Determination Of Antibiotics Residues And Dicyandiamide In Bovine Milk By UPLC-MS/MS

Milk is one of the mostly consumed foods in the world and it contains large amount of nutritions, such as saturated fat, protein and calcium, which are greatly helpful for growth and health. However, the abuse of veterinary drugs and feed additives often leads to many reports of antibiotics residues and harmful chemical substances detected in milk. Thus, it is necessary to develop effective analytical methods to detect those substances in milk. Due to some good features such as sensitive, fast and accurate, ultra performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) has been widely used for qualitative and quatitative analysis of trace residue in the sample with complicated matrix. The thesis is focesd on the application of UPLC-MS/MS for the analysis of antibiotics residues and dicyandiamide in milk.An UPLC-MS/MS method has been developed for the simultaneous determination of four β-lactam antibiotics (amoxicillin, ampicillin, cefotaxime and cefoperazone) and two β-lactamase inhibitors (tazobactam, sulbactam) in bovine milk. The analytes were extracted with water from bovine milk, and purified with Oasis HLB solid phase extraction (SPE) cartridges. The analytes were determined in less than3min by UPLC-MS/MS in positive and negative electrospray ionization (ESI) modes, separately. The method linear range was1-100μg/L for tazobactam, sulbactam, ampicillin and cefoperazone, and2-100μg/L for amoxicillin and cefotaxime. The recoveries for all six analytes in bovine milk ranged from82.5%to98.3%. The limits of detection and the limits of quantitation were0.1-0.2μ/L and0.3-0.5μg/L, respectively. The intra-and inter-day precisions were less than6%for each compound.An UPLC-MS/MS method, in combination of molecular imprinted solid phase extraction (MIP-SPE) technique, has been developed for the simultaneous determination of six aminoglycosides in milk. The analytes were extracted with30%TCA from bovine milk, and purified with MIP-SPE cartridges. The analytes were determined by UPLC-MS/MS in positive mode. The limits of detection were10-30μg/L. In comparison with WCX and HLB cartridges, MIP-SPE cartridges can decrease the matrix effect significantly.An UPLC-MS/MS method for the rapid and accurate determination of dicyandiamide in milk powders and bovine milk has been developed. The separation conditions were optimized. The dicyandiamide was detected by ESI+-MS under selected ion monitoring mode, and the quantified concentration range was5-200μg/L when using spiked matrix calibration standard curves. When using this method to determine real samples, the detection limits was10μg//kg and the recoveries were83.7%89.1%and96.7%for the spiked negative samples with50,100and200μg/kg dicyandiamide. The relative standard deviations were less than2%.