Miniaturized liquid-liquid extraction coupled with ultra-performance liquid chromatography/tandem mass spectrometry for determination of topramezone in soil, corn, wheat, and water.

A rapid and simple miniaturized liquid-liquid extraction method has been developed for the determination of topramezone in soil, corn, wheat, and water samples using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-electrospray ionization (ESI)/MS/MS). The established method for the extraction and purification procedure was based on liquid-liquid partitioning into an aqueous solution at a low pH (pH ≈ 2.5), followed by back-partitioning into water at pH > 9. Two precursor, product ion transitions for topramezone were measured and evaluated to provide the maximum degree of confidence in the results. Under negative ESI conditions, quantitation was achieved by monitoring the fragment at m/z = 334 and the qualitative fragment at m/z = 318, whereas also collecting the corresponding parent ion at m/z = 362. Chromatographic separation was achieved using gradient elution with a mobile phase consisting of methanol and a 0.01% aqueous ammonium hydroxide solution. Recovery studies for soil, corn, wheat, and water were conducted at four different topramezone concentrations (5 or 10, 50, 100, and 1,000 μg kg(-1)); the overall average recoveries ranged from 79.9% to 98.4% with intra-day relative standard deviations (RSD) of 3.1~8.7% and inter-day RSD of 4.3~7.5%. Quantitative results were determined from calibration curves of topramezone standards containing 1-500 μg L(-1) with an R(2) ≥ 0.9994. Method sensitivities expressed as limits of quantitation were typically 6, 8, 9, and 1 μg kg(-1) in soil, corn, wheat, and water, respectively. The results of the method validation confirmed that this proposed method was convenient and reliable for the determination of topramezone residues in soil, corn, wheat, and water.