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Introduction Carvacrol is an essential oil extracted from oregano which can be used as a natural additive in poultry litter and could have a positive impact not only on production rates but also on the quality of poultry meat. The aim of this study was to evaluate the effect of the addition of carvacrol to litter on weight gain and the occurrence of residues in chicken tissues. Material and Methods One-day-old Ross 308 chicks were used for the study and were randomly divided into two experimental groups. For 42 days, one group was kept in a room with litter enriched with carvacrol and the second group was kept in a room with litter without carvacrol. After 42 days, the birds were sacrificed and necropsied. Carvacrol content was determined in homogenised organ tissue samples by liquid chromatography–mass spectrometry. Results Weekly weighing results showed that exposure to carvacrol in litter had no impact on chicken body weight. The analysis of plasma, muscle, liver and lung tissue after 42 days’ exposure clearly indicated that there were residues of carvacrol in the analysed matrices. Conclusion Exposure of chickens to carvacrol left residues but did not affect body weight.

Introduction Carvacrol is an essential oil derived from oregano that is used as a natural additive to improve the efficiency of livestock nutrition. Residues of natural additives such as carvacrol should be monitored in food of animal origin to ensure consumer safety. The aim of this study was to appraise the quick, easy, cheap, effective, rugged and safe (QuEChERS) approach coupled with liquid chromatography and mass spectrometry as a means of carvacrol analysis in chicken tissue. Material and Methods A 5 ± 0.05 g portion of plasma, lung, muscle and liver was mixed for 15 min with 5 mL of 1-butanol and 20 mL of water, then centrifuged. A 0.5 mL volume from the top layer was transferred, then 60 mg of octadecylsilane sorbent, 30 mg of primary and secondary amine and 200 mg of MgSO4 were added. The extract was mixed and centrifuged. The top layer was filtered and then transferred to an autosampler vial for analysis by high-performance liquid chromatography–tandem mass spectrometry. Results The limit of detection was calculated at 0.06 μg g−1 and the limit of quantification was 0.2 μg g−1, with relative standard deviation repeatability and reproducibility below Conclusion The validation results showed that this method could be a good alternative to determination of carvacrol by gas chromatography and is suitable for carvacrol analysis in different matrices.

Human exposure to BPs is inevitable mostly due to contaminated food. In this preliminary study, for the first time, the presence of bisphenols (BPs) in aqueous humor (AH) collected from 44 patients undergoing cataract surgery was investigated. The measurements were performed using a sensitive ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS). Chromatographic separation was achieved using a reverse-phase column and a gradient elution mode. Multiple reaction monitoring (MRM) was used. The method was validated for bisphenol A (BPA) and bisphenol F (BPF). The limits of quantification (LOQs) of both investigated analytes were 0.25 ng mL−1. The method was linear in the range of 0.25–20.0 ng mL−1 with correlation coefficients (R2) higher than 0.98. Recovery of analytes was in the range of 99.9 to 104.3% and intra-assay and inter-assay precision expressed by relative standard deviations (RSD%) were less than 5%. BPA was detected in 12 AH samples with mean concentrations of 1.41 ng mL−1. BPF was not detected at all. Furthermore, two structural isomers termed BPA-1, and BPA-2 were identified, for the first time, in 40.9% of the AH samples, with almost twice higher mean concentrations of 2.15 ng mL−1, and 2.25 ng mL−1, respectively. The total content of BPs were higher in patients with coexisting ocular pathologies such as glaucoma, age-related macular degeneration (AMD), and diabetes in comparison to cataracts alone. However, the difference between these groups did not reach statistical significance (p > 0.05). Performed investigations indicate the need for further research on a larger population with the aim of knowing the consequences of BPs’ accumulation in AH for visual function.

The precise and reliable determination of buprenorphine concentration is fundamental in certain medical or research applications, particularly in pharmacokinetic studies of this opioid. The main challenge is, however, the development of an analytical method that is sensitive enough, as the detected in vivo concentrations often fall in very low ranges. Thus, in this study we aimed at developing a sensitive, repeatable, cost-efficient, and easy HPLC analytical protocol for buprenorphine in rabbit plasma. In order to obtain this, the HPLC-MS2 system was used to elaborate and validate the method for samples purified with liquid-liquid extraction. Fragment ions 468.6&rarr, 396.2 and 468.6&rarr, 414.2 were monitored, and the method resulted in a high repeatability and reproducibility and a limit of quantification of 0.25 &micro, g/L with a recovery of 98.7&ndash, 109.0%. The method was linear in a range of 0.25&ndash, 2000 &micro, g/L. The suitability of the analytical procedure was tested in rabbits in a pilot pharmacokinetic study, and it was revealed that the method was suitable for comprehensively describing the pharmacokinetic profile after buprenorphine intravenous administration at a dose of 300 &micro, g/kg. Thus, the method suitability for pharmacokinetic application was confirmed by both the good validation results of the method and successful in vivo tests in rabbits.

Introduction The major difficulty in analysis of nitrofurans in feed, feed water, and food of animal origin is that nitrofurans have low molecular weights and fast metabolism. The principal goal of this study was to prepare a procedure for the determination of nitrofurans and their metabolites by a single method in different types of feed, feed water, and food of animal origin. Material and Methods Two-gram samples were subjected to hydrolysis and derivatisation processes by addition of hydrochloric acid and 2-nitrobenzaldehyde. After incubation the sample was purified by solid phase extraction technique. Nitrofurans were analysed using ultra-high-pressure liquid chromatography-MS/MS (UHPLC-MS/MS). Results The results of validation fulfil the requirement of the confirmatory criteria according to the European Commission Decision 2002/657/EC regarding apparent recoveries (88.9%–107.3%), repeatability (2.9%–9.4%) and within-laboratory reproducibility (4.4%–10.7%). Conclusion The method can be successfully applied to monitor nitrofurans and their metabolites in different matrices.

Examination of fentanyl levels is frequently performed in certain scientific evaluations and forensic toxicology. It often involves the collection of very variable blood samples, including lipemic plasma or serum. To date, many works have reported the methods for fentanyl detection, but none of them have provided information about the impact on the assay performance caused by an excessive amount of lipids. This aspect may be, however, very important for highly lipophilic drugs like fentanyl. To address this issue, we developed the liquid chromatography method with mass spectrometry detection and utilized it to investigate the impact of lipids presence in rabbit plasma on the analytical method performance and validation. The validation procedure, conducted for normal plasma and lipemic plasma separately, resulted in good selectivity, sensitivity and linearity. The limits of detection and quantification were comparable between the two matrices, being slightly lower in normal plasma (0.005 and 0.015 µg/L) than in lipemic plasma (0.008 and 0.020 µg/L). Liquid–liquid extraction provided a low matrix effect regardless of the lipid levels in the samples (&lt, 10%), but pronounced differences were found in the recovery and accuracy. In the normal plasma, this parameter was stable and high (around 100%), but in the lipemic matrix, much more variable and less efficient results were obtained. Nevertheless, this difference had no impact on repeatability and reproducibility. In the present work, we provided reliable, convenient and sensitive method for fentanyl detection in the normal and lipemic rabbit plasma. However, construction of two separate validation curves was necessary to provide adequate results since the liquid-liquid extraction was utilized. Therefore, special attention should be paid during fentanyl quantification that involves lipemic plasma samples purified by this technique.

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.

Strychnine is an alkaloid with strong toxic properties. Poisoning results in muscular contractions and death through asphyxiation. Intentional or accidental poisonings with strychnine occur mainly in small animals, especially dogs and occasionally cats. Strychnine can be detected in the liver or stomach contents. Unfortunately, the determination of strychnine in these matrices, especially in postmortem examination, is subject to a significant matrix effect that makes it difficult to confirm the presence of the substance being determined. Therefore, we developed a new liquid chromatography method combined with mass spectrometry. One-gram homogenized samples were extracted and partitioned after adding acetonitrile and 5-mol solution of ammonium acetate. After extraction, the samples were analyzed using high-pressure liquid chromatography-MS/MS/MS. The results of validation fulfil the requirement of the confirmatory criteria according to SANTE/11945/2015 regarding apparent recoveries (98.97% to 104.0%), repeatability (2.9%&ndash, 4.1%), and within-laboratory reproducibility (3.3%&ndash, 4.6%). The method can be successfully applied to confirm strychnine poisoning cases.

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.

Tryptophan (TRP) is to an essential amino acid and its catabolites are significant to human health. By using ultra-high-performance liquid chromatography coupled to electrospray ionization triple quadrupole mass spectrometry (UHPLC-ESI-MS/MS), levels of three major components of kynurenic pathway namely tryptophan (TRP), kynurenic acid (KYNA) and kynurenine (KYN) in fluid from the anterior chamber of the eye were determined. The analysis was carried out on a Synergi 4 &mu, Fusion-RP column using gradient elution mode. For quantitative determination, l-tryptophan-amino-15N, 99 ATOM % 15N was used as an internal standard. The method was linear in the concentration range 4&ndash, 2000 ng mL&minus, 1 for TRP, KYNA and KYN. The mean recoveries measured at four concentration levels for TRP, KYN and KYNA included the following ranges 94.3&ndash, 96.1, 91.0&ndash, 95.0, and 96.0&ndash, 97.6%, respectively. The intra-day precision parameters were smaller than 4.4, 6.4 and 5% respectively. The developed method was applied to study the level of TRP, KYNA and KYN in eye fluid for the retrospective case series which included 28 patients suffering from cataracts and diabetes (n = 8). The experimental data was subjected to statistical analysis. The Mann-Whitney U-test revealed clear differences in the level of TRP catabolites and the ratios of TRP/KYN representing the activities of specific enzyme of kynurenine pathway in examined groups of patients. A level of probability p &lt, 0.05 was used throughout a paper to denote statistically significant differences between the groups.

The new sorbent for solid phase extraction (SPE), based on silica gel modified with a copper (II), was obtained and its application for phospholipids removal from the human plasma was tested. SPE column conditioning requirements, the volume of the plasma, the composition of the elution solvent were all established. The efficacy of the removal of phospholipids was compared for different methods such as standard protein precipitation or HybridSPE Phospholipid Ultra and HybridSPE-PPT. The sample clean-up was verified by mass spectrometry (MS) and by monitoring of chromatograms in the region between 190nm and 400nm. The Fourier Transform Infrared Spectroscopy FT-IR and confocal Raman microscopy were used to evaluating the silica gel modifications and to show the structure of lipids confined in the silica pores.

A simple method for the determination of chloramphenicol in 22 matrices was prepared based on the QuEChERS and HPLC-MS/MS combination. Following a hydrolysis step, the homogenized samples were extracted and partitioned after adding sodium chloride with acetonitrile. Chloramphenicol was analysed by HPLC-MS/MS in negative electrospray mode by monitoring the daughter ions m/z: 321→194 and 321→152. The limit of decision (CCα) was calculated at the range of 0.10 μg kg−1 to 0.15 μg kg−1 and detection capability (CCβ) from 0.12 μg kg−1 to 0.18 μg kg−1. Validation results showed that this method is suitable for the determination and confirmation of chloramphenicol in various matrices.

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.