Masa离子迁移谱用于痕量正硅酸四甲酯(TMOS)检测

Tetramethyl Orthosilicate (TMOS) detection by Advanced Ion Mobility Spectrometer - AIMS

Masa离子迁移谱检测痕量正硅酸四甲酯(TMOS)

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 Tetramethyl Orthosilicate TMOS

离子迁移谱技术具有灵敏度高（ppb范围）、响应速度快（ms范围）、设计紧凑、在亚大气压下工作以及能够分离异构体等优点。在这篇简短的报告中，我们展示了PAIMS技术在低ppb水平下的灵敏度和快速响应。作为一个案例化合物选择四甲基正硅酸TMOS

The TMOS Si(OCH3)4 of molar mass 152.25  g/mol, is frequently used in in organic synthesis . The TMOS at low  concentrations inhalation causes lung lesions, and at slightly higher  concentrations eye contact with the vapor causes blindness. Due to this  reasons is monitoring of TMOS in low concentration required especial in  clean industrial hall where it is frequently used.

TMOS-Si（OCH3）4分子量为152.25g/mol，是有机合成中常用的化合物。吸入低浓度TMOS会导致肺部损伤，而稍高浓度时，眼睛接触蒸汽会导致失明。因此，需要对低浓度的TMOS进行监测，特别是在洁净车间中经常使用。

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

在这份简短的实验室报告中，我们展示了大气压下运行的离子迁移谱仪在低ppb水平下连续监测TMOS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.

实验采用便携式高级离子迁移谱仪（PAIMS）、Masa空气发生器进行实验。PAIMS的工作参数见表1

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。将注射器放置在注射泵（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注射泵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响应完全稳定。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.

MaSaTECH软件允许我们使用一些拟合函数，如线性、指数、对数、logistic和广义logistic。对于TMOS，广义logistic与logistic拟合函数相结合，R2=0.9951。用峰面积与TMOS浓度的比值来建立校准表

Table2  TMOS校准表 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. 离子迁移谱仪的主要优点是响应速度快。在低迁移率模式下的自动峰值推导和独特测量允许我们的仪器快速峰值检测和识别。在线峰值推导还提供了有关目标峰强度的实时信息。峰值强度可立即计算每种化学品的浓度。