A new mixed C18-SCX SPE column and gas chromatography-mass spectrometry have been used for determination of six β2-agonists residues in pig's liver. After hydrolysis, the six β2-agonists were extracted with 6:4 (v/v) ethyl acetate-isopropanol and then cleaned on a commercial mixed-adsorbent solid-phase extraction column. The eluted solution was analyzed by gas chromatography-mass spectrometry (GC-MS) and quantified by the external standard method. Sample pre-treatment and GC-MS conditions were critically examined. The linear range was 0.005–2.00 mg L–1 and correlation coefficients were 0.9987–1.000. The LOD of mabuterol, clenbuteroland, and salbutamol was 0.2 μg kg–1. Average recoveries of these three compounds from spiked pig's liver ranged from 65.3 to 95.8% and relative standard deviations were between 5.4 and 9.9%. The LOD of cimaterol, bromobuterol, and ractopamine was 0.3 μg kg–1. Average recoveries of these three compounds from spiked pig's liver ranged from 63.8 to 88.1% and relative standard deviations were between 5.0 and 9.7%. These results indicate the method is highly sensitive, simple, inexpensive, and results in good purification. It could also meet requirements for analysis of pig's urine in domestic and import/export inspection work.
Authors:L. Zhou, J. Xu, L. Luan, J. Ma, Y. Gong, D. Qin, and C. Pan
Dithiocarbamates fungicides (DTCs) are worldwidely used fungicides. Residue analytical methods on DTCs are usually based on headspace gas chromatography, which are not much stable and precise. In this study, a specific, simple and reliable method for determining DTCs fungicides residues was optimized and validated. The DTCs in foods and soils were extracted with an alkaline solution of EDTA and l-cysteine, followed by pH adjusting and methyl derivatization in methyl iodine solution. The organic layer of the reactants was separated, concentrated under vacuum and reconstructed in acetonitrile. DTCs residues were eluted on a C18 column and detected by HPLC-DAD at 272 nm. The S-alkyl derivatives of thiram, mancozeb and propineb were separated at different retention times. At fortified levels of 0.05 mg/kg to 2 mg/kg (residue expressed as CS2, in mg/kg, the same below), it is found that recoveries for DTCs spiked in apple, cucumber, tomato, rice and soil samples ranged from 70.8% to 105.3%, with relative standard deviations (RSD) from 0.6% to 13.7%. Limits of detection (LODs) and quantification (LOQs) ranged from 0.003 to 0.026 mg/kg and from 0.011 to 0.105 mg/kg for various foods and soils. This method was also applied to real sample tests.
Authors:X. Li, J. Xu, Y. Jiang, L. Chen, Y. Xu, and C. Pan
High-performance liquid chromatography with a hydrophilic-interaction liquid chromatographic (HILIC) column has been successfully used to retain and separate the polar phosphonic herbicides glyphosate and glufosinate. Online electrospray tandem ion-trap mass spectrometric and DAD detection were used. The effects on the separation of mobile phase acetonitrile content, buffer concentration, and flow rate, and of column temperature, were investigated. With UV-visible detection at 195 nm, LOQ were <850 mg kg−1, showing the method is suitable for product quality control of these herbicides alone or in combination. Tandem mass spectrometric conditions were optimized for ion-trap detection. Quantification was by use of selected reaction monitoring transitions m/z 168 → 150 in negative-ion mode for glyphosate and m/z 182 → 136 in positive-ion mode for glufosinate. Limits of detection (LOD; S/N > 3) were 0.20 and 0.16 ng for glyphosate and glufosinate, respectively, and the respective limits of quantification (LOQ; S/N = 10) were 0.02 and 0.05 mg kg−1. Sample derivatization was not necessary to achieve low detection limits in residue analysis in this study. Recovery from watermelon, spinach, potato, tomato, radish-root, and water fortified with the herbicides ranged from 63.6 to 107.3% and relative standard deviations were <15.3%.