A mass fragmentographic method for the measurement in plasma of underivatized, dehydrated 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 was developed. Quantitative dehydration of vitamin D metabolites was achieved prior to gas chromatography using a new high-temperature injection system and a small precolumn packed with aluminium powder in the injection port, followed by mass fragmentography on an inexpensive bench-top mass spectrometer. Plasma (2 ml) was incubated with hexadeuteriated 25-hydroxyvitamin D3 prior to acetonitrile extraction and purification using cartridges pre-packed with microparticulate silica using reversed- and normal-phase solvent systems. After purification, capillary gas chromatography mass spectrometry was carried out following dehydration of the secosteroids on the aluminium power pre-column at 400°C. High-intensity dehydrated molecular ions were produced which were used for selected ion monitoring. The assay sensitivity for 25-hydroxyvitamin D was approximately 1 ng ml−1. The intra-assay variation was less than 7% and the recovery of added standard was quantitative. It is suggested that this method may be used to provide target values for much needed quality control schemes to monitor assays routinely used in the estimation of 25-hydroxyvitamin D. The behaviour of a number of other hydroxylated vitamin D metabolites, when injected without derivatization on to a gas chromatographic column, was also investigated.
                                    开发了一种用于测量血浆中未衍生的脱
水 25-羟基
维生素 D2 和 25-羟基
维生素 D3 的质量碎片分析方法。在进行气相
色谱分析之前,使用新型高温进样系统和进样口装有铝粉的小型预柱,对
维生素 D 代谢物进行定量脱
水,然后在廉价的台式质谱仪上进行质量碎片分析。将血浆 (2 ml) 与六
氘代 25-羟基
维生素 D3 一起孵育,然后使用反相和正相溶剂系统,使用预先填充有微粒
二氧化硅的柱进行
乙腈提取和纯化。纯化后,在 400°C 下在铝粉预柱上脱
水后进行毛细管气相色谱质谱分析。产生高强度脱
水分子离子,用于选择离子监测。 25-羟基
维生素 D 的测定灵敏度约为 1 ng ml−1。测定内变异小于 7%,添加标准品的回收率是定量的。建议该方法可用于为急需的质量控制方案提供目标值,以监测 25-羟基
维生素 D 估算中常规使用的测定法。许多其他羟基化
维生素 D 代谢物在未经衍生化的情况下注射时的行为还对气相色谱柱进行了研究。