Validation of a liquid chromatography-tandem mass spectrometry method for the simultaneous determination of sulfonamides, trimethoprim and dapsone in muscle, egg, milk and honey.

A quantitative multi-residue method that includes 13 sulfonamides, trimethoprim and dapsone was developed and validated according to Commission Decision 2002/657/EC for muscle, milk egg and honey samples. For all matrices, the same extraction procedure was used. Samples were extracted with an acetone/dichloromethane mixture and cleaned up on aromatic sulfonic acid (SO3H) SPE cartridges. After elution and concentration steps, analytes were identified and quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Data were acquired according to the multiple reaction-monitoring approach (MRM) and analytes were quantified both by the isotope dilution and the matrix-matched approaches calculating the response factors for the scanned product ions. The developed method shows good linearity, specificity, precision (repeatability and within-laboratory reproducibility), and trueness. Estimated CCß for sulfonamides ranged between 5.6 and 8.2 µg kg(-1) for eggs, between 11.1 and 69.9 µg kg(-1) for milk, between 64.7 and 87.9 µg kg(-1) for muscle, and between 2.7 and 5.3 µg kg(-1) for honey. CCß values for dapsone were 3.1, 0.6, 0.7 and 1.5 µg kg(-1) and for trimethoprim were 3.1, 6.7, 81.7 and 3.0 µg kg(-1) calculated for eggs, milk, muscle and honey, respectively. Recovery for all matrices was in the range from 89.1% and 109.7%. In matrix effect testing, no significant deviations were found between different samples of muscle and milk; however, a matrix effect was observed when testing different types of honey. The validation results demonstrate that the method is suitable for routine veterinary drug analysis and confirmation of suspect samples.

Distribution of sulfamonomethoxine and trimethoprim in egg yolk and white.

The distribution of sulfamonomethoxine (SMM) and trimethoprim (TMP) in egg yolk and white was measured during and after administration of a SMM/TMP combination in laying hens in doses of 8 g l(-)(1) and 12 g l(-)(1) in drinking water for 7 days. The SMM concentration reached maximal levels on day 2 of the post-treatment period for both doses (µg kg(-)(1)): 5920 and 9453 in yolk; 4831 and 6050 in white, in doses 1 and 2, respectively. Significant differences in the SMM and TMP concentrations between yolk and white in post treatment period were found. SMM dropped below the LOD (1.9 µg kg(-1)) in yolk after day 16 and 19 for doses 1 and 2. TMP reached maximal levels on day 3 after drug administration for doses 1 and 2 (µg kg(-)(1)): 6521 and 7329 in yolk, 1370 and 1539 in white. TMP residues were measured above LOD (0.3 µg kg(-)(1)) in yolk for both doses on day 37 post-treatment.

Deposition and depletion of maduramicin residues in eggs after oral administration to laying hens determined by LC-MS.

The coccidiostat maduramicin has been approved as a feed additive for chickens and turkeys, although it is prohibited for use in laying hens. In the present study, laying hens were divided into three groups and fed for 14 days with medicated feed containing maduramicin, at three different concentrations: 50, 100 and 500 µg kg(-1). Eggs were collected during treatment and for 26 days after the end of feeding with medicated feed. Maduramicin residues were found exclusively in egg yolk, with the highest concentration in egg yolk of 459 µg kg(-1) for the highest dose. The maximum concentration of maduramicin in whole egg was 16.6 µg kg(-1) for the group receiving feed containing the maximum permitted level of maduramicin in feed (50 µg kg(-1)). The half-life of elimination of maduramicin, calculated for post-treatment days 1-10, was 6.5 days. Twelve days after drug administration, the concentration of the maduramicin in egg yolk for Group 3 (fed with 500 µg kg(-1) maduramicin) still exceeded 20 µg kg(-1), while the concentrations for Groups 1 and 2 were 1.2 and 2.7 µg kg(-1), respectively.

Tylosin content in meat and honey samples over a two-year period in Croatia.

A total of 646 meat and 96 honey samples were examined over a 2-year period for the presence of tylosin residues. ELISA method used was validated according to the criteria of Commission Decision 2002/657/EC established for qualitative screening methods. The CCß values were 32.1 µg kg⁻¹ in muscle and 24.4 µg kg⁻¹ in honey. The recoveries from spiked samples ranged from 66.4-118.6%, with a coefficient of variation between 12.6% and 18.6%. All the investigated samples showed no presence of tylosin. Calculated estimated daily intakes show exposure levels lower than the acceptable daily intakes set by World Health Organization.

Lead content in multifloral honey from central Croatia over a three-year period.

Lead concentrations were analysed by atomic absorption spectrometry in multifloral honeys collected in central Croatia (Zagreb County) during a three-year period from 2009 to 2011. The mean levels of elements (µg/kg) in honey samples measured were: 90.8 in 2009, 189 in 2010 and 360 in 2011. Significant differences were observed, and Pb levels determined in 2009 were significantly lower than those in 2010 and 2011 (p < 0.05, both). In 2009 there was no concentration found above 300 µg/kg. However, in 2010 and 2011 levels exceeding 300 µg/kg were found in 28.6 % and 25 % of samples. Trace element levels of Pb determined in multifloral honey were generally higher than concentrations obtained from other geographical origins and neighbouring countries. These high concentrations of Pb may be related to the fact that the central region is becoming increasingly urban and the network of motorways is growing. Accordingly, the risk of positioning hives near zones of busy highways and railways is increasing. This underlines that particular attention should be paid to toxic Pb levels, due to their gradual increased during the study period.