Studies On The Adsorption Voltammetry Of Origanic Drugs At Carbon Paste Electrodes

Anodic adsorptive stripping voltammetric determinations of astemizole , rifampicini , ciprofloxacin and norfloxacin at carbon paste electrode (CPE) were described, Their electrode reaction mechanisms were investigated. The proposed methods were applied to determine practice samples with satisfied results.The paper consists of three chapters.In the first chapter, a highly selective and rapid new anodic adsorptive voltammetric method was developed for the determination of trace amount of astemizole at CPE in the current paper. The astemizole was adsorbed on the surface of a CPE in 0.40 mol/L HAc-NaAc buffer solution (pH4.6) yielding one oxidation peak at 0.84 V (vs.SCE) when scanning from 0.0 to 1.0 V. The linear relationship between the peak current and astemizole concentration is in the range of 2.0×10^-9 1.0×10^-7 mol/L (90 s accummulation). The correlation coefficient is 0.9980. Its detection limit is 6.0×10^-10 mol/L (S/N=3) for a 90 s accummulation. The relative standard deviation is 3.6% for 15 successive determinations of 1.0×10^-7 mol/L astemizole on a same electrode surface. The electrode reaction mechanism of astemizole was investigated. The proposed method was applied to determine astemizole in the astemizole tablet and the results were in good agreement with reference values of the spectrophometric determination.In the second chapter, rifampicini was adsorbed on the surface of a CPL in 0.40 mol/L NaAc-HAc buffer solution (pH4.9) yielding one oxidation peak at 0.86 V (vs.SCE) when scanning from 0.0 to 1.0 V. The linear relationship between the, peak current and rifampicini concentration is in the range of 1.0×10^-8 2.0×10^-6mol/L (90 s accummulation). The correlation coefficient is 0.9986. Its detection limit is 3.0x10"9 mol/L (S/N=3) for a 120 s accummulation. The RSD of 3.3%is obtained for 15 determinations of rifampicini at 4.0 X 10"7 mol/L level on a same CPE surface. The electrode processes of rifampicini were investigated. The proposed method was applied to direct determine trace rifampicini in the urine samples in good agreement with reference values of the spectrophometric determination.In the third chapter, ciprofloxacin and norfloxacin were adsorbed on the surface of CPE in 0.40 mol/L NH4Ac-HAc buffer solution, yielding one oxidation peak at 1.12 V (vs.SCE) and 1.16 V (vs.SCH) respectively, when scanning from 0.4 to 1.4 V. The linear relationship between the peak current and ciprofloxacin concentration is in the range of 8.0x10'9 8.0x10'7 mol/L (90 s accummulation). The correlation coefficient is 0.9988. Its detection limit is 2.4xlO"9mol/L (S/N=3) for a 110 s accumulation. The RSD of 3.1 % is obtained for 15 determinations of ciprofloxacin at 4.0 X 10" mol/L level on the same CPE surface. The linear relationship between the peak current and norfloxacin concentration is in the range of 4.0xl0"9 to 8.0xl0'7 mol/L for a 90 s accummulation. The correlation coefficient is 0.9960. Its detection limit is 1.0x10"9 mol/L (S/N=3) for 110 s accummulation. The RSD of 4.0% was obtained for 15 determinations of norfloxacin at 4.0 X 10' mol/L level on the same CPE surface.The electrode processes of ciprofloxacin and norfloxacin were investigated. The proposed method was applied to direct determine trace of ciprofloxacin and norfloxacin in the urine samples with satisfactory results.In a word, CPE is characteristics of low background currentsand flat measure baseline over a range of the large positive potentials in aqueous solution. Anodic adsorption voltammetry at CPE is an effective method for the determination of organic drugs.