New flow-multicommutation method for the photo-chemiluminometric determination of the carbamate pesticide asulam

This paper deals with a straightforward automated method for the determination of asulam in water based on the use of a flow manifold including three computer-controlled solenoid valves. The method involves irradiating on an aqueous solution of asulam in glycine buffer at pH 8.3 with UV light during 90 s, then follows the oxidation with potassium permanganate in a sulphuric medium and chemiluminescence-based detection of the resulting photoproducts. The limit of detection thus achieved is 40 mug l(-1). The detector response is linear up to a 5 mg l(-1) asulam concentration and the throughput is 30 samples h(-1). In parallel tests, oxidation with alkaline ferricyanide was also assessed and the results compared (sensitivity, selectivity and reproducibility) with those from oxidation with potassium permanganate in acidic medium. The use of a flow based on solenoid valves results in substantial reagent savings and constitutes a further extension of clean chemistry procedures. To the authors' knowledge, this is the first chemiluminescence-based determination of asulam and also the first based on multicommutation analysis. (C) 2004 Elsevier B.V. All rights reserved.