Table 1.PAIMS工作参数

The TMOS of analytical grade purity (Merck) was used in this experiment. The 1mL syringe of TMOS vapors diluted in ratio 1:20 with atmospheric air was used. The syringe was placed to syringe pump (Cronus) and interfaced via 2m long capillary of 0.15mm i.d. to PAIMS sample inlet. The long capillary with small i.d. was used in order to prevent diffusion. For calculation of concentration was used vapor pressure 12 mmHg (PubChem). The PAIMS operate in sub-atmospheric pressure and continuous sample sniffing was set to 60 mL/min. The sample inlet suck the atmospheric air, the vapors from the syringe was diluted to sample inlet flow by syringe pump.

本实验采用分析级纯度TMOS（Merck）。使用1mL TMOS蒸汽注射器，以1:20的比例与大气空气稀释。将注射器放置在*（Cronus）上，并通过内径为0.15mm的2m长毛细管连接至PAIMS样品入口。为了防止扩散，采用了内径较小的长毛细管。浓度计算采用蒸汽压12 mmHg（PubChem）。PAIMS在亚大气压下运行，连续样品进样设定为60 mL/min。样品入口吸入大气空气，注射器中的蒸汽通过*稀释至样品入口流量

结果和讨论

图2。IMS对1.3 ppm TMOS的响应。左IMS谱在降低移动性模式下测量，右2D图记录时间30秒

The IMS response on 1.3 ppm of TMOS is show on figure 2. As we can see from this figure there occur to formation of two peaks: TMOS with reduced mobility 1.69 cm2.V-1s-1 and 2TMOS with reduced mobility 1.27 cm2.V-1s-1. We suppose that there is going about formation of protonated monomer H+.TMOS (reduced mobility 1.69 cm2.V-1s-1) and proton bound dimer H+.(TMOS)2 (reduced mobility 1.27 cm2.V-1s-1). The 2D maps on the right side of figure 2 show perfect stability of IMS response during the scan time 30s. During the experiment also longer scan time was tested (20min) and only small deviation bellow 1% in peak intensity was observed.
The Limit Of Detection (LOD) for TMOS was measured directly and was determined 6.5 ppb. Figure 3 shows the IMS response for syringe rate 0.5 μL/min what represents 6.5 ppb.

图2显示了1.3ppm TMOS的IMS响应。从这张图中我们可以看到两个峰值的形成：迁移率降低1.69 cm2.V-1s-1的TMOS和迁移率降低1.27 cm2.V-1s-1的2TMOS。我们假设有质子化单体H+.TMOS（还原迁移率1.69cm2.V-1s-1）和质子束缚二聚体H+（TMOS）2（还原迁移率1.27cm2.V-1s-1）的形成。图2右侧的二维图显示，在30秒的扫描时间内，IMS响应*稳定。在实验期间，还测试了较长的扫描时间（20分钟），仅观察到峰值强度低于1%的小偏差。

直接测定TMOS的检出限（LOD）为6.5ppb。图3显示了注射速率为0.5μL/min的IMS响应，即6.5 ppb。

图3. TMOS浓度6.5ppb下IMS响应

The MaSaTECH software allow calculation of peak volume, peak area, averaged peak area along the monitoring time as well like peak intensity and averaged peak intensity along the monitoring time. The PAIMS results in good dynamic range from 6.5ppb to 3.9ppm as we can see from Figure 4.

MaSaTECH软件允许计算沿监测时间的峰值体积、峰值面积、平均峰值面积以及沿监测时间的峰值强度和平均峰值强度。从图4可以看出，PAIMS的动态范围从6.5ppb到3.9ppm。

Figure 4. TMOS 从 6.5ppb至3.9ppm范围IMS响应

MaSaTECH software allow us to use several fitting functions like linear, exponential, logarithmic, logistic and generalized logistic. For TMOS the generalized logistic in combination with logistic fitting function seems to be appropriate with R2=0.9951. The volume of peak area against the TMOS concentration was used for formation of calibration table.