Senem Sanli

Voltammetric and RP-LC assay for determination of benidipine HCl

The detailed electrooxidative behavior of benidipine (BEN) has been studied by using glassy carbon (GC) and boron-doped diamond (BDD) electrodes. Using cyclic voltammetry, depending on the pH values and the working electrodes, BEN showed one or two sharp and irreversible oxidation responses. The voltammetric experiments on some model compounds allowed elucidation of the oxidation mechanism of BEN. Highly sensitive, selective, rapid, and fully validated voltammetric methods for the determination of BEN in tablet dosage form were also presented. Under optimized conditions, the peak current showed a linear dependence with concentration in the range between 3.25 μg mL(-1) and 54.20 μg mL(-1) for GC and 1.08 μg mL(-1) and 54.20 μg mL(-1) for BDD electrodes by using differential pulse (DPV) and square wave (SWV) voltammetric techniques. In this study, acid dissociation constant (pK(a)) value of BEN was determined by using the dependence of the retention factor on the pH of the mobile phase using reverse phase-liquid chromatographic (RP-LC) method. The effect of the composition of the mobile phase on the ionization constant was studied by measuring the pK(a) at different acetonitrile-water mixtures, ranging between 50 and 65% (v/v). Also simple, accurate, precise and fully validated RP-LC method for the assay of BEN in dosage form has been developed. XTerra RP-18 column at 25 °C with the mobile phase of acetonitrile:water 55:45 (v/v) adjusted to pH 3.0 with 15 mM o-phosphoric acid was used. Isocratic elution was performed in less than 5.0 min with a flow rate of 1.0 mL min(-1). The RP-LC method allowed quantitation over the 0.25-15.00 μg mL(-1) range for BEN. The proposed voltammetric and RP-LC methods allow a number of cost and time saving benefits. BEN was also exposed to thermal, photolytic, oxidative stress, acid-base catalyzed hydrolyses, and the stressed samples were detected by the proposed RP-LC method.

Analytical application of polymethylene blue-multiwalled carbon nanotubes modified glassy carbon electrode on anticancer drug irinotecan and determination of its ionization constant value

The voltammetric behavior of anticancer drug irinotecan (IRT) was investigated at poly (methylene blue)/multi-walled carbon nanotube (PMB/MWCNT) modified glassy carbon electrode (GCE). The modified electrode surface was characterized by a scanning electron microscope (SEM). The PMB/MWCNT modified GCE exhibits a distinct shift of the oxidation potential of IRT on the cathodic direction and a considerable enhancement of the peak current compared with bare electrode. The calibration curve was linear between the concentration range 8.0 × 10(-6) and 8.0 × 10(-5)M with the detection limit of 2.14 × 10(-7)M by differential pulse voltammetry in pH 10.0 Britton-Robinson buffer solution. Controlled potential coulometry was applied to find transferred electron numbers due to the oxidation of IRT. In this study, the pKa value of IRT was also determined by the dependence of the retention factor on the pH of the mobile phase. The effect of the mobile phase composition on the ionization constant was studied by measuring the pKa at different acetonitrile-water mixtures, ranging between 35 and 50% (v/v) using the reversed-phase liquid chromatography (RP-LC) method with UV detector. IRT was exposed to thermal, photolytic, hydrolytic and oxidative stress conditions, and the stressed samples were detected by the proposed method. Sensitive, rapid, and fully validated electrochemical and RP-LC methods for the determination of IRT in its dosage form were presented in details.

Evaluation of Patulin in Commercial Baby Foods by solid Phase Extraction and Liquid Chromatography PDA Detection

Karakose A., Sanli S., Sanli N., Bulduk I. (2015): Evaluation of patulin in commercial baby foods by solid phase extraction and liquid chromatography PDA detection. Czech J. Food Sci., 33: 52–57. A simple, reliable, and rapid RP-LC method has been developed for the determination of patulin in commercial baby foods from Turkish markets. Solid phase extraction and liquid chromatography with photodiode array detection technique were used for the analysis of patulin in samples. Linearity was obtained in different concentration ranges between 0.001 and 0.050 µg/l. The recovery rates for patulin ranged from 92.85% to 100.45% with a coefficient of variation less than 3.0%. LOD and LOQ of the method were found to be 9.66 × 10 –6 and 2.93 × 10 –5 µg/ml, respectively. The proposed method has been extensively validated in accordance with ICH guidelines. It can be used by routine analysis laboratories within a short time of analysis. All of the detected samples containing patulin were below the level suggested by the World Health Organization.

A validated RP-LC method for salmeterol and fluticasone in their binary mixtures and their stress degradation behavior under ICH-recommended stress conditions

Simple, accurate, precise and fully validated analytical methods for the simultaneous determination of salmeterol xinafoate and fluticasone propionate in combined dosage forms have been developed. These drugs were exposed to thermal, photolytic, hydrolytic and oxidative stress conditions, and the stressed samples were detected by the proposed method. Additionally, pKa values of three ionizable drugs (salmeterol xinafoate, fluticasone propionate and thioridazine) were determined using by the dependence of the retention factor on pH of the mobile phase. The effect of the mobile phase composition on the ionization constant was studied by measuring the pKa in different acetonitrile-water mixtures, ranging between 50 and 65% (v/v) using LC-UV method.

DETERMINATION OF pK a VALUES OF SOME BUTYROPHENONES, THEIR SENSITIVE LC-UV ANALYSIS IN PHARMACEUTICAL DOSAGE FORMS AND STRESS DEGRADATION BEHAVIOR UNDER ICH-RECOMMENDED STRESS CONDITIONS

In this study, pKa values of some ionizable butyrophenones, namely, benperidol, droperidol, and haloperidol were determined using by the dependence of the retention factor on pH of the mobile phase. The effect of the mobile phase composition on the ionization constant was studied by measuring the pKa at different methanol–water mixtures, ranging between 50 and 65% (v/v) using an LC-UV method. Additionally, a simple, accurate, precise, and fully validated analytical method for the simultaneous and individual determination of benperidol, droperidol, and haloperidol in their dosage forms was developed. Butyrophenones were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were detected by the proposed method.