The Use of MIMS-MS-MS in Field Locations as an On-Line Quantitative Environmental Monitoring Technique for Trace Contaminants in Air and Water

Abstract

Membrane introduction mass spectrometry (MIMS) is emerging as an important technique for on-line, real-time environmental monitoring. Because MIMS interfaces are simple and robust, they are ideally suited for operation in MS instrumentation used for in-field applications. We report the use of an on-line permeation tube to continuously infuse an isotopically labeled internal standard for continuous quantitative determinations in atmospheric and aqueous samples without the need for off-line calibration. This approach also provides important information on the operational performance of the analytical system during multi-day deployments. We report measured signal stability during on-line deployments in air and water of 7% based on variation of the internal standard response and have used this technique to quantify BTEX (benzene, toluene, ethylbenzenes, and xylenes), pinenes, naphthalene and 2-methoxyphenol (guaiacol) in urban air plumes at parts-per-billion by volume levels. Presented are several recent applications of MIMS-MS-MS for on-line environmental monitoring in atmospheric and aqueous environmental samples demonstrating laboratory, remote and mobile deployments. We also present the use of a thermally assisted MIMS interface for the direct measurement of polyaromatic hydrocarbons, alkylphenols, and other SVOCs in the low ppb range in aqueous environmental samples and discuss improvements in both the sensitivity and response times for selected SVOCs. The work presented in this paper represents significant improvements in field deployable mass spectrometric techniques, which can be applied to direct on-site analytical measurements of VOC and SVOCs in environmental samples.

A Field-Portable Membrane Introduction Mass Spectrometer for Real-time Quantitation and Spatial Mapping of Atmospheric and Aqueous Contaminants

“…Overview A commercially available, portable cylindrical ion trap mass spectrometer system (Model Griffin 400; FLIR, West Lafayette, IN, USA), was modified in-house for in-field measurements by the addition of a MIMS sampling interface and internal standard (IS) infusion system, similar to that described previously [16]. In addition to the MIMS sampling system (which is described in detail below), the system also included several peripheral monitoring devices.…”

“…For this work, the MIMS interface was constructed using a PDMS hollow fiber membrane (0.94 mm o.d., 0.51 mm i.d., 10 cm length, Silastic brand; Dow Corning, Midland, MI, USA) and a flow-over sample cell design. A similar experimental arrangement has been described previously [16], though a major difference in design is the use of an in-house constructed aluminum block heater to maintain a constant membrane temperature. The lumen (permeate side) of the membrane was swept with a helium carrier gas (~1 mL/min), provided by a miniature 16 L helium cylinder (Model 49617HE; Leland Ltd., South Plainfield, NJ, USA).…”

“…The advent of portable chemical sensing technology has enabled a new framework for environmental monitoring, where it is possible to take high precision, high accuracy chemical measurements to the field [10][11][12][13][14][15][16][17][18]. Many of these analytical techniques, such as membrane introduction mass spectrometry (MIMS), can provide continuous monitoring time series data that resolve multiple analyte concentrations simultaneously [16,17,[19][20][21][22][23][24].…”

“…Many of these analytical techniques, such as membrane introduction mass spectrometry (MIMS), can provide continuous monitoring time series data that resolve multiple analyte concentrations simultaneously [16,17,[19][20][21][22][23][24]. When operated on a mobile platform, these instruments can track transient concentration excursions in both spatial and temporal domains that may be missed by grab sampling strategies [24].…”

“…Our research has involved the development of a portable MIMS system for the continuous analysis of VOCs and SVOCs in both atmospheric and aqueous samples that greatly improves upon our early work in this area [16,17,20]. In general, MIMS systems allow continuous sampling of VOC/SVOC analytes as they diffuse through a semiselective membrane, whereupon simultaneous quantification of multiple copermeating molecules occurs by mass spectrometry [20,25,26].…”