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Larsen FT, McPherson JN, McKenzie CJ, Lauritsen FR. An experimental laboratory reactor for quantitative kinetic studies of disinfection byproduct formation using membrane inlet mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2022; 36:e9339. [PMID: 35733413 PMCID: PMC9286867 DOI: 10.1002/rcm.9339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 06/16/2022] [Accepted: 06/17/2022] [Indexed: 06/15/2023]
Abstract
RATIONALE The type and quantity of environmentally problematic disinfection byproducts (DBPs) produced during chlorination of water depend on the natural organic matter and organic contaminants that raw water contains, and on the operational conditions of the drinking water treatment process. There is a need for a fast and quantitative method that determines which DBPs are produced and monitors the chemical dynamics during a drinking water treatment. METHODS A small experimental chemical reactor (50 mL) was mounted directly onto the membrane inlet interface of a membrane inlet mass spectrometer (MIMS). In this setup, the membrane was the only separation between the reaction mixture in the chemical reactor and the open ion source of the mass spectrometer 2 cm away. Water samples to be chlorinated were placed in the reactor and the chlorination reaction was initiated by injection of hypochlorite. The formation of intermediates and products was monitored using either full-scan mass spectra or selected ion monitoring of relevant ions. RESULTS An algorithm for analyte quantification was successfully developed for analysis of the complex mixtures of phenol (a model for waterborne organic compounds), chlorinated intermediates and trihalomethane products which simultaneously pass the membrane into the mass spectrometer. The algorithm is based upon the combined use of standard addition and an internal standard, and all analytes could be quantified at nanomolar concentrations corresponding to realistic water treatment conditions. Experiments carried out in the temperature range 15-60°C showed that the reaction dynamics change with operational parameters, for example in tap versus deionized water. CONCLUSIONS We have successfully shown that an experimental laboratory reactor directly interfaced with a MIMS can be used for quantitative monitoring of the chemical dynamics during a water treatment. This technique could provide rapid assistance in the optimization of operating parameters for minimizing DBP production.
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Affiliation(s)
- Freja Troj Larsen
- Department of Physics, Chemistry and PharmacyUniversity of Southern DenmarkOdense MDenmark
| | - James Neill McPherson
- Department of Physics, Chemistry and PharmacyUniversity of Southern DenmarkOdense MDenmark
| | - Christine Joy McKenzie
- Department of Physics, Chemistry and PharmacyUniversity of Southern DenmarkOdense MDenmark
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Ghosh Biswas R, Croxall MP, Lawrence RT, Soong R, Goh MC, Simpson AJ. A new perspective on the photocatalytic action of titanium dioxide on phenol elucidated using comprehensive multiphase NMR. NANOSCALE 2022; 14:9869-9876. [PMID: 35775921 DOI: 10.1039/d2nr01911f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Comprehensive Multiphase NMR (CMP-NMR) is a recently developed technique capable of simultaneously observing different phases - solutions, gels, and solids - while providing the chemical specificity of traditional NMR. With this new tool, the heterogeneous photocatalysis of phenol by titanium dioxide (P25 TiO2) is re-examined to gain information about the occurrence of reaction at different regions between the catalyst and the solution. It was found that the proportion of phenol in different phases changes over the course of the photodegradation period. The photocatalyst appears to preferentially degrade phenol molecules that are weakly associated with the surface, such that they have restricted mobility in a 'gel-like' state. Diffusion Ordered Spectroscopy (DOSY) corroborates the relative change in phenol signals between freely diffusing solution and diffusion restricted gels as measured using CMP-NMR. The surface of P25 TiO2 was found to foul over the course of the 200-hour photodegradation period that was monitored using the solid-state capabilities of the CMP-NMR. Finally, CMP-NMR showed differences in the photodegradation of phenol by P25 TiO2 to that of a TiO2-nitrogen doped graphene quantum dot (NGQD) composite. With the latter composite, no fouling of the surface was seen over time. This application of CMP-NMR to the field of catalysis demonstrates its potential to better understand and study photocatalytic systems in general.
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Affiliation(s)
- Rajshree Ghosh Biswas
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Ontario, M5S 3H6, Canada.
| | - Mark P Croxall
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Ontario, M5S 3H6, Canada.
| | - Reece T Lawrence
- Department of Materials Science and Engineering, University of Toronto, 184 College St, Toronto, Ontario, M5S 3E4, Canada
| | - Ronald Soong
- Department of Physical and Environmental Science, University of Toronto, Scarborough Campus, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada
| | - M Cynthia Goh
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Ontario, M5S 3H6, Canada.
- Department of Materials Science and Engineering, University of Toronto, 184 College St, Toronto, Ontario, M5S 3E4, Canada
| | - Andre J Simpson
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, Ontario, M5S 3H6, Canada.
- Department of Physical and Environmental Science, University of Toronto, Scarborough Campus, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada
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Casademont P, Cardozo-Filho L, Meurer E, Sánchez-Oneto J, Portela J. Gasification of olive oil mill waste by supercritical water in a continuous reactor. J Supercrit Fluids 2018. [DOI: 10.1016/j.supflu.2018.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Yan M, Zeng G, Li X, Zhao C, Yang G, Gong J, Chen G, Tang L, Huang D. Titanium dioxide nanotube arrays with silane coupling agent modification for heavy metal reduction and persistent organic pollutant degradation. NEW J CHEM 2017. [DOI: 10.1039/c6nj03196j] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
TiO2 catalysts have gained extensive attention owing to their excellent catalytic ability, relatively stable physical and chemical properties and competitive price.
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Affiliation(s)
- Ming Yan
- College of Environmental Science and Engineering
- Hunan University
- Changsha
- China
- Key Laboratory of Environmental Biology and Pollution Control (Hunan University)
| | - Guangming Zeng
- College of Environmental Science and Engineering
- Hunan University
- Changsha
- China
- Key Laboratory of Environmental Biology and Pollution Control (Hunan University)
| | - Xiaoming Li
- College of Environmental Science and Engineering
- Hunan University
- Changsha
- China
- Key Laboratory of Environmental Biology and Pollution Control (Hunan University)
| | - Chenghao Zhao
- College of Environmental Science and Engineering
- Hunan University
- Changsha
- China
- Key Laboratory of Environmental Biology and Pollution Control (Hunan University)
| | - Guang Yang
- College of Environmental Science and Engineering
- Hunan University
- Changsha
- China
- Key Laboratory of Environmental Biology and Pollution Control (Hunan University)
| | - Jilai Gong
- College of Environmental Science and Engineering
- Hunan University
- Changsha
- China
- Key Laboratory of Environmental Biology and Pollution Control (Hunan University)
| | - Guiqiu Chen
- College of Environmental Science and Engineering
- Hunan University
- Changsha
- China
- Key Laboratory of Environmental Biology and Pollution Control (Hunan University)
| | - Lin Tang
- College of Environmental Science and Engineering
- Hunan University
- Changsha
- China
- Key Laboratory of Environmental Biology and Pollution Control (Hunan University)
| | - Danlian Huang
- College of Environmental Science and Engineering
- Hunan University
- Changsha
- China
- Key Laboratory of Environmental Biology and Pollution Control (Hunan University)
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Cotto MC, Emiliano A, Nieto S, Duconge J, Roque-Malherbe R. Degradation of phenol by mechanical activation of a rutile catalyst. J Colloid Interface Sci 2009; 339:133-9. [PMID: 19682705 DOI: 10.1016/j.jcis.2009.07.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Accepted: 07/07/2009] [Indexed: 10/20/2022]
Abstract
In the present paper a novel mechanochemical process for the elimination of organic pollutants dissolved in water is proposed. In this regard, phenol aqueous solutions (100mgL(-1)) were ball-milled for 0, 12, 18, 24, 36, 48, and 72h with and without a well-characterized (XRD, SEM, and N(2) Adsorption), rutile powder catalyst and the reaction products analyzed with UV and GC/MS. It was found that when the catalyst was not included in the process, phenol was not affected, but when it was included, phenol was decomposed. The catalyst itself did not change and the reaction follows a pseudo-first-order kinetics. Besides, intermediates which are characteristic of the ()OH radical mechanism were found in the reaction products. Then, a mechanism similar to those accepted for other advanced oxidation processes was proposed. The value measured for the pseudo-first-order reaction constant was very low, indicating that the reported process is inefficient. Nevertheless, this problem could be solved by applying catalysts consisting of particles with smaller diameters.
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Affiliation(s)
- M C Cotto
- Institute of Physical Chemical Applied Research, School of Science, University of Turabo, P.O. Box 3030, Gurabo, PR 00778-3030
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Azevedo EB, Tôrres AR, Aquino Neto FR, Dezotti M. TiO2-Photocatalyzed degradation of phenol in saline media in an annular reactor: hydrodynamics, lumped kinetics, intermediates, and acute toxicity. BRAZILIAN JOURNAL OF CHEMICAL ENGINEERING 2009. [DOI: 10.1590/s0104-66322009000100008] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
| | - A. R. Tôrres
- Universidade do Estado do Rio de Janeiro, Brazil
| | | | - M. Dezotti
- Universidade Federal do Rio de Janeiro, Brazil
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Oxidation of Sodium Dodecylbenzenesulfonate with Chrysotile: On-line Monitoring by Membrane Introduction Mass Spectrometry. J SURFACTANTS DETERG 2007. [DOI: 10.1007/s11743-007-1032-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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8
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Real-time monitoring of a pharmaceutical process reaction using a membrane interface combined with atmospheric pressure chemical ionisation mass spectrometry. Anal Chim Acta 2005. [DOI: 10.1016/j.aca.2005.03.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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9
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Quici N, Morgada ME, Piperata G, Babay P, Gettar RT, Litter MI. Oxalic acid destruction at high concentrations by combined heterogeneous photocatalysis and photo-Fenton processes. Catal Today 2005. [DOI: 10.1016/j.cattod.2005.03.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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10
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Phase control and photocatalytic properties of nano-sized titania particles by gas-phase pyrolysis of TiCl4. CATAL COMMUN 2004. [DOI: 10.1016/j.catcom.2004.05.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Nelson JHL, Krogh ET, Gill CG, Friesen DA. Monitoring the TiO2-photocatalyzed destruction of aqueous environmental contaminants at parts-per-trillion levels using membrane introduction mass spectrometry (MIMS). JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2004; 39:2307-2317. [PMID: 15478924 DOI: 10.1081/ese-200026269] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Membrane introduction mass spectrometry (MIMS) was used to directly monitor the TiO2/UV-photocatalyzed destruction of acetophenone, toluene, and chloroform in H2O at ppm to pptr concentrations. The instrument response time was sufficiently rapid for these environmental contaminants (1-6min) that "real-time" monitoring of their degradation was possible. This method was used to follow the loss of toluene at pptr levels and the concomitant formation of one of its primary photo-oxidation intermediates, methylphenol. These results illustrate the potential use of MIMS as a sensitive on-line measurement technique for monitoring photocatalytic destruction of trace organic contaminants in water at environmentally relevant levels.
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Affiliation(s)
- Janet H L Nelson
- Applied Environmental Research Laboratories, Department of Chemistry, Malaspina University-College, Nanaimo, BC, Canada
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Yang J, Chen PY. Infrared reflection-absorption method for the detection of aromatic compounds in aqueous solutions with limited sample volumes. ANAL SCI 2002; 18:1247-52. [PMID: 12458711 DOI: 10.2116/analsci.18.1247] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
An infrared reflection-absorption (IR/RA) method was developed to detect aromatic organic compounds in aqueous solutions where the required sample volume can be as low as 50 microL. Two aluminum plates were used to form the sampling cell for the detection of small amount of aqueous samples. One plate was used as an IR reflection substrate and a second plate, in which several holes were drilled, was placed tightly on the top of the reflection plate to form cavities for sampling. The cavities were further coated with hydrophobic film. After the hydrophobic film dried, a certain amount of aqueous sample was injected to the cavity. Analytes in the aqueous solution were attracted into the hydrophobic film through the solid phase micro-extraction principle. After residual water was removed from the cavity, organic compounds absorbed by the hydrophobic film could be sensed using IR radiation based on the reflection-absorption mode. To investigate the applicability of this type of sensing method for small-volume detection, factors such as the volume of the aqueous solution, the sample concentration, size of the cavity and the sensitivity of this method were investigated. An examination of the linear relationship between the signals and the analyte concentrations showed regression coefficients that were generally in the range of 0.992 to 0.999 for the examined analytes in the concentration range of 10 to 100 ppm. Under the condition that the sample volume was 100 microL and based on three-times the spectra noise level, the calculated detection limits for this method were found at around 1 ppm for the examined analytes.
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Affiliation(s)
- Jyisy Yang
- Department of Chemistry, National Chung-Hsing University, Taichung, Taiwan 402.
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13
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Emilio CA, Jardim WF, Litter MI, Mansilla HD. EDTA destruction using the solar ferrioxalate advanced oxidation technology (AOT). J Photochem Photobiol A Chem 2002. [DOI: 10.1016/s1010-6030(02)00173-9] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Ketola RA, Kotiaho T, Cisper ME, Allen TM. Environmental applications of membrane introduction mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2002; 37:457-476. [PMID: 12112751 DOI: 10.1002/jms.327] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The purpose of this review is to highlight the versatility of membrane introduction mass spectrometry (MIMS) in environmental applications, summarize the measurements of environmental volatile organic compounds (VOCs) accomplished using MIMS, present developments in the detection of semi-volatile organic compounds (SVOCs) and forecast possible future directions of MIMS in environmental applications.
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Kotiaho T, Lauritsen FR. Chapter 16 Membrane inlet mass spectrometry. SAMPLING AND SAMPLE PREPARATION FOR FIELD AND LABORATORY 2002. [DOI: 10.1016/s0166-526x(02)80053-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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16
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Alberici RM, Sparrapan R, Jardim WF, Eberlin MN. Selective trace level analysis of phenolic compounds in water by flow injection analysis--membrane introduction mass spectrometry. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2001; 35:2084-2088. [PMID: 11393991 DOI: 10.1021/es001814i] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Flow injection analysis coupled with membrane introduction mass spectrometry (FIA-MIMS) with on-line derivatization is shown to allow fast, accurate, nearly interference-free, and sensitive (low microgram/L) quantitation of phenolic compounds in water. On-line FIA derivatization of the phenolic compounds is performed by acetic anhydride acetylation in a K2CO3-buffered alkaline medium. The phenol acetates so formed efficiently permeate a silicone membrane and are directly transferred to the mass spectrometer, in which they are analyzed with selectivity and high sensitivity via selected ion monitoring. FIA-MIMS analysis was performed for aqueous solutions of phenol, 2-methylphenol, 4-chlorophenol, 4-chloro-3-methylphenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol, and detection limits in the 0.5-20 micrograms/L (ppb) range were observed for an analytical frequency of six samples/h. FIA-MIMS for phenolic compound analysis is considerably less time-consuming and labor intensive than most chromatographic methods based on liquid-liquid extraction and preconcentration procedures and is therefore applicable for on-line and in-situ monitoring of phenols in wastewaters and in the environment. FIA-MIMS employing acetic anhydride derivatization is also virtually free of interferences since it combines chemical, membrane, and enhanced MS selectivity; hence quantitation of phenolic compounds can be performed in the presence of congeners.
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Affiliation(s)
- R M Alberici
- Institute of Chemistry, State University of Campinas-UNICAMP, CP 6154, 13083-970, Campinas, SP, Brazil
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Rios RV, da Rocha LL, Vieira TG, Lago RM, Augusti R. On-line monitoring by membrane introduction mass spectrometry of chlorination of organics in water. Mechanistic and kinetic aspects of chloroform formation. JOURNAL OF MASS SPECTROMETRY : JMS 2000; 35:618-624. [PMID: 10800051 DOI: 10.1002/(sici)1096-9888(200005)35:5<618::aid-jms986>3.0.co;2-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Chloroform formation during the chlorination of simple organic molecules modeling humic substances, such as phenol and di- and trihydroxybenzenes, was studied by on-line membrane introduction mass spectrometry (MIMS). Under the reaction conditions employed, chloroform was rapidly formed from 1,3-dihydroxybenzene, 1, 4-dihydroxybenzene, phenol and 1,2,3-trihydroxybenzene with yields of 17, 13, 7 and 5%, respectively. With the exception of aniline, which afforded a 17% chloroform yield, non-phenolic compounds, such as nitrobenzene, chlorobenzene, toluene, benzene and cyclohexanol, furnished low yields. Mechanistic studies showed that phenol is chlorinated consecutively and produces initially chlorophenol. It is suggested that chloroform might be formed mainly from chlorinated 3, 5-cyclohexadienone-type intermediates. MIMS was also used to determine the reaction rates and to study the kinetics of the chlorination. A good Hammett linear correlation for an electrophilic substitution mechanism was found for the compounds C(6)H(5)X (X = NH(2), OH, CH(3), H, Cl and NO(2)).
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Affiliation(s)
- R V Rios
- Chemistry Department, ICEx, Federal University of Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil
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Headspace membrane introduction mass spectrometry for trace level analysis of VOCs in soil and other solid matrixes. Anal Chem 2000; 72:2166-70. [PMID: 10815981 DOI: 10.1021/ac991121o] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new MIMS-derived technique, headspace membrane introduction mass spectrometry (HS-MIMS), is described for direct trace level analysis of volatile organic compounds (VOCs) in soil and other dry or wet solid matrixes. A silicone membrane interface is placed about 15 cm from the ion source, and a closed airspace (headspace) is created by connecting a toggle valve to the 1/4 in. tubing that connects the membrane interface to the ion source. For the VOC analysis, the headspace is evacuated and the solid sample vessel is heated to 90 degrees C. The VOCs are rapidly desorbed from the sample, pervaporated through the membrane, and preconcentrated for 4 min in the evacuated headspace. Then, the toggle valve is opened and the trapped VOCs are released into the ion source region of a quadrupole mass spectrometer. By electron ionization and selected-ion monitoring, a relatively sharp and intense peak is obtained and used for quantification. The HS-MIMS analysis shows excellent linearity and reproducibility and detection limits for many VOCs typically of 50-100 ng/kg (ppt).
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Johnson RC, Cooks RG, Allen TM, Cisper ME, Hemberger PH. Membrane introduction mass spectrometry: trends and applications. MASS SPECTROMETRY REVIEWS 2000; 19:1-37. [PMID: 10715830 DOI: 10.1002/(sici)1098-2787(2000)19:1<1::aid-mas1>3.0.co;2-y] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Recent advances in membrane introduction mass spectrometry (MIMS) are reviewed. On-line monitoring is treated by focusing on critical variables, including the nature and dimensions of the membrane, and the analyte vapor pressure, diffusivity, and solubility in the membrane barrier. Sample introduction by MIMS is applied in (i) on-line monitoring of chemical and biological reactors, (ii) analysis of volatile organic compounds in environmental matrices, including air, water and soil, and (iii) in more fundamental studies, such as measurements of thermochemical properties, reaction mechanisms, and kinetics. New semipermeable membranes are discussed, including those consisting of thin polymers, low vapor pressure liquids, and zeolites. These membranes have been used to monitor polar compounds, selectively differentiate compounds through affinity-binding, and provide isomer differentiation based on molecular size. Measurements at high spatial resolution, for example, using silicone-capped hypodermic needle inlets, are also covered, as is electrically driven sampling through microporous membranes. Other variations on the basic MIMS experiment include analyte preconcentration through cryotrapping (CT-MIMS) or trapping in the membrane (trap-and-release), as well as differential thermal release methods and reverse phase (i.e., organic solvent) MIMS. Method limitations center on semivolatile compounds and complex mixture analysis, and novel solutions are discussed. Semivolatile compounds have been monitored with thermally assisted desorption, ultrathin membranes and derivatization techniques. Taking advantage of the differences in time of membrane permeation, mixtures of structurally similar compounds have been differentiated by using sample modulation techniques and by temperature-programmed desorption from a membrane interface. Selective ionization techniques that increase instrument sensitivity towards polar compounds are also described, and comparisons are made with other direct sampling (nonchromatographic) methods that are useful in mixture analysis.
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Affiliation(s)
- R C Johnson
- Chemistry Department, Purdue University, West Lafayette, Indiana 47907, USA
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