Atrazine and 2, 4-D determination in corn samples using microwave assisted extraction and on-line solid-phase extraction coupled to liquid chromatography.

Abstract

On-line sample pretreatment (clean-up and analyte preconcentration) was coupled to sequential injection chromatography for the determination of 2, 4-D (2,4-dichlorophenoxyacetic acid) and atrazine in corn samples. Prior to their analysis, microwave-assisted approach was evaluated and optimized for the extraction of 2,4-D and atrazine in corn samples. Extraction was carried out using MeOH:water (30:70 v/v) solvent at 50°C for 15 min. The on-line SPE-HPLC/UV approach combined reversed solid-phase extraction using strata X sorbent with MeOH:H₂O (80:20 v/v) at 1 mL min^-1 as eluent for the enrichment of the analytes. C18 monolithic column with acetonitrile:10 mM acetate buffer pH 4 (20:80, v/v) was employed as mobile phase at 2 mL min^-1 flow rate for separation of the compounds before UV detection. Enrichment factors up to 13.4 were achieved with a 10 mL sample volume. The developed procedure showed linear response ranges from 0.07–0.70 mg kg⁻¹ for 2,4-D and atrazine with correlation coefficients >0.993. The LODs were 0.03 and 0.02 mg kg^-1 for 2,4-D and atrazine, respectively with RSD ranged from 4.0 to 7.2 % at 0.07 and 0.30 mg kg^-1. The recoveries of 2,4-D and atrazine in corn samples were from 82.6 and 98.2%. The proposed method showed good recoveries and reasonable precision for herbicide analysis in corn samples avoiding the time-consuming batch sample pretreatment step, thus minimizing risks of sample contamination and analyte losses.