Forbes Thomas P, Sisco Edward, Staymates Matthew, Gillen Greg
National Institute of Standards and Technology, Materials Measurement Science Division, Gaithersburg, MD, USA.
Anal Methods. 2017;9(34):4988-4996. doi: 10.1039/C7AY00867H. Epub 2017 May 4.
An ambient mass spectrometry (MS) platform coupling resistive Joule heating thermal desorption (JHTD) and direct analysis in real time (DART) was implemented for the analysis of inorganic nitrite, nitrate, chlorate, and perchlorate salts. The resistive heating component generated discrete and rapid heating ramps and elevated temperatures, up to approximately 400 °C s and 750 °C, by passing a few amperes of DC current through a nichrome wire. JHTD enhanced the utility and capabilities of traditional DART-MS for the trace detection of previously difficult to detect inorganic compounds. A partial factorial design of experiments (DOE) was implemented for the systematic evaluation of five system parameters. A base set of conditions for JHTD-DART-MS was derived from this evaluation, demonstrating sensitive detection of a range of inorganic oxidizer salts, down to single nanogram levels. DOE also identified JHTD filament current and in-source collision induced dissociation (CID) energy as inducing the greatest effect on system response. Tuning of JHTD current provided a method for controlling the relative degrees of thermal desorption and thermal decomposition. Furthermore, in-source CID provided manipulation of adduct and cluster fragmentation, optimizing the detection of molecular anion species. Finally, the differential thermal desorption nature of the JHTD-DART platform demonstrated efficient desorption and detection of organic and inorganic explosive mixtures, with each desorbing at its respective optimal temperature.
搭建了一种将电阻式焦耳加热热脱附（JHTD）与实时直接分析（DART）相结合的常压质谱（MS）平台，用于分析无机亚硝酸盐、硝酸盐、氯酸盐和高氯酸盐。通过让几安培的直流电流通过镍铬合金丝，电阻加热组件产生离散且快速的加热斜坡，并将温度升高至约400℃/秒和750℃。JHTD增强了传统DART-MS对以前难以检测的无机化合物进行痕量检测的实用性和能力。实施了部分因子实验设计（DOE）以系统评估五个系统参数。从该评估中得出了JHTD-DART-MS的一组基本条件，证明了对一系列无机氧化剂盐的灵敏检测，检测限低至单纳克水平。DOE还确定JHTD灯丝电流和源内碰撞诱导解离（CID）能量对系统响应的影响最大。调整JHTD电流提供了一种控制热脱附和热分解相对程度的方法。此外，源内CID可对加合物和簇碎片进行操作，优化分子阴离子物种的检测。最后，JHTD-DART平台的差示热脱附特性证明了对有机和无机爆炸混合物的有效脱附和检测，每种混合物在其各自的最佳温度下脱附。
