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An effective liquid chromatographic method with tandem mass spectrometric (LC-MS/MS) detection and identification was developed for the determination of thiamphenicol and florphenicol in the chicken liver and kidneys. After a preliminary dissolution in ethyl acetate and a homogenisation step, the obtained extract was evaporated to dryness and dissolved in water. The solution was clean up on an octadecyl (C18) solid phase extraction (SPE) cartridge. LC-MS/MS, electrospray ionisation in the negative ion mode was used for determination of the compounds followed by separation on the octadecyl column. The whole procedure was validated according to the requiments of Commission Decision 2002/657/EC and the samples were spiked with thiamphenicol and florphenicol at the levels of 50-75-100-500 µg kg⁻¹. At these levels, recovery ranged between 95.0% and 103.0%, and the within-laboratory reproducibility was lower than 5.03%. The limit of decision (CCα) for thiamphenicol and florphenicol in the kidneys were established at the level of 55.3 µg kg⁻¹ and 54.4 µg kg⁻¹, respectively, and in the liver at the level of 55.3 µg kg⁻¹ and 54.7 µg kg⁻¹. The results of the validation demonstrated that this method meets criteria for determination and confirmation of thiamphenicol and florfenicol in biological material.
A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the determination of melamine in feed samples. After a preliminary dissolution in acetonitryle and 0.05 M phosphate buffer, the obtained extract was sonicated for 10 min and supernatant was collected. The supernatant was cleaned up on SCX solid phase extraction cartridges. Melamine was determined, using electrospray ionisation in the positive mode, followed by separation on the carbon column Thermo Hypercarb. The whole procedure was validated for the identification and determination purposes. Feed samples were spiked with melamine solution at levels corresponding to 0.5-1.0-2.5-10.0 mg/kg. At the studied levels, trueness ranged between 78.0% and 82.3% and within-laboratory reproducibility expressed as a relative standard deviation was lower than 15%. The limit of detection was estimated at the level of 0.58 mg and limit of quantitation was 0.65 mg/kg.
An in-house reference material of chloramphenicol (CAP) in pigs muscle was prepared from the chloramphenicol treated animals. The incurred muscle material was diluted by mixing with blank muscle sample. The concentration of CAP at the level 0.33 µg kg⁻¹ was reached. For the homogeneity study, 10 random samples were analysed and the results were interpreted by Cochran's test and the sufficient homogeneity test. Additionally, the samples were tested for their stability according to the following scheme: 1, 7, 14, 28, 56, 84, and 112 d. It was confirmed that an appropriate homogeneity and stability of the produced in-house reference material was obtained.
Analytical methods based on gas chromatography- mass spectrometry (GC-MS/MS) and liquid chromatography- mass spectrometry (LC-MS/MS) were developed for the determination of chloramphenicol (CAP) in milk. GC-MS/MS was performed in negative chemical ionization (NCI) mode by monitoring the transitions - m/z 466→304, 466→322, and the results were compared with LC-MS/MS, in electrospray mode by monitoring the transitions of all the selected ions m/z 321→152, 321→257. The decision limit (CCα) for CAP determination by LC-MS/MS was established at a level of 0.11 µg/kg, while the corresponding value for GC-MS/MS was 0.083 µg/kg. Detection capability (CCß) for CAP by LC- MS/MS was 0.15µg/kg and for GC-MS/MS was 0.14 µg/kg. As it was found, both methods are useful for CAP determination in milk.
A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the determination of metabolites of furazolidone, furaltadone, nitrofurantoin, and nitrofurazone in eggs. The procedure requires an acid-catalysed release of protein-bound metabolites, followed by their in situ conversion into the 2- nitrobenzaldehyde (NBA) derivatives. The sample cleanup was performed on a solid phase extraction (SPE) cartridge. LC- MS/MS analysis was performed by positive electrospray ionisation (ESI) applying multiple reaction monitoring (MRM) of two transition reactions for each compound. The validation of the method was conducted following the European Union criteria for the analysis of veterinary drug residues in foods. The decision limits (CCα) were 0.16-0.24 µg/kg, and the detection capabilities (CCβ) 0.22-0.36 µg/ kg.
The occurrence of commonly used veterinary antimicrobial agents was investigated in 159 fresh water, 443 fish, and 150 sediment samples from Polish rivers and lakes. The agents included aminoglycosides, ß-lactams, diaminopyrimidines, fluoroquinolones, lincosamides, macrolides, pleuromutilins, sulfonamides, and tetracyclines. The analysis was performed by three different sample preparation procedures for each matrix and it was performed by liquid chromatography-tandem mass spectrometry with electrospray ionisation source in positive mode, under the same conditions. All analy tical methods used were validated and showed good sensitivity , accuracy, and precision. The LOQ was in the range from 5 µg/kg to 125 µg/kg for fish samples, from 0.02 µg/L to 10 µg/L for fresh water samples, and from 1 µg/kg to 8 µg/kg for sediment samples.
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