The spectrophotometric and colorimetric determination of the active substances in oxicam class drugs
One of the modern approaches in the pharmaceutical analysis is screening quality control - the preliminary assessment of drugs quality. This approach is the most relevant for low-cost, mass-used drugs, which include non-steroidal anti-inflammatory drugs, particularly, oxicams. It is optimal to use for screening only simple and cheap methods, one of which is a digital colorimetry. The method basis is the analysis of the sample by the mathematical processing of its digital images. To produce brightly colored samples the chromogenic substances forming with the drug substance stable compound can be used. The main advantages of colorimetry are rapidity, simplicity and low cost of analysis. The aim of this work is to develop methods of the spectrophotometric and colorimetric determination of meloxicam, lornoxicam and tenoxicam in the product of alkaline hydrolysed oxicams with 7-chloro-4-nitrobenzyl-2-oxa-1,3-diazole (NBD chloride). In this article, we presented an approach based on alkali hydrolysis of meloxicam, tenoxicam and lornoxicam, followed by the reaction with NBD chloride in borate buffer medium and measuring the optical density of the resulting colored solution spectrophoto-metrically or by digital image analysis of the sample. We experimentally selected optimum conditions for an analytical reaction - temperature, pH and time of interaction. The developed methods of the determination can be used at a range of concentrations between 1 and 10 micrograms / ml (0.5-5 ug / ml for meloxicam). The metrological characteristics of the colorimetric method is useful for screening the quality of oxicams, spectrophotometric - for routine drug analysis.