Molecular imprinting solid phase extraction for selective detection of methidathion in olive oil

A specific adsorbent for extraction of methidathion from olive oil was developed. The design of the molecularly imprinted polymer (MIP) was based on the results of the computational screening of the library of polymerisable functional monomers. MIP was prepared by thermal polymerisation using N,N’-methylene bisacrylamide (MBAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. The polymers based on the itaconic acid (IA), methacrylic acid (MAA) and 2-(trifluoromethyl)acryl acid (TFMAA) functional monomers and one control polymer which was made without functional monomers with cross-linker EGDMA were also synthesised and tested. The performance of each polymer was compared using corresponding imprinting factor. As it was predicted by molecular modelling the best results were obtained for the MIP prepared with MBAA. The obtained MIP was optimised in solid-phase extraction coupled with high performance liquid chromatography (MISPE-HPLC-UV) and tested for the rapid screening of methidathion in olive oil. The proposed method allowed the efficient extraction of methidathion for concentrations ranging from 0.1 to 9 mg L⁻¹ (r² = 0.996). The limits of detection (LOD) and quantification (LOQ) in olive oil were 0.02 mg L⁻¹ and 0.1 mg L⁻¹, respectively. MIPs extraction was much more effective than traditional C18 reverse-phase solid phase extraction.     

Quantitative analysis of phytoestrogens in kudzu-root, soy and spiked serum samples by high-pressure liquid chromatography

A sensitive and reliable HPLC method that allows simultaneous quantification of phytoestrogens extracted from kudzu-root and soy preparations, and serum samples has been developed. Kudzu-root and soy preparations were mixed with 5 microg flavone and 15 microg rutin (internal standards) and the phytoestrogens were extracted by using solid-phase (C18) extraction cartridges. Blank or spiked serum samples were extracted by using either C18 cartridges or trichloroacetic acid-methanol extraction. The extracts were analyzed by the HPLC equipped with a reverse-phase (250 x 4 mm, C18) column and UV, diode-array or MS detector. A linear gradient of acetic acid and acetonitrile provided excellent separation of glycoside and aglycone-phytoestrogens from kudzu root and soy preparations. The C18 cartridge extraction of serum yielded excellent recovery of both glycoside- and aglycone-phytoestrogens, while the trichloroacetic acid-methanol extraction yielded excellent recovery of glycoside but poor recovery of aglycone compounds. UV and MS detectors were suitable for phytoestrogen analysis in plant and serum samples, while the diode-array detector was suitable for generating the UV absorbance curve for phytoestrogens.