Photo-induced chemiluminescence-based determination of diphenamid by using a multicommuted flow system

This manuscript deals with the application of molecular connectivity calculations to predict the photo-induced chemiluminescent behaviour of the family of herbicides grouped as amides. Several compounds of this group were theoretically studied by means of a general discriminant equation formerly obtained, being 18 of them (plus eight from the chloroacetanilide sub-group) predicted with a high probability as photo-induced chemiluminescent. Empirical confirmation of the chemiluminometric behaviour was performed with some few commercially available amide herbicides.On the basis of these results, a new multicommutation-photo-chemiluminescent method is proposed for the determination of the diphenamid. The method is based on the photodegradation of the pesticide and then the resulting photo-fragment solutions are oxidized by K3[Fe(CN)6] in sodium hydroxide medium, at room temperature and 80 °C, for the photodegradation and chemiluminometric oxidation, respectively. The studied calibration up to 5.0 mg l−1, revealed a linear dynamic graph up to 20 mg l−1. The reproducibility between days resulted in a R.S.D. (in slope %) of 2.8 (n = 5) and the repeatability with a %R.S.D. (n = 20) of 4.3. LOD (s/n = 3) of 1 μg l−1 and sample throughput of 20 h−1. The influence of foreign compounds is also tested and the optimized flow assembly is applied to different kind of samples.