Simultaneous determination of salbutamol sulphate, bromhexine hydrochloride and etofylline in pharmaceutical formulations with the use of four rapid derivative spectrophotometric methods

Four simple, rapid, accurate, precise, reliable and economical spectrophotometric methods have been proposed for simultaneous determination of salbutamol sulphate (SS), bromhexine hydrochloride (BH) and etofylline (ET) in pure and commercial formulations without any prior separation or purification. They were first derivative zero crossing spectrophotometry (method 1), simultaneous equation method (method 2), derivative ratio spectra zero crossing method (method 3) and double divisor ratio spectra derivative method (method 4). The ranges for SS, BH and ET were found to be 1–35 μg mL−1, 4–40 μg mL−1 and 5–80 μg mL−1. For methods 1 and 2, the values of limit of detection (LOD) were 0.2314 μg mL−1, 0.4865 μg mL−1 and 0.2766 μg mL−1 and the values of limit of quantitation (LOQ) were 0.7712 μg mL−1, 1.6217 μg mL−1 and 0.9221 μg mL−1 for SS, BH and ET, respectively. For method 3, LOD values were 0.3297 μg mL−1, 0.2784 μg mL−1 and 0.7906 μg mL−1 and LOQ values were 0.9325 μg mL−1, 0.9282 μg mL−1 and 2.6352 μg mL−1 for SS, BH and ET, respectively. For method 4, LOD values were 0.3161 μg mL−1, 0.2495 μg mL−1 and 0.2064 μg mL−1 and LOQ values were 0.9869 μg mL−1, 0.8317 μg mL−1 and 0.6879 μg mL−1 for SS, BH and ET. The precision values were less then 2% R.S.D. for all four methods. The common excipients and additives did not interfere in their determinations. The results obtained by the proposed methods have been statistically compared by means of Student t-test and by the variance ratio F-test.