便携VOCs质谱仪系统设计与性能优化

Design and Performance Optimization of a Portable VOCs Mass Spectrometer System

原位实时监测可挥发性有机物(VOCs)对环境和人体健康至关重要,便携式质谱仪正在发展成为一种用于现场快速分析VOCs的新工具。本研究研制了一种基于非连续进样接口的便携式质谱仪,并结合了亚真空等离子体电离源。该便携质谱仪配备线性离子阱质量分析器,总质量约4.6 kg,尺寸217 mm×162 mm×106 mm,总功率不超过150 W。进样接口选用全金属电磁阀门作为大气压限流核心部件,避免了传统夹管阀需要使用橡胶等材质软管的缺陷,从而提升了进样装置的重复性和环境适应性。经过系统性的优化,仪器分辨率可达0.2 u(半峰宽),萘的分析灵敏度可达343μg/m^(3)。

Due to their high reactivity,volatile organic compounds(VOCs)can engage in physical and chemical reactions with particulate matter in the atmosphere,leading to air pollution.Extended exposure to VOCs may result in various health concerns,including respiratory system problems,neurological effects,skin and eye irritation,and an increased risk of certain cancers.Traditional benchtop mass spectrometers possess the advantages of high sensitivity and rapid analysis capabilities,but the large size typically confines their applications to professional laboratories.To overcome this limitation,portable mass spectrometers are emerging as a new tool for in-situ analysis.In this study,a portable mass spectrometer based on discontinuous atmosphere pressure interface was developed,which combined with a sub-vacuum plasma ionization source.Ion trap,known for its small size and adequate performance,was adopted in this miniaturized mass spectrometer.This portable mass spectrometer features a total weight of about 4.6 kg,with the dimensions of 217 mm×162 mm×106 mm,and operates with a power consumption under 150 W.On this design,a fully metallic solenoid valve was selected as the core component to limit atmospheric pressure,eliminating the need for the rubber tubing used in traditional pinch valves.Compared to traditional pinch valves,this solenoid valve ensures a more stable airflow during experiments.As a result,the repeatability and environmental adaptability of the portable mass spectrometer were improved.A certain delay marked as radio freqency(RF)delay was introduced between the injection and cooling periods,and the RF-delay time was optimized.Frequency scanning mode and amplitude scanning mode were tested in parallel.Despite of a trade-off in size,amplitude scanning offered improved resolution,enabling the differentiation of ions with close mass to charge ratios.After systematic optimization,satisfactory performances in mass resolution and sensitivity were achieved.The mass resolution of the mass spectrometer for dimethyl carbonate was improved to 0.2 u(FWHM),and a sensitivity of 60μg/m^(3) for naphthalene was achieved.The capability of mixed VOCs was also validated using dimethyl carbonate and trimethyl phosphate.This mass spectrometer developed in this study,characterized by its high portability and satisfactory performance,is expected to hold great potential for applications in VOCs analysis.