Optimization of two charge transfer reactions for colorimetric determination of two beta 2 agonist drugs, salmeterol xinafoate and salbutamol, in pharmaceutical and biological samples.

Beta 2 agonists are well known for their use in the treatment of asthma and COPD however in the last few years new indications of beta 2 agonist appeared like reduction of local fats and treatment of preterm labour which required the formulation of new dosage forms and administration strategies. The new developments require accurate, economic and feasible methods the determination of these drugs to facilitate testing the newly introduced dosage forms and to study the pharmacokinetics and pharmacodynamics regarding the modern uses. In this study two rapid, sensitive and economic colorimetric methods for the determination of salmeterol xinafoate and salbutamol in pharmaceutical dosage forms and spiked plasma were developed and validated. The developed methods depends on the optimized reaction of the studied drugs with two charge transfer reagents, 2,3-dochloro-5,6-dicyano-1,4-benzoquonone (DDQ) and chloranilic acid (CA) to produce coloured complexes measured at 460 and 529 nm for DDQ and CA respectively. The developed methods showed high accuracy of 99.52 ± 1.108, 101.03 ± 0.389, 100.04 ± 1.520 and 100.3 ± 0.951 for salmetrol xinafoate and salbutamol with DDQ and CA respectively. The proposed methods were successfully used for the determination of the studied drugs in their dosage forms and spiked plasma with high accuracy and precision and the results were compared to reported methods.