdt cdi biin hoa hgc v&i ty le Pd(N03)2:axit ascorbic = 20:200 (mg/l) cung v&i hai he thdng diiu chinh nen: hieu chinh nen dateri [deuterium arc background correction (DABC)] vd hi$u chinh nin Zeeman [Zeeman effect background correction (ZEBC)]. Ben canh do ky thugt lam giau mdu bdng ky thuat lam khd mdu nhiiu lan (reconcentralion) ket hgp chuong trinh nhiet ddi vai kim logi cdc di bay hai nhu Cd vd Hg tuone ung vai nhiet dg than hda Id 500°C vd 30(fC; nhiet dg nguyen tu hoa 1500 C vd 1400^C dd xdc dinh hdm lugng cdc kim logi nay dual dgng vSt (ca fig/l).
Abstract
USE OF THE CHEMICAL MODIFICATION AND THE MULTI-INJECTION TECHNIQUE IN THE ELECTROTHERMAL ATOMIC ABSORPTION SPECTROMETRIC DETERMINATION OF METALS IH SEA-WATER Having established the optimum parameters for the atoms of multi-injection technique combine use of chemically modified and corred system for determining direct metal content as Cd and Hg in sea water samples by atomic absorption spectroscopy graphite furnace (ETAAS). The effects of noise background to the inorganic salts in seawater is very important to have significantly reduced when using a mixture of chemical modified with ratio Pd(N0^2:ascorbic acid = 20:200 (mg/l ) along with two control systems background: deuterium arc background correction (DABC) and Zeeman effect background correction (ZEBC). Besides techniques to enrich by
Hoi mhi Khoa hgc va Cdng nghe biin loan quoc lan thir Y
reconcentralion combines program the heat for 'hetnetals such as Cd andHg corresponds to a charring temperature of SOCfC and 30(fC: atomisation temperature of ISOCPC and 140CPC were determined concentrations of trace metals in the pg/l.
Keywords: direct trace metal determination: sea-water: chemical modification: background correction: electrothermal atomic absorption spectrometry
I. M d BAU
Thuy ngan, cadimi co trong m6i truong thong qua Cac hoat dong ciia tu nhien va con nguoi (chu ylu tit cac boat dong ciia cac nganh cong nghiep hoa hgc, cac nha may san xuat thijt bi dien, cong nghi?p che tjo son, cong nghiep chit deo. Ham luong thuy ngSn, cadimi trong moi truong biln dang co chilu huong gia tang trong nhung nam gan day, nong do cua chung cao trong nuoc se anh huong den doi song ciia sinh v^t bien. Khi cac sinh vat bi nhiem doc, gidng nhu trong mot chu trinh sinh hgc den lugt chiing Iai la nguon thtic an cho con ngucri va chiing se dugc tich luy vao co the con nguoi voi nong do ngay cang cao [1].
Phucmg phap quang phi hip thu nguyen tii nhiet dien (ET-AAS) voi nhung dac tinh mi vi?t nhu: dg chgn Igc, do nhay va do chinh xac cao, gioi ban phat hign thap, c6 the xac dinh dugc cac kim loai 6 dang vet. Tuy nhien phuong phap nay van co nhugc diem co ban la chiu anh huong boi cac nhieu khong thugc nguon gfic ph6 gay ra dan den hieu suat nguyen tii hoa thap. Nham dat dugc dO xac thuc va dg nh^y cao, phuong phap ET-AAS cung voi ky* thuat 16 graphit co d§ on djnh (stabilized temperater platform fiimace-STFF) va cac chat cai bien hoa hgc da dugc nghien cuu ap dung nMm loai tru anh huong ciia cac nhieu khong thugc nguon goc pho. Cac chat cai bien hoa hgc dugc them vao mau phan tich va mau chuan se lam thay doi dac tinh nhiet hoa cac kim loai phan tich hoac/va cac chat tao nen de loai tru ho^c giam bot cac nhilu [2].
Trong nuoc biln thuy ngan va cadimi t6n tai duoi dang vlt va sieu vlt trong nin h6n hgp muoi la hon hgp phiic tap gay nhilu manh, vi vay mu6n nang cao hieu qua khi xac dinh cac kim loai nay cin phai tiln hanh lam giau mlu bang cac phucmg phap nhu tach, chiet, cgng ket, chung cit, kit tua cac kim loai cin phSn tich. Nhung cac phuong phap nay de nhiem ban dan hoac lam mit nguyen t l cin phan tich din din sai s6 he thing cua phep do Ion. Vi vay, phucmg phap lam giau nguyen t l phan tich trong cuvet graphit (in-situ) bang ky thuat tiem mau nhilu lin kit hgp sir dung chit cai biln dli boa hgc va he thing hi?u chinh nen se cho phep xac dinh true tilp ham lugng cac kim loai dl bay hoi nhu Cd va Hg trong cac mlu nuoc biln bing phucmg phap quang phi hip thu nguySn tu 16 graphit (ETAAS) ma khong cin xir ly mau truoc khi do [4].
Tiiu ban Sinh thdi, Mdi tru&ng vd qudn ly Biin 115
II. PHirOfNG PHAP 1. Dung cu v^ thi^t bi
- Can phan tich 0,000lg (Scaltec - Germany)
- Khi argon 99,99% cua Xi nghiep hoi ky nghe Nha Trang - Mang loc co kich thuoc 0,25|im (Whatman - Japan) - May loc nuoc sieu sach nu6c EASY pure II
- Lo graphit loai "Omega platform extended lifetime cuvettes" (Germany)
- Mdy quang ph6 hSp thu nguyen tCr cing cac bo phSn di kem: Thermo Elemental- Model Solaar M6 Dual Zeeman Atomic Absorption Spectrometer, Furnace autosampler FS95, den catot rong HCL data Coded, dugc dieu khien bang may tinh Intel Pentium V.
3,06 GHz (h6 trg sieu phan ludng HT); 512MB RAM; 40 GB HDD; 1,44 MB FDD voi phan mem dieu khien Solar Version 27
- Cac che do do quang ph6 dugc dan ra trong bang 2.1
Bdng 1. Cdc diiu kien do quang pho hdp thu nguyin tu su dung Id graphit logi "Omega platform extended lifetime cuvettes " [3]
Thong so Cd Hg
^(nm) Dg rgng khe (nm)
Thoi gian do (s) Kieu do Dong den (%)
228,8 D,S
3 Dien tich
50
253,7 0,5
3 Dien tich
90 2. Hoa chat
- Dung dich chuin Cd, lg/1 duoi dang Cd(N03)2.4H20 trong HNO3 0,5M (Fluka) - Dung dich chuin Hg, lg/1 duoi dang Hg(N03)2.H20 trong HNO3 2M (Fluka) - Dung dich Pd lg/1 duoi dang Pd(N03)2 trong HNO31M (Fluka)
- Dung dich acid ascorbic lg/1 trong nuoc (Roana-Hungary)
- Hon hgp Pd(N03)2:ascorbic acid = 20:200mg/l dugc sir dung de lam chat cai bien hoa hgc cho 2 nguyen t l Hg va Cd.
- Dung dich nuoc biln ting hop co nlng do 34,2%o: can 32g NaCl + 14gMgS04.7H20
^- 0,I5g NaHC03, tat ca cac hoa chat tren dugc hoa tan trong 1 .OOOmI nuoc sieu sach.
,[g Hgi nghj Khoa hoc vd Cong nghe biin todn qudc I
3. Xay dung 6a<mg chuan cua mlu nude biln tong hffp
Cac duong chuin cua Cd va Hg sir dung hIn hgp chit cai biln hoa hgc Pi^fOih ascorbic acid = 20:200mg/l tren nin nuoc biln ting hgp dugc thvc hien bang each tiern^ 10 lin dung dich chuin Cd co nlng dg tuong img la 0,1; 0,5; 1,0; 1,5; 2,0ng/l va Hg co nong dg tuong ling la 0,5; 1,0; 2,0; 4,0; 6,0ng/l. Thi tich dugc dua vao 16 bao gom 20|al mSu nuoc bien ting hgp + 1 jil Pd(N03)2 (co nlng do 44mgA) + 1^I ascorbic acid (co nong to 440mg/l). Tit ca cac thi tich tren diu dugc he Furnace autosampler FS95 hut tu dgng va dua vao 16 graphit.
4. Xay dung quy trinh xac dinh tren mau nude bien thyc
Mau nuoc biln thu vl dugc Igc qua mang Igc 0,25jun va axit hoa de bao toan cac nguyen tl kim loai. Dimg ky thuat tiem mlu nhilu lin voi 10 lan tiem bao gom 20|il mau nude biln ting hgp + lul Pd(N63)2 (co nlng do 44mg/l) + Ipl ascorbic_acid (co nong do 440mg/l). Chuong trinh nhiet dien bao gIm siy kho miu (lap Iai cho mli lan tiem mau) - nguyen tir hoa - lam sach 16 dugc chay lien tuc va do hip thu dugc ghi Iai. Phuong phdp them chuin dugc sir dung dl xac dinh ham lugng Cd va Hg trong nuoc bien.
III. KET QUA VA THAO LU^N
1. Anh huong nhiet do trong qua trinh nguyen tu hoa
Th6ng thuong qua trinh nguyen tir hoa nguyen t l phan tich bao gom 3 giai doan: siy kho - tro hoa - nguyen tir hoa. 6 giai doan say kho xay ra s\r bay hoi dung moi h6a tan mau, cin chgn thai gian, nhiet do say kho va toe do gia tang nhiet do cho phii hgp de khong lam bin mlu, mit mlu dan den sai lech ket qua phan tich. Do so Ian tiem mau la 10 lan nen so lan say kho miu ciing tuong tu nhu vay, ben canh do nhiet do say kh6 phii hgp dli vol cac mau vo co trong dung moi nuoc thuong la 100-150 C, do trong nuoc bien c6 them ham lugng muoi hoa tan Ion vi vay can nhiet dg cao khoang 150'^C.
Sau giai doan say kho, giai doan tro hoa chung toi chgn nhiet dg la 500'*C va SOO^C tuong img vol Cd va Hg dl trong giai doan ke tiep chiing toi thay dli nhiSt do nguyen tir de thu dugc do thi bieu dien tin hieu hap thu theo nhiet do nguyen tu hoa, duong cong tin hieu tang theo nhiet do roi sau do nam n^ang. Dieu do chi ra ring kh6ng co Igi gi them neu vugt qua diem toi uu dau tien. Thuc ra can phai tranh nhiet do cao khdng cin thilt dl tranh lam giam tuoi tho ciia 16 graphit. Bang thuc nghiem chiing t6i da khao sat dugc do hip thu cua Cd va Hg phu thugc vao nhigt do nguyen tir hoa va xac dinh nhiet do nguyen tu h6a tii uu cua Cd la 1.500°C va cua Hg la 1.400°C va chuong trinh nhiet dg dugc trinh bay tren bang 2.
Tiiu ban Sinh thdi. Moi tnr&ng vd qudn ly Bien 117
Nguyen tl Cd
Hg
Bans 2. Chuong trinh nhiet do ciia
Buoc siy kho Tro h6a Nguyen bi h6a Lam sach 16 Say kho Tro hoa NguySn tir hoa Lam sach 16
sl
lan 10
10 Nhiet do
(°C) 150 500 1500 2600 150 300 1400 2600
Id graphite sir dung khi do Toe dg gia
nhiet (s) 25 10 1 1 25 10 1 1
Thai gian luu(s)
25 10 6 3 25 10 6 3
mdu Luulugng Ar (ml/phiit)
300 300 0 300 300 300 0 300 2. Xay dung duotig chuan cho nguyen to Cd va Hg cua mau tong hop
, Tlicil£iun(s)
Hinh 1. Pho chudn Cd cua mdu tong hgp
&cdc nongdg O.l; 0.5; 1; 1.5; 2pg/L
Thcri 2i«n(s)
Hinh 2. Pho chudn Hg cua mdu tong hgp
& cdc ndng do 0.5; 1.0; 2,0; 4,0; 6, Opg/I Tren hinh 1 va hinh 2 ta nhan thay, khi dua hon hgp chat cai bien hoa hpc Pd(N03)2- ascorbic acid da thay xuat hien cac pho cua cac nguyen to Cd va Hg. Neu khong dung chat cai biSn hoa hpc thi khong thi phan tich true tiep dugc Cd va Hg duoi dang vet trong moi trucmg mau tong hgp voi nong dp muoi 34,2%o. Nhu vay khi co cac chat cai bien hoa hgc da thiic day qua trinh khir cac hgp chit chijra Cd va Hg ve Cd va Hg nguyen to turc da lam tSng kha nSng bay hoi cua nguyen t6 phan tich, giiip nguyen tu hoa nguyen to phan tich truoc cac thanh phan nen, dilu nay thi hien rat ro tren cac hinh 1, 2 va ciing diing theo tac gia Pilar Bermejo-Barrera va cac cgng sir [4]. Dp tuyen tinh va do chinh xac cua cac duong chuan co the dugc danh gid qua phuong trinh hoi quy thu dugc tir ket qua thuc nghiem.
Ket qua xu ly so lieu thuc nghiem bing phin mim Microcal Origin 6.0 cho thay, doi voi
118 Hgi nghi Khoa hgc vd Cdng nghe bien todn quoc oc lan thu V Cd phuong trinh hIi quy la y = 0,0192x + 0,002 ung voi ^ = 99 95 va <lg lech chuto 0 002_
Dli voi Kg phuong Uinh h5i quy co dang y = l,15243x + 0,002 ung vol if - 99,51 va do lech chuin 0,0454. Qua do cho thiy he sl tuong quan tuyen tinh r cua cac duoilg chuan ciia Cd va Hg diu co gia tri Ion hon 0,99 chiing to do chinh xac cao cua phuong phSp.
3. Xac dinh ham lumg kim loai Cd va Hg trong cac mau nu-6-c bien
TI»digimi(s) Hmh 3. Phd Cd trong mdu nude biin a cdc ndng do them 0,1: 0,2: 0,3; 0,4fig/l
Tlldi eian (s) Hinh 4. Phd Hg trong mdu nuac biin a cdc ndng dg them 0,1: 0,2: 0,3: 0,4pg/l D I xac dinh ham lugng Cd va Hg true tilp trong nuoc biln, chiing toi tiln hanh dimg phuong phap them chuin. Tren hinh 3 trinh bay phi va dl thi ciia nguyen t l Cd dimg ky thuat tiem mau nhilu lin kit hgp voi phucmg phap them chuan. Sir dung phan mem Microcal Origin 6.0 cho thay phuong trinh hoi quy doi voi nguyen to Cd la y = 2,1401x + 0,3329 ung voi r = 0,996 voi do lech chuin 0,005.
Tren hinh 4 trinh bay pho va do thi cua nguyen to Hg dung kj? thuat tiem mau nhieu lan ket hgp voi phucmg phap them chuan. Sii dung phan mem Microcal Origin 6.0 cho thay phucmg trinh hoi quy doi vol nguyen to Hg la y = 0,0027x + 0,0005 ling voi r = 0,998 v6i do lech chuin 0,004.
Bdns 3. Kit qud phdn tich true tiep hdm lucmg Cd vd Hg trong mgt sd mdu nude bien STT
1 2 3 4 5 6
Diem lay mau Da Tugng - Binh Tan Cang Cau Da B?nh vien 87 Dong De Cau Tran Phu Cau Binh Tan
Ham lugng Cd (^ig/i) 0,92 1,55 0,85 0,72 0,94 1,32
Ham lugng Hg (ng/1) 0,18 0,25 0,16 0,15 0,15 0,23
Tiiu ban Sinh thai, Moi tru&ng vd qudn ly Bien 119
Bang 3 trinh bay ket qua xdc dinh ham lugng cac kim loai trong mgt s6 mau nuoc biln thu thap tai Nha Trang. Co thi nhan thiy trong 6 mau nghien cuu ham lugng Cd va Hg dao dgng bien doi khong nhieu, chiing nSm trong khoang 0,15 d6n 0,25pg/l doi voi Hg va 0,72 din l,55^g/l d6i voi Cd. D6i voi nguyen to Cd rioi co n6ng dp thip nhit la D6ng D I va cao nhat Cang Cau Da, con doi voi Hg noi co nong dp cao nhit la Cang Ciu Da va noi diip nhit la D6ng Bi va Cau Trin Phii. Nguyen nhan co thi do Cang Ciu Da la cang chinh va Idn, luu lugng thuyen ra vao nhieu dan den viec thai nhilu chit thai nen anh huong moi trucmg.
KET LUAN
Da ket hgp su dung chat cai bien hoa hgc voi ky thuat tiem mlu nhilu lin trong phuong phap quang pho hip thu nguyen tii nhiet dien (ET-AAS) xac dinh vlt Cd va Hg true tilp trong nuoc bien. Phuong phap khong doi hoi cac buoc tach, lam giau nguyen t6 phan tich Cling nhu xu ly mau truoc khi do vi vay giam thoi gian, cong siic va gia thanh phan tich.
Ket qua thu dugc cho thay phuong phap su dung chat cai biln hoa hgc va ky thuat tiem mau nhieu Ian trong 16 graphit da cho hieu qua cao, co thi phan tich true tilp Cd va Hg duoi dgng vet (c5 pg/1) trong nliung mau nen phiic tap nhu nuoc biln.
TAI LIEU THAM KHAO
1. Concepci6n Almela, M Jesiis Clemente, Dinoraz Velez, Rosa Montoro, Total arsenic, inorganic arsenic, lead and cadmium contents in edible seaweed sold in Spain, 2006, Food and Chemical Toxicology, 44, 1901-1908.
2. Jordi Sardans, Fernando Montes, Josep Periuelas, 2010, Determination of As, Cd, Cu, Hg and Pb in biological samples by modem electrothermal atomic absorption spectrometry, Spectrochimica Acta Part B, 65, 97-112.
3. Methods Manual, Atomic Absorption Spectrometry, Thermo Elemental Issue 3,01-01.
4. Pilar B. B., Pineiro J.M. and Barrera A. B., 1998, Usefulness of the chemical modification and the multi-injection technique approaches in the electrothermal atomic absorption spectrometric determination of silver, arsenic, cadmium, chromium, mercury, nickel and lead in sea-water, Journal of Ana. At. Spec, Vol. 13. 777-786.
Ngic&i doc nhgn xet: TS. Nguyen Bi'rc Civ