Determination of organophosphorus insecticides by indole reaction

Abstract

Primijenjena je oksidaciona reakcija indola, čiji se tok prati mjerenjima intenziteta fluorescencije međuprodukata oksidacije, za kvantitativno određivanje organofosfornih insekticida. Rad je izveden s preparatima insekticida koji se praktički mnogo upotrebljavaju, kao i s nekim živežnim namirnicama onečišćenima insekticidima. Ustanovljene su konstante baždarnih pravaca za izvedbu takvih analiza, a određene su granice osjetljivosti ove analitičke metode za pojedine insekticide.A method for the quantitative determination of organophosphorus insecticides was devised which is based on the oxidation reaction of indole, 2, 3 benz(o)pyrrole, whose course is easily followed by photoelectric measurements of the intensity ,of fluorescence of oxidation products(indoxyl and indigo white). The preparations of insecticides which are widely applied in practice were used. Insecticides act as activators of the oxidation reaction, the time curves of the fluorescence intensity (Ø - t curve) being dependent upon the nature and concentration of the particular insecticide. These curves always show a maximum (Fig. I.) the maximal intensity of fluorescence (Ø m) being in linear relationship with the concentration (c) of insecticide (Fig. 2). The calibration lines (Ø m - c) were obtained with the constants which are characteristic of the particular insecticide. For some insecticides were found the values of these constants (a and b in Table 1). The concentration range (g/100 ml) in which a particular calibration line is valid, as well as the standard error of regression r. The sensitivity of the method varies from 5 to 350 µg of the lowest determinable quantity of the particular insecticide - Table 2. The method is not applicable for the determination of all organophosphorus insecticides but can be well supplemented with the absorptiometric (9) and luminol (10) method for the determination of organophosphorus insecticides