In this study, microbiological tests for the detection of beta-lactam antibiotics in meat and meat products were evaluated. The traditional FPT (four plate test, containing Bacillus subtilis and Kocuria rhizophila), BsDA (Bacillus stearothermophilus disc assay) and a newly developed microbiological test, Premi Test (containing Bacillus stearothermophilus) were included in the study. The limit of detection (LOD) of the Premi Test was compared with the LOD of the traditional methods. The detection limits of the tests were determined by using beta-lactam antibiotic standards dissolved in meat juice, as well as meat tissue obtained from laying hens after experimental administration of amoxicillin. Positive samples, based on inhibition of growth of the organism in the test, were confirmed by high performance liquid chromatography (HPLC). Growth inhibition in the traditional tests is visible as a clear zone on the plate, whereas for Premi Test, this is based on the absence of a colour change of the test. The LODs of antibiotics tested were as follows: Penicillin G (PENG) 5 microg kg(-1), amoxicillin (AMOX) 10 microg kg(-1), ampicillin (AMP) 25 microg kg(-1), oxacillin (OXA) 30 microg kg(-1), and cloxacillin (CLOX) 30 microg kg(-1) on the plate with Bacillus stearothermophilus. Beta-lactam antibiotics can be detected also on one plate seeded with Kocuria rhizophila, although the LODs are higher: PENG 10 microg kg(-1), AMOX 25 microg kg(-1), AMP 30 microg kg(-1), OXA 50 microg kg(-1), and CLOX 50 microg kg(-1). Premi Test was performed according to the Standard Operating Procedure intended for detection of beta-lactam antibiotics in poultry tissues with following LODs: PENG 4 microg kg(-1), AMOX 5 microg kg(-1), AMP 5 microg kg(-1), OXA 40 microg kg(-1), CLOX 50 microg kg(-1). All tests are able to detect beta-lactam antibiotics such as penicillin G, ampicillin, amoxicillin, oxacillin and cloxacillin below the maximum residue level (MRL). However, the detection limits of the Premi Test for PENG, AMOX and AMP were below the limits of BsDA and the plate containing Kocuria rhizophila.

The aim of this study was to monitor the carry-over of melamine and its metabolite cyanuric acid from melamine-contaminated feed administered to layers into eggs. Ten experimental Isa Brown layers (36 week of age) were fed melamine-contaminated feed containing 100 mg of melamine per kg of feed. The duration of the experiment was 6 weeks. Eggs were collected during whole experiment. Analysis of eggs was done by a simple extraction of melamine and cyanuric acid residues, using a water-acetonitrile mixture and analysed by gas chromatography -triple quadrupole mass spectrometry. Melamine and cyanuric acid residues were detected in all eggs collected from the experimental layers, immediately after the first administration of melaminecontaminated feed. The mean concentrations of melamine in the egg yolk and egg white recalculated on a dry matter basis were 1.90 mg·kg -1 ± 0.158 and 10.84 mg·kg -1 ± 3.951 (P ≤ 0.01); the cyanuric acid contents were 6.54 mg·kg -1 ± 0.2.466 and 4.07 mg·kg -1 ± 0.909, respectively. Melamine and cyanuric acid were not detected in eggs from control layers. Concentrations of melamine and cyanuric acid in eggs decreased quickly after melamine feeding was stopped. Our results indicate that melamine undergoes biotransformation to cyanuric acid in the layer's body that also passed into the eggs. The results verified the presence of distribution metabolic pathway of melamine and its easiest transfer into egg yolk. Moreover, the biotransformation of melamine into cyanuric acid in eggs of layers was confirmed.

A method based on the use of ultra performance liquid chromatography (UPLC) tandem mass spectrometry interfaced with electrospray (UPLC=MS=MS) was devised for the determination of coumarin residues in food samples. Sample treatment includes accelerated solvent extraction (ASE) using dichloromethane followed by a clean up on a gel permeation chromatograph. UPLC was performed on an Acquity UPLC BEH C 18 (100 mm  2.1 mm), the mobile phase was water-acetonitrile (50=50 v=v) (each component containing 0.1% formic acid) at a flow rate of 0.3 mL min À1 . For unequivocal identification of the substance, two ions were detected and chosen for multiple reactions monitoring (MRM). Validation was carried out on a spiked sample of vanilla milk rice and liquorice sweets. The described method meets all the criteria of Decision 2002=657=EC and is easy to use in routine analyses.