提出了同位素稀释-超高效液相色谱-串联质谱法(UHPLC-MS/MS)同时测定水产品中15种头孢菌素残留量的方法。称取处理好的样品5 g,加入100 μg·L^-1同位素内标混合溶液200 μL,静置30 min后,再加入酸性氧化铝2 g,用5 mL 80%(体积分数)乙腈溶液重复提取两次,合并上清液。将上清液转移至Oasis Prime HLB固相萃取小柱,收集流出液,于40℃氮吹至1 mL左右,再加入含0.1%(体积分数)甲酸的乙腈溶液1 mL,经0.22 μm尼龙滤膜过滤。以Agilent InfinityLab Poroshell 120 SB C₁₈色谱柱为固定相,以不同体积比的0.1%(体积分数)甲酸溶液和乙腈的混合液为流动相进行梯度洗脱,选择电喷雾离子源正离子(ESI⁺)模式和多反应监测(MRM)模式进行分析,内标法定量。结果显示:15种头孢菌素的质量浓度在一定范围内与其对应的响应值与内标响应值的比值呈线性关系,检出限(3S/N)为0.3~2.0 μg·kg^-1;对空白样品进行3个浓度水平的加标回收试验,回收率为75.9%~119%,测定值的相对标准偏差(n=6)为1.6%~6.5%。方法用于实际样品分析,其中1份草鱼样品中检出头孢氨苄,检出量为3.78 μg·kg^-1。

A method for the simultaneous determination of 15 cephalosporins in aquatic products by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was proposed. 200 μL of 100 μg·L^-1 isotope internal standard mixed solution was added into 5 g of the processed sample with settling for 30 min. Then 2 g of acidic alumina was added, and the sample solution was extracted twice with 5 mL of 80% (φ) acetonitrile solution. The supernatant combined was transferred to Oasis Prime HLB solid phase extraction small column. The collected eluate was blown to about 1 mL with nitrogen at 40 ℃. Then 1 mL of acetonitrile solution containing 0.1% (φ) formic acid was added, and 0.22 μm nylon membrane was used to filter. Agilent InfinityLab Poroshell 120 SB C₁₈ column was used as the stationary phase, and a mixture of 0.1% (φ) formic acid solution and acetonitrile at different volume ratios was used as the mobile phase for gradient elution. ESI⁺ and MRM mode were selected, and internal standard method was used for quantitative analysis. As shown by the results, linear relationships between values of mass concentration of 15 cephalosporins and ratios of its response value to internal standard response value were kept in definite ranges, with detection limits (3S/N) in the range of 0.3-2.0 μg·kg^-1. Recovery test was made on blank samples at 3 concentration levels by standard addition method, giving results in the range of 75.9%-119%, and RSDs (n=6) of the determined values were in the range of 1.6%-6.5%. This method has been applied to the analysis of actual samples, and cephalexin was detected in one grass carp sample with detection amount of 3.78 μg·kg^-1.