L. Chervyakova, T. Panchenko, O. Tsurkan

Multiquantitative control of pesticides in treated sugar beet seeds

Introduction

Multiquantitative control of pesticides in treated sugar beet seeds . A new method for precise, multiquantitative control of thiamethoxam, bifenthrin, hymexazole & thiram pesticides in treated sugar beet seeds using TLC.

Abstract

Goal. To develop a method for the determination of thiamethoxam, bifenthrin, hymexazole and thiram in treated sugar beet seeds in one analysis. Methods. The active substances were analyzed by method of thin-layer chromatography. The linear range of dependence of the area of chromatographic zones on the amount of active substance was estimated by mathematical and statistical method using correlation and regression analysis. Results. The determination of pesticides includes the main stages: characterization of active substances by polarity; their extraction from the analyzed matrix; chromatographic separation, identification and quantification. The dipole moment of a compound (μ, Debye) is an integral indicator in the analysis, characterizing its polarity and physicochemical properties. Accordingly: bifenthrine is a non-polar compound with a dipole moment of 0.38 D; thiram, hymexazole, thiamethoxam are low-polar compounds with a dipole moment of 3.45, 3.99, and 5.55 D, respectively. The extractant that provides the most complete extraction is ethanol (ε 24.3). Separation — in a thin layer of silica gel adsorbent with acidification of the thin layer with a 10% solution of acetic acid in ethanol in the mobile phase of hexane + ethanol (ε = 8.42). The compounds are identified under a chromatoscope (λ 254 nm) and using a silver ammonia reagent with UV irradiation (brown zones of localization of active substances on the light background of the chromatogram). The dependence of the area of the chromatographic zone of a compound (S, mm2) on its amount (C, μg) is linear in the detection range for: thiamethoxam 0.1 — 0.7 μg; thiram 0.1 — 1.0 μg; hymexazole 0.5 — 2.0 μg; bifenthrine 0.3 — 2.0 μg and is described by the corresponding regression equation: S = 8.345 S + 1.3395; S = 40.87 S + 6.4596; S = 8.83 S + 0.125; S = 4.4304 S + 4.8996. Conclusions. The developed methodology allows for the analytical control of thiamethoxam, thiram, hymexazole and bifenthrin in the treated sugar beet seeds in the presence of different combinations and quantities during one analysis with high accuracy, reliability and reproducibility.

Review

This manuscript addresses a significant need in agricultural quality control by proposing a multiquantitative method for the simultaneous determination of four key pesticides—thiamethoxam, bifenthrin, hymexazole, and thiram—in treated sugar beet seeds. The goal of developing a single analytical procedure for these compounds is highly relevant for ensuring compliance with regulatory standards and safeguarding food safety. The authors have adopted Thin-Layer Chromatography (TLC), a cost-effective and relatively rapid technique, to achieve this. The initial characterization of active substances based on their polarity, using dipole moment as an indicator, suggests a thoughtful approach to method development by considering the physicochemical properties of the analytes. The methodology details the extraction using ethanol, which is a common and relatively safe solvent, and subsequent separation on silica gel with an acidified hexane + ethanol mobile phase. Identification is performed using UV light and a silver ammonia reagent, indicating a robust detection strategy for diverse compounds. The abstract presents specific linear ranges for each pesticide and corresponding regression equations for quantification. However, a notable error appears in the presentation of these equations (e.g., "S = 8.345 S + 1.3395"), where the dependent variable 'S' (area) is used inappropriately on both sides, suggesting a typo where 'C' (concentration or amount) should be used on the right side. Additionally, the description of "acidification of the thin layer with a 10% solution of acetic acid in ethanol in the mobile phase" is somewhat ambiguous, requiring clarification on whether the stationary phase or the mobile phase itself is acidified. While the abstract concludes with strong claims regarding the high accuracy, reliability, and reproducibility of the developed methodology, these assertions are not quantitatively substantiated within the provided text. For a method to be considered robust and suitable for analytical control, critical validation parameters such as Limits of Detection (LOD), Limits of Quantification (LOQ), recovery rates, and precision (expressed as relative standard deviation, RSD) are essential. The absence of these data in the abstract makes it difficult to fully assess the method's practical applicability and its ability to meet specific regulatory requirements for pesticide residues. Despite these points, the work represents a valuable step towards developing a practical and accessible analytical tool, provided that comprehensive validation data are presented in the full manuscript to support the claims of high performance.

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