LAUSR

Determination of pyraclostrobin in ginseng samples by molecularly imprinted dispersive solid-phase extraction (MIDSPE) coupled with high-performance liquid chromatography (HPLC) method was developed. Molecularly imprinted polymers (MIPs) were prepared by precipitation polymerization using pyraclostrobin as template, methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) and azobisisobutyronitrile (AIBN) as cross-linker and initiator, respectively. The mixture of butanone (MEK) and n -heptane (7:3, V:V) was used as solvent and porogen. The microspheres were characterized by laser particle size analyzer, scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). Binding experiments showed high binding capacity of polymers, and that the maximum adsorption of MIPs and NIPs to pyraclostrobin was 73.01 mg g −1 and 59.14 mg g −1 . Selective adsorption experiments verified that polymers had specific and selective recognition site for pyraclostrobin. Comparing MIPs with C 18 , the recoveries of pyraclostrobin from blank ginseng samples spiked at 0.05, 0.1, and 1.0 mg kg −1 ranged between 77.6% and 93.5% with the standard deviation of 2.18–6.07 and the relative standard deviations (RSDs) between 2.47 and 6.99% ( n  = 5). The recoveries of pyraclostrobin that used C 18 as sorbent were found to be 53.04–63.86% with the standard deviation of 1.13–2.83 and the relative standard deviations of 1.07–4.99%. The data indicated that the method for the analysis of the pyraclostrobin in ginseng samples can achieve good recoveries, repeatability and reproducibility. The linear regression equation was calculated as y  = 2.09935e−006 x  + 0.0176235 ( R 2  = 0.998656). The limit of detection (LOD, S/N  = 3) was 0.01 mg kg −1 . The confidence interval for the slope at the 95% confidence level was [356084.1828, 899542.8563], and the confidence interval for the intercept was [− 755349.2710, 72645.0856]. The MIDSPE-HPLC method showed specific selective separation and enrichment of trace pyraclostrobin in ginseng samples. The raw samples were tested and results were all below the maximum Residue Limit (MRL) 0.1 mg kg −1 in the European Union.