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Publications (4)4.61 Total impact

  • K Stastny, K Frgalova, A Hera, M Vass, M Franek
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    ABSTRACT: An improved LC-MS/MS method for the determination of semicarbazide in whole egg is described. Waters OASIS-MCX cation exchange purification cartridges increased the sensitivity for analysis by LC-MS/MS. The validation study was carried out according to criteria and requirements of Commission Decision 2002/657/EC for confirmatory analysis and provided the data as follows: The correlation coefficient for the matrix calibration curve, in the range of 0-5 microg kg(-1), was r=0.9968. The detection capability and decision limit, measured according to ISO11843-2, were CCalpha=0.20 microg kg(-1) and CCbeta=0.25 microg kg(-1). Repeatability (CVSr) and within-laboratory reproducibility (CVSwr) determined for the concentration levels of 0.2, 0.5 and 1.0 microg kg(-1) SEM ranged from 11.9 to 5.7% and 11.8 to 6.3%, respectively. The validated method was applied to investigate SEM stability in incurred materials (egg homogenates) during long-term storage at -20 degrees C and 4 degrees C. The study proved by a two-sampling test that SEM at levels of 17. 7, 1.2, 10.6 and 0.47 microg kg(-1) was stable for up to 12 months.
    Journal of Chromatography A 07/2009; 1216(46):8187-91. · 4.61 Impact Factor
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    ABSTRACT: An enzyme-linked immunosorbent assay (ELISA) method is described for the semi-quantitative determination of semicarbazide (SEM), the marker residue for the banned nitrofuran drug, nitrofurazone, in chicken eggs. The sample homogenate is subjected to acid hydrolysis and derivatisation with o-nitrobenzaldehyde, followed by ethyl acetate/hexane extraction and detection by ELISA. The ELISA procedure has been validated using 0.3, 1.0 and 3 microg kg(-1) of SEM in fortified samples. Detection capability (CC(ss)) was based on the acceptance of 5% false compliant results for a given concentration level according to Commission Decision 2002/657/EC and was determined to be 0.3 microg kg(-1) with a respective limit of detection of 0.13 microg kg(-1). A validated LC-MS/MS method was used for the analysis of incurred egg samples and the results compared with ELISA. A good correlation between the results obtained from ELISA and LC-MS/MS within the concentration range 0.12-20.3 microg kg(-1) was observed in samples collected from chickens fed with a medicated ration of nitrofurazone (r = 0.992, n = 14). Validated ELISA enabled reliable monitoring of SEM levels in eggs collected from incurred chickens over a 90-day period.
    Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment 09/2008; 25(8):930-6.
  • G Vargas, J Havel, K Frgalová
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    ABSTRACT: In this work, a new capillary zone electrophoresis (CZE) method has been developed for the analysis of thyreostatic drugs (TD) such as methylthiouracil (MTU), propylthiouracil (PTU), and thiouracil (TU) in urine specimens. An untreated fused-silica capillary tube (75 microns i.d., 57 cm total length, 49.5 cm length to the detector) was used in all of the experiments. Optimal conditions were found using 50 mM borate buffer, pH 7.6, applied voltage 15 kV, 25 degrees C, and 30 sec of hydrodynamic injection. UV detection at 276 nm was employed. Ethylacetate extraction of the compounds was made before the analysis of each urine sample. An electrostacking procedure to increase the sensitivity was applied. The method developed was used for the analysis of several thousands of samples as part of a veterinary control procedure (Institute for State Control of Veterinary Biological and Medicaments, Brno, Czech Republic). The following detection limits were reached: 0.3 ppm (PTU and MTU) and 0.5 ppm (TU). The standard deviation for PTU, MTU, and TU determination was 1.12, 0.98, and 3.8% rel., respectively.
    Journal of capillary electrophoresis 5(1-2):9-12.
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    ABSTRACT: A monoclonal-based ELISA, coupled with an assay buffer, solvent and solid phase extraction proce - dures, was validated for use in the monitoring of egg samples for 3-amino-2-oxazolidinone (AOZ). The procedures allow the detection of protein bound AOZ in the form of 2-nitrophenyl derivative (NPAOZ) in sample supernatant or extract after acid hydrolysis and derivatisation with o-nitrobenzaldehyde. The assays were validated according to criteria set down by Commission Decision (2003) for the performance and validation of analytical methods for chemical residues. The detection capability of ELISA's for AOZ in eggs (set on the basis of acceptance of no false negatives) was 0.6, 0.3 and 0.3 µg/kg for buffer, solvent and solid phase extraction, respectively. These values are well below the maximum required performance limit (MRLP) of 1 µg/kg for tissue bound residues of nitrofuran antibiotics. An excellent correlation of results ( r = 0.99, n = 14) obtained by the ELISA and LC-MS/MS techniques within the concentration range of 0-5 µg/kg was found in the incurred egg samples. The eggs collected from layer chickens fed 30 and 400 mg/kg of furazolidone for 10 days were monitored by ELISA until AOZ concentrations approached the LoD.