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A portable gas chromatograph for real-time monitoring of aromatic volatile organic compounds in air samples. J Chromatogr A 2020; 1625:461267. [DOI: 10.1016/j.chroma.2020.461267] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 05/18/2020] [Accepted: 05/19/2020] [Indexed: 11/18/2022]
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Wang J, Ma J, Zellers ET. Room-temperature-ionic-liquid coated graphitized carbons for selective preconcentration of polar vapors. J Chromatogr A 2020; 1609:460486. [PMID: 31506165 DOI: 10.1016/j.chroma.2019.460486] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/22/2019] [Accepted: 08/26/2019] [Indexed: 11/26/2022]
Abstract
Most adsorbent materials used for preconcentrating and thermally desorbing volatile and semi-volatile organic compounds (S/VOCs) in portable or "micro" gas chromatographic (GC/µGC) instruments preferentially capture non-polar or moderately polar compounds relative to more polar compounds. Here, we explore the use of a known trigonal-tripyramidal room-temperature ionic liquid (RTIL) as a surface modifier for the graphitized carbons, Carbopack B (C-B) and Carbopack X (C-X), with the goal of enhancing their capacity and selectivity for polar S/VOCs. Breakthrough tests were performed by challenging tubes packed with ∼2.5 mg of C-B or RTIL-coated C-B (RTIL/C-B) with 13 individual S/VOCs, including several organophosphorus compounds and reference alkyl and aromatic hydrocarbons of comparable vapor pressures, at concentrations ranging from 14 to 130 mg/m3. The 10% breakthrough volume, Vb10, was used as the measure of capacity. For the RTIL/C-B, the Vb10 values of the five organophosphorus vapors tested were consistently ∼2.5 times larger than those for the untreated C-B, and Vb10 values of the four non-polar reference vapors were 11-26 times smaller for the RTIL/C-B than for the untreated C-B. For compounds of similar vapor pressure the capacity ratios for polar vs. non-polar compounds with the RTIL/C-B ranged from 1.8 to 34. Similar results were obtained with C-X and RTIL/C-X on a smaller set of compounds. Tests at 70% relative humidity or with a binary mixture of a polar and non-polar compound had no effect on the capacity of the RTIL/C-B, and there were no changes in Vb10 values after several months of testing that included cycling from 25 to 250 °C. Capacity was strongly correlated with vapor pressure. Attempts to reconcile the selectivity using models based on linear-solvation-energy relationships were only partially successful. Nonetheless, these results indicate that RTIL coating of carbon adsorbents affords a simple, reliable means of rendering them selective for polar S/VOCs.
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Affiliation(s)
- Junqi Wang
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States; Center for Wireless Integrated MicroSensing & Systems, University of Michigan, Ann Arbor, MI 48109-2122, United States
| | - Jialiu Ma
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States
| | - Edward T Zellers
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States; Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI 48109-2029, United States; Center for Wireless Integrated MicroSensing & Systems, University of Michigan, Ann Arbor, MI 48109-2122, United States.
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3
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Regmi BP, Agah M. Micro Gas Chromatography: An Overview of Critical Components and Their Integration. Anal Chem 2018; 90:13133-13150. [DOI: 10.1021/acs.analchem.8b01461] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Bishnu P. Regmi
- VT MEMS Lab, Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Masoud Agah
- VT MEMS Lab, Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States
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Xu M, Tang Z, Duan Y, Liu Y. GC-Based Techniques for Breath Analysis: Current Status, Challenges, and Prospects. Crit Rev Anal Chem 2015; 46:291-304. [DOI: 10.1080/10408347.2015.1055550] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Besalú E, Castellanos M, Sanchez JM. Sequential discriminant classification of environments with different levels of exposure to tobacco smoke. THE SCIENCE OF THE TOTAL ENVIRONMENT 2014; 490:899-904. [PMID: 24908649 DOI: 10.1016/j.scitotenv.2014.05.093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 05/08/2014] [Accepted: 05/21/2014] [Indexed: 06/03/2023]
Abstract
The use of biomarkers permits the detection of smoking having taken place in an environment. However, no single biomarker is able to differentiate clearly between different types of environments. Multivariate classification models have helped us to differentiate between outdoors, non-smoking indoors, well ventilated smoking indoors, and smoking environments without good air exchange. We found that the variables that enabled us to classify environments most accurately were indoor temperature, 2,5-dimethylfuran and ethyltoluene. A successful prediction rate of 86.5% was obtained by applying both direct fitting and cross validation discriminant (leave-one-out) analyses. Our results show that although a good air exchange ratio decreases the levels of volatile organic compounds in indoor air due to tobacco smoke, significant contamination still remains.
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Affiliation(s)
- Emili Besalú
- Department of Chemistry, University of Girona, Campus Montilivi s/n, 17071 Girona, Spain; Institut de Química Computacional i Catàlisi (IQCC), University of Girona, Campus Montilivi s/n, 17071 Girona, Spain.
| | - Mar Castellanos
- Department of Neurology, Dr Josep Trueta University Hospital, Girona, Spain; Cerebrovascular Unit, Girona Biomedical Research Institute (IdIBGi), Girona, Spain.
| | - Juan M Sanchez
- Department of Chemistry, University of Girona, Campus Montilivi s/n, 17071 Girona, Spain; Cerebrovascular Unit, Girona Biomedical Research Institute (IdIBGi), Girona, Spain.
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Kim SK, Chang H, Zellers ET. Microfabricated gas chromatograph for the selective determination of trichloroethylene vapor at sub-parts-per-billion concentrations in complex mixtures. Anal Chem 2011; 83:7198-206. [PMID: 21859085 DOI: 10.1021/ac201788q] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A complete field-deployable microfabricated gas chromatograph (μGC) is described, and its adaptation to the analysis of low- and subparts-per-billion (ppb) concentrations of trichloroethylene (TCE) vapors in complex mixtures is demonstrated through laboratory testing. The specific application being addressed concerns the problem of indoor air contamination by TCE vapor intrusion. The μGC prototype employs a microfabricated focuser, dual microfabricated separation columns, and a microsensor array. These are interfaced to a nonmicrofabricated front-end pretrap and high-volume sampler module to reduce analysis time and limits of detection (LOD). Selective preconcentration and focusing are coupled with rapid chromatographic separation and multisensor detection for the determination of TCE in the presence of up to 45 interferences. Autonomous operation is possible via a laptop computer. Preconcentration factors as high as 500 000 are achieved. Sensitivities are constant over the range of captured TCE masses tested (i.e., 9-390 ng), and TCE is measured in a test atmosphere at 120 parts-per-trillion (ppt), with a projected LOD of 40 ppt (4.2 ng captured, 20 L sample) and a maximum sampling + analytical cycle time of 36 min. Short- and medium-term (1 month) variations in retention time, absolute responses, and response patterns are within acceptable limits.
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Affiliation(s)
- Sun Kyu Kim
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan 48109-2029, United States
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Sukaew T, Chang H, Serrano G, Zellers ET. Multi-stage preconcentrator/focuser module designed to enable trace level determinations of trichloroethylene in indoor air with a microfabricated gas chromatograph. Analyst 2011; 136:1664-74. [DOI: 10.1039/c0an00780c] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Alonso M, Godayol A, Anticó E, Sanchez JM. Assessment of environmental tobacco smoke contamination in public premises: significance of 2,5-dimethylfuran as an effective marker. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:8289-94. [PMID: 20919722 DOI: 10.1021/es1016075] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Contamination by environmental tobacco smoke (ETS) on premises where smoking is permitted is evaluated. Although all target VOCs evaluated show significant differences between smoking and nonsmoking indoors, the results obtained indicate that 2,5-dimethylfuran is the most appropriate and effective marker of ETS contamination given that this compound is only detected in environments where people have smoked and so the detection of this compound cannot be attributed to other contamination sources such as traffic. Moreover, the air levels of this compound due to coffee aroma are below the detection limits for this methodology. A preliminary study is performed to evaluate whether 2,5-dimethylfuran, a smoking breath biomarker, can be detected in passive smokers working in smoking environments. The compound was continuously detected in the breath of nonsmoking employees after being in direct contact with ETS for just a few hours. The Tedlar gas sampling bags had 5% loss of 2,5-dimethylfuran after 3 h of storage, which we took as the maximum recommended period for air sample storage.
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Affiliation(s)
- Monica Alonso
- Chemistry Department, University of Girona, Campus Montilivi s/n, 17071-Girona, Spain
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Rairigh DJ, Warnell GA, Zellers ET, Mason AJ. CMOS Baseline Tracking and Cancellation Instrumentation for Nanoparticle-Coated Chemiresistors. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2009; 3:267-276. [PMID: 23853265 DOI: 10.1109/tbcas.2009.2023511] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Chemiresistor (CR) sensors and sensor arrays coated with thiolate-monolayer-protected gold nanoparticle (MPN) interfaces show great promise as detectors in gas-chromatographic microsystems with applications in biomedical and environmental analysis including breath biomarkers of disease. This paper describes a new readout circuit that overcomes the wide range of baseline resistances and drift in baseline values inherent to MPN-coated CRs to achieve a 57 ppm readout resolution. The 0.5-mum CMOS circuit operates at 5 V and provides a response resolution of 74 muV. It can cancel baseline voltages from 0.3 to 4.3 V with an accuracy of 4.2 mV and can track and compensate for drifts up to 30 mV/min. Performance was verified with MPN-coated CRs, where drift was measured and effectively cancelled. The circuit topology and size support an on-chip MPN-coated CR sensor array.
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Zhong Q, Steinecker WH, Zellers ET. Characterization of a high-performance portable GC with a chemiresistor array detector. Analyst 2009; 134:283-93. [DOI: 10.1039/b810944c] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Ohira SI, Toda K. Micro gas analyzers for environmental and medical applications. Anal Chim Acta 2008; 619:143-56. [DOI: 10.1016/j.aca.2008.05.010] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Revised: 05/04/2008] [Accepted: 05/06/2008] [Indexed: 10/22/2022]
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Steinecker WH, Rowe MP, Zellers ET. Model of Vapor-Induced Resistivity Changes in Gold−Thiolate Monolayer-Protected Nanoparticle Sensor Films. Anal Chem 2007; 79:4977-86. [PMID: 17523593 DOI: 10.1021/ac070068y] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An investigation of the modulation of charge transport through thin films of n-octanethiolate monolayer-protected gold nanoparticles (MPN) induced by the sorption of organic vapors is presented. A model is derived that allows predictions of MPN-coated chemiresistor (CR) responses from vapor-film partition coefficients, and analyte densities and dielectric constants. Calibrations with vapors of 28 compounds collected from an array of CRs and a parallel thickness-shear-mode resonator are used to verify assumptions inherent in the model and to assess its performance. Results afford insights into the nature of the vapor-MPN interactions, including systematic variations in apparent film swelling efficiencies, and show that the model can predict CR responses typically to within 24%. Using CRs of different dimensions, vapor sensitivities are found to be virtually independent of the MPN film volume over a range of 104 (device-area x MPN layer thickness). Sensitivities vary inversely with analyte vapor pressure similarly for the two sensor types, but the CR sensor affords significantly greater signal-to-noise ratios, yielding calculated detection limits in the low-part-per-billion concentration range for several of the analytes tested. The implications of these results for implementing MPN-coated CR arrays as detectors in microanalytical systems are considered.
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Affiliation(s)
- William H Steinecker
- Engineering Research Center for Wireless Integrated MicroSystems, Department of Chemistry, University of Michigan, 109 South Observatory, Ann Arbor, Michigan 48109-2029, USA
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