The Experts below are selected from a list of 2415 Experts worldwide ranked by ideXlab platform
Lei Zhang - One of the best experts on this subject based on the ideXlab platform.
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a rapid method for determination and confirmation of the thyreostats in milk and urine by matrix solid phase dispersion and gas chromatography mass spectrometry
Analytica Chimica Acta, 2005Co-Authors: Lei ZhangAbstract:Abstract A rapid and simple method for determination and confirmation of the thyreostats in milk and urine has been developed. The samples were extracted and purified by matrix solid-phase dispersion (MSPD) with silica gel as the solid support, and the thyreostats including tapazole, 2-Thiouracil, 6-methyl-2-Thiouracil, 6-propyl-2-Thiouracil and 6-phenyl-2-Thiouracil have been separated and detected by gas chromatography–mass spectrometry in selected ion mode with dimethylThiouracil as internal standard after derivatization with pentafluorobenzylbromide and N -methyl- N -(trimethylsilyl)-trifluoroacetamide. The derivatization reaction was conducted in a strong basic condition, which can improve the derivatization yields of the thyreostats in the presence of the matrix. The relative abundances of the selected ions in the chromatograms of the derivatives were stable and consistent, and can be used for the confirmatory purpose. The average recoveries of the five thyreostatic compounds in milk and urine were above 70% in most cases with the relative standard deviations between 2.1 and 7.9%. The limit of detection was 0.0016 μg g −1 for the thyreostats except for that of tapazole, which was 0.004 μg g −1 .
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simultaneous determination of thyreostatic residues in animal tissues by matrix solid phase dispersion and gas chromatography mass spectrometry
Journal of Chromatography A, 2005Co-Authors: Lei ZhangAbstract:A method for determination of thyreostatic residues in animal tissues by matrix solid-phase dispersion (MSPD) and gas chromatography-mass spectrometry in selected ion detection mode was developed. Thyreostatic compounds in different matrices were extracted and purified by combination of MSPD and subsequent solid-phase extraction. Silica gel was selected as the solid support of both procedures and the conditions of the procedures were optimized. Thyreostats were derivatized with pentafluorobenzylbromide (PFBBr) in strong basic medium and then with N-methyl-N-(trimethylsilyl)-trifluoroacetamide (MSTFA), which can improve the yields of derivatization for thyreostats, the repeatability, and therefore the limits of detection (LOD) of thyreostats. The limits of detection reached 10 μg/kg (2-Thiouracil, 6-methyl-2-Thiouracil and 6-propyl-2-Thiouracil), 20 μg/kg (6-phenyl-2-Thiouracil) and 50 μg/kg (tapazole) with high recoveries (more than 70% for most of thyreostats) and relative standard deviations between 4.5% and 8.7%.
M D Prat - One of the best experts on this subject based on the ideXlab platform.
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analysis of thyreostatic drugs in thyroid samples by ultra performance liquid chromatography tandem mass spectrometry detection
Analytica Chimica Acta, 2008Co-Authors: S Abuin, Francesc Centrich, Antoni Rubies, R Companyo, M D PratAbstract:A method based on ultra-performance liquid chromatography-electrospray ionisation-tandem mass spectrometry for the determination of six thyreostatic drugs in thyroid tissue has been optimised and validated in accordance with the Decision 2002/657/EC. Samples are extracted with methanol and the extracts cleaned-up on silica cartridges. The recoveries range from 40% for 6-phenyl-2-Thiouracil to 79% for 2-Thiouracil. Quantification is carried out with blank tissue samples spiked with the analytes in the range 25-500 microg kg(-1). 5,6-Dimethyl-2-Thiouracil is used as internal standard. CCalpha and CCbeta are in the ranges 4.3-16.1 microg kg(-1) and 8.7-20.7 microg kg(-1), respectively. Accuracy, expressed as percentage of error, is lower than 6% and relative standard deviation in reproducibility conditions falls between 5.6 and 10.3%. Nowadays, the proposed method is routinely implemented in the laboratory of the Agencia de Salut Publica de Barcelona and allows processing of up to 20 samples per day.
Alessandra Gentili - One of the best experts on this subject based on the ideXlab platform.
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Subcritical water extraction of thyreostats from bovine muscle followed by liquid chromatography-tandem mass spectrometry
2018Co-Authors: Silvia Rocchi, Fulvia Caretti, Virginia Pérez-fernández, Pierpaolo Tomai, Roberta Curini, Lucia Mainero Rocca, Chiara Dal Bosco, Alessandra GentiliAbstract:Thyreostats can be used fraudulently to promote a rapid increase in weight of breeding animals at low cost. Their severe toxicological effects impose the development of reliable analytical methods to be used in monitoring plans. This work describes an alternative approach to isolate residues of Thiouracil, methyl-Thiouracil, propyl-Thiouracil, phenyl-Thiouracil, tapazole and mercaptobenzimidazole from bovine muscle tissue. The developed procedure is based on the following three steps: i) matrix solid-phase dispersion with C18 for the preliminary sample preparation; ii) subcritical water extraction (SWE) at 160°C and 100 bar; iii) clean-up on an Oasis HLB cartridge. The quantitative determination was performed by LC-MS/MS in dual polarity ionization by using internal standardization. The SWE-LC-MS/MS method was validated according to the identification criteria of the Commission decision 2002/657/EC. The relative recoveries ranged from 72 to 97%; within-lab reproducibility was less than 18%. The decision limit and the detection capability of all analytes were below the recommended concentration, set at 10 µg kg−1, but the validation results demonstrated that this method could only be applied for screening of Thiouracil and methyl-Thiouracil. Besides the analytical advantages related to the use of water as solvent extraction, the procedure allowed significant removal of lipids, whose detrimental effects on instrumentation and MS sensitivity are well-known.
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Residue analysis of thyreostats in baby foods via matrix solid phase dispersion and liquid chromatography – dual-polarity electrospray – tandem mass spectrometry
2016Co-Authors: Alessandra Gentili, Valeria De Pratti, Fulvia Caretti, Virginia Pérez-fernández, Pierpaolo Tomai, Roberta Curini, Lucia Mainero RoccaAbstract:This paper describes a rapid method for confirming residues of thyreostats in meat-based baby foods by using liquid chromatography – dual polarity electrospray – tandem mass spectrometry (LC-ES(±)-MS/MS). Six thioureylenes, belonging to the group of Thiouracil and imidazole, were selected for this work: Thiouracil (TU), methylThiouracil (MTU), propylThiouracil (PTU), phenylThiouracil (PhTU), mercaptobenzimidazole (MBI) and tapazole (TAP). The amphoteric nature of these compounds allows their electrospray detection in both positive and negative ionisation. Nevertheless, MS detection is not favoured by their low molecular weights, while their chromatographic retention is also thwarted by their high polarity. A pentafluorophenyl (PFP) core-shell phase column was selected to avoid peak asymmetry or peak splitting, and a dual-polarity ionisation method was optimised to obtain a sensitivity as high as possible. The method was validated according to the Commission Decision 657/2002/EC. A simple and fast procedure based on matrix solid phase dispersion (MSPD) was optimised to extract analytes from baby foods with recoveries exceeding 82%. Limit of decision (CCα) and detection capability (CCβ) were lower than the permissible maximum concentration (10 ng g−1). The validated method was then applied to assess the potential occurrence of the six selected thyreostats in nine commercial products. All the samples were found free of contamination.
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analysis of antithyroid drugs in surface water by using liquid chromatography tandem mass spectrometry
Journal of Chromatography A, 2014Co-Authors: Virginia Perezfernandez, Alessandra Gentili, Fulvia Caretti, Roberta Curini, Stefano Marchese, Maria Angeles Garcia, Daniela PerretAbstract:Abstract This paper describes development and validation of a new method for the simultaneous determination of six antithyroid drugs (ATDs) in surface waters by using liquid chromatography–triple quadrupole mass spectrometry (LC–MS/MS). Target compounds include two ATD classes: Thiouracil derivatives (Thiouracil (TU), methyl-Thiouracil (MTU), propyl-Thiouracil (PTU), phenyl-Thiouracil (PhTU)) and imidazole derivatives (tapazole (TAP), and mercaptobenzimidazole (MBI)). Sensitivity and selectivity of the LC-multiple reaction monitoring (MRM) analysis allowed applying a simple pre-concentration procedure and “shooting” the concentrated sample into the LC–MS/MS system without any other treatment. Recoveries were higher than 75% for all analytes. Intra-day precision and inter-day precision, calculated as relative standard deviation (RSD), were below 19 and 22%, respectively. Limits of detection (LODs) ranged from 0.05 to 0.25 μg/L; limits of quantitation (LOQs) varied between 0.15 and 0.75 μg/L. The validated method was successfully applied to the analysis of ATD residues in surface water samples collected from the Tiber River basin and three lakes of Lazio (central Italy). The analytes were quantified based on matrix-matched calibration curves with mercaptobenzimidazole-d4 (MBI-d4) as the internal standard (IS). The most widespread compound was TAP, one of the most common ATDs used in human medicine, but also TU and MBI were often detected in the analysed samples.
Fulvia Caretti - One of the best experts on this subject based on the ideXlab platform.
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Subcritical water extraction of thyreostats from bovine muscle followed by liquid chromatography-tandem mass spectrometry
2018Co-Authors: Silvia Rocchi, Fulvia Caretti, Virginia Pérez-fernández, Pierpaolo Tomai, Roberta Curini, Lucia Mainero Rocca, Chiara Dal Bosco, Alessandra GentiliAbstract:Thyreostats can be used fraudulently to promote a rapid increase in weight of breeding animals at low cost. Their severe toxicological effects impose the development of reliable analytical methods to be used in monitoring plans. This work describes an alternative approach to isolate residues of Thiouracil, methyl-Thiouracil, propyl-Thiouracil, phenyl-Thiouracil, tapazole and mercaptobenzimidazole from bovine muscle tissue. The developed procedure is based on the following three steps: i) matrix solid-phase dispersion with C18 for the preliminary sample preparation; ii) subcritical water extraction (SWE) at 160°C and 100 bar; iii) clean-up on an Oasis HLB cartridge. The quantitative determination was performed by LC-MS/MS in dual polarity ionization by using internal standardization. The SWE-LC-MS/MS method was validated according to the identification criteria of the Commission decision 2002/657/EC. The relative recoveries ranged from 72 to 97%; within-lab reproducibility was less than 18%. The decision limit and the detection capability of all analytes were below the recommended concentration, set at 10 µg kg−1, but the validation results demonstrated that this method could only be applied for screening of Thiouracil and methyl-Thiouracil. Besides the analytical advantages related to the use of water as solvent extraction, the procedure allowed significant removal of lipids, whose detrimental effects on instrumentation and MS sensitivity are well-known.
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Residue analysis of thyreostats in baby foods via matrix solid phase dispersion and liquid chromatography – dual-polarity electrospray – tandem mass spectrometry
2016Co-Authors: Alessandra Gentili, Valeria De Pratti, Fulvia Caretti, Virginia Pérez-fernández, Pierpaolo Tomai, Roberta Curini, Lucia Mainero RoccaAbstract:This paper describes a rapid method for confirming residues of thyreostats in meat-based baby foods by using liquid chromatography – dual polarity electrospray – tandem mass spectrometry (LC-ES(±)-MS/MS). Six thioureylenes, belonging to the group of Thiouracil and imidazole, were selected for this work: Thiouracil (TU), methylThiouracil (MTU), propylThiouracil (PTU), phenylThiouracil (PhTU), mercaptobenzimidazole (MBI) and tapazole (TAP). The amphoteric nature of these compounds allows their electrospray detection in both positive and negative ionisation. Nevertheless, MS detection is not favoured by their low molecular weights, while their chromatographic retention is also thwarted by their high polarity. A pentafluorophenyl (PFP) core-shell phase column was selected to avoid peak asymmetry or peak splitting, and a dual-polarity ionisation method was optimised to obtain a sensitivity as high as possible. The method was validated according to the Commission Decision 657/2002/EC. A simple and fast procedure based on matrix solid phase dispersion (MSPD) was optimised to extract analytes from baby foods with recoveries exceeding 82%. Limit of decision (CCα) and detection capability (CCβ) were lower than the permissible maximum concentration (10 ng g−1). The validated method was then applied to assess the potential occurrence of the six selected thyreostats in nine commercial products. All the samples were found free of contamination.
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analysis of antithyroid drugs in surface water by using liquid chromatography tandem mass spectrometry
Journal of Chromatography A, 2014Co-Authors: Virginia Perezfernandez, Alessandra Gentili, Fulvia Caretti, Roberta Curini, Stefano Marchese, Maria Angeles Garcia, Daniela PerretAbstract:Abstract This paper describes development and validation of a new method for the simultaneous determination of six antithyroid drugs (ATDs) in surface waters by using liquid chromatography–triple quadrupole mass spectrometry (LC–MS/MS). Target compounds include two ATD classes: Thiouracil derivatives (Thiouracil (TU), methyl-Thiouracil (MTU), propyl-Thiouracil (PTU), phenyl-Thiouracil (PhTU)) and imidazole derivatives (tapazole (TAP), and mercaptobenzimidazole (MBI)). Sensitivity and selectivity of the LC-multiple reaction monitoring (MRM) analysis allowed applying a simple pre-concentration procedure and “shooting” the concentrated sample into the LC–MS/MS system without any other treatment. Recoveries were higher than 75% for all analytes. Intra-day precision and inter-day precision, calculated as relative standard deviation (RSD), were below 19 and 22%, respectively. Limits of detection (LODs) ranged from 0.05 to 0.25 μg/L; limits of quantitation (LOQs) varied between 0.15 and 0.75 μg/L. The validated method was successfully applied to the analysis of ATD residues in surface water samples collected from the Tiber River basin and three lakes of Lazio (central Italy). The analytes were quantified based on matrix-matched calibration curves with mercaptobenzimidazole-d4 (MBI-d4) as the internal standard (IS). The most widespread compound was TAP, one of the most common ATDs used in human medicine, but also TU and MBI were often detected in the analysed samples.
Roberta Curini - One of the best experts on this subject based on the ideXlab platform.
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Subcritical water extraction of thyreostats from bovine muscle followed by liquid chromatography-tandem mass spectrometry
2018Co-Authors: Silvia Rocchi, Fulvia Caretti, Virginia Pérez-fernández, Pierpaolo Tomai, Roberta Curini, Lucia Mainero Rocca, Chiara Dal Bosco, Alessandra GentiliAbstract:Thyreostats can be used fraudulently to promote a rapid increase in weight of breeding animals at low cost. Their severe toxicological effects impose the development of reliable analytical methods to be used in monitoring plans. This work describes an alternative approach to isolate residues of Thiouracil, methyl-Thiouracil, propyl-Thiouracil, phenyl-Thiouracil, tapazole and mercaptobenzimidazole from bovine muscle tissue. The developed procedure is based on the following three steps: i) matrix solid-phase dispersion with C18 for the preliminary sample preparation; ii) subcritical water extraction (SWE) at 160°C and 100 bar; iii) clean-up on an Oasis HLB cartridge. The quantitative determination was performed by LC-MS/MS in dual polarity ionization by using internal standardization. The SWE-LC-MS/MS method was validated according to the identification criteria of the Commission decision 2002/657/EC. The relative recoveries ranged from 72 to 97%; within-lab reproducibility was less than 18%. The decision limit and the detection capability of all analytes were below the recommended concentration, set at 10 µg kg−1, but the validation results demonstrated that this method could only be applied for screening of Thiouracil and methyl-Thiouracil. Besides the analytical advantages related to the use of water as solvent extraction, the procedure allowed significant removal of lipids, whose detrimental effects on instrumentation and MS sensitivity are well-known.
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Residue analysis of thyreostats in baby foods via matrix solid phase dispersion and liquid chromatography – dual-polarity electrospray – tandem mass spectrometry
2016Co-Authors: Alessandra Gentili, Valeria De Pratti, Fulvia Caretti, Virginia Pérez-fernández, Pierpaolo Tomai, Roberta Curini, Lucia Mainero RoccaAbstract:This paper describes a rapid method for confirming residues of thyreostats in meat-based baby foods by using liquid chromatography – dual polarity electrospray – tandem mass spectrometry (LC-ES(±)-MS/MS). Six thioureylenes, belonging to the group of Thiouracil and imidazole, were selected for this work: Thiouracil (TU), methylThiouracil (MTU), propylThiouracil (PTU), phenylThiouracil (PhTU), mercaptobenzimidazole (MBI) and tapazole (TAP). The amphoteric nature of these compounds allows their electrospray detection in both positive and negative ionisation. Nevertheless, MS detection is not favoured by their low molecular weights, while their chromatographic retention is also thwarted by their high polarity. A pentafluorophenyl (PFP) core-shell phase column was selected to avoid peak asymmetry or peak splitting, and a dual-polarity ionisation method was optimised to obtain a sensitivity as high as possible. The method was validated according to the Commission Decision 657/2002/EC. A simple and fast procedure based on matrix solid phase dispersion (MSPD) was optimised to extract analytes from baby foods with recoveries exceeding 82%. Limit of decision (CCα) and detection capability (CCβ) were lower than the permissible maximum concentration (10 ng g−1). The validated method was then applied to assess the potential occurrence of the six selected thyreostats in nine commercial products. All the samples were found free of contamination.
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analysis of antithyroid drugs in surface water by using liquid chromatography tandem mass spectrometry
Journal of Chromatography A, 2014Co-Authors: Virginia Perezfernandez, Alessandra Gentili, Fulvia Caretti, Roberta Curini, Stefano Marchese, Maria Angeles Garcia, Daniela PerretAbstract:Abstract This paper describes development and validation of a new method for the simultaneous determination of six antithyroid drugs (ATDs) in surface waters by using liquid chromatography–triple quadrupole mass spectrometry (LC–MS/MS). Target compounds include two ATD classes: Thiouracil derivatives (Thiouracil (TU), methyl-Thiouracil (MTU), propyl-Thiouracil (PTU), phenyl-Thiouracil (PhTU)) and imidazole derivatives (tapazole (TAP), and mercaptobenzimidazole (MBI)). Sensitivity and selectivity of the LC-multiple reaction monitoring (MRM) analysis allowed applying a simple pre-concentration procedure and “shooting” the concentrated sample into the LC–MS/MS system without any other treatment. Recoveries were higher than 75% for all analytes. Intra-day precision and inter-day precision, calculated as relative standard deviation (RSD), were below 19 and 22%, respectively. Limits of detection (LODs) ranged from 0.05 to 0.25 μg/L; limits of quantitation (LOQs) varied between 0.15 and 0.75 μg/L. The validated method was successfully applied to the analysis of ATD residues in surface water samples collected from the Tiber River basin and three lakes of Lazio (central Italy). The analytes were quantified based on matrix-matched calibration curves with mercaptobenzimidazole-d4 (MBI-d4) as the internal standard (IS). The most widespread compound was TAP, one of the most common ATDs used in human medicine, but also TU and MBI were often detected in the analysed samples.
