HKUST-1 metal-organic framework for dispersive solid phase extraction of 2-methyl-4-chlorophenoxyacetic acid (MCPA) prior to its determination by ion mobility spectrometry

The authors describe a method for the extraction of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) from agricultural products. The metal organic framework (MOF) HKUST-1 (acopper(II) benzene-1,3,5-tricarboxylate) was used as a sorbent for efficient clean-up and preconcentration of MCPA. The effects of pH value, stirring time, amount of sorbent on extraction were optimized by central composite design. Ultrasonic waves were used for desorption procedure and its advantage was demonstrated for an increase in extraction recovery. Corona discharge ion mobility spectrometry (IMS) was then applied for fast and sensitive determination of MCPA. The method was validated in terms of sensitivity, recovery and reproducibility. Under the optimum conditions the calibration plot is linear between 0.035-0.200 mu g. L-1. The detection limit is 10 ng L-1, with relative standard deviations of <5%. Real samples (water, soil and agricultural product) were spiked and then analyzed by this method, and the results revealed efficient solid phase extraction and recovery.