COMPUTER-ASSISTED OPTIMIZATION OF A FLOW-INJECTION METHOD FOR THE ASSAY OF PROMETHAZINE, CHLORPROMAZINE AND TRIMEPRAZINE IN DRUG FORMULATIONS

A simple, accurate and fast method for the determination of promethazi ne, chlorpromazine and trimeprazine neuroleptics in drug formulations by flow injection spectrophotometric detection was developed. The meth od was based on the oxidation of the drug with potassium dichromate in sulphuric acid media. Optimum conditions were obtained by using the m odified simplex computer progmmme. A 110-mul sample volume was taken a s reasonable for all the compounds. The optimum conditions reached wer e 76-cm coil length, 6.00 ml/min flow rate, 3.10 M sulphuric acid and 0.00167 M dichromate for promethazine; 94-cm coil length, 5.00 ml/min flow rate, 1.48 M sulphuric acid and 0.00185 M dichromate for chlorpro methazine and 80-cm coil length, 6.00 ml/min flow rate, 3.44 M sulphur ic acid and 0.000 500 M dichromate for trimeprazine. High sample throu ghput of at least 200 samples per hour was obtained for all compounds. Acceptable relative standard deviations in the range +/- 0.4-0.9%, an d good accuracy in the range 99.5-99.9% were attained when the method was statistically compared with the BP method and when applied to prop rietary drugs, without suffering interferences.