Pulsed flow chemistry: a new approach to solution handling for flow analysis coupled with chemiluminescence detection

Novel instrumentation for flow analysis, coupled with chemiluminescence detection, and based on pulsed flow chemistry is described. The pulsed flow chemistry manifold allows for rapid and efficient mixing of chemiluminescent reagent with sample immediately in front of the detector, thus giving high precision (less than 1% RSD) and detectability, particularly for rapid, short-lived emissions. The instrument is also characterised by a compact size, high sampling frequency (120-300 samples per hour) and low reagent consumption (less than 500 mu l per cycle). Other flow analysis modes (e.g., flow injection, continuous flow and stopped-flow) are available by simply altering software settings. The suitability of the system was shown by using chemiluminescence reactions of analytical significance, namely the oxidation of luminol with hexacyanoferrate(iii) in the presence of 4-hydroxy-3-methoxybenzeneacetic acid (homovanillic acid), and the reduction of acidic potassium permanganate by morphine in the presence of polyphosphates. The latter reaction was used to determine morphine in aqueous process samples and the results obtained with the pulsed flow instrument displayed good agreement (mean difference of 1.8%) with those of a previously validated flow injection analysis method.