Chemometric optimization of a low-temperature plasma source design for ambient desorption/ionization mass spectrometry ☆
Chemometric optimization of a low-temperature plasma source design for ambient desorption/ionization mass spectrometry ☆
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DOI：
10.1016/j.sab.2014.08.034
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发表时间：
2015-03
期刊：
影响因子：
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通讯作者：
Anastasia Albert;C. Engelhard
中科院分区：
文献类型：
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作者：
Anastasia Albert;C. Engelhard
低温等离子体（LTPs）是原子和分子质谱（MS）有吸引力的来源。在过去，由Harper等人首次描述的LTP探针在各种应用中成功地用于直接分子质谱分析，只需最少的样品预处理。不幸的是，解吸/电离源本身在商业上是不可用的，过去使用的是具有不同几何形状和操作配置的定制LTP设置。在本研究中，采用基于系统实验和多元数据分析的快速化学计量学方法来优化LTP探针的几何形状和相对于质谱仪大气压入口的定位。研究了探针几何形状、电极结构、石英管尺寸、探针定位和操作条件等参数。结果表明，等离子体到质谱仪的入口距离、等离子体到样品板的距离以及两者之间的夹角是非常重要的。外电极宽度、电极位置、石英管内径、石英壁厚和气体流量对分析性能有额外的影响。所有实验都是通过对样品进行额外加热来增强热解吸并最大化信号（T = 150°C）。经过软件辅助优化，获得了有吸引力的检出限（例如，4-乙酰氨基噻吩为1.8 × 10−7mol/L）。此外，相对标准偏差（RSD）从优化前的高达30%的值提高到程序完成后的< 15% RSD。这种用于方法优化的化学计量学方法不仅限于LTP-MS，而且被认为对其他基于等离子体的仪器也有吸引力。
Low-temperature plasmas (LTPs) are attractive sources for atomic and molecular mass spectrometry (MS). In the past, the LTP probe, which was first described by Harper et al., was used successfully for direct molecular mass spectrometric analysis with minimal sample pretreatment in a variety of applications. Unfortunately, the desorption/ionization source itself is commercially not available and custom-built LTP set-ups with varying geometry and operational configurations were utilized in the past.In the present study, a rapid chemometrics approach based on systematic experiments and multivariate data analysis was used to optimize the LTP probe geometry and positioning relative to the atmospheric-pressure inlet of a mass spectrometer. Several parameters were studied including the probe geometry, electrode configuration, quartz tube dimensions, probe positioning and operating conditions. It was found that the plasma-to-MS-inlet distance, the plasma-to-sample-plate distance, and the angle between the latter are very important. Additional effects on the analytical performance were found for the outer electrode width, the positioning of the electrodes, the inner diameter of the quartz tube, the quartz wall thickness, and the gas flow. All experiments were performed using additional heating of the sample to enhance thermal desorption and maximize the signal (T = 150 °C). After software-assisted optimization, attractive detection limits were achieved (e.g., 1.8 × 10− 7mol/L for 4-acetamidothiophenol). Moreover, relative standard deviation (RSD) improved from values of up to 30% before optimization to < 15% RSD after the procedure was completed. This chemometrics approach for method optimization is not limited to LTP-MS and considered to be attractive for other plasma-based instrumentation as well.