Validated electroanalytical determination of flavoxate hydrochloride and tolterodine tartrate drugs in bulk, dosage forms and urine using modified carbon paste electrodes

Simple, precise, inexpensive and sensitive voltammetric methods have been developed for the determination of flavoxate HCl (FLXHC) and tolterodine tartrate (TOLT) in the bulk, pharmaceutical dosage forms and human urine using ferrocene modified carbon paste electrode (FMCPE) for FLXHC and polyethylene glycol modified carbon paste electrode (PEGMCPE) for TOLT. The electrochemical behavior of FLXHC and TOLT showed irreversible diffusion-controlled oxidation processes in Britton-Robinson (BR) buffer over the entire pH range from 2 to 6 for FLXHC and from 2 to 9 for TOLT. The peak current was evaluated as a function of some variables such as pH, scan rate and number of cycles of ferrocenium solution and PEG concentration. The linear ranges were 7.8 × 10−6–1.2 × 10−4 mol L−1 and 7.6 × 10−7–2.2 × 10−4 mol L−1 for FLXHC and TOLT, respectively. The limits of detection and quantification were 5.9 × 10−7 and 2 × 10−6 for FLXHC and 8.6 × 10−8 mol L−1 and 2.9 × 10−7 mol L−1 for TOLT. The percentage recoveries were found in the following ranges: 99.2–101.1% and 99.7–101.1% for FLXHC and TOLT, respectively. Keywords: Flavoxate HCl, Tolterodine tartrate, Carbon paste electrode, Ferrocene, Polyethylene glyco

Lanthanum(III) potentiometric sensors based on ethyl benzoyl acetate

Modified carbon paste electrode (CPE) and screen printed electrode (SPE) based on ethyl benzoyl acetate (EBA) were prepared and investigated as lanthanum ion selective electrodes. Effect of various plasticizers (o-NPOE, TCP, DBP, DOS, and DOP) and ionophore content was studied. The reaction mechanism between La(III) and β-diketone ionophore at the electrode surface was studied through scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and IR spectra measurement. The best performance was obtained using modified SPE and CPE electrodes with o-NPOE and TCP plasticizers. These electrodes showed potentiometric response with a Nernstian slope of 21.0, 19.5 and 20.5 mV decade−1 over a concentration range from 1.0 × 10−6 to 1.0 × 10−2 mol L−1 with a fast response time of 9, 10 and 13 s over the linear concentration range for modified SPE (electrode I; TCP plasticizer) and two modified CPE plasticized with o-NPOE (electrode II) and TCP (electrode III), respectively. The electrodes exhibited constant potentiometric response in pH range 4–8, 5–8 and 4–7 for electrodes I, II and III, respectively. They showed satisfactory good sensitivity toward lanthanum ions with regard to most common transition metal ions. The sensors were applied for determination of La(III) ion in different water samples (tap water and wastewater) with satisfactory and good reproducibility results. Keywords: SPE, CPE, Lanthanum(III), β-diketone, SEM, ED

Extractive spectrophotometric determination of sulphonamide drugs in pure and pharmaceutical preparations through ion-pair formation with molybdenum(V) thiocyanate in acidic medium

A simple and sensitive extraction-spectrophotometric method is described for the determination of sulfonamide drugs, namely sulphamethoxazole, sulphaguanidine, sulphaquinoxaline, sulphametrole and sulphadimidine, in both pure form and in the dosage forms available in Egyptian markets. The method is based on ion-pair formation between the sulphonamides and Mo(V)-thiocyanate inorganic complex in a sulphuric acid medium followed by extraction of the coloured ion-pairs with 1,2-dichloroethane. The optimum conditions are established. The method permits the determination of sulphonamide drugs over the concentration range of 5–50 μg ml−1. The Sandell sensitivity (S), molar absorptivity, correlation coefficient and regression equations, and limits of detection (LOD) and quantification (LOQ) are calculated. The law values of standard deviation (0.09–0.38) and relative standard deviation (0.10–0.550) reflect the accuracy and precision of the proposed method. The method is applicable for the assay of the investigated drugs in different dosage forms and the results are in good agreement with those obtained by the official pharmacopeial method

In situ modified screen printed and carbon paste ion selective electrodes for potentiometric determination of naphazoline hydrochloride in its formulation

The construction and performance characteristics of new sensitive and selective in situ modified screen printed (ISPE) and carbon paste (ICPE) electrodes for determination of naphazoline hydrochloride (NPZ-HCl) have been developed. The electrodes under investigation show potentiometric response for NPZ-HCl in the concentration range from 7.0Ã10â7 to 1.0Ã10â2 M at 25 °C and the electrode response is independent of pH in the range of 3.1â7.9. These sensors have slope values of 59.7±0.6 and 59.2±0.2 mV decadeâ1 with detection limit values of 5.6Ã10â7 and 5.9Ã10â7 M NPZ-HCl using ISPE and ICPE, respectively. These electrodes show fast response time of 4â7 s and 5â8 s and exhibits lifetimes of 28 and 30 days for ISPE and ICPE, respectively. Selectivity for NPZ-HCl with respect to a number of interfering materials was also investigated. It was found that there is no interference from the investigated inorganic cations, anions, sugars and other pharmaceutical excipients. The proposed sensors were applied for the determination of NPZ-HCl in pharmaceutical formulation using the direct potentiometric method. It showed a mean average recovery of 100.2% and 102.6% for ISPE and ICPE, respectively. The obtained results using the proposed sensors were in good agreement with those obtained using the official method. The proposed sensors show significantly high selectivity, response time, accuracy, precision, limit of detection (LOD) and limit of quantification (LOQ) compared with other proposed methods. Keywords: ISPE and ICPE, Potentiometry, Naphazoline hydrochloride, Eye drop