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A multi-residue method for the determination of 34 antibacterial drugs (three aminoglycosides, nine β-lactams, nine fluoroquinolones, three macrolides, five sulfonamides, trimethoprim and four tetracyclines) in fish samples by LC-MS/MS was developed. The procedure enables the isolation of residues based on double extraction of the fish sample with m-phosphoric acid and heptafluorobutyric acid as an ion-pair agent and acetonitrile. All compounds were determined at the same time on a C18 column with gradient elution. The method was validated according to the requirements of European Decision 2002/657/EC. Specificity, recovery, repeatability, within-laboratory reproducibility, decision limit CCα and detection capability CCβ were calculated. CCα ranged from 55.3 to 1085 µg kg(-1) and CCβ ranged from 59.5 to 1141 µg kg(-1). The overall recoveries were from 96% to 111% with respect to the internal standards.

A tulathromycin concentration and pharmacokinetic parameters in plasma and lung tissue from healthy pigs and Actinobacillus pleuropneumoniae (App)-infected pigs were compared. Tulathromycin was administered intramuscularly (i.m.) to all pigs at a single dose of 2.5 mg/kg. Blood and lung tissue samples were collected during 33 days postdrug application. Tulathromycin concentration in plasma and lung was determined by high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) method. The mean maximum plasma concentration (Cmax ) in healthy pigs was 586 ± 71 ng/mL, reached by 0.5 h, while the mean value for Cmax of tulathromycin in infected pigs was 386 ± 97 ng/mL after 0.5 h. The mean maximum tulathromycin concentration in lung of healthy group was calculated as 3412 ± 748 ng/g, detected at 12 h, while in pigs with App, the highest concentration in lung was 3337 ± 937 ng/g, determined at 48 h postdosing. The higher plasma and lung concentrations in pigs with no pulmonary inflammation were observed at the first time points sampling after tulathromycin administration, but slower elimination with elimination half-life t1/2el  = 126 h in plasma and t1/2el  = 165 h in lung, as well as longer drug persistent in infected pigs, was found.

A liquid chromatographic method coupled with tandem mass spectrometry for determination of residues of β-lactams, macrolides, tetracyclines, quinolones, sulfonamides, and lincosamides in eggs has been described. Analytes were isolated from egg samples by solvent extraction method and extracts were cleaned by filtration on OASIS HLB cartridges. The whole procedure was validated according to European Commission Decision 2002/657/EC. The recovery ranged between 86% and 110%. The repeatability was below 16% and within-laboratory reproducibility was lower than 20%. The method was successfully applied in the official control of antibacterial compounds residue in Poland.

For the measurement of tulathromycin distribution in swine plasma an accurate and reliable analytical method was developed. The extraction was performed with oxalic acid buffer (pH=4.0). Plasma samples were cleaned up by solid phase extraction procedure using polymeric cartriges. Chromatographic separation was achieved on a C 18 analytical column using mobile phase consisting of acetonitrile, 0.1% formic acid in gradient mode. Detection was carried out by liquid chromatography tandem mass spectrometry. Azithromycin was used as internal standard. The method has been successfully validated. The recovery from spiked samples ranged from 94% to 110%. The limit of detection was 2 ng/mL and the limit of quantification was 5 ng/mL. The method was developed to investigate the pharmacokinetics of tulathromycin in swine plasma. Applicability of the method was tested with plasma from swine administered with a single dose of tulathromycin.

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The aim of this study was the comparison of the tissue pharmacokinetics of tulathromycin in healthy pigs and pigs experimentally infected with Actinobacillus pleuropneumoniae (App). Tulathromycin was given to 24 healthy and 24 infected pigs by intramuscular injection at a single dosage of 2.5 mg kg(-1) body weight (b.w.). Pigs were euthanised at each group and then samples of liver, kidney, muscle, injection site and skin with fat were taken at scheduled time points. Drug concentrations were determined by LC-MS/MS. In this study, higher values of the area under the concentration-time curves (AUC) were calculated in all tissue samples taken from infected than healthy pigs. In pigs with App the AUCs of liver, kidney, muscle, skin with fat and injection site were 1111, 1973, 235, 181 and 2931 mg kg(-1) h, while in pigs without inflammation they were 509, 1295, 151, 111 and 1587 mg kg(-1) h, respectively. Maximum drug tissue concentrations (Cmax) in infected animals were 2370, 6650, 2016, 666 and 83,870 µg kg(-1), while in healthy pigs they were 1483, 6677, 1733, 509 and 55,006 µg kg(-1), respectively. The eliminations half-times (T1/2) were respectively longer in all tissue samples taken from infected animals (from 157.3 to 187.3 h) than in healthy ones (from 138.6 to 161.2 h). The tulathromycin tissue concentrations were significantly higher (p < 0.05) in all tissue samples of the infected pigs compared with the healthy animals at 360 h (from 0.0014 to 0.0280) and at 792 h (from 0.0007 to 0.0242) after drug administration. The results suggest that the tissue pharmacokinetic properties and residue depletion of tulathromycin can be influenced by the disease state of animals.

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.