research article determination of total germanium in ...en the three-electrode system was immersed...

Hindawi Publishing CorporationInternational Journal of ElectrochemistryVolume 2013 Article ID 735019 7 pageshttpdxdoiorg1011552013735019

Research ArticleDetermination of Total Germanium in ChineseHerbal Remedies by Square-Wave Catalytic Adsorptive CathodicStripping Voltammetry at an Improved Bismuth Film Electrode

Shangwei Zhong1 Jiali Su2 Liang Chen1 Jiefeng Tong3 Wenfang Jia3

Xiangjun Li2 and Hong Zou1

1 Department of Chemistry Capital Normal University 105 North Xisanhuan Road Beijing 100048 China2 College of Chemistry and Chemical Engineering University of Chinese Academy of Sciences 19A Yuquan Road Beijing 100049 China3Haozhuang Hospital of Yingze District Taiyuan Shanxi 030045 China

Correspondence should be addressed to Xiangjun Li lixiangjucasaccn and Hong Zou zouhlixj163com

Received 1 July 2013 Accepted 12 August 2013

Academic Editor Sheng S Zhang

Copyright copy 2013 Shangwei Zhong et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

A catalytic adsorptive cathodic stripping voltammetricmethod on an improved bismuth film electrode (BiFE) for the determinationof trace germanium in the presence of pyrogallol has been investigated A well-defined and sensitive stripping peak of Ge(IV)-pyrogallol complex was observed at minus079V (versus SCE) in a 01M acetate buffer solution (pH 48) at a deposition potential ofminus034V The reduction current is catalytically enhanced by adding KBrO

3 The experimental variables and potential interference

were studied Compared with the BiFE plated in the solution prepared based onHAc-NaAc without trisodium citrate the improvedBiFE electrodeposited in the solution of HAc-NaAc containing trisodium citrate displayed a better electroanalytical performancefor the determination of germanium(IV) Under the optimized conditions the detection limit of Ge(IV) was 60 ng Lminus1 and therelative standard deviation (RSD) was 373 at 5 120583g Lminus1 level (119899 = 9) This method was successfully applied to determine the totalgermanium in several Chinese herbal remedies

1 Introduction

Germanium is an essential trace element in human bodyand very important for our health Either overaccumulationor deficiency of germanium could result in various diseasessuch as acute renal failure [1] Germanium compoundsdisplay a number of biological activities [2] and are describedas antioxidants and immunostimulatory medicine that areused to inhibit the progress of cancer and destroy cancercells [3] Organogermanium compounds are considered topromote health and cure diseases [4]

Various analytical methods for determining the trace andultratrace levels of germanium in medicine [4] food [5ndash7] water [8] and soil [5] have been reported for exampleinductively coupled plasma-mass spectrometry (ICP-MS)connected with solid phase extraction [4 8] and combination

of hydride generation [9] graphite furnace atomic absorp-tion spectroscopy (GF AAS) [6 10] the spectrophotometricmethod [11] the hydride generation atomic fluorescencespectrometry method [12] the luminol chemiluminescenceflow method [13] and electrochemical methods [5 7 14ndash16]Among these methods electrochemical methods show obvi-ous advantages in accuracy sensitivity simplicity low costand analytical speed [7] Adsorptive stripping voltammetry(AdSV) is well suited to determine the trace metal elementsThe AdSV procedures developed for the determination ofgermanium were based on the adsorptive accumulation of agermanium complex on the hanging mercury drop electrode(HMDE) [5 14ndash18] or the mercury film electrode (MFE) [7]Despite the advantages of mercury electrodes for strippingvoltammetry the toxicity of mercury or mercury salts couldnot be neglected since mercury causes risks to public health

2 International Journal of Electrochemistry

and unavoidably contaminates the environment in practiceSo it is significant to develop alternative electrodes to replacethe mercury electrode In recent decades bismuth film elec-trode (BiFE) consisting of a thin bismuth film deposited ona suitable substrate material such as glassy carbon electrodehas been developed and shown a similar performance withmercury electrode [19 20] Since the toxicity of bismuth andits salts is negligible the BiFE is considered to be environmentfriendly and might be a satisfying alternative to MFE More-over the BiFE has been widely used to determinate manytrace elements such as Cr(VI) [21 22] As(III) [23] Co(II)and Ni(II) [24] and Cd(II) and Pb(II) [19] However there isno report about the determination of germanium in Chineseherbal remedies by using BiFEs so far And our group foundthat the analytical performance of bismuth film electrode wassignificantly improved by adding citrate to a relatively higherpH electrodeposition solution [25]

In this study a new and sensitive analytical method wasdeveloped for the determination of germanium based onsquare-wave catalytic adsorptive cathodic stripping voltam-metry using an improved BiFE as the working electrodeand pyrogallol as a complexing ligand The optimization ofthe developed technique was achieved by testing the rele-vant experimental parameters such as pH value depositiontime deposition potential and pyrogallol concentrationThemethod was successfully applied to determine the tracegermanium in several Chinese herbal remedies

2 Experimental

21 Apparatus and Reagents An Autolab PST050 electro-chemistry workstation (Radiometer France) and a micro-wave digestion system (CEM Model MDS-2000 USA) wereused A three-electrode electrochemical cell system was usedwith the multimode electrode the working electrode was abismuth film electrode (BiFE) the reference electrode was asaturated calomel electrode (SCE) and the auxiliary electrodewas a platinum wire PGENERAL TAS-990 atomic absorp-tion spectrophotometer (Chengdu Superman SampT Co LtdChina)

All the reagents used were of analytical grade purityunless otherwise stated The 1000mg Lminus1 bismuth solutionwas prepared by dissolving proper amount of Bi(NO

3)3sdot5H2O

(Sinopharm Chemical Reagent Co Ltd China) in 5HNO

3 The germanium standard solutions were made from

a stock of 1000 120583gmLminus1 Ge(IV) (China Iron amp Steel ResearchInstitute) by dilution with water as required A 01M HAc-NaAc (pH 48) served as a supporting electrolyte in theanalysis step Stock solution (002mol Lminus1) of pyrogallol wasprepared weekly and was stored at 4∘C in a refrigeratorA pH meter (PB-10 Sartorius China) was used for pHmeasurements All aqueous solutions were prepared usingultrapure water (Milli-Q systems USA)

22 Procedure

221 SWAdCSV Measurements of Germanium(IV) Prior tobismuth film formation the glassy carbon electrode (GCE)

was polished with a 03ndash005120583m alumina slurry on a feltpad thoroughly rinsed with water and then sonicated in5 HNO

3 ethanol and distilled water A bismuth film

was prepared on a GCE by applying minus10 V for 5min in a100mg Lminus1 bismuth(III) and 1mol Lminus1 acetate buffer media(pH 45) with 008mol Lminus1 sodium citrate Then the three-electrode system was immersed into 30mL 01mol Lminus1 HAc-NaAc (pH 48) solution that contained 3 times 10minus4mol Lminus1KBrO

3 13 times 10minus3mol Lminus1 pyrogallol was added into the

volumetric cell The preconcentration potential (minus034Vversus SCE) was applied while the solution was stirred for150 s The solutions were stopped and followed by a 15 sequilibration time And then the voltammogram recordedby applying a negative scan from minus05 to minus10 V using thesquare-wavemode with the following parameters frequency25Hz scan increment 4mV pulse height 50mV After theground voltammogram has been obtained the adsorptivestripping experiment was repeated for the addition of propergermanium stock solution The electrode was cleaned atminus13 V for 10 s before each measurement

222 Determination of Germanium(IV) in Real Samples Theanalysis procedure of Chinese herbal remedies sample wasas follows the 05 g sample 5mL HNO

3 and 1mL H

2O2

were placed into a microwave digestion tank overnight andthen digested according to a microwave digestion procedure(5min at 180∘Cand then 15min at 200∘C)After cooling downnaturally the seal pot of the digestion tank was opened andeach solution was heated to empty it of HNO

3on a hotplate

(120∘C) Then the digestion tank was cooled down to roomtemperature and diluted to 25mL in a volumetric flask withdouble-distilled water These sample solutions were analyzedby SWAdCSV as mentioned above

3 Results and Discussion

31 Electrochemical Behavior of Germanium(IV)-PyrogallolComplex at the Improved Bismuth Film Electrode Figure 1shows the SWAdCSV response for 10 120583g Lminus1 Ge(IV) obtainedat (c) BiFE plated in 1molL acetate buffer (pH 45) withouttrisodium citrate and (d) the improved BiFE plated in 1molLacetate buffer (pH 45) containing 008molL trisodiumcitrate And it was obvious that the BiFE (d) electrodepositedinHAc-NaAcmediumcontaining sodiumcitrate also showeda better electroanalytical performance for determination ofGe(IV) than the BiFE (c) According to Zhang et al [25]and Nunes and Faria [26] the significant improvement wasdue to the addition of trisodium citrate that helped form ahomogeneous structure by aggregates of spherical particleswith a few nanometers in diameter We also investigatedthe effect of KBrO

3on the electrochemical behavior of

germanium(IV)-pyrogallol complex at the improved bismuthfilm electrode No striping peak of pyrogallol was observed(see Figure 1(a)) When Ge(IV) was present together withpyrogallol in the solution a well-defined stripping peak ofthe Ge(IV)-pyrogallol complex was observed at a potential ofminus079V (see Figure 1(b)) When KBrO

3was added into the

above solution the reduction peak current of the complex

International Journal of Electrochemistry 3

0

2

4

6

8

10d

c

b

a

minus10 minus09 minus08 minus07 minus06 minus05

Eacc (V versus SCE)

Curr

ent (120583

A)

Figure 1 Square-wave stripping voltammograms recorded at theimproved BiFE plated in 1mol Lminus1 acetate buffer (pH 45) containing008molL trisodium citrate (a b and d) and the BiFE (c) platedin 1molL acetate buffer (pH 45) without trisodium citrate (a)01mol Lminus1 HAc-NaAc (pH 48) + pyrogallol (13times10minus3mol Lminus1) (b)a + 10 120583g Lminus1 Ge(IV) (c d) b + 2 times 10minus4mol Lminus1 KBrO

3 deposition

potentialminus034V deposition time 150 s SW frequency 25Hz scanincrement 4mV pulse height 50mV

significantly increased (see Figure 1(d))The catalytic currentoccurred at the reduction potential of the Ge(IV)-pyrogallolcomplex owing to the addition of BrO

3

minus On the basis of theexperimental results the possible reaction mechanism is thatGe(IV) forms complex with pyrogallol which subsequentlyis adsorbed on surface of the BiFE During the voltammetricscan Ge(IV) in the complex is reduced to Ge(0) which isthen oxidized chemically to Ge(IV) by BrO

3

minus And then thereoxidizedGe(IV) contributes to the reduction current againproducing the catalytic cycle (see Figure 2)

Cyclic voltammograms (in the range from minus05 to minus10 V)of the Ge(IV)-pyrogallol complex with and without Ge(IV)after preconcentration at the BiFE were shown in Figure 3The pyrogallol (see Figure 3(a)) shows that neither oxidationpeak nor reduction peak was observed in the potential win-dow studied here under the selected experiment conditionAfter adding Ge(IV) the Ge(IV)-pyrogallol complex showeda cathodic peak at minus079V (see Figure 3(b)) arising from thereduction of the Ge(IV) in Ge(IV)-pyrogallol complexes toGe(0) There was no peak observed in the anodic scan indi-cating that the reduction of the complex was an irreversibleprocess

32 The Selection of Optimum Experimental Conditions Inorder to establish the optimum experimental conditions for aSWAdCSVmethod to determine germanium(IV) using BiFEthe following parameters that might affect the voltammetricsignal of the complex as variables were investigated pHpyrogallol and KBrO

3concentrations adsorptive accumu-

lation time (119905acc) and accumulation potential (119864acc) of thegermanium(IV)-pyrogallol complexes

321 The Effect of the Supporting Electrolyte and pH In ourexperiment the stripping behavior of the Ge(IV)-pyrogallolcomplex at the improved bismuth film was determined indifferent supporting electrolytes including HAc HAc-NaAcHNO

3 HCl H

2SO4 NH3-NH4Cl and NH

4Ac The results

showed that HAc-NaAc buffer solution was more suitable forthe stripping of Ge(IV)-pyrogallol complex due to the well-defined stripping peak low background current and highsensitivity

The effect of pH on the stripping peak current of Ge(IV)-pyrogallol complex was investigated in 01mol Lminus1 HAc-NaAc solutions at different pH values (see Figure 4)The peakcurrents of the complex varied with the change of pH from40 to 54 The pH of the solution also had an influence onthe peak potentials which changed to more negative valuesfor higher pH values For example for a pH of 40 the peakpotential of Ge(IV) was minus743mV for a pH of 54 the peakpotential was minus821mV The stripping peak current reachedthe maximum at pH 48 When pH was higher than 48 thestripping peak currents began to decreaseThus the optimumcondition of pH values is pH 48

322 The Effect of Pyrogallol Concentration The effect ofthe pyrogallol concentration on peak current of the Ge(IV)-pyrogallol complex was investigated in the range 30 times 10minus4ndash15 times 10

minus3mol Lminus1 (see Figure 5) At low pyrogallol concen-trations the complexation of Ge(IV) with pyrogallol was notcompleted So the peak currents increased with increasingpyrogallol concentration up to 13 times 10minus3mol Lminus1 Whenpyrogallol concentration was higher than 13 times 10minus3mol Lminus1the peak current started to decrease It is possible thatthere was competitive adsorption of the free pyrogallol onthe electrode surface Therefore for the following work apyrogallol concentration of 13 times 10minus3mol Lminus1 was used

323The Effect of KBrO3Concentration The effect of KBrO

3

concentrations on the stripping peak current of the Ge(IV)-pyrogallol complex was studied The results indicated thatKBrO

3enhanced the stripping sensitivity of the complex

At KBrO3concentrations smaller than 3 times 10minus4mol Lminus1

the peak height increased rapidly with increasing KBrO3

concentration but subsequently it increases slowly anddistortion of the cathodic side of the peak was observedTherefore the concentration 3times10minus4mol Lminus1 was used in thefurther experiments

324 The Effect of Accumulation Potential and Accumula-tion Time The effects of the accumulation potential andaccumulation time on the stripping peak current of Ge(IV)-pyrogallol complex on the improved bismuth film electrodewere studied The preconcentration potential was examinedover the range from minus034 to minus038V in the experimentwith a deposition time 180 s and is shown in Figure 6 Thelargest peak current was obtained at a deposition potential ofminus034V and the peak current decreased slowly at more neg-ative potentials Electrostatic exclusion may be responsiblefor the observed effect Since the germanium(IV)-pyrogallol


Ge(IV) + pyrogallol Ge(IV) minus pyrogallol + 4e Ge(0) + pyrogallolBrO

3

minus

Figure 2

0

5

10

15

20

25

b

a


Eacc (V versus SCE)

Curr

ent (120583

A)

Figure 3 Cyclic voltammograms recorded at a BiFE plated in1mol Lminus1 acetate buffer (pH 45) containing 008molL trisodiumcitrate (a) 01mol Lminus1 HAc-NaAc (pH 48) + pyrogallol (13 times10

minus3mol Lminus1) + 2 times 10minus4mol Lminus1 KBrO3 (b) a + Ge(IV) (20120583g Lminus1)

deposition potential minus034V deposition time 150 s potential scanrate 50mV sminus1

40 42 44 46 48 50 52 54 564

5

6

7

8

9

pH

minus074

minus076

minus078

minus080

minus082

(b)

(a)

Eac

c(V

ver

sus S

CE)

Curr

ent (120583

A)

Figure 4 The effect of pH of the supporting electrolyte on thestripping peak current (a) and the position of peak (b) of Ge(IV)-pyrogallol complex in 01mol Lminus1 HAc-NaAcn + pyrogallol (13 times10

minus3mol Lminus1) + 3 times 10minus4mol Lminus1 KBrO3 Ge(IV) concentration

10120583g Lminus1 Other conditions as in Figure 1

complex appears to be negatively charged a more positivepotential is favorable for its adsorption at BiFE but toopositive potential would damage the BiFE Thus minus034Vwas selected as the accumulation potential in the furtherprocedures

The dependence of the maximum stripping peak cur-rent on the accumulation time was examined for samples

0 2 4 6 8 10 12 14 16 180123456789

101112

Curr

ent (120583

A)

c(pyrogallol)(10minus4 M)

Figure 5The effect of the pyrogallol concentration on the strippingpeak current of Ge(IV)-pyrogallol complex in 01mol Lminus1 HAc-NaAc + 3 times 10minus4mol Lminus1 KBrO

3 Ge(IV) concentration 10 120583g Lminus1

Other conditions as in Figure 1

0

2

4

6

8

10

minus034 minus035 minus036 minus037 minus038

Eacc (V versus SCE)

Curr

ent (120583

A)

Figure 6 The effect of preconcentration potential on the strippingpeak current of Ge(IV)-pyrogallol complex Other conditions as inFigure 1

containing 5 120583g Lminus1 and 10 120583g Lminus1 germanium(IV) in therange of 0ndash270 s (see Figure 7) The maximum peak heightwas observed at 150 s and 210 s for 10 120583g Lminus1 and 5 120583g Lminus1germanium(IV) respectively and was constant during thelonger timeTherefore a deposition time of 180 s was selectedfor the rest of this work However in the real sampleanalysis the deposition time should be delayed due to the lowconcentration of germanium(IV)


Table 1 Results for the determination of total germanium in several Chinese herbal remedies and the recovery rate

Sample GF AAS Founda RSD () RecoveryAddition Founda Recovery rate ()

Cultivated ganoderma lucidum (120583g gminus1)b 322 318 141 1000 1315 997Wild ganoderma lucidum (120583g gminus1)b 129 132 305 500 634 1004Polygonum multiflorum thunb (120583g gminus1)b 047 049 362 500 538 978a119899 = 3

bFrom a pharmacy Beijing China

50 100 150 200 250 3000

1

2

3

4

5

6

7

8

9

Curr

ent (120583

A)

tacc (s)

Figure 7 The dependence of the stripping current of Ge(IV)-pyrogallol complex on the accumulation time pyrogallol concen-tration 13 times 10minus3mol Lminus1 5120583g Lminus1 (998771) Ge(IV) and 10 120583g Lminus1 (◼)Ge(IV) Other conditions as in Figure 1

33 Linear Range Detection Limit and ReproducibilityUnder the optimum experimental conditions a linear rela-tionship between the peak current and the germanium(IV)concentration was obtained in the range of 05 to 17120583g Lminus1(see Figure 8) in the presence of dissolved oxygen The linearregression equation was 119894 = 0886119888 + 0856 where 119894 and 119888are peak current (120583A) and Ge(IV) concentration (120583g Lminus1)respectively and the linear correlation coefficient (1198772) was0995 The voltammogram obtained for the lowest concen-tration with an accumulation time of 540 s was 60 ng Lminus1and the relative standard deviation from the nine paralleldeterminations of Ge(VI) at 5 120583g Lminus1 was 373

34The Interference Twomajor sources of interference wereinvestigated First potential interferences from other metalions in the determination of germanium(IV) were studiedVarious ions were examined as possible interferences bythe addition of the interfering ions to a solution containing10 120583g Lminus1 Ge(IV) using the optimum experimental condi-tions The results indicated that a 500-fold excess of Mg(II)a 200-fold excess of Cd(II) Co(II) Cr(III) Fe(III) Ni(II)Pb(II) Zn(II) and Mn(II) and a 5-fold excess of Sn(II)Sb(III) did not interfere in the determination of Ge(IV) withan error less than 5

0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14 16 1802468

1012141618

j

a


Eacc (V versus SCE)

Curr

ent (120583

A)

Curr

ent (120583

A)

c(Ge(IV))120583gmiddotLminus1

Figure 8 Adsorptive stripping curves of Ge(IV) concentrationsfrom 0 to 17120583g Lminus1 (andashj) (a 0 b 05 and cndashj 1ndash17 (in the stepof 2120583g Lminus1)) obtained at the bismuth film electrode Pyrogallolconcentration 13 times 10minus3mol Lminus1 Other conditions as in Figure 1

In addition naturally occurring organic compounds canbe adsorbed onto the electrode surface and interfere with theadsorptive voltammetric analysisThe interference of anionicsurfactant sodium dodecylbenzene sulfonate (SDBS) andthe cationic surfactant cetyltrimethylammonium bromide(CTMAB) was investigated The Ge(IV) signal diminishedby 49 and 67 after addition of 348mg Lminus1 SDBS and364mg Lminus1 CTMAB respectively

35 Analysis of Samples In our experiment the devel-oped method was applied to determine of total germaniumin several Chinese herbal remedies cultivated ganodermalucidum wild ganoderma lucidum and polygonum multi-florum thunb The samples were pretreated according to theprocedure described in Section 2 and then the sample solu-tionswere used for germaniumdeterminationThe results arelisted in Table 1 and the recovery rate is from 978 to 1004And the accuracy of the proposed method was assessed bycomparing the results obtained by SWAdCSV with thoseobtained by GF AAS

4 Conclusions

In this study we developed a new method for determiningthe total germanium by square-wave catalytic adsorptive


stripping voltammetry at an improved bismuth film elec-trode And we got the optimum condition for the germaniumdetermination Total germanium in several Chinese herbalremedies was determined by using this optimized methodand the results were consistent with those obtained byGF AAS It is demonstrated that the catalytic adsorptiveGe(IV)-pyrogallol-KBrO

3system is suitable for determining

trace germanium with high sensitivity simplicity and goodreproducibility and with being environment friendly

Conflict of Interests

The authors have declared no conflict of interests

Authorsrsquo Contribution

Shangwei Zhong and Jiali Su have equally contributed to thiswork

Acknowledgment

This work was supported by the Beijing City Board ofEducation Fund (no KM201110028009)

References

[1] N Nagata T Yoneyama and K Yanagida ldquoAccumulation ofgermanium in the tissues of a long-term user of germaniumpreparation died of acute renal failurerdquo Journal of ToxicologicalSciences vol 10 no 4 pp 333ndash341 1985

[2] H Aso F Suzuki and T Yamaguchi ldquoInduction of interferonand activation of NK cells and macrophages in mice by oraladministration of Ge-132 an organic germanium compoundrdquoMicrobiology and Immunology vol 29 no 1 pp 65ndash74 1985

[3] G B Gerber and A Leonard ldquoMutagenicity carcinogenic-ity and teratogenicity of germanium compoundsrdquo MutationResearch vol 387 no 3 pp 141ndash146 1997

[4] P Krystek and R Ritsema ldquoAnalytical product study ofgermanium-containing medicine by different ICP-MS applica-tionsrdquo Journal of Trace Elements inMedicine and Biology vol 18no 1 pp 9ndash16 2004

[5] S Jinhui and J Kui ldquoAdsorptive complex catalytic polarographicdetermination of germanium in soils and vegetablesrdquo AnalyticaChimica Acta vol 309 no 1ndash3 pp 103ndash109 1995

[6] M McMahon F Regan and H Hughes ldquoThe determinationof total germanium in real food samples including Chineseherbal remedies using graphite furnace atomic absorptionspectroscopyrdquo Food Chemistry vol 97 no 3 pp 411ndash417 2006

[7] S Y Ly S S Sang K K Sung S J Young and H L ChangldquoDetermination of Ge(IV) in rice in a mercury-coated glassycarbon electrode in the presence of catecholrdquo Food Chemistryvol 95 no 2 pp 337ndash343 2006

[8] A Sabarudin T Umemura and S Motomizu ldquoChitosanfunctionalized with di-2-propanolamine its application as solidphase extractant for the determination of germanium in watersamples by ICP-MSrdquo Microchemical Journal vol 99 no 1 pp34ndash39 2011

[9] K Jin Y Shibata and M Morita ldquoDetermination of germa-nium species by hydride generationndashInductively coupled argonplasmamass spectrometryrdquoAnalytical Chemistry vol 63 no 10pp 986ndash989 1991

[10] Y Sohrin K Isshiki T Kuwamoto and E Nakayama ldquoDeter-mination of germaniumby graphite-furnace atomic-absorptionspectrometryrdquo Talanta vol 34 no 3 pp 341ndash344 1987

[11] L Zaijun T Jian L Huizhen Z Xia and Y Rui ldquoDeter-mination of trace amounts of germanium in food and fruitby spectrophotometry with p-methybenzeneazosalicylfluronerdquoJournal of Food Composition and Analysis vol 20 no 1 pp 1ndash62007

[12] S Jianbo T Zhiyong T Chunhua C Quan and J ZexiangldquoDetermination of trace amounts of germanium by flow injec-tion hydride generation atomic fluorescence spectrometry withon-line coprecipitationrdquo Talanta vol 56 no 4 pp 711ndash7162002

[13] T Fujiwara K Kurahashi T Kumamaru and H Sakai ldquoLumi-nol chemiluminescence with heteropoly acids and its applica-tion to the determination of arsenate germanate phosphateand silicate by ion chromatographyrdquo Applied OrganometallicChemistry vol 10 no 9 pp 675ndash681 1996

[14] C Sun Q Gao and L Liu ldquoAdsorptive strippingmeasurementsof germanium(IV) in the presence of pyrogallolrdquo Talanta vol42 no 7 pp 881ndash884 1995

[15] Y-H Li X-H Chen M-H Huang and F-Q Zhou ldquoCatalyticadsorptive stripping voltammetry of germanium(IV) in thepresence of gallic acid and vanadium(IV)-EDTArdquo Electroanal-ysis vol 19 no 6 pp 704ndash708 2007

[16] J L M Alvarez J A G Calzon and J M L Fonseca ldquoSquare-wave voltammetry of the o-catecholmdashGe(IV) catalytic systemafter adsorptive preconcentration at a hanging mercury dropelectroderdquo Talanta vol 53 no 4 pp 721ndash731 2001

[17] J C Aguilar and J De Gyves ldquoDetermination of germa-nium(IV) in sulphide ores by differential pulse polarographyin pyrogallol-sulfuric acid mediardquo Analytica Chimica Acta vol306 no 2-3 pp 243ndash247 1995

[18] C Sun Q Gao J Xi and H Xu ldquoDetermination of germa-nium(IV) by catalytic cathodic stripping voltammetryrdquo Analyt-ica Chimica Acta vol 309 no 1ndash3 pp 89ndash93 1995

[19] J Wang J Lu S B Hocevar P A M Farias and BOgorevc ldquoBismuth-coated carbon electrodes for anodic strip-ping voltammetryrdquo Analytical Chemistry vol 72 no 14 pp3218ndash3222 2000

[20] L Lin S Thongngamdee J Wang Y Lin O A Sadik and S-YLy ldquoAdsorptive stripping voltammetric measurements of traceuranium at the bismuth film electroderdquoAnalytica Chimica Actavol 535 no 1-2 pp 9ndash13 2005

[21] L Lin N S Lawrence S Thongngamdee J Wang and YLin ldquoCatalytic adsorptive stripping determination of tracechromium (VI) at the bismuth film electroderdquo Talanta vol 65no 1 pp 144ndash148 2005

[22] E O Jorge M M Rocha I T E Fonseca and M M MNeto ldquoStudies on the stripping voltammetric determinationand speciation of chromium at a rotating-disc bismuth filmelectroderdquo Talanta vol 81 no 1-2 pp 556ndash564 2010

[23] L Jiajie and Y Nagaosa ldquoCathodic stripping voltammetricdetermination of As(III) with in situ plated bismuth-filmelectrode using the catalytic hydrogen waverdquoAnalytica ChimicaActa vol 593 no 1 pp 1ndash6 2007

[24] M Morfobos A Economou and A Voulgaropoulos ldquoSimulta-neous determination of nickel(II) and cobalt(II) by square waveadsorptive stripping voltammetry on a rotating-disc bismuth-film electroderdquoAnalytica ChimicaActa vol 519 no 1 pp 57ndash642004

[25] Q Zhang S Zhong J Su X Li and H Zou ldquoDetermination oftrace chromium by square-wave adsorptive cathodic stripping


voltammetry at an improved bismuth film electroderdquo Journal ofthe Electrochemical Society vol 160 no 4 pp H237ndashH242 2013

[26] L M S Nunes and R C Faria ldquoThe influence of the electrode-position conditions on the electroanalytical performance of thebismuth film electrode for lead determinationrdquo Electroanalysisvol 20 no 20 pp 2259ndash2263 2008

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and unavoidably contaminates the environment in practiceSo it is significant to develop alternative electrodes to replacethe mercury electrode In recent decades bismuth film elec-trode (BiFE) consisting of a thin bismuth film deposited ona suitable substrate material such as glassy carbon electrodehas been developed and shown a similar performance withmercury electrode [19 20] Since the toxicity of bismuth andits salts is negligible the BiFE is considered to be environmentfriendly and might be a satisfying alternative to MFE More-over the BiFE has been widely used to determinate manytrace elements such as Cr(VI) [21 22] As(III) [23] Co(II)and Ni(II) [24] and Cd(II) and Pb(II) [19] However there isno report about the determination of germanium in Chineseherbal remedies by using BiFEs so far And our group foundthat the analytical performance of bismuth film electrode wassignificantly improved by adding citrate to a relatively higherpH electrodeposition solution [25]

In this study a new and sensitive analytical method wasdeveloped for the determination of germanium based onsquare-wave catalytic adsorptive cathodic stripping voltam-metry using an improved BiFE as the working electrodeand pyrogallol as a complexing ligand The optimization ofthe developed technique was achieved by testing the rele-vant experimental parameters such as pH value depositiontime deposition potential and pyrogallol concentrationThemethod was successfully applied to determine the tracegermanium in several Chinese herbal remedies

2 Experimental

21 Apparatus and Reagents An Autolab PST050 electro-chemistry workstation (Radiometer France) and a micro-wave digestion system (CEM Model MDS-2000 USA) wereused A three-electrode electrochemical cell system was usedwith the multimode electrode the working electrode was abismuth film electrode (BiFE) the reference electrode was asaturated calomel electrode (SCE) and the auxiliary electrodewas a platinum wire PGENERAL TAS-990 atomic absorp-tion spectrophotometer (Chengdu Superman SampT Co LtdChina)

All the reagents used were of analytical grade purityunless otherwise stated The 1000mg Lminus1 bismuth solutionwas prepared by dissolving proper amount of Bi(NO

3)3sdot5H2O

(Sinopharm Chemical Reagent Co Ltd China) in 5HNO

3 The germanium standard solutions were made from

a stock of 1000 120583gmLminus1 Ge(IV) (China Iron amp Steel ResearchInstitute) by dilution with water as required A 01M HAc-NaAc (pH 48) served as a supporting electrolyte in theanalysis step Stock solution (002mol Lminus1) of pyrogallol wasprepared weekly and was stored at 4∘C in a refrigeratorA pH meter (PB-10 Sartorius China) was used for pHmeasurements All aqueous solutions were prepared usingultrapure water (Milli-Q systems USA)

22 Procedure

221 SWAdCSV Measurements of Germanium(IV) Prior tobismuth film formation the glassy carbon electrode (GCE)

was polished with a 03ndash005120583m alumina slurry on a feltpad thoroughly rinsed with water and then sonicated in5 HNO

3 ethanol and distilled water A bismuth film

was prepared on a GCE by applying minus10 V for 5min in a100mg Lminus1 bismuth(III) and 1mol Lminus1 acetate buffer media(pH 45) with 008mol Lminus1 sodium citrate Then the three-electrode system was immersed into 30mL 01mol Lminus1 HAc-NaAc (pH 48) solution that contained 3 times 10minus4mol Lminus1KBrO

3 13 times 10minus3mol Lminus1 pyrogallol was added into the

volumetric cell The preconcentration potential (minus034Vversus SCE) was applied while the solution was stirred for150 s The solutions were stopped and followed by a 15 sequilibration time And then the voltammogram recordedby applying a negative scan from minus05 to minus10 V using thesquare-wavemode with the following parameters frequency25Hz scan increment 4mV pulse height 50mV After theground voltammogram has been obtained the adsorptivestripping experiment was repeated for the addition of propergermanium stock solution The electrode was cleaned atminus13 V for 10 s before each measurement

222 Determination of Germanium(IV) in Real Samples Theanalysis procedure of Chinese herbal remedies sample wasas follows the 05 g sample 5mL HNO

3 and 1mL H

2O2

were placed into a microwave digestion tank overnight andthen digested according to a microwave digestion procedure(5min at 180∘Cand then 15min at 200∘C)After cooling downnaturally the seal pot of the digestion tank was opened andeach solution was heated to empty it of HNO

3on a hotplate

(120∘C) Then the digestion tank was cooled down to roomtemperature and diluted to 25mL in a volumetric flask withdouble-distilled water These sample solutions were analyzedby SWAdCSV as mentioned above

3 Results and Discussion

31 Electrochemical Behavior of Germanium(IV)-PyrogallolComplex at the Improved Bismuth Film Electrode Figure 1shows the SWAdCSV response for 10 120583g Lminus1 Ge(IV) obtainedat (c) BiFE plated in 1molL acetate buffer (pH 45) withouttrisodium citrate and (d) the improved BiFE plated in 1molLacetate buffer (pH 45) containing 008molL trisodiumcitrate And it was obvious that the BiFE (d) electrodepositedinHAc-NaAcmediumcontaining sodiumcitrate also showeda better electroanalytical performance for determination ofGe(IV) than the BiFE (c) According to Zhang et al [25]and Nunes and Faria [26] the significant improvement wasdue to the addition of trisodium citrate that helped form ahomogeneous structure by aggregates of spherical particleswith a few nanometers in diameter We also investigatedthe effect of KBrO

3on the electrochemical behavior of

germanium(IV)-pyrogallol complex at the improved bismuthfilm electrode No striping peak of pyrogallol was observed(see Figure 1(a)) When Ge(IV) was present together withpyrogallol in the solution a well-defined stripping peak ofthe Ge(IV)-pyrogallol complex was observed at a potential ofminus079V (see Figure 1(b)) When KBrO

3was added into the

above solution the reduction peak current of the complex


0

2

4

6

8

10d

c

b

a


Eacc (V versus SCE)

Curr

ent (120583

A)


3 deposition



3


3







3 HCl H


4Ac The results






3









3

minus

Figure 2

0

5

10

15

20

25

b

a


Eacc (V versus SCE)

Curr

ent (120583

A)




40 42 44 46 48 50 52 54 564

5

6

7

8

9

pH

minus074

minus076

minus078

minus080

minus082

(b)

(a)

Eac

c(V

ver

sus S

CE)

Curr

ent (120583

A)






0 2 4 6 8 10 12 14 16 180123456789

101112

Curr

ent (120583

A)





0

2

4

6

8

10


Eacc (V versus SCE)

Curr

ent (120583

A)








50 100 150 200 250 3000

1

2

3

4

5

6

7

8

9

Curr

ent (120583

A)

tacc (s)




0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14 16 1802468

1012141618

j

a


Eacc (V versus SCE)

Curr

ent (120583

A)

Curr

ent (120583

A)





4 Conclusions










Acknowledgment


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

2

4

6

8

10d

c

b

a


Eacc (V versus SCE)

Curr

ent (120583

A)


3 deposition



3


3







3 HCl H


4Ac The results






3









3

minus

Figure 2

0

5

10

15

20

25

b

a


Eacc (V versus SCE)

Curr

ent (120583

A)




40 42 44 46 48 50 52 54 564

5

6

7

8

9

pH

minus074

minus076

minus078

minus080

minus082

(b)

(a)

Eac

c(V

ver

sus S

CE)

Curr

ent (120583

A)






0 2 4 6 8 10 12 14 16 180123456789

101112

Curr

ent (120583

A)





0

2

4

6

8

10


Eacc (V versus SCE)

Curr

ent (120583

A)








50 100 150 200 250 3000

1

2

3

4

5

6

7

8

9

Curr

ent (120583

A)

tacc (s)




0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14 16 1802468

1012141618

j

a


Eacc (V versus SCE)

Curr

ent (120583

A)

Curr

ent (120583

A)





4 Conclusions










Acknowledgment


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



3

minus

Figure 2

0

5

10

15

20

25

b

a


Eacc (V versus SCE)

Curr

ent (120583

A)




40 42 44 46 48 50 52 54 564

5

6

7

8

9

pH

minus074

minus076

minus078

minus080

minus082

(b)

(a)

Eac

c(V

ver

sus S

CE)

Curr

ent (120583

A)






0 2 4 6 8 10 12 14 16 180123456789

101112

Curr

ent (120583

A)





0

2

4

6

8

10


Eacc (V versus SCE)

Curr

ent (120583

A)








50 100 150 200 250 3000

1

2

3

4

5

6

7

8

9

Curr

ent (120583

A)

tacc (s)




0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14 16 1802468

1012141618

j

a


Eacc (V versus SCE)

Curr

ent (120583

A)

Curr

ent (120583

A)





4 Conclusions










Acknowledgment


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of






50 100 150 200 250 3000

1

2

3

4

5

6

7

8

9

Curr

ent (120583

A)

tacc (s)




0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14 16 1802468

1012141618

j

a


Eacc (V versus SCE)

Curr

ent (120583

A)

Curr

ent (120583

A)





4 Conclusions










Acknowledgment


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of









Acknowledgment


References






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

research article determination of total germanium in ...en the three-electrode system was immersed...

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