TAP CHI HOA HOC
DOI-1015625/0866-7144.2014-0018
T. 52(4) 490^94 THANG 8 NAM 2014
NGHIEN CU'U XAC DINH VET CHI (Pb), INDI (In) VA CADIMI (Cd) B A N G PHU'ONG PHAP VON-AMPE HOA TAN ANOT SU" DUNG DIEN e y e PASTE 6 N G N A N O C A C B O N B I ^ N TJNH BANG BizOa
Nguyen Thi Thu Phuwng'', Trinh Xuan Gian^
'Khoa Cdng nghi Hda hgc. Trudng Dgi hgc Cong nghiep Hd Ngi
^ Vien Hda hgc, Viin Han ldm Khoa hgc vd Cong nghe Viet Nam Den Toa soan 23-4-2014
Abstract
This paper reports the use of Bi203-modified carbon nanombes paste electrode (Bi203-CNTPE) for trace lead (Pb), cadmium (Cd) and indium (In) determination by differential pulse anodic stripping voltammetry (DP-ASV). The stripping peak current (Ip) has a linear relationship with concentration in the range of Pb(II), In(III) and Cd(II) are 1.21>'10"^Mto4.83xlO"^M, 5.22>cl0"''Mto 12.17x10"''M, 2.23>cl0'^ M to 8.93xl0"^M, respectively, with a deposition time of 60 s at deposition potential of-1.2 V, in 0.1 M acetate buffer (pH = 4.5) and 0.1 M KBr. The 3o detection limit (n = 10) of Pb, in and Cd is 0.83x10"^ M, 6.47x10"^ M, 1.38x10'^ M, respectively. The electrode was applied to determination of Pb(II), In(III) and Cd(II) in water sample.
Keywords: Stripping Voltammetry, Bi203-CNTPE, lead, indium, cadmium.
1. MO DAU
Chi (Pb), Indi (In) va Cadimi (Cd) la nbiJng kim logi dge hgi d ham lugng nho [1]. Co nhigu phuonj phap nhu: quang ph6 hip thy nguyen tii (AAS) [2]
ph6 kh6i plasma cao tin (ICP-MS) [3], pho phat xa nguyen tir sir dung ngu6n cam iing cao tin plasma (ICP-OES) [4],... da dugc siir dyng de phan tich vgt cac kim loai Iren. De co dugc nhirng phuang phap ke tren can phai co trang thiet bi phiirc tap va dau tu ldn. Phuong phip Von-Ampe hoa tan sir dung dien cyc thiiy ngan la phuong phap co do chinh xic va do nhgy cao da dugc nghien cihi de xac dinh lugng vgt va sigu vet nhieu kim logi, trong do co Pb, In va Cd vdi gia tbanh thap. Gin day, di co nhimg nghien cuu gidi thigu dign cyc bitmut nhu: dien cue mang bitmul insitu va exsilu (BiFE), dien cyc kh6i bitmut (BiBE), dien cue paste cacbon bien ti'nh bing bgt bitmut (Bi-CPE) va dien cyc paste cacbon bign tinh bing BiiOs (Bi203-CPE) [5]. Cung da c6 mgt s6 cong trinh nghign ciru phan tich ddng thdi ham lugng Pb, Cd, In bing dien cue mang bitmul Iren nen dign cyc paste nano cacbon [1], phin tich him lugng In trong sy co mat cua Pb, Cd bing dign cyc mang bitmul Iren dign cyc than thiiy tinh [6].
Trong bai bio nay chiing toi trinh bay ket qua nghien ciiu phan tich xic dinh ham lugng vet chi, indi, cadimi bing phuang phap Von-Ampe hoa tan
anot su dung dign cyc paste ong nanocacbon bien ti'nh bing BijOs (BijOj-CNTPE).
,g 2. THU'C NGHIEM
2.1. Thiet bi, dung cu va boa chat
May cue ph6 da chirc nang 797 VA Computrace do hang Metrohm (Thuy Si) san xuit.
- Can phan tich 4 sd TE 2I4S, sai so 0,1 mg do hang Sartorius (Diirc) san xuit; may cit nudc hai lan Hamilton-WSC/4D (Anh); cic dyng cy c6i, chay ma nao (Trung Qudc); dung cu thuy tinh, micropipet (Dire),....
- Ong nanocacbon (Han Quoc), dau parafin (Nhat Ban).
- NaOH, CH3COOH, KBr, BizOa, AI2O3 dgu la boa chat tinh khiet ciia Merck; dung dich lim viec cLia ion Cd , In * v i Pb * dugc pha tir dung djch chuan gdc co ndng do 1000 ppm su dyng cho AAS.
- Nudc cat diing dg pha che boa chat va rira dyng cy la nudc cat hai Ian, sieu sach.
2.2. Chuan bi dien cue Iam viec BiiOs-CNTPE Trgn dgu dng nanocacbon, diu parafin va BiiOj theo ty lg ong nanocacbon, Bi203, diu parafin la 58:7:35 (tinh theo phan tram ve khoi lugng) bing
TCHH, T. 52(4), 2014
coi chiy ma nao. Hdn hgp vgt ligu thu dugc dem siy d 105 "C trong 2 gid dugc hdn hgp vat lieu nhao.
Nhoi hdn hgp nbSo thu dugc vio ong dign cyc teflon, phan tren dign cyc cd gin chdt kim logi de ket noi vdi may cyc pho da ning Iim dien cyc Iim vigc. Mai bdng dign cyc tren giay Igc am, sau dd mai bong bing bgt AI2O3 0,05 pm.
3. KET QUA v A T H A O LUAN
3.1. Nghien ciru dudng Von-Ampe vong cua Pb^%
In**. Cd^*tren di^n cue BiiGj-CNTPE Khi su dyng dien cyc Bi203-CNTPE dien phin dung dich chda Pb^*, In^* va Cd^* trong dung dich dgm axetat 0,1M, pH = 4,5 vi KBr 0,1 M bing phuang phap Von-Ampe vdng (CV) thu dugc 3 dinh pic Clia Pb^", In'*, Cd^* lin lugt tgi cic thg Ep (Pb) = -0,499 V; Ep (In) = -0,672 V; Ep (Cd) = -0,773 V va 1 dinh pic Clia Bi'* tai thg +0,006 V (binh I); dong dinh hoa tan (Ip) ciia ca 3 ion tuong doi cao chung to tinh dign h6a cua Cd , In'* vi Pb tren dien cue Bi203-CNTPE la rit tot vi cd the su dung dien cyc nay de phan tieh ddng thdi Pb^*, In'* vi Cd^* trong dung djch.
Cac digu kien thyc nghigm (DKTN): The dign phan (Edep): -1,2 V; thdi gian dign phan (tjep): 60 s;
t6c dg quet the (v); 15 mV/s; khoang quet the (Erangc): "1,3^0,3 V; t6c dg quay dign cyc (co): 2000 vong/phiit; thdi gian syc khi nito: 120 s; Ihdi gian nghi (tres,): 20 s; the lim sgch li +0,3 V Uong 60 s.
3.2. Nghien ciiru dieu ki|n ghi do
Ket qui khio sit inh hudng ciia thg dign phan (Edep) den Ip cho thay khi tSng the dign phan lam giau tir -0,9 V dgn -1,4 V thi dong dinh boa tan ciia Pb, Cd va In thay d6i ding ke. Tuy nhien, khi dign phan tir -0,9 V den -1,1 V, dinh pic thip; khi dign phan lam giau d the am ban -1,2 V co the co cac ion kim logi khic ciing bj khir tren bg mat dign cyc lim vigc. Vi vgy, chiing toi chgn Edep = -1,2 V cho nhimg nghign ciru tiep theo.
Khi thay doi thdi gian dign phan Iim giau (Idep) tir 30-^300 s thi Ip cua Pb ting din theo thdi gian dign phan do thdi gian dign phan cing liu thi lugng chat dugc tich luy trgn be mit dign cyc cang ldn. Tuy nhign, khi ting t^ cd the lim tich luy them cac kim logi can trd nhu Zn, Cu .... Mgt khac, tgi thdi gian dign phan hi 60 s den 120 s, khi tien hinh do Igp lai 5 lan, phgp do cd dg l^p lgi tot, Ip tuong doi cao vi cfin doi ngn chiing tdi lya chgn tdep = 60 s den 120 s 14 thfch hgp. Trong cic nghien cuu tiep theo chung t6i dign phin trong thdi gian 60 s.
Nguyin Thi Thu Phuong vd cgng su Khi khio sit inh hudng ciia toe do quel the dgn Ip chiing t6i thay tai t6c dg q^uet thg 0,015 V/s, pic co hinh dang cin ddi, dudng nen thip, dinh pic cao, dg lip lai cao nen chiing t6i chgn tdc do quet the thich hgp Ii 0,015 V/s.
Cic dieu kign ghi do thich hgp khac khi ghi do dung djch chira Pb^*, Cd^* va In'* trong dung djch dgm axetat 0,1M, pH = 4,5 vi KBr 0,1 M bao gom:
Er^ge = -1,2 V den +0,3 V; thg Iam sach: +0,3 V trong 60 s; U^ = 20 s; bien dg xung: 0,03 V; thdi gian tao xung: 0,04 s; co = 2000 vong/phut va thdi gian sue khi nito dudi oxi: 120 s.
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Hmh 1: Pho dd ghi do tin higu Ip ciia Pb, In vi Cd bing phuong phap CV
(1). Ngn dgm axetat vi KBr 0,1 M, pH = 4,5, (2). Ngn dgm axetat v^ KBr 0,1 M, pH = 4,5 vi [Pb^*] = 0,24 * 10-^ M, [Cd^*] - 0,45 «10"* M, [hi'*] - 0,87 x 10"^ M 3.3. Anb budng lan nhau giii^ ba ion nghien curu
Co djnh nong dg ciia mgt ion, them dan lugng chinh xac 2 ion nghien cuu con lgi vao dung dich vi ghi do dudng ASV. Ket qui cho thay:
- Khi CO dinh ndng dg [Pb^*] = 6 ppb, ting dan nong dg Cd, In thi neu [Cd^*], [In'*] nho hon 45 ppb thi hoan toan co the djnh lugng dugc d6ng thai ci 3 ion, khi ti le [Cd^*], [In'*] ldn han 45 ppb thi pic ciia Cd bi che ngn khong djnh lugmg chinh xic dugc Cd.
- Khi c6 djnh nong dg ciia [Cd^*] = 5 ppb, ting din nong dg In, Pb (hinh 2a) thi neu [Pb ], [In'*]
nho hon 150 ppb thi hoin loan co the djnh lugmg chinh xic d6ng thdi ca 3 ion, khi [Pb^*], [In'*] ldn hem 150 ppb thi khdng djnh lugng dugc chinh xic In.
- Khi co djnh ndng dg cua [In'"] = 12 ppb, them din lugng chinh xac Cd, Pb (hinh 2b), neu [Cd^'], [Pb'*] nho ban 70 ppb thi hoan toan co the djnh lugng chinh xac dugc ci 3 ion, khi [Cd^^j, [ i V ' ] tdn hem hoic bing 100 ppb, co sy chen lan pic ciia Cd va In nen khong djnh lugng dugc Cd, In,
491
TCHH, T. 52(4), 2014
3.4. KhoaDg tuyen tinh, df lap lai, do nhay, gioi ban phat hien va gioi han dinh luffng
KJioang tuyln tinh: Khi ghi do ph6 do DP- ASV xac djnh khoang tuy6n tinh cua Pb, In va Cd (hinh 3 a) cho k6t qua khoang tuyen tinh rat rong:
l,21'<10'+4,S3xlO' M (d6i vcri Pb); 5,22x10*^
12,17«10' M (dai vai In); 2,23xl0''+8,93xl0' M (doi vdi Cd). Xay dimg duong chuan trong cac khoang tuyen tinh nay duQC phuang trinh duang chuan ciia 3 ion: Pb: y = 2,325x - 0,326 vai R ' = 0,995; In: y - 0,615x - 3,117 voi R^ = 0,993; Cd: y = I,418x - 1,212 vcri R^ = 0,997 (hinh 3b, 3c, 3d).
Nghien cuu xac dinh vet chi (Pb)...
BQ lap Iai: Tiln hanh ghi do lap l^i 10 lan dung djch chiia d6ng thai [Pb^*] = 1,45x10' M; [In=*] = 6,09x10-' M; [Cd^*] = 2,68x10'' M thu dugc RSD^
= 1,93 %; RSDto = 3,54 %; RSDcd= 1,72 %.
Dp nhay ciia phucmg phap tuong doi trong khoang tir 0,88+1,14 pA/ppb (dai voi Pb);
0,04+0,32 nA/ppb (dai voi In); 0,69+1,14 pA/ppb (doi vai Cd).
Gioi ban phat hien (LOD) ciia phuang phap xac djnh theo qui tie 3a ia LODpt = 0,83 >; 10"' M; LOD|,
= 6,47x10 M;LODcd= 1 , 3 8 X 1 0 ' M ; giai hjn djnh luong (LOQ) la: LOQpt = 2,78x10' M; LOQ,. - 2 , 1 5 x 1 0 ' M ; L O Q Q , = 4 , 6 0 X 1 0 ' M .
•900m .QOOm -700in -600m -SOOm -40Om -SCBm U ( V )
mnh 2a: Pha do DP-ASV ciia Pb, Cd va In (Co djnh [Cd"] - 5 ppb; [Pb'^; [In'*] I k liurt 14
(I). 5 ppb, (2), 10 ppb, (3) - 20 ppb, (4). 40 ppb, (5). 70 ppb, (6). 100 ppb, (7). 150 ppb)
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mnh 2b: Pho d6 DP-ASV cua Pb, Cd va In (06 djnh [In'T - 12 ppb; [Pb"]; [Cd"] lin luot 14 (1). 5
ppb, (2). 10 ppb, (3). 20 ppb, (4). 40 ppb, (5). 50 ppb)
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•1,00 -eOOm -BOQm -400m . , OM mnh 3a: Pho do DP- ASV ghi do xac djnh khoang tuySn tinh ciia Pb, In va Cd ((1) [Cd"] - [Pb"] - 2,5 ppb v4 [In"] = 6 ppb; (2) [Cd"] = [Pb^*] = 4 ppb vS [In"] - 8 ppb; (3) [Cd"] - [Pb"] = 6 ppb v4
[ln"]=10 ppb; (4) [Cd=T - [Pb"] - 8 ppb v4 [In"] - 12 ppb; (5) [Cd"] - [Pb'T =10 ppb v4 [In"] = 14 ppb)
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mmh 3c: D u o n g chuSn x a c djnh In
3.5. Phan tieh man that
Sir dung dien cue BiiOs-CNTPE di phan tich ham lugng Pb, Cd va In trong mlu nuac thai khu Cong nghi?p Yen Phong, huyen Yen Phong, tinh Bac Ninh theo phuang phap DP-ASV nghien cuu dugc.
Mlu dugc liy tit ngay 16/2/2014 dSn ngay 26/3/2014. Mlu sau khi lay dirge xii ly so bg bing dung djch axit HNO3 dac tcri pH = 1, sau do dugc mang ve phong phan ti'ch, xii Iy va Igc. Dung djch Igc thu dirge tien hanh co 5 lln sau do phan tich ham lirgng Cd, Pb, In tren thiJt bj phan lich cue ph8 797 VA Computrace ciia Metrohm vai nen va cac dilu kien thi'ch hgp da dugc khao sat theo phugng phap them chuan. "Trong so 5 mau co 4 mlu co Cd (ham lugng tir 1,27 ppb^3,25 ppb), I mlu co ham lugng Cd nho han giai han phat hien (GHPH); 2 mlu c6 In (ham lugng tir 0,83+0,98 ppb), 3 mlu co ham lugng In nho han gioi ban phat hien (GHPH) va ca 5 mlu deu CO Pb (ham lugng tir 2,76=14,39 ppb). Ph8 da thu dugc the hien 0 hinh 4.
4. KET LUAN
Da nghien ciiu cac dieu kien thirc nghiem de xay dimg quy trinh phan tich ham lugng Pb", In" va Cd" bang phucmg phap DP-ASV sir dung dien cue paste ong nano cacbon bien tinh bang Bi203 (Bi203- CNTPE). Cac dieu kien thuc nghiem tai uu bao gom: nln axetat 0,1 M, pH = 4,5 va KBr 0,1 M; the dien phan Iam giau -1,2 V; thai gian dien phan lain giau 60 s; bien dg xung 30 mV; tac dg quet the 0,015 V/s; toe dp quay dien circ 2000 vong/phut.
Dien circ (Bi203-CNTPE) da dugc nghien ciiu sir d(ing de djnh lugng ba kim Ioai nghien ciru trong khoang tuyen tinh tuang doi rgng 1,21x10 + 4,83x10"' M (doi vai Pb); 5,22x10"' M-I2,I7xlO"'
14
1 2 - 10
C.10(8)(moM) mmh 3d: D u o n g c h u i n xac djnh Cd M (dai vol In); 2,23x10"' M + 8,93x10"' M (dai voi Cd), dg lap lai tot, giai han phat hien t h i p (LODpb = 0,83x10"' M ; L O D i , - 6,47x10"' M ; L O D c , 1,38x10"'M). Dien c u e d u g c ling d u n g d i phan tich ham lugng Pb, In va Cd trong m l u n u a c cho k i t qua tot.
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Hmh 4: Pho do ghi do D P - A S V phan tich m i u that {1): d o mau; (2), (3), (4): do them c h u i n TAI LIEU T H A M K H A O
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Fast determination of Cd, Fe. Pb, and Zn in food using AAS, Food Analytical Methods, 2, 110-115 (2009).
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5. R. Ouyang, Z. Zhu, C. E. Tamm, J. Q. Chambers, Zi- Ling Xue. Simultaneous stripping detection ofZn(II),
Nghien cicu xdc dfnh vet chi (Pb)...
Cd(II) and Pb(II) using a bimetallic Hg-Bi/single- walled carbon nanotubes composite electrode.
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A. Charalambous, A. Economou. A study on the utility of bismuth-film electrodes for the determination of In(III) in the presence ofPb(II) and Cd(II) by square wave anodic stripping voltammetry, Analytica Chimica Acta, 547, 53-58 (2005).
Lien hi: Nguyen Thi Thu Phirong Khoa Cong nghe Hoa hgc Trucmg Dai hoc Cong nghiep Ha Noi Phirong Minh Khai, Quan Bic Tur Liem, Ha Noi Email; [email protected].
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