Study And Application Of Zero Current Potentiometry About Several Pencil Graphite Film Electrodes

The zero current potentiometry is a new method of measurement which theinterface potential will be regularly changed owing to specific reaction betweenelectrode sensitive film and the analytes of solution. It is formed that workingelectrode and counter electrode which are connected by specific film electrodeimmerse into the system to be studied with reference electrode. The present researchadopts zero current potentiometry to examine the zero current potential response byusing pencil graphite film electrodes and the application of actual pH. The specificresearch results will be shown as follows:(1) The study of application and pH response with zero current potentiometry aboutpencil graphite film(a) The application and pH response with zero current potentiometry ahout poly silkfilmIn0.9g·L-1silk,pH7.0-PBS buffer solution, poly silk film modified pencilgraphite electrode is obtained by adopting cyclic voltammetry to scan25laps in speedof0.1V·s-1within a range of-0.8～1.2V, Ezcpof poly silk film and pH in BR solutionfollow which fits in with a Nernst response in the range of pH4.78～9.91:Ezcp(V)=0.3587-0.029pH(R=-0.998,n=6). By a batch of five poly silk film electrodesmeasuring, the relative standard deviation of slope about Ezcp-pH linear equations is2.41%. Meanwhile, by testing five times with one electrode, the relative standarddeviation of slope is2.45%. Therefore, a new method of measuring PH is formed byusing zero current potentiometry with poly silk film. The actual pH of HAc-NaAc,PBS and Hcl-NaAc is consistent with pH meter results by means of poly silk film.(b) The application and pH response with zero current potentiometry ahout polyleucine filmIn1.5×10-3mol·L-1leucine,pH6.98-PBS buffer solution, poly leucine filmmodified pencil graphite electrode is obtained by adopting cyclic voltammetry to scan8laps in speed of0.1V·s-1within a range of-1.6～2.8V Ezcpof poly leucine film andpH(1.81～7.24) in BR solution follow a negative linear correlation: Ezcp(V)=0.3454-0.061pH（R=0.997，n=7）. By a batch of five poly silk film electrodes measuring, the relative standard deviation of slope about Ezcp-pH linear equations is1.99%.Meanwhile, by testing five times with one electrode, the relative standard deviation ofslope is2.98%. Besides, the acidity of tomato and grape juice tested by poly leucinefilm matches the pH meter. Thereupon, the new system of testing fruit acids isconstructed by poly leucine film.(c) The application and pH response with zero current potentiometry ahout polyC.I.Reactive Yellow2filmIn8×10-5mol·L-1,pH6.09-BR buffer solution, poly C.I.Reactive Yellow2filmmodified pencil graphite electrode is obtained by adopting cyclic voltammetry to scan10laps in speed of0.1V·s-1within a range of-0.8～0.8V Within pH3.78～10.88, Ezcpof C.I.Reactive Yellow2film presents a relative steady linear correlation, namely,Ezcp(V)=0.5046-0.058pH(R=-0.993,n=10), By a batch of five poly silk film electrodesmeasuring, the relative standard deviation of slope about Ezcp-pH linear equations is1.54%. Meanwhile, by testing five times with one electrode, the relative standarddeviation of slope is0.76%. Therefore, the new PH testing system is produced. the pHof Na2HPO4-Citric acid, HAc-NaAc tested by C.I.Reactive Yellow2film matches thepH meter.(2) The determination of Ce4+with zero current potentiometry by poly serine filmIn1.5×10-3mol·L-1,pH6.09-PBS buffer solution, poly serine film modifiedpencil graphite electrode is obtained by adopting cyclic voltammetry to scan10lapsin speed of0.1V·s-1within a range of-1.4～3.0V,Ce4+with4×10-8～5×10-7mol·L-1and Ezcpof poly serine film on the pencil graphite possess the fowling linearcorrelation: Ezcp(V)＝0.1151﹢0.016logCce4+(R=0.995,n=8), when SLS with8×10-4mol·L-1is added to HAc-NaAc(pH4.7). So a new testing Ce4+method canbe adopted by using the zero current potentiometry of L-serine film. Furthermore,Ca2+,Mg2+, Fe3+, SO42-,Ni+, NO3+,Cu2+and Zn2+will not interfere with thedetermination of Ce4+when they largely coexist with each other. Meanwhile, thepractical average recovery rate between80～111.32%seems to confirm this method’sfeasibility.(3) The determination of BSA with zero current potentiometry by poly malachitegreen composite filmThe Ezcpof malachite green film scanned3laps within the range of0～1.5V canbetter determine bovine serum albumin in4×10-7～1×10-6mol·L-1, proline, histidine,cysteine, serine, phenylalanine, glycine, Ca2+,Mg2+,Fe3+,Cu2+will not interfere with the determination, the practical average recovery rate between90.7～107.8％seemsto confirm this method’s feasibility.(4) Interaction of malachite green and bovine serum albumin with zero currentpotentiometryIn3×10-5mol·L-1,pH4.7-HAc-NaAc buffer solution, With induced zero currentpotentiometry, as its methodology，this paper studies the interactions of bovine serumalbumin with malachite green film/pencil graphite electrodeobtained by self-adsorption.The results show that there is a liner relationship between zero currentpotention Ezcpof malachite green film and log[BSA] in the case of4×10-7～4×10-8mol·L-1:Ezcp(V)=0.1422+0.016log[BSA](R=0.992,n=5).The binding constant βbetween MG and BSA through the equation is(2.5±1)×104L·mol-1and the bindingratio m is0.8±0.2, which is consistent with the previous study.