Determination of morphine in water immiscible process streams using sequential injection analysis coupled with acidic permanganate chemiluminescence detection

A procedure for the determination of morphine in non-aqueous, water immiscible, process streams by sequential injection analysis is presented. Detection was based upon the chemiluminescence reaction of morphine with acidic potassium permanganate in the presence of sodium polyphosphate, which was carried out in a heterogeneous reaction environment. The calibration graph (range 0.005-0.12% m/v) was non-linear, with a polynomial equation of best fit of y = -384x² + 139x - 4.84 (R² = 0.9990), where y represents the singal (mV) and x represents the morphine concentration (% m/v), and was analytically useful over the range 0.01-0.1% m/v. Precision (as measured by relative standard deviation) was 6.0% for 10 replicate analyses of a non-aqueous morphine standard (0.075% m/v). Methyltriphenylphosphonium permanganate was investigated as an alternative chemiluminescent reagent and was found to deliver a similar analytical performance to potassium permanganate. Sequential injection analysis coupled with chemiluminescence detection afforded results for the determination of morphine in non-aqueous process samples which were in good agreement with those obtained using a standard liquid chromatographic method, with an analytical throughput in excess of 120 h^-1.