A simple spectrophotometric method for the determination of captopril in pharmaceutical preparations using ammonium molybdate

Spectroscopic Fingerprinting of Aminoglycosides and Determination of Neomycin Sulphate Through Oxidative Ion-pair Complex Formation using Ammonium Molybdate

Background:

Aminoglycosides are non-chromophoric antibiotics. The official method of assay in pharmacopoeias is microbiological. Bioassay methods are potency-semi-quantitative, laborious and time-consuming. In contrast, spectrophotometric methods are rapid, convenient, specific, sensitive and selective. The presence of NH2 and -OH functional groups in aminoglycosides makes them susceptible to redox reaction.

Objective:

A simple, cheap, quick, accurate and reliable spectrophotometric method for aminoglycoside analysis using neomycin as prototype via oxidation by ammonium molybdate reagent is proposed.

Methods:

Four aminoglycosides - amikacin, gentamicin, neomycin and streptomycin, were oxidized using ammonium molybdate (pH<2). These were scanned to obtain visible-spectrophotometric fingerprints. Two assay methods were developed. Method I involved the determination of the drug via the linear proportionality between neomycin and residual molybdate measured at 780nm and 850nm. Method II, an indirect determination using ion-pair reaction of excess molybdate and methyl orange measured at 430nm and 480nm.

Results:

All aminoglycosides formed blue complex, with distinct spectra peaks at 500nm, 640nm, 780nm and 850nm.The limit of detection and limit of quantification were from 0.33 to 2.32 μgmL-1 and 1.00 to 7.03 μgm L-1 respectively for both methods. Percentage recoveries ranged from 89.60 and 113.05 %, while precision and accuracy as RSD ranged from 0.23 to 3.55%. The regression coefficient (R2) ranged from 0.9968 to 0.9995. Percentage neomycin in dosage forms ranged from 95.67- 104.16% and 96.04 - 99.46% for methods I and II, respectively.

Conclusion:

The methods were successfully applied for neomycin sulphate determination in tablets and drops, therefore aminoglycosides could be assayed via the proposed methods.

Ratiometric captopril assay based on the recovery of the Bi(iii)-quenched yellow fluorescence of dually emitting carbon nanodots

Dual emissions of carbon nanodots, as a ratiometric nanosensor, could be used to detect captopril based on the switch effect of Bi³⁺.

Development and application of a portable instrument for drugs analysis in pharmaceutical preparations

This article describes the application and performance of an inexpensive, simple and portable device for colorimetric quantitative determination of drugs in pharmaceutical preparations. The sensor is a light detector resistor (LDR) incorporated into a black PTFE cell and coupled to a low-cost multimeter (Ohmmeter). Quantitative studies were performed with captopril/p-chloranil/H2O2 and methyldopa/ammonium molybdate systems. Calibration curves were obtained by plotting the electrical resistance of the LDR against the concentration of the colored species in the ranges 1.84 × 10-4 to 1.29 × 10-3mol L-1 and 5.04 × 10-4 to 2.52 × 10-3 mol L-1 for captopril/p-chloranil/H2O2 and methyldopa/ammonium molybdate systems, respectively, exhibiting good coefficients of determination. Statistical analysis of the results obtained showed no significant difference between the proposed methodologies and the official reported methods, as evidenced by the t-test and variance ratio at a 95% confidence level. The results of this study demonstrate the applicability of the instrument for simple, accurate, precise, fast,in situ and low-cost colorimetric analysis of drugs in pharmaceutical products.

Kinetic and density functional theory (DFT) studies of in vitro reactions of acrylamide with the thiols: captopril, l-cysteine, and glutathione

In vitro kinetic studies with DFT computations to explain the potential of acrylamide metabolism/toxicity with thiols in vivo.

In vitro studies on the reaction rates of acrylamide with the key body-fluid thiols l-cysteine, glutathione, and captopril

The mechanisms of interactions of acrylamide with l-cysteine, glutathione and captopril were studied in vitro. Experimental second order rate constants calculated at 303 K were 0.34 ± 0.02, 0.18 ± 0.02, and 0.13 ± 0.01 dm3 mol−1 s−1 for l-cysteine, glutathione, and captopril, respectively, potentially involving inter- and intra-molecular H-bonding in the acrylamide-glutathione complex.

A surface plasmon resonance sensing method for determining captopril based on in situ formation of silver nanoparticles using ascorbic acid

A new method has been proposed to sensitive detection of captopril based on surface plasmon resonance band of silver nanoparticles (AgNPs). The stable and well-dispersed AgNPs with strong plasmon resonance signal were synthesized in situ using a simple and rapid procedure by applying ascorbic acid as reducer and sodium dodecyl sulfate as stabilizer, at room temperature. It was found that, the decreasing of AgNPs plasmon absorbance is proportional to the concentration of captopril which allows the spectrophotometric sensing of this compound. The presented method is capable of determining captopril over a range of 0.20-2.75 μmol L(-1) with a limit of detection 0.07 μmol L(-1). The relative standard deviation for eight replicate measurements of 1.00 and 2.50 μmol L(-1) of captopril was 2.37% and 1.02%, respectively. The method was applied to the determination of captopril in pharmaceutical formulations with satisfactory results, which were in agreement with those of the official method.