Determination of morphine in process streams by sequential injection analysis with chemiluminescence detection

A procedure for the determination of morphine in process streams by sequential injection analysis based on the chemiluminescence reaction of morphine with acidic potassium permanganate in the presence of sodium hexametaphosphate is presented. The chemiluminescence emission has been monitored using an in-house detection system which consisted of a fibre optic flowthrough cell and a sensitive, low dark current, photomultiplier tube. The calibration graph (range 2 × 10^–8 to 1 × 10^–4 mol/l) was not linear over the entire range of concentration, with a polynomial equation of best fit of y = 1.0 × 10¹⁵ x³ – 2.2 × 10¹¹ x² + 1.3 × 10⁷ x – 8.3. The calibration function approximates linearity over the concentration range 2.5 × 10^–6 to 3.0 × 10^–5 mol/l where the slope of the log-log plot is 1.09 ± 0.16. The detection limit was estimated at about 10^–8 mol/l from the response of the lowest calibration standard (2.5 × 10^–8 mol/l) which gave a signal to noise ratio of 3 : 1. Although the structurally related codeine did not interfere significantly the results suggest that this method may be susceptible to matrix effects, dependent on the location of sampling from the process stream.