Analitycal aspects of the determination of inorganic pesticides in fruit products

Goal. Development of the method of analytical determination of the mixture of phosphoric acid and aluminum phosphite in the fruits of stone and grain crops by the photometric method. Method. The mixture of active substances was determined by the photometric method. The linear range of dependence of the optical density of solutions of the derivative on the mass concentration of active substances was estimated by a mathematical and statistical method. Results. The determination of inorganic compounds includes the same steps as the determination of organic compounds: sampling and storage of samples, extraction of the pesticide from the sample, purification of the extract from co-extractive compounds and concentration, identification and quantification by an appropriate method. Taking into account that aluminum phosphite and phosphoric acid are polar compounds (according to the extraction method), the mixture of the active substances under study is extracted with a solution of mineral acid with an appropriate dielectric constant. Identification of the phosphite mixture is carried out after performing a qualitative reaction of phosphorus-molybdenum derivative formation. The quantitative determination of the mixture of phosphoric acid and aluminum phosphite in the sample is determined by the calibration dependence of the optical density of the resulting solution of phosphorus-molybdenum derivative (D) on the mass concentration of phosphites in the extract (C, μg/ml). This dependence is linear in the concentration range of 0.25—0.50 μg/ml and is described by the regression equation D = 0.0450 × С + 0.0091. Conclusion. The developed method for determining the mixture of phosphoric acid and aluminum phosphite provides for the determination of the mass fraction of active substances in stone fruit and pome fruits in the concentration range from 0.10 mg/kg to 2.00 mg/kg with high accuracy (2.7—6.6%) and reproducibility and can be used to control the quality of fruit products at the level of hygienic standards.