Membrane Inlet Mass Spectrometry Techniques and Their Applications

KeyWord:membrane inlet  mass spectrometry  ionization source  application

Abstract:

      Membrane inlet mass spectrometry£¨MIMS£© utilizes a semi-permeable membrane to selectively transfer the target molecules in gas£¬liquid or solid mixtures into a mass spectrometer£¬yielding on line monitoring volatile organic compounds. It has been widely used for the continuous monitoring on line without chromatographic separation and sample pretreatment£¬where the inferences from the bulk of the sample matrix could be avoided£®In this review£¬the principle and structure of MIMS instrument were introduced£¬including the membrane materials£¬ionization sources£¬the mass spectrometers and also interface configurations£®The progresses of MIMS instruments in the laboratory were presented£¬especially on the combination of membrane with the single photon ionization time of flight mass spectrometry£®A new membrane inlet with buffer cell for time of flight mass spectrometry was developed to increase the limit of detection£®Then£¬the combination of helical hollow fiber membrane inlet with time of flight mass spectrometry and ion mobility spectrometry was introduced for detection trace volatile organic compounds in air and water£®Moreover£¬the in-source stretched hollow fiber membrane inlet and in-source helical hollow fiber membrane interface were also developed for higher limit of detection and faster responding time£®Recently£¬MIMS has been widely used in a lot of field including environmental pollutions monitoring£¬also the field of ecology£¬life sciences£¬microbial metabolism£®In the field of environment£¬some methods based on MIMS were developed to measure the chlorinated and brominated-amines£¬aromatic pollutants in drinking water£®MIMS also was used for direct analysis of the naphthenic acids in constructed wetland samples and polyaromatic hydrocarbons in soil and aqueous samples£®In the field of ecology£¬MIMS was used to investigate the abundance and concentration of aqueous nitrate£¬nitrite and ammonium£®It also used to measure the denitrification£¬anammox£¬DNRA rates£¬and net N2 flux in paddy soil£®In the field of life sciences£¬membrane inlet ion mobility spectrometry was used for on-line measurement of trace propofol in exhaled air£®MIMS was used to detect the representative bacteric metabolites and classify four kinds of bacteria£®In the field of microbial metabolism£¬MIMS was used for quantitative understanding of inorganic carbon uptake flux and carbon concentrating mechanisms in metabolically engineered cyanobacteria£®MIMS was also used to study the CO2 and HCO?3 permeabilities of isolated chloroplasts and the conversion of nitric oxide into nitrous oxide by algal photosynthesis£®The new applications of membrane inlet mass spectrometry in recent years were presented£¬and the potential trends in future were also looked forward to£¬namely£¬1£© to develop the quantitative method based on MIMS£»2£© to improve the sensitivity and portability of MIMS for field applications£»3£© to extend the new application field such as the monitoring the volatile organic compounds in marine environment with MIMS£®