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71.
Three-phase solvent bar microextraction (TPSBME) technique is described for the quantitative determination of trace amounts of clenbuterol (CB) in urine samples using liquid chromatography (LC) and electrospray tandem mass spectrometry (ES-TMS). CB was extracted from a basified urine sample (donor phase) into the organic solvent residing in the pores of a freely moving hollow fiber and then back extracted into an acidic solution (acceptor phase) inside the lumen of the hollow fiber. The ends of the fiber were pressure-sealed. Here, forward and back extraction took place spontaneously. We studied various parameters affecting the extraction efficiency viz. type of organic solvent (octanol, nonanol and dihexyl ether) used for immobilization in the pores of the hollow fiber, i.e. extraction time (10-40 min), stirring speed (0-1000 rpm), effect of sodium chloride (0-25%, w/v) and concentration of the donor (0.25-3 M NaOH) and the acceptor (0.5-5 M formic acid) phases. After extraction, CB was analyzed by injecting the analyte enriched acceptor phase into LC combined with ES-TMS. Enrichment factor (79), repeatability (R.S.D. = 5.1%), correlation coefficient (0.9972, for the range of 0.1-4 ng mL−1), detection limit (7 pg mL−1) were also investigated. The present technique is compared with the reported solid phase microextraction techniques in terms of selectivity, analysis time per extraction, cost of analysis per extraction, and precision. Among all microextraction techniques reported, this technique is the most economical sample preparation/preconcentration technique to our knowledge. The method was applied for the analysis of CB in human urine. 相似文献
72.
G. Van Vyncht S. Preece P. Gaspar G. Maghuin-Rogister E. DePauw 《Journal of chromatography. A》1996,750(1-2):43-49
β-Agonists are substances used in veterinary and human medicine for the treatment of pulmonary disorders. They have found a use as growth promoters to improve meat-to-fat ratios in cattle but they are not authorized for use in the European Union. Due to their presence in trace levels (usually less than 1 μg/kg), to the diversity of the illegally used compounds and to the complexity of the biological matrices analysed, the detection of these residues requires a very sensitive and specific method of determination. This work describes the strategy of analysis we developed for five β-agonists in urine and liver. The combination of improved solid- or liquid-phase extraction methods and LC or GC-MS-MS (in the multiple reaction monitoring mode) has shown to provide a system suitable for the control of these substances. The efficiency of extraction and the sensitivity and selectivity allow this multiresidue detection down to, and below, the UK regulatory level of 0.5 μg/kg. Moreover, the use of LC removes the need for the derivatisation step (cyclic methylboronate derivatives) which is required prior to GC-MS-MS analysis. 相似文献
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建立了测定盐酸克仑特罗片剂含量的高效液相色谱法。选用Agilent Eclipse XDB-C8柱(4.6 mm×250 mm,5μm),流动相为甲醇-水(40∶60,含20 mmol.L-1磷酸二氢钾,以磷酸调至pH 4.0),流速为1.0 mL.min-1,检测波长240 nm,线性范围为0.50~50.0 mg.L-1(r=0.999 9),检出限为0.5 ng,回收率在98.5~102.0%之间,RSD为2.06%~3.07%(n=5)。 相似文献
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