Keil Adam, Talaty Nari, Janfelt Christian, Noll Robert J, Gao Liang, Ouyang Zheng, Cooks R Graham
Chemistry Department, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA.
Anal Chem. 2007 Oct 15;79(20):7734-9. doi: 10.1021/ac071114x. Epub 2007 Sep 15.
The first coupling of atmospheric pressure ionization methods, electrospray ionization (ESI) and desorption electrospray ionization (DESI), to a miniature hand-held mass spectrometer is reported. The instrument employs a rectilinear ion trap (RIT) mass analyzer and is battery-operated, hand-portable, and rugged (total system: 10 kg, 0.014 m(3), 75 W power consumption). The mass spectrometer was fitted with an atmospheric inlet, consisting of a 10 cm x 127 microm inner diameter stainless steel capillary tube which was used to introduce gas into the vacuum chamber at 13 mL/min. The operating pressure was 15 mTorr. Ions, generated by the atmospheric pressure ion source, were directed by the inlet along the axis of the ion trap, entering through an aperture in the dc-biased end plate, which was also operated as an ion gate. ESI and DESI sources were used to generate ions; ESI-MS analysis of an aqueous mixture of drugs yielded detection limits in the low parts-per-billion range. Signal response was linear over more than 3 orders of magnitude. Tandem mass spectrometry experiments were used to identify components of this mixture. ESI was also applied to the analysis of peptides and in this case multiply charged species were observed for compounds of molecular weight up to 1200 Da. Cocaine samples deposited or already present on different surfaces, including currency, were rapidly analyzed in situ by DESI. A geometry-independent version of the DESI ion source was also coupled to the miniature mass spectrometer. These results demonstrate that atmospheric pressure ionization can be implemented on simple portable mass spectrometry systems.
本文报道了大气压电离方法——电喷雾电离（ESI）和解吸电喷雾电离（DESI）与微型手持式质谱仪的首次联用。该仪器采用直线离子阱（RIT）质量分析器，由电池供电，便于携带且坚固耐用（整个系统：10千克，0.014立方米，功耗75瓦）。该质谱仪配备了一个大气入口，由一根内径为127微米、长10厘米的不锈钢毛细管组成，用于以13毫升/分钟的流速将气体引入真空腔。工作压力为15毫托。由大气压离子源产生的离子通过入口沿离子阱轴引导，通过直流偏置端板上的一个孔进入，该端板也用作离子门。使用ESI和DESI源产生离子；对药物水性混合物进行ESI-MS分析，检测限低至十亿分之几。信号响应在超过3个数量级的范围内呈线性。串联质谱实验用于鉴定该混合物的成分。ESI还应用于肽的分析，在这种情况下，观察到分子量高达1200道尔顿的化合物产生多电荷物种。通过DESI对沉积在包括货币在内的不同表面上或已存在于这些表面上的可卡因样品进行了快速原位分析。一种与几何形状无关的DESI离子源版本也与微型质谱仪联用。这些结果表明，大气压电离可以在简单的便携式质谱系统上实现。
