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XACD!NH LI/0NG VETCHI (Pb) BANG PHl/ONG PHAP VON-AMPE H 6 A T A N A N O T SUf DUNG DIEN COC PASTE ONG NANO CACBON BIEN TfNH BANG BI^O,
DETERMINATION OF TRACE AMOUNTS OF LEAD (Pb) BY ANODIC STRIPPING VOLTAMMETRY USING Bi^O,- MODIFIED CARBON NANOTUBE PASTE ELECTRODE
Nguyen Thi Thu Phi/tfng, Trjnh Xuan Gian
Tom t i t
Dien ciTc paste ong nano cacbon bien tinh bang Bi^O^ (Bi^O,-CNTPE) duoe che tao va su'dung de xac dinh Idcmg v^t chl b3ng phu'Ong phap Von-Ampe hoa tan anot xung vi phan (DP-ASV), Khoang phu thupc tuy^n tinh gida eifcmg do dong pic (Ip) vao nong do ciia Pb(ll) tif 1,92.10''M den 2,4.1(r'M khi ^ e n phan lam giau 120s d the dien phin -1,2V trong dung dich dem axetat 0,1M (pH = 4,5). Do lech chuan tuong doi (RSD) eua dung dich chda 1,45.1(J^M Pb(ll) la 2,67% (n = 10), gidi han phat hien theo quy tac 3o la 1,03.10'M. Dien cUc dUflc dng dyng de xae dinh ham luong Pb{ll) trong mau nudc.
Abstract
Bi203-modified carbon nanotube paste electrode [Bi,0,-CNTPE) mi manufactured and used for the determination of trace amounts of lead by differential pulse anodic stnppingvoltammetry method (DP-ASV).
The stripping peak current (Ip) has a linear relationship with concentration in ttie range of 1,92.1&'M to 0,24.1ff*M of Pb(ll) viFith a deposition time of 120s at deposition potential o f - 1 3 , in 0,1M acetate buffer solution (pH =4,S).The relative standard deviation (RSD) for a solution containing 1,45.10-"M of Pb(ll} was 2,67% (n=10), and the 3o detection limit was 1,03.10-'M. The electrode was applied to determine Pb(ll) in water sample.
Key words: anodic stripping voltammetry, Bi203, Pb, carbon nanotube paste electrode.
ThS. Nguyen Thj Thu Phifdng
Khoa Cong nghe H(!ia, Tnfctng Dai hpc Cong nghiep Ha Noi PGS.TS.Trinh Xuan Gian
Vien HPa hoc, Vien Han lam Khoa hocvH Cong ngh& Vi§t Nam Email: tnnhxuangian^yahoo com
Hgiynhanbii: 06/06/2013 Ng^y chap nhan dang: 16/08/2013
i.MdoAu
Chi la nguyen to rat dpc doi vdi moi tradng s6ng cung nhu doi v6i con ngudi [1]. Phucrng phap Von-Ampe hoa tan anot (ASV) la phuang phap co do chinh xac, do nhay cao thudng ducJc sCrdung de xac dinh lucmg vet cac kim loai, trong do co IUdng vet cua chi. Dien cue thuy ngan nhU dien cUc giot thuy ngan treo (HMDE), dien cUc mang thuy ngan (MFE) la nhCmg dien cue pho bien
va truyen thong de xac dinh luong vet chi b^ng ASV. Tuy nhien Hg la nguyen t6 CO ddc tinh cao, ^nh hUdng Idn den silc kh6e con ngUdi va mdi trUdng, nen viec tim kiem dien cUc mdi thay the dien cUc Hg la rat can thiet. Da cd nhieu cdng trinh nghidn cu'u tim kiem dien cue thay the Hg nhu cacbon, bitmut [2,3]. Trong hon hop bdt nhao lam vat lieu dien cUc paste nano carbon thi dng nanocacbon la mpt vat lieu mdi dang rat duoc quan
tam SLf dung nhu la vat lieu thay the bot graphit hoac cacbon quang pho... (5ng nanocacbon co the dupc tron vdi dau parafin, dau silicon, chat long ion. ..[4,5].
Theo hudng ke tren, chung tdi da nghien cu'u ch^ tao dien cue paste dng nano cacbon bien tinh bSng Bi^O^
(BijOj-CNTPE) sCr dung trong nghien ctfu va phan tich ham lUpng vet Pb trong m^u nUdc.
2. THl/C NGHIEM
2.1. Thiet bj •- Dung cu - Hoa chat - May cUc pho da nang 797 VA Computrace do hang Metrohm (Thuy Si) san xuat.
- Can phan tich 5 so TE 214S, sai so 0,1 mg do hang Sartorius (Dtfc) s i n xuat; eae dung cu cdi, chay ma nao {Trung Qudc); dung cu thuy tinh, micropipet (Dtife}...
6ng nanocacbon (Nhat), dau parafin (Nhat), Bi^Oj (Du'c). Cac dung dieh khac duoc pha che tCf hda chat tinh khiet dung phan tich eua Merck va nUdc cat hai lan, sieu sach.
2.2. Chuan bj dien cUc lam viec Can ehinh xac 0,1050g ong nanocacbon cho vao trong coi ma nao, them tiep 0,0036g 61^0^, 45MI dau parafin, trdn deu bang ehay ma nao. Hon hop vat li&u thu duac dem say d 105°C trong 2 gid duoc hon hc^p vat lieu nhao. Nhdi hon hop nhao thu dUOc vao ong teflon dai 52mm, dudng kinh trong 3mm, phan tren cd gSn
S o 17.2013-TapdiiKHOAHOC&CONGNGHE 163
•ariCTBiracoNGNGHE
Bang 1. Anh hUdng cua E^ va t^^ tdi Ip ciia Pb'*
E.,(V) UllA) t»,(s)
Km
-0,9 0,81 60 0,41
-1 0,82 90 0,72
-1.1 0,68 120 0,88
-1,2 0,89 180 1,24
-1,3 0,84 250 1,45
-1,4 0,89 300 1,98 c h d t k i m loai c d t h e ket n d i v d i m a y c u e
p h o d a n a n g n h u m p t d i e n eUe l a m v i e c 2 . 3 . Ket q u d
2.3.1. Khao sdt dUdng Von-Ampe vdng cua Ptr'* trin dien c u t Bip-CNTPE Khi SLf dung dien cue Bi^Oj-CNTPE de dien phan dung djch ehUa Pb^* trong dung djch dem axetat (CH,COOH va CH3COONa0,1 M; pH = 4,5) bSng phuong phap Von-Ampe vdng (CV) thi xuat hien dinh pic cua Pb'^ Ddng dinh hda tan (ip) eua Pb^* tUdng ddi cao ehCfng td hoat tinh dien hda cCia p y * tr^n i^en cue Bip^-CNTPE la rat tot {hinh 1). Qua trinh nay duoc gi^i thich nhu sau; Khi dien phan lam giau Pb^"", xay ra qua trinh khCf Pb^* va tao thanh hop chat gian kim loai Pb^Bi vdi Icifp Bi tren be mat dien cue Khi ta tien hanh ghi dong hda tan bang each phan cue nguae lai thi xay ra qua trinh oxi hoa Pb Bt - 2e - * Pb^* -H Bi; Pb^* sinh ra
kim loai khac cung bi khCr tren be mat dien cue lam viec. VI vay chung tdi chon E^^ =-1,2V cho nhCfng nghien ciAi tiep theo (hinh 3).
•125 -lOD .IsHiT^n -ISim 0 29 Hinhl.Phddoghidotinhilul bSngCV
^OOm 'TEOn .GDDm S l l n i KEw .300m
Hinh 2. Pho do ghi do tin hlSu I eua Pb'*
se lai djch chuyen vao trong dung dich.
Ghi ddng ion Pb''^ nay se thu dUdc pie hda tan cua Pb'* [3].
(1): Nen dem axetat 0,1 M,pH = 4,5 (2): Nen dem axetat 0,1 IVl,pH = 4,5 va[Pb'1 = 0,20.10-6M
Dieu kien thUc nghiem {DKTN): E^^p - -1,2V; t^^p - 120s; V = 15mV/s; E^^^^^ = -1,3^-HO,3V;U)^ 1600 vdng/phut.
DKTN: [Pb'1 = 1,00.10-8M; E^^^ = -1,2V, t^^p - 120s; V = 15mV/s; u = 1600 vdng/phut.
2.3.2. Khao sdt dnh hudng cua thanh phan nen va pH dung djch
Thyc hien thi nghiem dien phan dung dich [Pb'*] = 1,00.10-''M lan lUcrt trong 4 thanh phan nen kh^c nhau:
dem axetat (CH^COOH va CHjCOONa 0,1 M, pH = 4,5); dem axetat + KCI 0,1 M;
dem axetat + NaOH 0,1 M; dem axetat + NaNOj 0,1 M {cac DKTN gidng hinh 1). Ket qua (hinh 2) cho thay khi dung hdn hpp dem axetat CHjCOOH va CHjCOONa 0,1 M, pH = 4,5) thi pic thu 6iiac rat can ddi, I cua Pb ed gia tri Idn hon so vdi eae nen cdn lai.
Chung toi tiep tuc khSo sat pho do eua dung dich chu'a Pb'+ trong nen dem axetat NaCH^COO 0,1 M va CH3COOH 0,1 M d cac pH khac nhau (cac dieu ki&n do gidng hinh 1), ket quli (Hinh 3) cho thay d pH ^ 4,5 pie thu cd dinh pic eao hdn so vdi cac pH khae, pie cung can ddi hon nen nen dem axetat CH3COOH va CHjCOONa 0,1 M {pH = 4,5) dUdc chpn eho cac nghien cLfu tiep theo
2.3.3. Ket qua khao sat dnh hudng cua the dien phdn (E^i va thdi gian dien phdn lam giau (t^J
Khi tang the dien phan lam giau tir -0,9V den -1,4V thi ddng dinh hda tan cua Pb thay doi dang ke (b^ng 1). Tuy nhien, khi dien phan tCr-0,9V den-1,1V, dinh pie thap; khi dien phan lam gi^u d the am hdn -1,2V cd the cd cac ion
II
Hlnh 3. Anh hifdng ciia pH den I cua Pb'*
Khi thay doi thdi gian dien phan lam giau { t ^ J tCf 60-300s thi Ip cua Pb tang dan theo thdi gian dien phSn {B^ng 1} do thdi gian dien phSn cang lau thi lupng chat dupe tieh luy trgn bl mat dien cue cang Idn. Tuy nhien, khi tang t . cd the lam tich luy them ciz kim loai c^n trd nhU Zn, Cu... Mat khac, tai thdi gian di^n phan 120s, khi tien hanh do lap lai 5 lan, phep do co dd l^p lai tdt, I tuang doi cao va can doi nen chung tdi lUa chon t^^ = 120s cho cac"
thi nghiem tiep theo.
2.3.4. Khao sdt dnh hudng cua tSc dp quay dien cUc lam viec (ta); toe dit quet the(v}; bien dp xung (AE)
Khao sat toe 66 quay dien cUc (u) trong khoang 1000-^2200 vdng/phiit Ket qua cho thay d to = 1600 vdng/
phut thi ddng dinh hda tan I eOa Pb Idn nhat, dong thdi eho dd lap lai t6t nhat. Do vay u = 1600 vdng/phut dUflc chpn cho eac thi nghiem tiep theo.
Khao sat tde dd quet the t£f 0,005-^0,05 V/s cho t h % toe dp quft v
= 0,015V/scho gia t n l cua Pb tot nhat Ket qua nghien cufu anh hUdng cOa bien dp xung cho thay tai bien dp xung 0,05V pie can ddi, dp ldn cao nen gia trj bien dp xung 0,05V la thich hc^.
2.3.5. Khoang tuyin tinh, dd ldp lai, dp nhay, gidi ban phdt hiin vd 9M han dinh luang
Khoang tuyen tinh: Khi dien phcin dung dich chda Pb cd ndng dp tang dan ta0,42 -;- 50 pg/l (tuang 1,92.10'M den
\ Tap dif KHOA HOC & CONG NGHE • S o 1 7 , 2 0 1 3
SClENCETECHNOLOGYl
2,410-'M), c h u n g t d i nhan thay t r o n g khoang nong d p nay Pb cd d p tuyen tinh t d t (b^ng 2, hinh 4). Tien hanh xay dung d u d n g chuan trong khoang tuyen tinh nay (hinh 5) hp phUOng trinh d u d n g chuan y = 0,3941 x+ 0,4441 (R' = 0,9971).
B^ng 2. Sif phu 1^ eiia Pb''^ vao ndng do Pb'*
IWau n u o c h o T a y
W|ifl/I) 0,42
10 20 30 40 50
l,(|iA) 0,12 0,43 1,90 3,00 4,66 8,39 12,07 15,77 20,47
20 011.
150LL
10 CU.
50011.
. 1
M
i ! 1'
/ - '.^ i
-900m -800m -700m -6O0m -500m -4O0m -SOOm U|V)
Hinh 4. Pho do ghi do khoing tuyen tinh eua Pb'*
V = 03941x +04441 ^ R' = 0 9971
Nang do Pb jppb) Hinh 5. fiddng chuan xac dmh ham lugng Pb'*
Do lap lai: Tien hanh d o lap lai 10 an (n =10) d u n g dich chUa [Pb'*] = 1,45.10-^M c h o d p lap lai kha t d t , RSD
=2,67%.
D p nhay cua phUcJng p h a p t u o n g Joi t r o n g khoang tUO,3-0,63MA/ppb.
pb c = +/-
UfV) Hinh 6. Ket qua phan tich mau nude (Ml) Gidi han phat hien (LOD) cua phuang phap xac djnh t h e o qui tac 3a la LOD = 1,03.10-'M; gidi han dinh luong (LOO) eua phUdng phap la: LOQ
= 3,40.10-'M.
2.4. Cf ng dung phan t i c h mau nudrc SCf dung dien cue BijO^ - CNPE de phan tich ham lupng Pb trong mau nudc hoTay theo phuong phap DP- ASV.
Mau nUdc duoc lay tai hd Tay {tif ngay 22-^24/3/2013), mau sau khi lay dupe xCf l>? so bd b i n g d u n g djch axit HNOj. Sau d o dupc bao q u ^ n d nhiet dp 4-10''C, mang ve p h d n g phan tich va xCr ly mau. Sau d o phan tieh tren may cue p h o da nang 797 VA Computrace.
Ket qua phan tich cae mau nUdc t h e o p h u o n g phap t h e m ehuan cho thay ham luong eua Pb n a m t r o n g khoiing tCf 0,019 - 0,021 pg/l (bang 3). Ddi chieu vdi Quy ehuan ky thuat qude gia ve eh^t lupng nude mat QCVN 08:2008/
BTNMT t h i eac m a u nay d e u dat gia trj nam t r o n g gidi han cho phep (hinh 6).
Bang 3. Ket qua phan tieh mau Kihieu
mau Ml M2 M3 M4 MS
Ngay lay mau 22/3/2013 22/3/2013 23/3/2013 24/3/2013 24/3/2013
Ham lUCng Pb(|ig/I)
0,021 0,019 0,019 0,020 0,021
3. K^T L U A N
Da nghien cufu cac dieu kien thUc nghiem de xay dUng quy trinh phan tich ham luong Pb'* bang phuang phap DP-ASV sCf dung dien cuc paste dng nano caebon bien tinh b i n g Bi 0
0.021 ps'L 0.002 Mg/L(9.58%)
-lOOe-a-SOOe^ 0 5 00e-9lOOe-B 150e-B
c(g'Li
(BijOj-CNTPE). Cac dieu kien thUe nghiem bao g d m : t h e dien phan -1,2V;
thdi gian dien phan 120s, bien d p xung 50mV; toe d p quet t h e 0,015V/s; tde d p quay dien cac 1600 vdng/phut. Dien cUc duoc si!f dung cho ket qua khocing tuyen tinh t u a n g ddi rpng, d o lap lai tdt, gidi han phat han va gidi han dinh luong thi'p. Dien cUc dUOc Ung dung de phan tich mau nudc cho ket qua t o t
Phin bien khoa hoc: TS. Vu Thi Huong TAI LlEU THAM KHAO
[1]. Cao Van Hoang, Trmh Xuan Gi3n, Trmh Anh fide, Tif Vong Nghi, Cao The Ha, Nguyen Van Hop, Nguyen Thj Lieu, Difong Thi Tu Anh, Nghien edu xac dmh dong thdi lifong vet indi (In), cadimi (Cd) va chi (Pb) bang phifdng phap Von-Ampe hda tan anot vdi ldp mang bitmut tren dien eUc paste nano cacbon.
Tap chi hoa hoc,T 48 (4Q, Tr. 479 - 484 (2010) [2]. Niiria Serrano, Aristides Alberich, Jose Manuel Diaz-Cruz, Cristina Arino. Miquel Esteban, Coating methods, modifiers and applications of bismutti screen-printed electrodes. Trends in Analytical Chemistry, Vol. 46,15-29, (2013)
[3]. Fabiana Arduinl, Josefina Quintana Calvo, Aziz Amine, Giuseppe Pallesehi, Danila Moscone, Bismuth-modified electrodes for lead detection.
Trends in Analytical Chemistry, Vol,29, No 11 (2010) [4]. Ivan S'vancara, Karel Vytr'as, Kurt Kalcher, Alain Walcarius, Joseph Wang, Carbon Paste Electrodes in Facts, Numbers, and Notes: A Review on the Occasion of the 50-Years Jubilee of Carbon Paste in Electrochemistry and Electroanalysis. Electroanalysis, 21,No. 1,7-28(2009)
[5]. Gregory G. Wildgoose, Craig E. Banks, Henry C. Leventis,andRichard G. ComptonA, Chemically Modified Carbon Nanotubesfor Use in Electroanalysis.
Microehim Acta 152,187-214 [2006)
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