TAP CHl KHQA HQC vA CQNG NGH$, Tnrimg Dai hpc Khoa hoc - DH Hue Tap 7, Si 1 (2017)
K H A O S A T M O T S O Y E U T O A N H H l T d N G D E N T I N H I E U V O N - A M P E H O A T A N X U N G V I P H A N C U A H g "
T R E N D I E N C ^ C K I M ClTOTVG P H A T ^ B o
Le Thi Thiiy'', H o i n g T h i i Long^
' Sa Khoa hpc & Cdng nghi tinh Quang Nam Khoa Hoa hoc, truang Dgi hpc Khoa hpc, Dgi hpc Hui
* Email: lethuy09.qn(^gmailcom TOWTAT
Diin cue kim cuang pha tap Bo dd dupc su dung di ghi dudng von-ampe hoa tan xung vi phdn cda dung dich H^. Trong dung dich nin chua H^' 5 ppb, KCl 0.03 M. At/" 0.5 ppm, dink hoa tan cua thuy ngdn xudt hign sau khi ldm giau a -900 mV trong 300 s. Ldm sgch diin arc sau mdi phep do a thi 800 mV trong 10 s khong ldm tang gid tri cua Ip, nhtmg da ldm tdng ddng ki dp lap lgi cua phep do. Kit qud do lap lai 18 ldn cho thdy. Ip do dupc lap lgi rdt tot ngay a nong dg /fg" 1 ppb. Vai thai gian dien phdn ldm gidu 300 s, gidi hgn phdt hiin cda H^ tinh theo quy tdc Said 0.08ppb, gidi hgn djnh lupng Id O.Sppb.
Tir khda: BDD, diin c\rc kim cuang, thdy ngdn. von-ampe hda tan.
I . D A T V A N D E
Thuy ngin li kim loai ngng cd ddc tinh cao ddi vdi con ngudi va nhifu loii sinh vat khac. Trong cic ngudn nude, thuy ngan thudng tdn tai d dgng vet vi sifu vet. Df phit hifn vi dinli lugng dugc Hg frong miu nude, can su dung cic phuang phip phin tfch cd df nhgy cao nhu quang pho hip thu nguyen td (AAS), quang phi huJTih quang nguyfn tii (AFS), khdi phi plasma cap cam dng (ICP-MS)... [1]. Mge du cd do nhgy va do chinh xac cao, nliung cac phuang phap neu trfn dfu phai su dyng thift bj dat tien, chi phi phin tich cao. Vdi muc dich giam chi phi phin tich, nhilu nghifn cdu da va dang dugc thuc hien df dinh lugng thuy ngan bang cic phuong phip phin tich difn hda, die bift la phucmg phap von-ampe hda tan anot (ASV). Difn cyc lim vifc thutmg dugc sd dung dl phan tich thiiy ngin bing phuang phip ASV la difn cyc ran dia vang, difn cyc sgi vang, vi sgi vang hogc than thiiy tinh ket hgp mang vang [1]. Do cd nhieu uu diem so vdi cac Ioai difn cyc truyen thong, gin day, difn cyc kim cuong pha tgp bo (boron doped diamond, BDD) dang dugc quan tim nghifn ciiu df xic djnh thuy ngan bang phuang phip ASV [2-6]. Mac du da cd nhieu cdng trinh nghien cdu phat frien phuang phip difn hda df xac dinh Hg, nhung vi nhifu ly do khic nhau, van chua cd mdt phuang phip difn hda nao dk dinh lugng Hg dugc ap dung rgng rai frong thyc t l [3].
Khao sit mpt so yeu ti inh huang din tin biiu von-ampe hda tan xung vi phan cda Hg"...
Bai bao niy trinh bay mgt sd kit qua khao sat dieu kifn dl ghi tin hifu von-ampe hoa tan xung vi phan (DP-ASV) cua tiiuy ngan frfn difn cue BDD va mdt sd yeu td anh hudng nhim cung cip cic thdng tin ban diu de phit friln phuong phap difn hda ?£ac dinh ion kim logi nay.
2. THirC NGHIEM 2.1. Hda chat va dyng cy
Cic dung djch chuin Hg° dugc chuin hi tii dung dich chuin gdc Hg" 1000 mg/L (Merck). Dung djch Cu° 10 ppm dugc chuin bj td dung djch Cu° 1000 ppm (Merck). Dung dich Au 10 mM dugc chuin bi bing cich hda tan HAuCU.SHiO (Merck) frong dung dich HCl 0,1 M.
Cac loai thudc tiid khac deu dugc pha che td hda chat tinh kliift diing cho phan tich (Merck).
Diing nude cat 2 lan df pha chf hda chit. Cac tiii ngliiem dugc tifn hanh frfn thiet bi 797 VA Compufrace (Mefrohm) vdi hf 3 difn eye: difn cyc BDD (Wmdsor Scientific, Anh); difn cyc so sanh: Ag/AgCI/KCI 3M va difn cyc phy frg Pt.
2.2. Tiln hanh Chudn bi dien cue
Lip difn cyc BDD vao binh difn phan chda HCl 1,5 M va hogt hda d thi -2 V frong khoang thdi gian 300 s; tiip tuc hogt hda difn cyc trong dung dich frfn bing each quet the theo che dg von-ampe vdng tu -500 mV dfn +800 mV, tic dp quet thi 35 mV/s, lap lai 10 vdng. Liy difn cyc ra khdi binh difn phan, rua can than bing nude cit 2 lin tnrdc khi sd dyng.
Ghi du&ng von-ampe hoa tan
Phuang phip von-ampe hda tan df dinli lugng Hg fren difn cyc BDD, dya frfn ca so cac phan iing difn hda sau [5]:
Giai dogn lim giiu: Hg" + 2e ^ Hg"
Giai dogn hda tan: Hg" - 2e ^ Hg"
NIU trong miu cd chua ion Cl" thi cd till xiy ra phan iing:
Hg^* + Hg" + 2Cr ->. HgiCb-l-
Hg2Cl2 ket tiia Ifn be mat difn cyc va khd bi hda tan frong giai doan lam sach difn hda, do do lam giam dg lap lgi cua tin hifu phan tich. Dl khic phuc, cd thi them Au™ [5], hoic Cu"
[2] vao dung dich phan tich. Trong giai dogn lira giau, Au", Cu" bim len bl mit difn cyc tao hdn hdng vdi Hg", hgn chi sy tgo thanh Hg2Cl2.
Cho dung dich nghien cuu chua Hg", KCl, Au™ vao binh dien phin. Difn phin lam giau d till (Edq,) vi tiidi gian (tjep) dk tgp tiimg Hg vi Au Ifn be mgt difn cyc. Kit tiuic giai doan niy, ngung quay difn cyc va nghi 5 s - 10 s. Sau dd, quet till tiieo chieu duong din tii Edep dfn +800 mV bing ky thuat xung vi phin (DP). Dl phfp do cd do lap lai tit, tiln hanh Iam sgch
TAP CHl KHOA HQC VA CQNG NGH$, Tnrimg Dgi hpc Khoa hpc - DH Hui Tip 7, Si 1 (2017) BDD sau mdi phep do bing ky thuit difn hoa. Xic dinh the (Ep) va dong (lp) dinh hoi tan td dudng von-ampe hda tan thu dugc. Xac dinh ning df thOy ngin bang phuang phap thfm chuin.
3. KET QUA VA THAO L U A N
Dya vao nhifu edng bo trude diy, mft so dieu kifn thi nghifm (DKTN) ban diu di dugc cl dinh df tifn hanli cac thi nghif in khao sat va dugc frinh bay d bang 1.
Sdng I. Mot sd dilu kifn c6 dinh ban diu dl ghi In DP-ASV cua Hg" fren dien cyc BDD STT
2 3 4 6
Cac thong sd Thf difn phan lam giau Thdi gian dien phin Tdc do quay Khoing quet the
Ky hifu Edep
tdED fO UraDBS
BffD vi mV
s rpm
V
Gia tri - 9 0 0
300 1400 -1 - 1,4 Cic thi nghifm so bd da dugc thyc hifn vdi cac chat difn ly nen (HCl, H2SO4 va KCl) va chit tgo mang (Au™, Cu"). Ket qua cac thi nghifm cho thay, chi cd dung dich nfn chua KCl kit hgp vdi Au™ mdi cho phep ghi dugc Ip nhgy va lgp lgi. Do dd, thanh phan dung djch nfn nay dugc chpn de tien hinh cic thi nghifm khao sat sau.
3.1. Anh hudng ciia ning dp KCl
Cd dinh cac dilu kifn ban diu, chuin hi dung dich phin tich chda Hg° 5 ppb, Au™ 1,5 ppm, KCl cd ndng dp tang din tii 0 M den 0,3 M. Kit qua thuc nghifm cho thiy khi tang dan ndng dp KCl td 0 M din 0,3 M, cudng dd dinli hda tan cua thuy ngin (lp) bit diu tang din sau do giim. Cd thi do khi ndng do Cl" cao thi kit tiia Hg2Cl2 kho tan kit tiia Ifn bl mat dien cyc nhilu hon, can frd qua trinh dien hda. Ngugc lgi khi nong df Cl" thap thi ndng dd Cl" khdng du dl tgo phuc vdi Au™, anh hudng din qua trinh khd ving va tao hdn hdng vdi thuy ngan, nen Ip ciia thuy ngan giam va cd dp lgp Igi kem. Klu dung djch phin tich khdng chda KCl, khdng nhihig dinh cua Hg° khdng xuit hifn rd, ma dinh hoa tan ciia vang cung bj tach ddi, khdng can dii. CJ ning dp KCl la 0,03 M, Ip cua Hg" cao va can dii nen ndng dp nay dugc chpn cho cac thi nghifm tiep theo.
r 10
\'<
-Ip(uA) —0—RSD(%)>>"-'
0 0.03 0.06 0.09 0.12 0.15 0.18 0.21 0.24 0.27 0.3 0.33 CKCICM)
Hinb L Biln thien ciia gii frj Ip vi RSD theo ning dp KCl.
DKTN: H^ 5 ppb; AiF 1.5 ppm; cdc DKTN khdc nhu a bang 1.
Khio sat m^t so yiu to anh huung dlsn tin hiiu von-ampe hda tan xung viphin ciia H^ ...
3.2. Anh hudng cua nong do Au
Trong qua trinh dien phan lam giau, Au™ chuyln thanh Au" kit tiia Ifn bl mit dien cue tgo hdn hong vdi Hg" hgn chf sy tgo thinh kft tiia khd tan Hg2Cl2 len be mit difn cyc.
D I danh gia anh hudng ciia ndng dp Au™ dfn tin hifu hda tan ciia Hg° tiln hanh thi nghifm nhu sau: Cd dinh ndng dp Hg'' va KCl frong dung djch phan tich tuong dng li 5 ppb va 0,03 M, tiiay ddi ndng dg Au™ tii 0,25 ppm den 3,0 ppm. Kft qua ghi Ip cho tiiiy khi ndng do Au™ < 0,5 ppm, Ip tiiip va do lap lgi khdng tit (RSD = 7,0 %). Nguyfn nhin cd till do d ndng dp Au™ niy tgo ra lugng Au" kit tiia tren bf mgt difn cyc khdng du dl hinh thanh hdn hing voi Hg" dk hgn chi qui frinh tao tiianh kit tiia Hg2Cl2, lam tin hieu hda tan cua Hg" giim dang ]sk.
Ddi vdi ndng dg Au™ > 0,5 ppm tin hifu hda tan ciia Hg° cao va lap lai tot. De tiet kifm hda chit, chiing tdi chpn ndng dp Au'" la 0,5 ppm dl tifn hanh cac tiii nghiem tif p theo.
r 10
—•—Ip(uA) --*--RSD(%)
^ 3 -^2
4 Q 2
0 0.5 1 J . 5 , ^2 2.5 3 CAU (ppm)
Hinh 2. Biln thien cua Ip vi RSD theo ndng dp Au"".
DKTN: 77/5ppb; KCl0.03 M; E^p = -900mV:t^p = 300s.
33. Anh faudng ciia the va thdi gian dien phan la giau 3.3.1. Thf dien phin lam giau (Udep)
Trong giai doan lam giau khi ap vao difn eye mdt the dd am, Hg" bj khu ve Hg vi tgo hdn hdng vdi Au kun logi frfn bf mat difn cyc lam vifc. Do dd, tai thf dd am Hg sS dugc lam giau frfn bf mat difn cyc lam vifc. Khao sit inh hudng cua the difn phan lim giau trong klioang tii -700 mV din -1200 mV, cd thf tiiiy khi Ujq, bing -900mV, lp dgt gia fri cyc dai, ddng thdi do lap Igi cda kit qui do Ip tit (Ip- 3,04 pA; RSD = 4,7%). Vi vgy, till difn phan lam giau -900 mV dugc chgn de su dung cho cac tiii ngliif m tiep theo.
3.3.2. Thai gian difn phin lim giau (tjep)
Cudng do ddng dinh hda tan phy thugc nhifu vao thdi gian dien phin lam giiu. De xac djnh dugc thdi gian difn phan thich hgp vdi dung djch phan tich chua Hg" 5 ppb, da tiln hanh ghi Ip d cac thdi gian difn phin tang din tu 60 s dfn 580 s. Khi tang thdi gian difn phan lam giiu tu 60 s din 580 s, hifu qua lam giau tang do do Ip tang din. Khi tj^p = 300 s, cudng df ddng dmh hoa tan da dat gia tii tuong ddi ldm, do lap lgi tit (^=2,32 pA; RSD = 3,4%). D I tilt kiem thdi gian thyc hifn thi nghifm, thdi gian difn phan 300 s dugc chpn dl tiln hanh cac nghien ciiu tiep theo.
TAP CHl KHQA HQC VA CONG NGH$. Tnrimg Dgi hoc Khoa hpc - DH Hue Tip 7. So 1(2017)
60 120 180 240 300 360 420 480 540 600 td,p(s)
Hinh 4. Anh hudng ciia thdi gian dien phin lim giiu den lp cua Hg"
DKTN: / / / 5ppb: Ai/" 1.5ppm; KCl 0.03 M;
Ej,p = -900mV.
-1300-1200-1100-1000-900 -800 -700 -600 U^^tmV)
Hinh 3. Anh hudng cua thi dien phin lim giiu din Ip ciia Hg"
DKTN H^' 5ppb; Aif0.5ppm; KCl 0.03 M;
t^p = 300s.
3.4. A n h h i r d n g c u a t h e v a t h d i g i a n l a m sach 3.4.1. Thf Iim sach (Udeau)
Khi ket thuc qua trinh hda tan, lam sgch bf m a t dien c y c bang c i c h i p v i o m f t the d u o n g h o n t b i hda tan cua c h i t p h i n tich (gpi la t h i lam sgch) df hda tan kim logi cung n h u cac san p h i m k h i c da tgp trung frfn b l m i t difn cyc frong giai dogn lam giau. Tifn hanh khao sat Utiean frong Idioaug t u 0,6 V den 1,4 V. Kft q u i t h y c nghifm cho t h i y Udean = 0,8 V , Ip dgt gia tri cyc dai (Ip=3,4), dp lap lgi ^ t v d i R S D = 2 % .
3.4.2. Thdi gian lam sach (tdean)
Khi tang thdi gian lam sach trong k h o i n g t d 0 s d i n 120 s, gia tri trung b m h ciia Ip h i u n h u khdng thay doi. Tuy v i y , khi khdng ap thf lam sgch (tdean = 0 s) thi dp lap lai ciia k i t q u i d o khdng tot, cd the d o khi khdng t i l n hanh giai dogn lam sgch bf mat difn c y c bj thay doi sau c i c phep do lifn t i i p va anh h u d n g dfn dp on dinh ciia q u i trmli dien cyc. O tciean = 10 s thi Ip cao v i d o lap lgi r i t t i t ( R S D = 0,9%). D o do, tciean=10 s, d u g c su dung dk t i l n hanh c i c nghifn cihi tiep theo.
0.5 0.6 0.7 0.8 0,9 1 1.1 1.2 1.3 1.4 1.5 Eck.nC'nV)
Hinh 5. Anh hudng cua thi Iim sgch din Ip cua Hg"
DKTN: Hg"5ppb: AiflO.Sppm: KCl0.03 M: Ej,, --900mV: li:, = 300s.
Hinh 6. Aiih hirdng cda thfri gian lam sach den Ip cuaHg"
DKTN: H^'Sppb: A,f0,5ppm: KCl 0.03 M: £ * ,
=-900 mV:lj„-300 s
Khio sit mpt so yeu ti inh huung din tin higu von-ampe hoa tan xung vi phin cda H^ ..
3.5. Anh hudng ciia toe dp quay cyc (ra)
Tdc dp quay ciia difn cyc inh hudng nhifu dfn qua trinh van chuyfn chat phan tich dfn bl mgt dien cyc. Vi vgy, se anh hudng din cac qua frmh difn hda trong cac giai dogn phin tich bing phuang phip von-ampe hoa tan. Tien hanh khio sat anh hudng cua tdc dg quay cue (ta) tir 200 din 1600 vong/phut. Kft qui khao sit cho thiy, Ip tang ty If vdi tic do quay ciia difn circ.
Do lgp Igi ciia Ip tdt khi tic dg quay cyc dgt td 1000 vong/phut frd Ifn. Dl tranh tinh frgng dung dich hi bin Ifn thanh binh khi quay cyc vdi tic dg ldn, tie dp quay 1200 vdng/phiit (Ip =4,26 pA; RSD =1,4%) dugc lya chpn dl tiln hanh cic thi nghifm tiip theo.
3.6. Anh hudng ciia cac thong so i^ thnat von-ampe xung vi phan
Cac thdng sd ciia ky thuat von-ampe xung vi phin cd Hfn quan chat che vdi nhau, chung cd tic dgng tdng hgp din thf dinh hda tan (Ep) va Ip ciia thuy ngan.
3.6.1. Bien df xung (Uampii)
Bifn dp xung la mgt frong nhdng yeu td anh hudng Idn den chieu cao (]^) vi be rpng peak. Ghi Ip ciia Hg" khi bifn dii Uampii frong khoang 10 mV - 100 mV. Kit qua thi nghiem cho thiy, khi tang bien dp xung td 10 mV din 70 mV thi Ip tang din td 0,9 jiA din 5,16 pA. Sau do, nfu tiip tyc tang Uamph td 70 mV din 100 mV till Ip tang chgm, ddng thdi cd sy dich chuyln the dinh hda tan cda Hg^vl phia am din. Chpn Uao^ii= 70 mV(]^=5,21 ^A;RSD= 1,3%) dl tiln hanh cac khao sit tiep theo.
3.6.2. Tdc df quetthl(v) 8 1 _
A ~
20 30 40 50 60 70 80
U.»,pN(niV) 10 15 20 25 30 35 40 45 50
V (mV/s)
Hinh 7. Anh hudng ciia bidn do xung (U ampiO din Ip Hinh 8. Anh hudng cia tic df qu^t till den Ipcvia
cua Hg". Hg".
DKTN: Hg"5ppb; AiJ^0.5ppm; KCl0.03 M; Ea,p DKTN: / / / 5 p p b ; AiF0.5ppm; KCl 0,03 M; £*,,
= -900 mV; t^p = 300 s. = -900 mV; tj,p = 300 s.
Tifn hinh ghi Ip cua dung dich phan h'ch chua Hg'' 5 ppb khi bifn ddi v td 5 den 50 mV/s. Vi tic dp quet thi phu thufc vio thdi gian mdi budc thf (t^ep) va budc thi (Us,ep) nen de bifn doi tic do quet thi tu 5 den 50 mV/s, gid cd djnh Us,ep= 6 mV vi thay doi t^ep tu 0,12 s den 1,2 s. Ket qua cho thiy, khi tdc dp quet tang Ifn td 5 din 35 mV/s thi Ip tang Ifn rit nhanh, sau dd ting chgm Igi. Ci tie dg quet till 35 mV/s, Ip cao, do lap Igi tit (Ip = 6,11 ^A; RSD = 0,8%)
TAP CHl KHQA HQC VA C6NG NGH$. Tni^g Dgi hpc Khoa hpc - DH Hui Tip 7, Si 1 (2017) nfn chgn tdc dp quet till nay dl khao sat cic thi nghifm tiep theo.
3.7. Dp lap lai, khoang tuyen dnh v^ gidi han phat hifn 3.7.1. Do lip lgi
Tifn hanh ghi ^ lap lai cua dung dich nghifn cdu vdi cac dieu kien thich hgp di dugc lya chpn d trfn. Kft qua thi nghifm cho thiy do lip Igi ciia kit qua ghi Ip tit ngay d ndng dg nhd ciia Hg" la 1 ppb (Jp^^ =2,30 pA; RSD = 4,7%, n=9); Khi ndng dp H ^ la 5 ppb do lip Igi cua Ip rit tit, vdi RSD = 1,0% (n=9).
3.7.2. Khoang tuyen tinh
Ghi Ip cua cac dtmg dich phin tich vdi ndng dg thuy ngin tang din tii 0,4 din 10 ppb.
Kft qua dugc bifu dien frong hinh 9.
Kft qua thi nghifm cho tiiay Ip cd tiif ph\i thufc tuyfn tinli vio nong do Hg" frong khoing ndng do tii 0,4 den 3,0 ppb. Khi ndng dg Hg" tang fren 5 ppb thi Ip giiin, dilu nay khdng phu hgp vdi quy luit thdng thudng (khi tang dan ndng do cua chit phan tich thi Ip se thudng ting, sau do tang chgm dan v i cd the dgt gia frj bao hda). Hifn tugng bit thudng nay cd till li do ndng df Au" da diing de ngan chgn sy tgo thanh kft tiia Hg2Cl2 frong thi nghifm nay cdn qui thip vi chi phu hgp vdi ning dg Hg" la 5 ppb. Vi vgy, khi tang nong dg Hg", mi khdng ting Au"", Hg" ket tiia frfn bl mat difn cue nhanh chdng bi chuyfn tiiinh Hg2Cl2 che phii difn cyc, lam Ip cda thiiy ngan giam mgnh.
Cng (ppm)
Hinh 9. Biln thien ciia tin hieu hda tan Ip theo ning df Hg".
Sd dyng phuong phip bmh phuang tdi thifu df xac dinh phuong trinli hdi quy tuyfn tinh Ip - Cngn frong khoing ndng dg cua Hg° td 0,4 dfn 3,0 ppb, ta cd phuang frinh sau:
Ip = (1,707+0,065) CHg°
hf so tuong quan: R = 0,9957.
3.7.3. Gidi han phat hifn va gidi hgn dinh lugng
Dya vao cic kit qui thi nghifm da diing df xac dinh khoang tuyen tinh va phuong trinh hii quy tuyin tinh, ip dung quy tic 3a, cd thf xac dinh dugc gia fri gidi hgn phit hien (LOD) va gidi han dinh lugng (LOQ) cua phep dinh lugng Hg":
LOD = 0,08 ppb; LOQ = 0,3 ppb 83
Khio sit mdt si yiu ti anh huang din tin higu von-ampe hda tan xung vi phin cua H^ ...
4. K E T L U ^
Cd t h i ghi d u g c tin hieu von-ampe hda tan xung vi phan ciia d u n g dich H g " fren difn cyc kun c u a n g pha tap b o frong dung dich nfn c h d a KCl 0,03 M ; Au"' 0,5 ppm. T h i dien phan i i m giau thich h g p l i -900 m V . Trong dieu kien thi nghifm ciia bai b i o , k h o i n g tuyfn tinh cua Ip-Cng kha h?p (0,08 - 3,0 ppb). Dieu n i y cd thf d o nong dp Au™ thfm vao buih difn phan con kha thap, c h u a p h u h g p vdi cac khoang n d n g dp ldn cua Hg". V d i 300 s difn phan lam giau, L O D va L O Q (theo quy t i c 3 o ) lan lugt la 0,08 ppb va 0,3 p p b . Cac k i t qua khao s i t budc diu, cho thay cd thf tiep t^ic nghifn cdu d e phat frifn p h u o n g phap dinh lugng H g " b i n g ky thu^
von-ampe h d a tan andt xung vi p h i n dung difn c y c kim c u o n g p h a tap bo.
T A I L I E U T H A M K H A O
[1]. Mana Zaib et al. (2015). Electrochemical determination of inorganic mercury and arsenic - A review, Biosens. Bioelectron, 74, pp. 895-908.
[2]. Chaiyo S., et al. (2014). Highly sensitive determination of mercury using copper enhanced by diamond elecfrode coupled with sequential injection-anodic sfripping voltammetry, Anal Chem.
Acta, %52, pp. 55-62.
[3]. Kenedy J.H. (1990). Analytical Chemistry Principles, Saunder College Publishing, USA, 2°* ed.
[4]. Macpherson J.V. (2015). A practical guide to using boron doped diamond m elecfro-chemical, Phys.
Chem. Chem. Phys., 17, pp. 2935-2949.
[5]. Manivaiman (2005). Mecury detection at boron doped diomond elecfrodes using a rotating disk technique. J. Electronal.Chem, 557, pp. 287-293.
[6]. Seehra M., Manivannan A., Fujishma A. (2004). Dectection of mercury at ppb level in solution using boron-doped diamond elecfrode. Fuel Process. Technol, 85, pp. 513-519.
TAP CHl KHQA HQC VA CONG NGHB. Tnr^g Dgi hpc Khoa hpc - DH Hui Tap 7, Si 1 (2017)
A N E W E S T I G A T I O N O F F A C T O R S A F F E C T I N G D I F F E R E N T I A L P U L S E S T R I P P I N G V O L T A M M E T R I C S I G N A L S O F H g "
O N B O R O N D O P E D D I A M O N D E L E C T R O D E
Le Thi T h u y ' ' , Hoang Thai Long^
' Quang Nam Department of Science & Technology
^ Department of Chemistry, Hue University College of Sciences
* Email: lethuy09.qn@^ail.com ABSFRACr
Boron doped diamond (BDD) electrode was used to obtain the differential pulse stripping voltammograms cfH^ solutions. In a solution containing H^ 5 ppb. KCl 0.03 M and At/"
0.5 ppm. stripping peak ofHgf'was recorded after a deposition step of 300 s at -900 mV.
After each run, BDD electrode was electrochemically cleaned by applying a cleaning potential of 800 mV in 10 s. This cleaning step did not increase stripping current ofH^, but significantly improved the repeatability. Results of 18 replicated measurements indicated Ihat. the repeatability oflp were good even at very low concentration of H^'.
With a deposition rime of 300s, the limit of detection and limit of quantification of H^' calculated using "3 arule" were 0.08 ppb and 0.3 ppb, respectively.
Key words: BDD, diamond electrode, mercury, voltammetry.
