Selective stopped-flow determination of manganese with luminol in the absence of hydrogen peroxide

A novel stopped-flow chemiluminescence method for the determination of manganese by reaction with luminol in the presence of high concentrations of sodium chloride and the absence of hydrogen peroxide is proposed. Light emission takes place over a very short interval (less than ca. 200 ms). The activity of other ions that react with luminol under the experimental conditions used in the absence of hydrogen peroxide is examined. The proposed method permits the sensitive determination of manganese (detection limit 1.8 × 10−8 M), with high precision (R.S.D. < 1%), selectivity (thanks to the presence of triethanolamine) and sample throughput (100 samples h−1). It was applied to the determination of manganese in certified biological samples. A possible mechanism for the sodium chloride effect was proposed.