Kress Michael, Meissner Dieane, Kaiser Patricia, Wood William Graham
Reference Laboratories, Institute for Documentation and Standardization in the Medical Laboratory (INSTAND) e. V., Düsseldorf, Germany.
Clin Lab. 2002;48(11-12):635-46.
This article describes the process of "repairing" a method which has gone out of control, using the gas-chromatographic isotope-dilution mass spectrometric (GC-IDMS) determination of total glycerides in serum, measured as glycerol. The original method used 13C2-glycerol as aqueous internal standard and 12C-tripalmitin dissolved in toluene as external standard. The modified method used tripalmitin as internal and external standard, the former being labelled uniformly on the glycerol moiety of tripalmitin (13C3-tripalmitin). In addition, glycerol-free human serum albumin was added to the external standards to "trap" the glycerol physically during evaporation of the extraction solvent after alkaline hydrolysis. The modified method was more stable than the original one and the intensity of the MS-signal in the modified method was at least 100 times stronger in the external standards than in the original method. The precision of the modified method in measuring total glycerides in serum samples (as total glycerol) was better than in the original method, the coefficients of variation being under 1.5% at concentrations between 0.8 and 3.5 mmol/l.
本文描述了一种“修复”失控方法的过程，该方法采用气相色谱同位素稀释质谱法（GC-IDMS）测定血清中的总甘油酯，以甘油进行测量。原方法使用13C2-甘油作为水相内标，将溶解于甲苯中的12C-三棕榈酸甘油酯作为外标。改进后的方法使用三棕榈酸甘油酯作为内标和外标，前者在三棕榈酸甘油酯的甘油部分均匀标记（13C3-三棕榈酸甘油酯）。此外，在碱性水解后提取溶剂蒸发期间，向外部标准中加入无甘油的人血清白蛋白，以便从物理上“捕获”甘油。改进后的方法比原方法更稳定，改进后方法中外标中质谱信号强度比原方法至少强100倍。改进后方法在测量血清样品中总甘油酯（以总甘油计）时的精密度优于原方法，在浓度为0.8至3.5 mmol/l时变异系数低于1.5%。
