仪器对液相色谱-同位素稀释质谱测试结果的影响

以同位素稀释质谱法测定奶粉中氯霉素为例，比较了近几年商品化的API5000、Q-trap5500、Agilent 6490、Waters XEVO TQS 4种高效液相色谱-串联三重四极杆质谱仪（LC-MS/MS）的关键指标，并重点研究了由于离子源设计导致的样品基质中残留化合物对氯霉素及其氘代同位素试剂测量的基质效应差异。通过比较测量氯霉素的线性、灵敏度和精密度等指标，发现这4种仪器测量氯霉素的线性和检测灵敏度差异不大。在0.2~1.0 ng/g痕量浓度范围分析时，在低浓度点时，不同仪器上两种化合物的离子化差异较大，测量精密度在1.0%~9.8%之间；在高浓度时，仪器对目标物响应的影响较小。考察了各仪器对不同基质溶液所产生的基质效应，发现在所有仪器上被测物与其同位素稀释剂的响应均存在差异，且随浓度增大差异越来越明显；不同预处理方法下得到的样品基质溶液，在不同仪器可能出现抑制或增强两种相反的基质效应现象，且强度差异也较大。表明基质中不同类型的干扰物在不同类型的离子源上的离子化模式与机理可能存在较大差异，从而导致同位素试剂之间响应的差异，在准确测量中必须分别进行基质效应的验证与确认。

Instrument Influences on the Measurement Results of Isotope Dilution Mass Spectrometry

High performance liquid chromatography-tandem triple quadrupole mass spectrometry（LC-MS/MS） instrument influences on the measurement results of isotope dilution mass spectrometry method were studied with the measurement of chloramphenicol in milk powder. The basic parameters of API5000, Q-trap5500, Agilent6490, Waters XEVO TQS were investigated e.g. linearity, sensitivity and precision. The results showed that the linearity and sensitivity of the four instruments were good and similar each other, but the precision was quite different with the relative standard deviations of 1.0%—9.8% at the concentration range of 0.2—1.0 ng/g. The affection of instruments was obviously observed in the level of lower concentration. Matrix effect of different instruments during the measurements process was studied. The response of the analyte and its isotope diluent were different in all of mass spectrometers. And the disparity increased with the growing of the concentration of analyte. The use of different apparatus might cause different and even opposite matrix effects such as matrix inhibition and enhancement. And the differences of the effects could be significant. Therefore, the instruments may be play a very important role during the detection programs using LC-MS/MS. The impact of the LC-MS/MS instrument on the measurement results should be given full consideration in the application of isotope dilution mass spectrometry.