Introduction: Quercetin is a polyphenolic flavonoid which has been used in traditional Chinese medicine as a natural therapeutic agent with a broad spectrum of activities (antioxidant, anticancer, neuroprotective, anti-inflammatory, antiviral and antibacterial). The aim of this study was to develop and validate a rapid and simple ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method for the determination of quercetin in milk.
Material and Methods: Sample preparation was based on a liquid-liquid extraction with 0.5% formic acid in acetonitrile. The chromatographic separation was performed on a ZORBAX SB-C18 column with methanol and 0.5% formic acid as a mobile phase.
Results: The procedure was successfully validated. The mean recovery of the analyte was 98%, with the corresponding intra- and inter-day variation less than 10% and 15%, respectively, and the repeatability and reproducibility were in the range of 3%–7.2% and 6.1%–12%, respectively. The lowest level of quantification was 1.0 μg/kg.
Conclusion: The proposed method was successfully applied in evaluating the pharmacokinetics of quercetin in milk obtained from dairy cows with clinical mastitis after intramammary administration.
The study presents a method for determination of enrofloxacin and ciprofloxacin in albumin and freeze-dried-eggs with the use of liquid chromatography with fluorescence detection. The procedure enables a simple isolation of fluoroquinolones from albumin based on extraction with acetonitrile, and from freeze-dried-eggs with acetonitrile under alkaline conditions. The samples have been analysed on ultracarb C8 liquid chromatography column. The gradient elution programmes consisted of the mixture of 0.03 M phosphoric acid with 0.002 M sodium 1-heptanesulfonate monohydrate and acetonitrile. The method has been validated according to requirements of the European Decision 2002/657/EC. Recoveries ranged from 78% to 83% for spiked freeze-dried-eggs and from 89% to 91% for albumin. The developed method can be applied for determination and confirmation of enrofloxacin and ciprofloxacin in albumin and freeze-dried-eggs.
Introduction: The main problem in poultry farming is the difficulty in producing food of animal origin without using antibacterial agents. Because most antibacterial compounds are dispensed in water, some water supply systems can be contaminated by antibiotics which are then administered to the animals unintentionally. This can lead to unexpected increases in antibiotic residues in food of animal origin. The aim of the present study was to determine whether the constant exposure of chicken broilers to enrofloxacin affects the withdrawal time of a therapeutic doxycycline that is intentionally administered to the chickens.
Material and Methods: The concentrations of doxycycline, enrofloxacin, and ciprofloxacin were determined by LC-MS/MS in muscles and liver of the chickens.
Results: Doxycycline residue concentrations in the chicken tissues from the group that received trace amounts of enrofloxacin were nearly 50% greater than those of the group that received only doxycycline.
Conclusion: These results indicated that constant exposure to enrofloxacin in trace amounts significantly influences the residual doxycycline concentration in chicken tissues.
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 analytical 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.
Introduction: The main problem in determination of chloramphenicol in food of animal origin is a large number of matrices. The main target of this study was to create a method for determination and confirmation of chloramphenicol in products and food of animal origin. Material and Methods: Each 5 g matrix sample was mixed with 5 mL of water and 10 mL of acetonitrile/ethyl acetate, homogenised, and centrifuged. The organic layer was evaporated and redissolved in 6 mL of 4% NaCl. The extract was cleaned up by SPE technique. Chloramphenicol was analysed by LC-MS/MS in electrospray mode. Results: The procedure was validated according to the Commission Decision No. 2002/657/EC. The apparent recoveries were in the range of 92.1% to 107.1% with a repeatability less than 11.0% (4.4%-11.0%) and within-laboratory reproducibility below 13.6% (4.7%-13.6%). Conclusion: The method was successfully validated and proved to be efficient, precise, and useful for quantification of chloramphenicol in more than 20 different matrices.
Introduction: There are many veterinary products containing β-lactam antibiotics which are used for mastitis treatment in cows. The aim of the study was to determine whether mastitis could have any effect on amoxicillin (AMX) or penicillin G procaine (PEN) withdrawal period from milk, in the context of current maximum residue limits established by the European Commission.
Material and Methods: The study was conducted on 17 dairy Black and White cows with clinical mastitis during the lactation period. The first group (n = 8) received 200 mg of amoxicillin (AMX), whereas the second group (n = 9) received 200,000 IU/mg of penicillin G procaine (PEN) by intramammary administration. For the measurement of AMX and PEN concentrations in milk, the liquid chromatography tandem mass spectrometry method was applied. Pharmacokinetic calculations were performed using Phoenix WinNonlin 6.4 software.
Results: The determined AMX and PEN half-life values in the mammary gland suggest that the drug withdrawal is at a level of 99.9% within 81 h (≈3.5 days) and 116 h (≈5 days) after administration of AMX and PEN, respectively. The present research indicates that, at 60 h after administration, the average PEN concentration in the milk from cows with clinical signs of mastitis may still reach 4.96 g/kg and that of AMX can even be 6.92 g/kg.
Conclusion: The results obtained confirm that, in mastitis cases, a 72-h withdrawal period is sufficient for elimination of AMX to a lower level than the established maximum residue limit (MRL) values. However, in the case of PEN, at 69 h after administration, the drug concentration may be close to that of the determined MRL.