Flow injection analysis of some phenolic sympathomimetic drugs

A new, rapid and economical flow-injection (FI) method For deter-mining some phenolic sympathomimetic drugs is proposed. These drugs are etilefrine hydrochloride (ET), fenoterol hydrobomide (FT), hexoprenaline sulphate (HP), orciprenaline sulphate (OP) and reproterol hydrochloride (RT). The determination is based on the reaction of the studied phenolic sympathomimetic drugs with 4-aminoantipyrine (4-AAP) and potassium hexacyanoferrate (III). The chemical reaction variables and also the Fl variables, were optimized on the basis of sensitivity, sampling rate and reagent consumption. The proposed technique was applied to the analysis of pure raw materials in concentrations ranging from 2-20 mug.ml(-1) in case of ET, 4-30 mug.ml(-1) in case of FT and OP and from 8-50 mug.ml(-1) in case of HP and RT. Samples can be introduced at rates of about 130 pet. hour. The suggested procedure retained its accuracy and precision when applied to the analysis of pharmaceutical dosage forms containing the corresponding drugs, as judged by the RSD (%) and students' test. The results of the analysis were found to agree statistically with those obtained by applying either the official or the referee methods. Furthermore, the validity of the results was assessed by applying the standard addition technique.