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Tolgyesi A.,Food Toxicological National Reference Laboratory | Tolgyesi A.,University of Geneva | Sharma V.K.,Florida Institute of Technology | Fekete S.,University of Geneva | And 2 more authors.
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2012

This paper describes a newly developed method for the simultaneous determination of eight corticosteroid residues in bovine muscle, liver and kidney samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The determination of methylprednisone, the main metabolite of methylprednisolone, in bovine tissues using LC-MS/MS is carried out for the first time. The method development demonstrates that the pH is important in optimizing the sample preparation. Tests performed using different solid-phase extraction (SPE) cartridges were enabled to produce conditions for reducing the matrix effects (ion suppression and enhancement) of analysis. Acidic condition and mixed-mode cation exchange SPE columns resulted in the most suitable clean-up for muscle and liver, and also yielded acceptable results for kidney. The enhanced sample clean-up resulted in excellent clear baselines of ion transitions, and therefore, a higher delta electron multiplier voltage (ΔEMV) could be set in the MS/MS detector. The application of 500. V of ΔEMV improved the signal responses, however, the noise level did not change, and consequently, the overall sensitivity and analytical limits (limit of detection, limit of quantification) could be enhanced. In the HPLC separation, the recently introduced Kinetex phenyl-hexyl core-shell type column was used that enabled baseline separation for dexamethasone and its β-epimer, betamethasone. Dexamethasone and betamethasone were eluted within 12. min and such reduced retention, obtained with core-shell HPLC type column, further enhanced the sensitivity. The method was validated according to the European Union (EU) 2002/657/EC Decision; the studied parameters met the EU standards. The decision limits and limit of detections were calculated in each matrix for all corticosteroids and varied from 0.01 to 13.3. μg/kg and from 0.01 to 0.1. μg/kg, respectively. © 2012 Elsevier B.V.

Tolgyesi T.,Food Toxicological National Reference Laboratory | Tolgyesi L.,Hewlett - Packard | Bekesi K.,Food Toxicological National Reference Laboratory | Sharma V.K.,Florida Institute of Technology | Fekete J.,Budapest University of Technology and Economics
Meat Science | Year: 2014

Two high performance liquid chromatographic methods (HPLC-DAD and LC-MS/MS) were developed to analyze tetracycline (TC) residues in pig meat (pork) samples. The method involved a sample preparation using a solid-liquid extraction (SLE) by McIlvaine buffer, followed by a solid-phase extraction (SPE) clean-up using Strata-XL cartridges. The developed sample clean-up resulted in a selective chromatogram in the HPLC-DAD separation and a reduced matrix effect (ME) in LC-MS/MS analysis. Moreover, HPLC columns packed with core-shell particles were tested for separation, which further enhanced the sensitivity and the selectivity of determinations. The validation of the methods for pig samples was carried out according to European Union 2002/657/EC decision. In addition, validation was also performed for bovine, chicken, and turkey meat samples using HPLC-DAD method. The performance characteristics of determinations were evaluated with both spiked and incurred samples, and were systematically compared. LC-MS/MS technique was found to be more accurate for spiked samples; however, HPLC-DAD method resulted in more reliable concentrations for incurred samples. © 2013 Elsevier Ltd.

Tolgyesi A.,Food Toxicological National Reference Laboratory | Tolgyesi A.,Budapest University of Technology and Economics | Sharma V.K.,Florida Institute of Technology | Fekete S.,Budapest University of Technology and Economics | And 3 more authors.
Journal of Pharmaceutical and Biomedical Analysis | Year: 2012

A rapid liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed to identify and to quantify nitroimidazoles, metronidazole (MNZ), ronidazole (RNZ) and dimetridazole (DMZ) and their corresponding hydroxy metabolites, MNZ-OH and 2-hydroxymethyl-1-methyl-5-nitroimidazole (HMNNI) in plasma, milk, muscle, egg, honey and feed samples. The same sample clean-up procedure including a novel solid-phase extraction (SPE) on polymeric Strata-SDB cartridges was used for each matrix. The analytes were separated on Kinetex XB C-18 core-shell type HPLC column using isocratic elution mode with a mobile phase containing 0.1% formic acid in water/methanol (88/12, v/v, pH 2.6) at a flow rate of 0.7. ml/min. The main advantage of the developed method is that the analysis time of only 3. min, which is about three to ten times shorter than in other reported HPLC methods. The developed method was validated using a matrix-comprehensive in-house validation strategy. The matrix effect of LC-MS/MS analysis was also investigated. Results are presented from the successful application of the developed method to an incurred pork meat certified reference material and to incur porcine plasmas in a proficiency test in year 2011. © 2012 Elsevier B.V.

Tolgyesi A.,Food Toxicological National Reference Laboratory | Tolgyesi A.,Budapest University of Technology and Economics | Berky R.,Budapest University of Technology and Economics | Bekesi K.,Food Toxicological National Reference Laboratory | And 3 more authors.
Journal of Liquid Chromatography and Related Technologies | Year: 2013

This paper presents new reversed phase liquid chromatographic methods (HPLC-FLD and LC-MS/MS) for the quantification of sulfonamides in spiked and incurred honey samples. The sample preparation was optimized using Oasis HLB (hydrophilic-lipophilic balance) solid-phase extraction (SPE) cartridge. Elutions of sulfonamides were carried out under acidic, neutral, and basic conditions using methanol. Recoveries under acid condition were in the range from 66.8-90%, which were approximately 10% higher than those obtained under other conditions. The sample clean-up was also tested using Strata-XL cartridges. The HPLC-FLD separation was performed using a Varian C18 column and a ternary (methanol-acetonitrile-phosphate buffer, pH 5) mobile phase resulting good selectivity for the determination. The robustness of the ternary gradient method was evaluated by computer simulation (DryLab). LC-MS/MS separation was carried out on a Kinetex XB core-shell type HPLC column that enabled a low limit of detection (0.01-0.5 μg/kg) and faster separation (6 min). The developed methods were validated in accordance with the European Union Commission Decision 2002/657/EC and were applied successfully for more than four hundred honey samples (under a national monitoring program). The concentrations of sulfadimethoxine, sulfachloropyridazine, and trimethoprim residues in samples were found in a concentration range from 0.03 up to 686 μg/kg. © 2013 Copyright Taylor and Francis Group, LLC.

Tolgyesi A.,Food Toxicological National Reference Laboratory | Kunsagi Z.,Food Toxicological National Reference Laboratory
Microchemical Journal | Year: 2013

This paper describes a new liquid chromatography-tandem mass spectrometric method for the simultaneous analysis of T-2 and HT-2 in cereal. Extracted samples were cleaned-up on Strata-XL solid-phase extraction cartridges, and subsequent, analyzed with LC-MS/MS equipped with multimode ion source (MMI). The HPLC separation was tested with both fully porous (Gemini C-18) and core-shell type (Kinetex XB C-18) columns. The core-shell column allowed enhanced peak shapes for both toxins. During the MS/MS detection three time segments were set, in which different ionization modes were employed in the MMI. The LC-MMI-MS/MS method was optimized and validated for flour samples in line with Commission Regulation (EC) No 401/2006 and European Union 2002/657/EC decision. All studied parameters met the method performance criteria. The limit of detection was calculated by multiplying the signal-to-noise (SNR) ratio by three and the evaluated values were 0.5μg/kg and 1.5μg/kg for T-2 and HT-2, respectively. Moreover, the developed method was tested for other cereal products at an international proficiency test study in 2009. Results obtained from the performance test strengthened the effectiveness of the described approach. © 2011 Elsevier B.V.

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