Theoretical analysis of probe dynamics in flow injection/membrane introduction mass spectrometry

Tsai, Gow Jen.; Austin, Glen D.; Syu, Mei-Jywan; Tsao, George T.; Hayward, Mark J.; Kotiaho, Tapio; Cooks, R. Graham

doi:10.1021/ac00021a014

Cited by 38 publications

(31 citation statements)

References 15 publications

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“…Sampling can be rapid with more concentrated solutions because non-steady state responses can be used. Conversely, trace analyses are in principle best done by waiting for steadystate conditions to be established; however, the extra time required to achieve steady state must be weighed against the magnitude of the gain in signal strength (Tsai et al, 1991). The use of large membrane areas, however, is always to be recommended for increased sensitivity.…”

Section: B Sampling Flow Injection Analysis and Quanti®cationmentioning

confidence: 99%

“…The use of large membrane areas, however, is always to be recommended for increased sensitivity. When monitoring VOCs in the pptr to ppm concentration range,¯ow rates associated with liquid solutions are typically a few mL/min (LaPack et al, 1991;Tsai et al, 1991;Maden & Hayward, 1996), whereas they are up to 400 mL/min for gaseous samples .…”

Section: B Sampling Flow Injection Analysis and Quanti®cationmentioning

confidence: 99%

See 1 more Smart Citation

Membrane introduction Mass Spectrometry: Trends and applications

Johnson

Cooks

Allen

et al. 2000

Mass Spectrom. Rev.

237

182

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Section: B Sampling Flow Injection Analysis and Quanti®cationmentioning

confidence: 99%

Section: B Sampling Flow Injection Analysis and Quanti®cationmentioning

confidence: 99%

Membrane introduction Mass Spectrometry: Trends and applications

Johnson

Cooks

Allen

et al. 2000

Mass Spectrom. Rev.

237

182

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“…MIMS is applied to selectively transport analytes that bear particular functional groups and enrich them relative to the inlet solution [5]. Tsai et al [6] have made a theoretical analysis of flow injection MIMS. They modeled the dynamics of the flow cell volume and membrane permeation to obtain analyte flux profiles for a variety of inlet concentration profiles that all return to zero flux between repetitions.…”

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confidence: 99%

A mathematical study of sample modulation at a membrane inlet mass spectrometer—Potential application in analysis of mixtures

Overney

Enke

1996

J. Am. Soc. Mass Spectrom.

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An ANSI C program that simulates the diffusion profiles of sample modulation at a membrane inlet system has been developed to study the characteristics of modulated diffusion profiles. The program produces concentration profiles within the membrane and flux values at the exit side of the membrane as a function of time. Sample concentration on the inlet side can be switched between zero and an arbitrary value with a square or asymmetric cycle. Achievement of steady-state diffusion between alternations is not required. With this computer simulation, the flux profiles of analytes through a membrane inlet have been studied as a function of diffusion coefficient, modulation frequency, and concentration. The amplitude, shape, and time lag or phase angle of the flux profile are shown to be related directly to analyte concentration and diffusivity. A method that involves a set of linear equations is proposed to resolve mixtures of diffusing analytes based on differences in the time dependence of their flux profiles. (J Am Soc Mass Spectrom 1996, 7, 93-100) T he direct analysis of mixtures by mass spectrometry depends upon principal component analysis to determine the sample components that contributed to the mixture spectrum. This method relies on constant response factors for each component and is limited in sample complexity and dynamic range. To obtain additional data for component resolution, discrimination along the time axis by (1) componentspecific time-dependent response and (2) individual intensity time profiles for each mass-to-charge ratio can be used. A commonly employed example of this approach is gas chromatography-mass spectrometry (GC/MS). Chromatography provides different response time profiles for nearly all components, but the time between successive determinations of sample composition cannot be less than the longest component retention time. To provide more frequent updates on samples with varying composition, we are exploring the use of a membrane inlet with modulated sample introduction.A majority of the membrane inlet work or membrane introduction mass spectrometry (MIMS) to date has employed steady-state diffusion through membranes [1][2][3][4]. MIMS is applied to selectively transport analytes that bear particular functional groups and enrich them relative to the inlet solution [5]. Tsai et al. We report here on the results of our mathematical simulation of the modulated diffusion process. The sample stream modulation is provided by an alternating valve that opens and closes periodically. We have ignored mixing on the sample side of the membrane because our experimental system uses a tubular membrane with negligible dead time and dead volume. A time-dependent response pattern, called a chronogram, is produced for the ions of each mass-to-charge ratio in the mixture spectrum. The shapes and amplitudes of the chronograms depend on the concentrations and diffusivities of the mixture components.We have developed a computer program to simulate the Fickian diffusion process (which obeys Fick's f...

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“…30 The second step of diffusion through the membrane is known to be the rate-determining process, whereas partitioning at the high-pressure surface and desorption from the low-pressure surface are considered to be instantaneous. 31 Thus, the permeation process across the membrane delays the response of the mass spectrometer to the analyte present in the sample. The time-dependent signal includes a measure of the time taken to achieve a maximum signal response to a sample of fixed concentration (i.e., to achieve a steady-state composition).…”

Section: Resultsmentioning

confidence: 99%

Characterization of a Membrane Interface for Analysis of Air Samples Using Time-of-flight Mass Spectrometry

Jang¹,

Oh²,

Park³

et al. 2010

Bulletin of the Korean Chemical Society

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In the present study, we constructed a membrane inlet assembly for selective permeation of volatile airborne organic compounds for subsequent analysis by time-of-flight mass spectrometry. The time-dependent diffusion of analytes through a 75 µm thick polydimethylsiloxane membrane was measured by monitoring the ion signal after a step change in the sample concentration. The results fit well to a non-steady-state permeation equation. The diffusion coefficient, response time, and sensitivity were determined experimentally for a range of polar (halogenated) and nonpolar (aromatic) compounds. We found that the response times for several volatile organic compounds were greatly influenced by the alkyl chain length as well as the size of the substituted halogen atoms. The detection limits for benzene, ethylbenzene, and 2-propanol were 0.2 ppm, 0.1 ppm, and 3.0 ppm by volume, respectively, with a linear dynamic range greater than three orders of magnitude. These results indicate that the membrane inlet/time-of-flight mass spectrometry technique will be useful for a wide range of applications, particularly for in situ environmental monitoring.

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Theoretical analysis of probe dynamics in flow injection/membrane introduction mass spectrometry

Cited by 38 publications

References 15 publications

Membrane introduction Mass Spectrometry: Trends and applications

Membrane introduction Mass Spectrometry: Trends and applications

A mathematical study of sample modulation at a membrane inlet mass spectrometer—Potential application in analysis of mixtures

Characterization of a Membrane Interface for Analysis of Air Samples Using Time-of-flight Mass Spectrometry

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