Development and Deployment of Atmospheric Pressure Ionization Mass Spectrometer for Determining SO2, DMS, DMSO, and DMSO2 on Aircraft and Ship Platforms

9617362 Bandy本研究的目标是开发和测试用于测定二甲基硫(DMS)、二甲基亚砜(DMSO)、二甲基砜(DMSO2)和二氧化硫(SO2)的仪器，其检测下限为1万亿分之一体积分数(PPTV)，信噪比为3，采样频率为每秒1。采用的方法将基于大气压电离四极杆质谱仪(APIMS)。DMS、DMSO和DMSO2的正离子APIMS和SO2的负离子APIMS已在实验室中得到证实。APIMS仪器将基于Extrel质谱学四极杆系统，该系统在研究人员之前的项目中已有多年的现场使用。通过使用同位素标记的分析物的变体作为内标，这些APIMS仪器的准确度和精密度将大大提高，这些内标过去已经采用了带有同位素标记的标准(GC/MS/ILS)的气相色谱-质谱联用(GC/MS/ILS)。使用这种方法，仪器的精密度和准确度与仪器的灵敏度和其他因素无关，例如采样中分析物的损失。此外，由于来自标准的信号对于每个样品都是可用的，并且标准的浓度是已知的，因此可以精确地计算每个样品的仪器灵敏度和检测下限。为了验证这种用于现场测量环境空气中这些硫化物的新仪器方法，APIMS仪器将与现有的GC/MS/ILS仪器相互比较，后者是NASA-CITE-3和NSF-GASIE评估的一部分。为了最大限度地减少拟议工作的成本，将使用手头的质谱仪来建造和部署用于现场测试的APIMS。这将需要对实验室仪器进行一些修改，以达到安全和操作方面的适航标准。最终目标是实现对这套硫化物的测量时间比当前GC/MS技术快200-4000倍。这些新仪器将更小、更轻、功耗更低，适用于高空飞机。如果单个四个APIMS的初始现场测试表明干扰显著，将使用三重四极质谱计进一步评估所需分析物专属性的离子化学。在成功测试APIMS对这些硫化物的初始现场测量之后，将开发APIMS，用于在出现显著DMS水平的区域对DMS通量进行涡旋相关测量。

9617362 Bandy The objectives of this study are to develop and test instrumentation for determining dimethyl sulfide (DMS), dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO2), and sulfur dioxide (SO2) with a lower limit of detection of 1 part-per-trillion-by-volume (pptv) with a signal to noise ratio of 3 at a sample frequency of 1 per second. The approach to be employed will be based on atmospheric pressure ionization quadrupole mass spectrometry (APIMS). Positive ion APIMS for DMS, DMSO, and DMSO2 and negative ion APIMS for SO2 have been demonstrated in the laboratory. The APIMS instruments will be based on Extrel Mass Spectrometry quadrupole systems, which have many years of field use in the investigator's previous projects. The accuracy and precision of these APIMS instruments will be substantially enhanced by using isotopically labelled variants of the analytes as internal standards that have been deployed in the past using gas chromatography - mass spectrometry with isotopically labelled standards (GC/MS/ILS). Using this approach the precision and accuracy of the instrument are independent of the instrument sensitivity and other factors, such as, analyte loss in sampling. Furthermore, because the signal from the standard is available for each sample and the concentration of the standard is known, the instrument sensitivity and lower limit of detection can be precisely computed for each sample. To validate this new instrumental approach for field measurements of these sulfur compounds in ambient air, the APIMS instruments will be intercompared to an existing GC/MS/ILS instrument, which was a part of the NASA-CITE-3 and NSF-GASIE evaluations. To minimize the cost of the proposed work the mass spectrometers on hand will be used to build and deploy the APIMS for field tests. This will require some modification to laboratory instruments to attain airworthiness standards in safety and operation. The end goal is to achieve measurement times 200-4000 times faster than the curr ent GC/MS techniques for this suite of sulfur compounds. These new instruments will be much smaller, lighter, and consume lower power for high altitude aircraft use. If initial field tests with the single quad APIMS indicate that interferences are significant, a triple quadrupole mass spectrometer will be employed to further evaluate the ion chemistry for the required analyte specificity. Successful tests of the APIMS for initial field measurements of these sulfur compounds will be followed by development of an APIMS for eddy correlation measurements of DMS fluxes in regions where significant DMS levels occur.