Molecularly imprinted solid-phase extraction coupled with gas chromatography for the determination of four chloroacetamide herbicides in soil
A molecularly imprinted solid phase extraction (MISPE) coupled with gas chromatography (GC) for the simultaneous separation and determination of four chloroacetamide herbicides, alachlor, acetochlor, pretilachlor and metolachlor, in soil was developed. Molecularly imprinted polymers (MIPs) with butachlor as the dummy template were synthesized via precipitation polymerization, where methacrylic acid (MAA) was used as the functional monomer, ethylene glycol dimethacrylate (EDMA) as the crosslinker and acetonitrile as the porogen. Fourier-transform infrared spectrometry (FTIR) and scanning electron microscopy (SEM) were used to characterize the polymers. Under the optimum SPE conditions, the polymer sorbents can selectively extract and enrich alachlor, acetochlor, pretilachlor and metolachlor. A comparison experiment also showed that the MISPE cartridges were better than the nonimprinted and C18 cartridges in terms of recovery. The mean recoveries of the four chloroacetamide herbicides from blank soil spiked at 0.1, 0.5, and 1 μg mL−1 ranged between 80.6 and 90.2% with relative standard deviations (RSD) of less than 8% (n = 5). The limit of detection (LOD) and the limit of quantification (LOQ) of the four analytes were in the range of 1.0 × 10−12 to 5 × 10−11 g and 0.0005–0.025 mg kg−1, respectively. The presented MISPE-GC method exhibited highly selective separation and enrichment of trace chloroacetamide herbicides and could be potentially applied to the determination of chloroacetamide herbicides in soil.