Determination of lasalocid residues in the tissues of broiler chickens by liquid chromatography-tandem mass spectrometry

Lasalocid is a polyether ionophoric coccidiostat used for the prevention of coccidiosis in poultry at a prescribed concentration and during a certain time interval. Due to a public health concern about the presence of coccidiostat residues in poultry, the aim of the present study was to determine the levels of lasalocid residues in the edible tissues of broiler chickens (breast muscle, thigh muscle, heart, liver, gizzard, kidneys and skin/fat) fed commercially produced feed containing 100 mg kg(-1) of lasalocid in complete feed throughout the 5-day withdrawal period (WP). The residues were investigated by liquid chromatography coupled with electrospray ionisation (ESI) tandem mass spectrometry (MS/MS) with triple quadrupole. The limit of detection (LOD) and the limit of quantification (LOQ) of the method were 0.47 and 1.44 mu g kg(-1), respectively. The average recovery based on the matrix-fortified calibrations for chicken tissues ranged between 79% and 98%. Lasalocid was found to accumulate in the liver, followed by the heart, skin/fat, kidneys, thigh muscle and gizzard. The lowest concentrations of lasalocid residues were found in the breast muscle. On day 5 of the WP, residue concentrations of lasalocid did not decline below the LOQ of the method, but were far below the maximum residue level (MRL) established for lasalocid in poultry from 20 to 100 mu g kg(-1) by European Commission Regulation (EU) No. 37/2010. The results confirmed that the WP established for lasalocid is sufficient to ensure the decline of its residues in the tissues of broiler chickens to the safe residue level.