使用全真空FTIR光谱仪的气体分析系统（N2气体中微量H2O）

先前已经报道了使用长路径长度气室分析低浓度气体，然而，当目标气体的吸收峰与大气水蒸气的峰重叠时，或者当目标气体本身是H2O或CO2时，其在大气中预滤，可能难以准确地定量低浓度气体。这是因为即使使用真空FT-IR仪器，也不可能在存在长路径长度池的情况下排空样品室。本申请说明中介绍的全真空气体分析系统在样品室中集成了一个特殊的气室，使整个光路在气室就位的情况下保持在全真空下。该全真空模型使得即使在0.1ppm水平下也能够定量H2O的浓度。仪器和测量：对于测量，有单独的真空管线用于FT-IR仪器和气室的抽空，单独的组件具有独立的抽空能力。在气室中添加真空计可以控制极低浓度的气体样品。测量示例：尝试对氮气中微量的水蒸气（H2O）进行定量。在稀释浓度为0.0、0.51、1.02和2.48ppm的标准样品期间，通过监测压力计稀释浓度为100ppm的水蒸气Application NoteNo.230TR0187-E No.230TR0187-E JSCO Gas Analysis System using Full Vacuum Type FT/IR (Trace amount of H2O in N2 gas) Introduction The analysis of low concentration gases using long pathlength gas cells has been reported previously， however， it can be dif f icult to accurately quantitate gases at low concentrations when the absorption peaks of the target gas overlap with the peaks of atmospheric water vapor or， when the target gas i tself is H，O or CO，， which are presnet in the atmosphere. This is because even 2.2222with a vacuum FT-IR i nstrument ， i t was not possible to evacuate the sample chamber with the long pathlength cell present. The full vacuum gas analysis system introduced in this application note has a special gas cell integrated into t he sample chamber ， a l lowing the ent i re light path to remain under full vacuum with the gas cel l in place. This full vacuum model makes i t possible to quantitate concentrations of H，O even at the 0.1 ppm level. Instrument and Measurement For the measurement， there are separate vacuum li nes for evacuation of the FT-IR instrument and the gas cel l . with independent evacuation capability for the separate components. low concentrations of the gas samples. Cell specification Cel l type：Mult i -pass ‘White’cell Pathlength ：10 meters Cel l body：Stainless steel Mirror material：Stainless steel Mirror surface：Gold coated O-ring：Viton Window：CaF2Heating：Possible， max. 100℃Cel l capacity：Approx.2 L Gas in/output port：1/4 inch VCR Fig. 1 Full vacuum type FT-IR gas analysis system (10 meter cel l ) Measurement example The quantitation of a trace amount of water vapor (H，0) within ni t rogen gas was attempted. Water vapor with a concentration of 100 ppm was diluted by monitoring the pressure gauge during dilution of the standard samples with concentrations of 0.0， 0.51，1.02 and 2.48 ppm. Figure 2 shows the IR spectra of water vapor for each concentration. For t he 0 ppm concentration， there was no absorption due to water vapor observed in the spec t rum. The calibration curve in Figure 3 was created using the absorption peak at 1653 cm. Wavenumber [cm] Fig.2 Expanded region for spectra o f low concentration H，O Condition Fig. 3 H，O calibration curve