Simultaneous determination of thiodicarb and its main metabolite residues in cotton by ultra-performance liquid chromatography coupled to tandem mass spectrometry

Abstract

An ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method was developed for the simultaneous determination of thiodicarb and its main metabolite (methomyl and methomyl-oxime) residues in cotton leaves and cotton seeds. The mass spectrometer was operated in multiple reaction monitoring mode with positive electrospray ionization. The samples were extracted by acetonitrile, the extract was cleaned up by Pesti-Carb/NH 2 solid phase extraction column, then separated by reversed phase liquid chromatography, and determined by UPLC-MS/MS. It showed that the recoveries ranged from 67.5% to 109.2% at spiked levels of 0.01-0.1 mg kg À1 , while the relative standard deviation was 2.8% to 9.1%. The limit of the detection was 0.2-1.3 mg kg À1 , and the limit of quantification was 0.9-4.0 mg kg À1 .

Laboratory validation of an LC-MS/MS method for simultaneous determination of carbamate residues in vegetables

“…Several analytic approaches used to determine carbamate residues in agricultural products and water included gas chromatography with derivatization (Lanqas et al, 1996;Zhang and Lee, 2006;Liu et al, 2005) and high-performance liquid chromatography (HPLC) with various detectors such as a fluorescence detector (Vassilakis et al, 1998;Caballo-López and Luque De Castro, 2003), a UV/Vis detector (Gou et al, 2000;Bernal et al, 1997;Ouertani et al, 2016;Kongphonprom et al, 2016;Ruengprapavuta et al, 2020), LC-MS (Liu et al, 2005), and LC-MS/MS (Dearmond et al, 2015;Wu et al, 2013). However, carbamate pesticides are easily decomposed due to thermal instability during direct GC analysis (Wu et al, 2013). In another method, LC/UV, HPLC with fluorescence detection by post-column derivatization is widely applied for the analysis of carbamate pesticides (Caballo-López and Luque De Castro, 2003;Vassilakis et al, 1998).…”

“…The disadvantages of both methods are that they are time-consuming and have low sensitivity. Compared with LC-MS, LC-MS/MS has both high selectivity and sensitivity for target analytes, including pesticides residues in fruit and vegetables (Dearmond et al, 2015;Wu et al, 2013;Stachniuk and Emilia, 2016;Ramadan et al, 2016). Among them, LC-MS/MS-multiple reaction monitoring (MRM) mode is currently considered the most suitable technique to detect multiple classes of target compounds due to its highly selective and sensitive detection of analytes.…”

“…This indicates that the LC-MRM-MS/MS technique provides clear identification and reliable confirmation (Stachniuk and Emilia, 2016). It was reported that the presence of matrix components could affect the ionization of the target analytes when atmospheric pressure chemical ionization (APCI) or electrospray ionization (ESI) was used (Dearmond et al, 2015;Wu et al, 2013;Stachniuk and Fornal, 2016;Ramadan et al, 2016). It was also considered that very tiny matrices from biological samples can damage the pump head and the column of the HPLC instrument.…”