Detection limits of electron and electron capture negative ionization-mass spectrometry for aldehydes derivatized with <i>o</i>-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride
作者:Josef Beránek、Darrin A. Muggli、Alena Kubátová
DOI:10.1016/j.jasms.2009.12.009
日期:2010.4.1
In contrast to common expectations, the differences in limits of detection (LODs) between electron capture negative ionization (ECNI) and electron ionization (EI) mass spectrometry (MS) were found to be insignificant for a wide range of aldehydes derivatized with o-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride. Comparison of the two ionization methods based on LOD confidence intervals revealed that a traditional presentation of the LOD or limit of quantitation (LOQ) as a single value may over/underestimate the significance of obtained results. LODs were between 20 and 150 pg injected for the majority of tested derivatized carbonyls using both ionization methods. ECNI-MS improved LODs by ∼10- to 20-fold only for two derivatized aldehydes, 4-hydroxybenzaldehyde and 5-(hydroxymethyl)furfural. Selectivity of ECNI did not appear to be beneficial when analyzing a wood smoke particulate matter (WS-PM) extract, possibly because the majority of interferences were removed during sample preparation (i.e., liquid-liquid extraction). The impact of four different data acquisition modes of transmission quadrupole (TQ)-MS on LODs and their precisions was also investigated. As expected, LODs in the selected ion monitoring (SIM) were ∼two to four times lower than those obtained using total ion current (TIC) mode. More importantly, TQ-MS in the selected ion-total ion (SITI) mode (i.e., acquiring SIM and TIC data in a single analysis) provided signal-to-noise ratios and precisions, which were comparable to SIM alone.
与常见预期相反,电子捕获负离子化(ECNI)和电子离子化(EI)质谱(MS)在检测限(LOD)方面的差异,对于一系列与o-(2,3,4,5,6-五氟苯基)-羟胺盐酸盐衍生化的醛类物质,发现并不显著。基于LOD置信区间对这两种离子化方法的比较显示,传统将LOD或定量限(LOQ)呈现为单一值的方法,可能会高估或低估所获得结果的重要性。使用这两种离子化方法测试的大多数衍生化羰基物质的LOD在20到150皮克克之间。ECNI-MS仅对两个衍生化醛类物质,即4-羟基苯甲醛和5-(羟甲基)呋喃醛,将LOD提高了约10到20倍。ECNI的选择性在分析木烟颗粒物(WS-PM)提取物时似乎并不有利,这可能是因为在样品准备过程中(即液-液提取)大多数干扰物质已被去除。还调查了四种不同数据采集模式下的传输四极杆(TQ)-MS对LOD及其精度的影响。正如预期的那样,选择离子监测(SIM)模式下的LOD大约比使用总离子流(TIC)模式获得的值低两到四倍。更重要的是,TQ-MS在选择离子-总离子(SITI)模式下(即在一次分析中同时获得SIM和TIC数据)提供的信噪比和精度与单独的SIM相当。