Development and validation of a kinetic-spectrophotometric method for the trace determination of 2-methyl-4-chlorophenoxyacetic acid in baby teas and baby food samples using solid phase extraction followed by high-performance liquid chromatography.

The aim of this study was to develop a kinetic-spectrophotometric method for 2-methyl-4-chlorophenoxy acetic acid (MCPA) determination and apply it for pesticide determination in baby tea and baby food samples, using solid-phase extraction (SPE) followed by the kinetic-spectrophotometric method and the high-performance liquid chromatography (HPLC) method. This method is based on the inhibited effect of MCPA on the oxidation of sulfanilic acid (SA) by hydrogen peroxide in the presence of Co²⁺ ion as catalyst in alkaline medium. The reaction was monitored spectrophotometrically by measuring the increase in absorbance with time of the reaction product at 368 nm. Under the experimental conditions used, MCPA showed a linear dynamic range of 0.14 to 2.0 μg mL⁻¹, and from 2.0 to 20.00 μg mL⁻¹ with relative standard deviations (RSD) from 1.07 to 4.35%. The limit of detection and the limit of quantification were 0.052 and 0.107 μg mL⁻¹. The method was successfully applied to determination of MCPA residues in baby tea and baby food samples. Solid-phase extraction (SPE) was used for extraction of MCPA from samples using Chromabond® C₁₈ cartridges. The HPLC method was used as a comparative method to verify the results of kinetic method. The results obtained by two different methods showed good agreement. The proposed method is highly sensitive, simple, easy, requires cheap reagents, and leads to good recovery levels. It is linear, precise, and accurate. It can be successfully used for the routine analysis of MCPA in baby tea samples, and baby food samples. [ABSTRACT FROM AUTHOR]