& We present a sensitive and selective method for detecting imidocarb in bovine tissues and milk samples using a solid-phase extraction (SPE) with diatomaceous earth column and liquid chromatography with electrospray tandem mass spectrometry (LC-ESI-MS=MS) on positive mode. Chromatographic separation was performed on a TSK-GEL ODS 100 V column using 0.1% formic acid in water=methanol. Limit of detection (LOD) was 0.5 ng=mL for standard solution. Limit of quantitation (LOQ) was ranged from 1.0 to 10 lg=kg for bovine tissue and milk samples. The linearity of the calibration curve was excellent in matrix matched standards, and yielded the coefficients (r 2 ¼ 0.997-0.999, range from LOQ to 250, 750, or 5000 lg=kg) of imidocarb. Recoveries were in the range of 73.3-98.6% with associated precision values (within-day: 1.0-6.7%, n ¼ 6, and between-day: 2.0-7.7% for 3 days) for repeatability and reproducibility. This developed method is well adapted for residue analysis of imidocarb in bovine tissues and milk based on maximum tolerated residue levels.
A highly sensitive and selective method using LC-ESI-MS/MS and tandem-SPE was developed to detect trace amounts of avoparcin (AV) antibiotics in animal tissues and milk. Data acquisition using MS/MS was achieved by applying multiple reaction monitoring of the product ions of [M + 3H](3+) and the major product ions of AV-alpha and -beta at m/z 637 --> 86/113/130 and m/z 649 --> 86/113/130 in ESI(+) mode. The calculated instrumental LODs were 3 ng/mL. The sample preparation was described that the extraction using 5% TFA and the tandem-SPE with an ion-exchange (SAX) and InertSep C18-A cartridge clean-up enable us to determine AV in samples. Ion suppression was decreased by concentration rates of each sample solution. These SPE concentration levels could be used to detect quantities of 5 ppb (milk), 10 ppb (beef), and 25 ppb (chicken muscle and liver). The matrix matching calibration graphs obtained for both AV-alpha (r >0.996) and -beta (r >0.998) from animal tissues and milk were linear over the calibration ranges. AV recovery from samples was higher than 73.3% and the RSD was less than 12.0% (n = 5).
Due to the globalization of food production and distribution, the food chain has become increasingly complex, making it more difficult to evaluate unexpected food changes. Therefore, establishing sensitive, robust, and cost-effective analytical platforms to efficiently extract and analyze the food-chemicals in complex food matrices is essential, however, challenging. LC/MS-based metabolomics is the key to obtain a broad overview of human metabolism and understand novel food science. Various metabolomics approaches (e.g., targeted and/or untargeted) and sample preparation techniques in food analysis have their own advantages and limitations. Selecting an analytical platform that matches the characteristics of the analytes is important for food analysis. This review highlighted the recent trends and applications of metabolomics based on "foodomics" by LC-MS and provides the perspectives and insights into the methodology and various sample preparation techniques in food analysis.
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