PAIMS高级离子迁移谱用于六甲基二硅氮烷HMDS检测

Hexamethyldisilazane (HMDS) detection by Advanced Ion Mobility Spectrometer - AIMS

    The ion mobility spectrometry technique offers advantages like high sensitivity (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 technique at low ppb level. As a case compound was chosen hexamethyldisilazane HMDS.

离子迁移谱技术具有高灵敏度（ppb范围）、响应速度快（ms范围）、结构紧凑、常压操作、分离异构体等优点。在这篇简短的报告中，我们展示了低ppb水平下IMS技术的灵敏度和快速响应。以六甲基二硅氮烷HMDS为例。

The HMDS C6H19NSi2 of molar mass 161.4 g/mol, is frequently used in various fields like semiconductor industry, photolithography, electron microscopy and many others. The HMDS is toxic irritates skin and eyes and after decomposition can emit highly toxic nitrogen oxide fume. Due to this reasons is monitoring of HMDS in low concentration required especial in clean industrial hall like semiconductor hall are.

分子量为161.4g/mol的HMDS C6H19NSi2，广泛应用于半导体工业、光刻、电子显微镜等领域。HMDS有毒，对皮肤和眼睛有刺激作用，分解后会释放出剧毒的氮氧化物烟雾。因此需要对低浓度的HMDS进行监测，特别是在洁净车间，如半导体车间。

Fig.1. Hexamethyldisilazane

In this short Laboratory Report we demonstrate the ability of Ion Mobility Spectrometer operated in sub-atmospheric pressure for continuous monitoring of HMDS at low ppb level.

在这篇简短的实验室报告中，我们证明了离子迁移率谱仪在低ppb水平下工作在大气压下连续监测HMDS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.

实验

本实验采用便携式先进离子迁移率谱仪（PAIMS）。PAIMS的操作参数见表1。

Table1. PAIMS 操作参数

The HMDS of analytical grade purity (Merck) was used in this experiment. The 1mL syringe of HMDS 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 13.8mmHg (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HMDS（Merck）。使用1ml注射器，将HMDS蒸汽按1:20的比例与大气稀释。注射器被放置在注射泵（Cronus）上，并通过内径为0.15mm、长度2M毛细管连接到PAIMS样品入口。为了防止扩散，使用了内径较小的长毛细管。浓度计算采用蒸汽压13.8mmHg（PubChem）。PAIMS在亚大气压下工作，连续吸样设定为60ml/min，进样口吸入大气压空气，用进样泵将注射器中的蒸汽稀释至进样口流量。

结果和讨论

Figure 2. IMS对300 ppb HMD的响应。左IMS谱在降低移动性模式下测量，右2D视图记录时间为30秒

The IMS response on 300 ppb of HMDS is show on figure 2. As we can see from this figure there occur to formation of two peaks: HMDS1 with reduced mobility 1.82 cm2.V-1s-1 and HMDS2 with reduced mobility 1.56 cm2.V-1s-1. We suppose that there is going about formation of protonated monomer H+.HMDS (reduced mobility 1.82 cm2.V-1s-1) and proton bound dimer H+.(HMDS)2 (reduced mobility 1.56 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.
 

图2显示了HMD 300 ppb上的IMS响应。从图中我们可以看到，出现了两个峰值：迁移率降低的HMDS₁为1.82  cm~2.V-1s-1，迁移率降低的HMDS₂为1.56   cm~2.V-1s-1。我们假设正在形成质子化单体H+.HMDS（降低迁移率1.82cm~2.V-1s-1）和质子结合二聚体H+（降低迁移率1.56cm~2.V-1s-1）。图2右侧的二维图显示，在扫描时间30s内，IMS的响应非常稳定。在实验期间，还测试了较长的扫描时间（20分钟），仅观察到低于峰值强度1%的小偏差。

The Limit Of Detection (LOD) for Hexamethyldisilazane was measured directly and was determined 7.5 ppb. Figure 3 shows the IMS response for syringe rate 0.5 μL/min what represents 7.5 ppb.
直接测定六甲基二硅氮烷的检出限为7.5ppb。图3显示了注射速率为0.5μL/min时的IMS响应，即7.5 ppb。

Figure 3.  HMDS在 7.5 ppb 浓度下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 7.5ppb to 1.5ppm as we can see from Figure 4.

MaSaTECH软件可以计算监测时间内的峰值体积、峰值面积、平均峰值面积以及监测时间内的峰值强度和平均峰值强度。PAIMS的动态范围从7.5ppb到1.5ppm，如图4所示。

MaSaTECH software allow us to use several fitting functions like linear, exponential, logarithmic, logistic and generalized logistic. For HMDS the generalized logistic fitting function seems to be appropriate with R2=0.9939 .

MaSaTECH软件允许我们使用几种拟合函数，如线性、指数、对数、logistic和广义logistic。对于HMDS，适用于广义logistic拟合函数R2=0.9939。

Fast Response
The main advantage of linear Ion Mobility Spectrometers is related with fast response. The automatic peak derivation and unique measurements in reduced mobility mode allows our instruments fast peak detection and recognition. The online peak derivation giving also real-time information about intensity of target peak. The peak intensity can be used for immediate calculation of concentration for each chemical.

快速反应
离子迁移谱仪的主要优点是响应速度快。在低迁移率模式下，自动峰值推导和独特的测量使我们的仪器能够快速检测和识别峰值。在线峰值推导也给出了目标峰值强度的实时信息。峰值强度可用于立即计算每种化学品的浓度。