An in-source stretched membrane inlet for on-line analysis of VOCs in water with single photon ionization TOFMS

Abstract

An in-source, stretched, hollow fiber membrane (HFM) inlet has been developed to improve the sensitivity of on-line time-of-flight mass spectrometry (TOFMS) with a vacuum ultraviolet (VUV) lamp based single photon ionization (SPI) source for the direct analysis of liquid samples. A 2-cm HFM was stretched to 8 cm in length, and placed in the ion source and directly under the VUV lamp window with a distance of 15 mm. Compared with the conventional flow-through configuration under the same experimental conditions, the signal intensities of selected volatile organic compounds (VOCs) of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), benzene, toluene and p-xylene were increased over 5-fold in magnitude, and the response time was shortened to one-third. The limits of detection (LOD) of MTBE, ETBE, benzene, toluene and p-xylene ranged from 0.25 to 1.3 mg L À1 with a measurement time of 60 s, and three orders of linear range were obtained with correlation coefficients of 0.9972-0.9992. The present results suggest that the in-source stretched HFM is a simple and effective way to increase the sensitivity and shorten response time of the membrane inlet, and we believe that it will also be beneficial to other types of on-line mass spectrometer for the on-line analysis of VOCs in water with a VUV lamp based SPI ion source.

A hand-portable digital linear ion trap mass spectrometer

“…The analytes with ionization energies (IEs) lower than 10.6eV can be ionized by SPI. The IEs for most VOCs are below 10.6 eV; 25 thus, SPI is suitable for the ionization of VOCs with a certain selectivity [26][27][28] Compared with electron impact ionization, SPI is a soft ionization method with less fragmentation. 29 In our study, clean spectra with little background noise were observed because the photon energy in the SPI source is not sufficient to ionize the gases (i.e., H 2 O, N 2 , O 2 , and CO 2 ) from the matrix/background.…”

Monitoring of chemical transformations by mass spectrometry

“…SPI was applied for the analysis of complex samples such as volatile organic compounds (VOCs). 32,111,112 SPI was accomplished using a commercial krypton discharge lamp (10.6 eV) with a photon ux of about 10 11 photons per s, while the CI was achieved through ion-molecule reactions with O 2 + reactant ions generated by photoelectron ionization.…”

Photoionization-Generated Dibromomethane Cation Chemical Ionization Source for Time-of-Flight Mass Spectrometry and Its Application on Sensitive Detection of Volatile Sulfur Compounds

“…PI is another widely used soft ionization method for online mass spectrometry. − It is suitable for pressure from vacuum to atmospheric pressure. Light sources, such as synchrotron radiation-based, laser-based, and low pressure discharge VUV lights, were mostly utilized.…”