超高效液相色谱-稳定性同位素稀释质谱法测定预包装食品中不同阶段美拉德反应产物含量

建立基于稳定同位素内标稀释的超高效液相色谱-串联三重四极杆质谱同步检测预包装食品中羧甲基赖氨酸(Nε-(carboxymethyl)-lysine,CML)、羧乙基赖氨酸(Nε-(carboxyethyl)-lysine,CEL)、甲基乙二醛-羟基咪唑酮异构体(methyglyoxal-derived hydroimidazolones,MG-H1、MG-H2、MG-H3)、乙二醛-氢咪唑酮(glyoxal-derived hydroimidazolone,G-H1)、糠氨酸7种不同阶段美拉德反应产物(Maillard reaction products,MRPs)的含量。采用Kinetex C18色谱柱进行分离,多反应监测模式进行定量分析。该方法的加标回收率为88.4%~111.3%,精密度相对标准偏差小于9%,检出限和定量限分别为2.1~14.2 ng/mL和7.4~41.2 ng/mL。采用该方法对134种常见预包装食品中的7种MRPs进行定量,并对得到的数据进行主成分分析和相关性分析。结果表明,CML、MG-H1/3、MG-H2和G-H1是预包装食品中主要的MRPs,各MRPs含量之间呈显著正相关,而且与蛋白质、脂肪、总糖含量呈显著正相关。该方法表现出良好的线性度、准确度和精密度,适用于预包装食品中不同种MRPs的快速检测。

Modified Method for Efficiency Calibration of High Energy γ Detector

A modified method of absolute efficiency calibration for germanium detector has been developed based on the fact that the intensities of captureγ-rays can be determined by the 1368KeVγ-rays from sodium activation when a NaCl sample is irradiated by thermal neutrons.As a verification of this method,the intensity of the 4.44MeVγ-ray from an Am-Be neutron source was determined.