Nifedipine and atenolol dugs are conjugated in several anti-hypertensive pharmaceutical formulations. Herein, a reproducible and sensitive voltammetric procedure has been developed for the simultaneous analysis of nifedipine and atenolol for the first time using MgO - nanoplatelets modified screen-printed electrodes (MgO - SPEs) via differential pulse voltammetry (DPV). Two very well-resolved and reproducible signals/oxidation peaks with a voltammetric separation of 0.35 V were obtained in Britton–Robinson (BR) buffer (pH 9). The MgO NPLs are found to exhibit a high electrocatalytic activity and improved voltammetric response compared to unmodified (bare) SPEs. Under optimum pH conditions (pH 9), the DPV curves exhibit linear responses to nifedipine and atenolol over the concentration ranges of 0.2–104.41 µM and 6.66–909.09 µM with detection limits of 0.032 µM and 1.76 µM, respectively. The applicability of the MgO-SPEs is successfully utilized for simultaneous determination of nifedipine and atenolol in pharmaceutical tablets and human urine samples with good accuracy and precision, these results agreeing with independent high-performance liquid chromatography (HPLC).

The screen-printed technique is widely used as an efficient tool for electrochemical analysis in environment, clinical and agri-food areas. Significantly, it has the ability to transfer electrochemical laboratory experiments into the field. In the present work, we report a highly sensitive, simple, low-cost protocol for determination of amlodipine (AML) using bare/unmodified and DNA-modified screen-printed electrodes (SPEs). The immobilization of DNA molecules onto SPE offers promising robust and chemically stable molecular wires, which provides a unique opportunity for charge transfer processes. Consequently, the electroanalytical sensing of AML was explored at bare/unmodified and DNA-modified SPEs in a linear range between 0.066–1.0 µM and 0.066–2.0 µM with the detection limit (3) found to be 20.70 nM and14.94 nM, whilst corresponding sensitivities of: 0.43 A L mol-1 and 4.23 A L mol-1 respectively. Although, the superior electrochemical signature of bare SPEs is evident, the immobilization of DNA onto SPEs enhances the sensitivity 10-times more than the bare SPEs. Furthermore, the optimized electroanalytical protocol using the unmodified SPEs, which requires no pre-treatment and electrode modification step, was then further applied to the determination of AML in real samples.

The screen-printed technique is widely used as an efficient tool for electrochemical analysis in environment, clinical and agri-food areas. Significantly, it has the ability to transfer electrochemical laboratory experiments into the field. In the present work, we report a highly sensitive, simple, low-cost protocol for determination of amlodipine (AML) using bare/unmodified and DNA-modified screen-printed electrodes (SPEs). The immobilization of DNA molecules onto SPE offers promising robust and chemically stable molecular wires, which provides a unique opportunity for charge transfer processes. Consequently, the electroanalytical sensing of AML was explored at bare/unmodified and DNA-modified SPEs in a linear range between 0.066–1.0 µM and 0.066–2.0 µM with the detection limit (3) found to be 20.70 nM and14.94 nM, whilst corresponding sensitivities of: 0.43 A L mol-1 and 4.23 A L mol-1 respectively. Although, the superior electrochemical signature of bare SPEs is evident, the immobilization of DNA onto SPEs enhances the sensitivity 10-times more than the bare SPEs. Furthermore, the optimized electroanalytical protocol using the unmodified SPEs, which requires no pre-treatment and electrode modification step, was then further applied to the determination of AML in real samples.

Two simple, selective, precise and highly sensitive high-performance thin-layer chromatography (HPTLC) methods have been developed and validated for analysis of five angiotensin II receptor antagonists, namely losartan, irbesartan valsartan, candesartan and olmesartan, which are widely used in clinical practice. HPTLC of the drugs was performed on pre-coated silica gel HPTLC plates 60 F254 by development using a mobile phase composed of chloroform–acetone–glacial acetic acid (7.8:1.5:0.7 m v/v/v), which was suitable for all of the studied drugs. The first method depended on utilizing reflectance/fluorescence mode for detection while the second method depended on using 2,3,5,6-tetrachloro-1,4-benzoquinone as spraying reagent for the first time to form orange spots scanned at 460 nm. A good linear relationship was obtained over the concentration ranges of 1.2–60 and 360–3000 ng/band while detection and quantification limits were in the ranges of 0.07–0.43, 45.2–140.49 and 0.21–1.29, 137.05–425.74 ng/band for reflectance/fluorescence and reflectance/absorbance methods respectively. The developed methods were applied successfully for their determination in tablets and spiked human plasma for reflectance/fluorescence method with good accuracy and precision, and so can be applied in the pharmacokinetic and bioavailability studies.

Two simple, selective, precise and highly sensitive high-performance thin-layer chromatography (HPTLC) methods have been developed and validated for analysis of five angiotensin II receptor antagonists, namely losartan, irbesartan valsartan, candesartan and olmesartan, which are widely used in clinical practice. HPTLC of the drugs was performed on pre-coated silica gel HPTLC plates 60 F254 by development using a mobile phase composed of chloroform–acetone–glacial acetic acid (7.8:1.5:0.7 m v/v/v), which was suitable for all of the studied drugs. The first method depended on utilizing reflectance/fluorescence mode for detection while the second method depended on using 2,3,5,6-tetrachloro-1,4-benzoquinone as spraying reagent for the first time to form orange spots scanned at 460 nm. A good linear relationship was obtained over the concentration ranges of 1.2–60 and 360–3000 ng/band while detection and quantification limits were in the ranges of 0.07–0.43, 45.2–140.49 and 0.21–1.29, 137.05–425.74 ng/band for reflectance/fluorescence and reflectance/absorbance methods respectively. The developed methods were applied successfully for their determination in tablets and spiked human plasma for reflectance/fluorescence method with good accuracy and precision, and so can be applied in the pharmacokinetic and bioavailability studies.

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Two simple and sensitive spectrofluorimetric methods were developed for determination of three water-soluble vitamins (B1, B2, and B6) in mixtures in the presence of cyanocobalamin. The first one was for thiamine determination, which depends on the oxidation of thiamine HCl to thiochrome by iodine in an alkaline medium. The method was applied accurately to determine thiamine in binary, ternary, and quaternary mixtures with pyridoxine HCl, riboflavin, and cyanocobalamin without interference. In the second method, riboflavin and pyridoxine HCl were determined fluorimetrically in acetate buffer, pH 6. The three water-soluble vitamins (B1, B2, and B6) were determined spectrofluorimetrically in binary, ternary, and quaternary mixtures in the presence of cyanocobalamin. All variables were studied in order to optimize the reaction conditions. Linear relationship was obeyed for all studied vitamins by the proposed methods at their corresponding exc or em. The linear calibration curves were obtained from 10 to 500 ng/mL; the correlation ranged from 0.9991 to 0.9999. the suggested procedures were applied to the analysis of the investigated vitamins in their laboratory-prepared mixtures and pharmaceutical dosage forms from different manufacturers. The RSD range was 0.46-1.02%, which indicates good precision. No interference was observed from common pharmaceutical additives. Good recoveries (97.6  0.7 – 101.2  0.8%) were obtained. Statistical comparison of the results with reported methods shows excellent agreement and indicates no significant difference in accuracy and precision.