In this present work two colorimetric methods were developed based on donor-acceptor complexes of alverine citrate (ALV) and tapentadol (TAP) with cobalt thiocyanate. These methods were developed on Perkin Elmer LAMBDA 25 UVVIS spectrophotometer with 1cm quartz cells. The colored species formed are the coordination complexes of the drugs (electron donor) and the central metal atom of cobalt thiocyanate (electron acceptor) which is extractable into nitrobenzene from aqueous solution. The reaction conditions were optimized and validated to achieve maximum colour intensity. The colored complexes show maximum absorbance measured at 625 nm for both ALV and TAP. The absorbances were found to increase linearly with an increase in concentration which was corroborated by the calculated regression coefficients (0.9998-0.9999). Linearity was obeyed in the range of 100-600 µg/ml for both ALV and TAP, respectively. The molar absorptivity, sandells sensitivity, LOD, LOQ and other validation parameters have been evaluated extensively as per ICH guidelines and all the parameters were found within the acceptance criteria for both methods. The proposed methods were proven to be more accurate, simple, precise and rapid by statistical validation of recovery studies and could be suitable for regular analysis.
Key words: Alverine citrate, cobalt thiocyanate, nitrobenzene, tapentadol.
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