The new spectrophotometric methods for the estimation of Butorphanol tartarate in bulk and pharmaceutical formulations

Six simple and sensitive spectrophotometric methods (I, II, III, IV, V and VI) in the visible region have been developed for the quantitative estimation of Butorphanol tartarate in bulk drug and pharmaceutical formulations. These methods are based on the reaction of oxidative coupling reaction with 3-methyl-2-benzothiazolinone hydrazone (MBTH), 1,10-phenanthroline, ferric chloride Gibb's reagents, FC reagent, and potassium ferricyanide to form green, red, dark colored, bluish green, dark colored and bluish green chromogen with absorption maxima at 424 urn, 515 mu, 795 mu, 588 nm, 756.5 nm and 786 nm Beer's law is obeyed in the concentration range of 5-25 mu g/ml, 5-25 mu g/ml, 1-5 mu g/ml, 5-25 mu g/ml, 2-12 mu g/ml and 1-5 mu g/ml respectively. The results of analysis have been validated statistically and by recovery studies. The methods were found to be accurate, precise, rapid, and economic.