掺杂剂辅助离子迁移谱技术检测低ppt水平氨(NH3)

The ion mobility spectrometry technique offers advantages such as high sensitivity (ppt-ppb range), fast response (ms range), compact design, operation in atmospheric pressure and ability to separate the isomeric compounds. In this short report we demonstrate the sensitivity and fast response of IMS for Ammonia (NH₃) species.

The NH₃ is a small molecule with a molar mass of 17.03 g/mol. Ammonia is an inorganic compound of nitrogen and hydrogen. It is a colorless gas with a distinct pungent smell. Biologically, it is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to 45 percent of the world's food and fertilizers. Monitoring of NH3 is also important in semiconductor industry.

In many semiconductors, applications need to be the presence of Ammonia monitored at low ppb and ppt levels.

离子迁移谱技术具有高灵敏度（ppt-ppb范围）、快速响应（ms范围）、紧凑设计、在大气压下操作和分离异构化合物能力等优点。在这篇简短的报告中，我们展示了IMS对氨（NH3）物种的敏感性和快速反应。

NH₃是一个小分子，摩尔质量为17.03 g/mol。氨是氮和氢的无机化合物。它是一种无色气体，具有明显的刺激性气味。从生物学角度来看，它是一种常见的含氮废物，特别是在水生生物中，它作为世界45%的粮食和肥料的前体，大大满足了陆生生物的营养需求。NH₃的监测在半导体工业中也很重要。

在许多半导体中，应用需要在低ppb和ppt水平下监测氨的存在。

In this short Laboratory Report, we demonstrate the ability of Dopant Assisted Ion Mobility Spectrometer for detection of NH₃ at low ppt level.

在这篇简短的实验室报告中，我们展示了掺杂辅助离子迁移谱仪在低ppt水平下检测氨NH₃的能力。

Experiment
The Portable-Advanced Ion Mobility Spectrometer (PAIMS) was used in this experiment. The operating parameters of PAIMS are listed in Table 1.
Table 1. PAIMS operating parameters.

本实验使用便携式高级离子迁移谱仪（PAIMS）。PAIMS的操作参数如表1所示。

表1.PAIMS实验参数

The gas dilutor from Molecular Analysis 7800 Series was used in this work, for generation of low ppb concentrations of NH₃ in zero air. The PAIMS operates at atmospheric pressure and continuous sample sniffing was set to 600 mL/min. The sample inlet sucks the atmospheric air. The air from the gas dilutor was sniffed to PAIMS.

Dimethyl methyl phosphonate (DMMP) was used as a dopant for our IMS. Using of dopant increases sensitivity and selectivity of IMS but also strongly reduces interferences of other VOC presented in the atmosphere, thereby DMMP improving identification and quantification of Ammonia.

本实验使用Molecular分析系列7800气体稀释器，在零空气中生成低ppb浓度的NH₃。PAIMS在大气压下运行，连续样本进样嗅探设置为600 mL/min。样品入口进样。气体稀释器中的空气被嗅到PAIMS离子迁移谱分析仪。
甲基膦酸二甲酯（DMMP）被用作IMS的掺杂剂。使用掺杂剂提高了IMS的灵敏度和选择性，但也大大减少了大气中其他VOC的干扰，从而DMMP改进了氨的识别和定量。

Results and discussion

The IMS response for 137 ppb of NH3 is shown in figure 3 (black line). As we can see from this figure, the NH3 results in the formation of the peak with reduced mobility of 1.31 cm2.V-1s-1. The red line in figure 3 represents the IMS response for 1 ppb of NH₃.

图3（黑线）显示了137 ppb NH₃的IMS响应。如图所示，NH₃导致峰的形成，迁移率降低1.31 cm².V^-1s^-1。图3中的红线表示1 ppb NH₃的IMS响应。

Figure 4 shows the calibration plot of IMS response for 0.1, 1, 6.7, 20, 82 and 137 ppb of NH3. The MaSaTECH software allows calculation of peak volume, peak area, as well as peak intensity. The peak intensity was considered for calculation. The Generalized Logistic Fitting with R2=0.995 was chosen as optimal. Considering the noise level of 3x, we calculate the limit of detection (LOD) for NH3 at a value of 60 ppt. The upper detection limit was also calculated to be 1ppm.

图4显示了0.1、1、6.7、20、82和137 ppb NH3的IMS响应校准图。MaSaTECH软件可以计算峰体积、峰面积和峰强度。计算时考虑了峰值强度。R2=0.995的广义Logistic拟合被选为最佳拟合。考虑到噪音水平为3x，我们计算出NH₃的检测限（LOD）为60 ppt。检测上限计算为1ppm。

Conclusion
In this short laboratory report, we demonstrate the ability of PAIMS to detect NH₃ at low ppt concentration. The LOD for NH3 was 60 ppt. As the MaSaTECH PAIMS allows modification of experimental setups like sample gas flow and drift-gas flow, the improvements of sensitivity bellow 60 ppt should be also possible.

在这篇简短的实验室报告中，我们证明了PAIMS便携式高级离子迁移谱仪在低ppt浓度下检测NH₃的能力。NH₃的LOD为60 ppt。由于MaSaTECH PAIMS允许修改样品气流和漂移气流等实验参数设置，因此也可以将灵敏度提高到60 ppt以下。

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