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Yan X, Qu H, Chang Y, Duan X. Application of Metal-Organic Frameworks in Gas Pre-concentration, Pre-separation and Detection. ACTA CHIMICA SINICA 2022. [DOI: 10.6023/a22030134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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2
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Phyo S, Choi S, Jang J, Choi S, Lee J. A 3D-printed metal column for micro gas chromatography. LAB ON A CHIP 2020; 20:3435-3444. [PMID: 32789372 DOI: 10.1039/d0lc00540a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this work, a 3D-printed metal column was developed for micro gas chromatography (GC) applications and its properties and gas separation performances were characterized. By using a Ti6Al4V grade 23 powder, a square spiral one meter-long column (3D-column) was 3D-printed on a planar substrate of 3.4 × 3.3 × 0.2 cm and then perhydropolysilazane (PHPS) was deposited as a pre-treatment agent, followed by a coating of stationary phase (OV-1) onto the inner wall of the micro-channel. The 500 μm-diameter circular channel and two 800 μm-wide ports of the 3D-column were confirmed to be uniform by 3D X-ray microscopy without any distortion. The physical and thermal properties of the 3D-column were found to be very similar to that of the standard Ti6Al4V grade 23 alloy with near zero porosity (∼0.07%). The 3D-column with pre-treatment and stationary coating demonstrated efficient separation performance of gas mixtures containing alkanes, aromatics, alcohols, and ketones compared to a bare or only pretreated 3D-column in terms of the peak shape, broadening, and resolution (R > 1) within 2-3 min. The well-matched thermal responses to the target temperatures were demonstrated at the ramping rates of 10-20 °C min-1 upto 200 °C with uniform heat distribution over the 3D-column. In addition, the column bleed profiles showed that the 3D-column with PHPS had a 71% lower baseline intensity at 350 °C than that without PHPS. The 3D-column was then employed to separate a gas mixture of twelve alkanes (C9-C18, C22, C24) without any significant column bleeding and peak tailing. Therefore, the thermal responses and stability of the 3D-column promise its applicability in high temperature GC applications.
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Affiliation(s)
- Sooyeol Phyo
- Center for Environment, Health, and Welfare Research, Korea Institute of Science and Technology (KIST), Seoul, 02792, Republic of Korea.
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3
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Day C, Rowe N, Hutter T. Nanoporous Silica Preconcentrator for Vapor-Phase DMNB, a Detection Taggant for Explosives. ACS OMEGA 2020; 5:18073-18079. [PMID: 32743181 PMCID: PMC7391368 DOI: 10.1021/acsomega.0c01615] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 06/30/2020] [Indexed: 06/01/2023]
Abstract
The detection of trace amounts of explosives in the vapor phase is of great importance. Preconcentration of the analyte is a useful technique to lower the detection limit of existing sensors. A nanoporous silica (pSiO2) substrate was evaluated as a preconcentrator for gas-phase 2,3-dimethyl-2,3-dinitrobutane (DMNB), a volatile detection taggant added by law to plastic explosives. After collection in pSiO2, the DMNB vapor was thermally desorbed at 70 °C into a gas chromatography-mass spectrometry sorbent tube. This was analyzed for the total mass of DMNB collected in pSiO2. The loading time and loading temperature of pSiO2 were varied systematically between 15 and 60 min and 5-20 °C, respectively. The preconcentrator's performance was compared to that of a nonporous substrate of the same material as a control. The collection efficiency of pSiO2 was calculated as approximately 20% of the total DMNB that passed over it in 30 min, at a concentration of 0.5 ppm in N2 carrier gas. It had enhancement factors compared to the nonporous substrate of 12 and 16 for 0.5 and 4.1 ppm DMNB, respectively, under the same conditions. No advantage was found with cooling pSiO2 below room temperature during the loading phase, which removes any need for a cooling system to aid preconcentration. The low desorption temperature of 70 °C is an advantage over other preconcentration systems, although a higher temperature could decrease the desorption time.
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Affiliation(s)
- Coco Day
- Department
of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
| | - Nathan Rowe
- Defence
Science and Technology Laboratory, Porton
Down, Salisbury, Wiltshire SP4 0JQ, U.K.
| | - Tanya Hutter
- Department
of Mechanical Engineering, Materials Science and Engineering Program
and Texas Materials Institute, The University
of Texas at Austin, Austin, Texas 78712, United States
- SensorHut
Ltd, Cambridge CB4 0DS, U.K.
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4
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Lee J, Lee J, Lim SH. Micro gas preconcentrator using metal organic framework embedded metal foam for detection of low-concentration volatile organic compounds. JOURNAL OF HAZARDOUS MATERIALS 2020; 392:122145. [PMID: 32070927 DOI: 10.1016/j.jhazmat.2020.122145] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 01/14/2020] [Accepted: 01/19/2020] [Indexed: 06/10/2023]
Abstract
Analysis of volatile organic compounds (VOCs) is essential for on-site environmental monitoring and toxic chemicals detection. However, quantitatively detecting VOC gases is difficult because of their low gas concentration (<100 ppb), and preconcentration is necessary to overcome the detection limitations of various gas sensors. Many studies on micro preconcentrators (μ-PC) have been reported, however, these devices suffer from high desorption temperatures and significant pressure drops, which degrade sensing ability and increase operating costs, respectively. Due to these disadvantages, such devices are not yet commercially available. In this study, a μ-PC was developed using metal organic framework embedded metal foam (MOFM) as an adsorbent. The preconcentration performance of the μ-PC was evaluated based on several key parameters, such as desorption temperature, adsorption time, and initial sample concentration. In addition, the MOFM and commercial adsorbents were each packed in the same μ-PC chip, respectively, to compare their preconcentration and pressure drop performances. The MOFM-adsorbent-packed μ-PC demonstrated the preconcentration factors were 2.6 and 4 times higher, and the pressure drops were 4 and 3 times lower than those of the commercial adsorbents under the same conditions owing to the high specific surface area and the efficient flow distribution of the MOFM adsorbent.
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Affiliation(s)
- Janghyeon Lee
- Department of Mechanics and Design, Kookmin University, Seoul 02707, South Korea
| | - Junsuk Lee
- Department of Mechanics and Design, Kookmin University, Seoul 02707, South Korea
| | - Si-Hyung Lim
- School of Mechanical Engineering, Kookmin University, Seoul 02707, South Korea.
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5
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Park J, Thomasson JA, Gale CC, Sword GA, Lee KM, Herrman TJ, Suh CPC. Adsorbent-SERS Technique for Determination of Plant VOCs from Live Cotton Plants and Dried Teas. ACS OMEGA 2020; 5:2779-2790. [PMID: 32095701 PMCID: PMC7033990 DOI: 10.1021/acsomega.9b03500] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Accepted: 01/29/2020] [Indexed: 05/08/2023]
Abstract
We developed a novel substrate for the collection of volatile organic compounds (VOCs) emitted from either living or dried plant material to be analyzed by surface-enhanced Raman spectroscopy (SERS). We demonstrated that this substrate can be utilized to differentiate emissions from blends of three teas, and to differentiate emissions from healthy cotton plants versus caterpillar-infested cotton plants. The substrate we developed can adsorb VOCs in static headspace sampling environments, and VOCs naturally evaporated from three standards were successfully identified by our SERS substrate, showing its ability to differentiate three VOCs and to detect quantitative differences according to collection times. In addition, volatile profiles from plant materials that were either qualitatively different among three teas or quantitatively different in abundance between healthy and infested cotton plants were confirmed by collections on Super-Q resin for dynamic headspace and solid-phase microextraction for static headspace sampling, respectively, followed by gas chromatography to mass spectrometry. Our results indicate that both qualitative and quantitative differences can also be detected by our SERS substrate although we find that the detection of quantitative differences could be improved.
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Affiliation(s)
- Jinhyuk Park
- Department
of Biological and Agricultural Engineering, Texas A&M University, College Station, Texas 77843, United States
- E-mail: . Tel: +1-979-224-7055
| | - J. Alex Thomasson
- Department
of Biological and Agricultural Engineering, Texas A&M University, College Station, Texas 77843, United States
| | - Cody C. Gale
- Department
of Entomology, Texas A&M University, College Station, Texas 77843-2475, United States
| | - Gregory A. Sword
- Department
of Entomology, Texas A&M University, College Station, Texas 77843-2475, United States
| | - Kyung-Min Lee
- Office
of the Texas State Chemist, Texas A&M AgriLife Research, Texas A&M University System, College Station, Texas 77841, United States
| | - Timothy J. Herrman
- Office
of the Texas State Chemist, Texas A&M AgriLife Research, Texas A&M University System, College Station, Texas 77841, United States
| | - Charles P.-C. Suh
- Insect
Control and Cotton Disease Research Unit, USDA, ARS, 2771 F&B
Road, College Station, Texas 77845, United States
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6
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A carbon nanotube sponge as an adsorbent for vapor preconcentration of aromatic volatile organic compounds. J Chromatogr A 2019; 1605:460363. [DOI: 10.1016/j.chroma.2019.460363] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 06/17/2019] [Accepted: 07/09/2019] [Indexed: 11/20/2022]
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Development of Open-Tubular-Type Micro Gas Chromatography Column with Bump Structures. SENSORS 2019; 19:s19173706. [PMID: 31455012 PMCID: PMC6749250 DOI: 10.3390/s19173706] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 08/14/2019] [Accepted: 08/23/2019] [Indexed: 12/18/2022]
Abstract
Gas chromatography (GC) is the chemical analysis technique most widely used to separate and identify gas components, and it has been extensively applied in various gas analysis fields such as non-invasive medical diagnoses, indoor air quality monitoring, and outdoor environmental monitoring. Micro-electro-mechanical systems (MEMS)-based GC columns are essential for miniaturizing an integrated gas analysis system (Micro GC system). This study reports an open-tubular-type micro GC (μ-GC) column with internal bump structures (bump structure μ-GC column) that substantially increase the interaction between the gas mixture and a stationary phase. The developed bump structure μ-GC column, which was fabricated on a 2 cm × 2 cm μ-GC chip and coated with a non-polar stationary phase, is 1.5 m-long, 150 μm-wide, and 400 μm-deep. It has an internal microfluidic channel in which the bumps, which are 150 μm diameter half-circles, are alternatingly disposed to face each other on the surface of the microchannel. The fabricated bump structure μ-GC column yielded a height-equivalent-to-a-theoretical-plate (HETP) of 0.009 cm (11,110 plates/m) at an optimal carrier gas velocity of 17 cm/s. The mechanically robust bump structure μ-GC column proposed in this study achieved higher separation efficiency than a commercially available GC column and a typical μ-GC column with internal post structures classified as a semi-packed-type column. The experimental results demonstrate that the developed bump structure μ-GC column can separate a gas mixture completely, with excellent separation resolution for formaldehyde, benzene, toluene, ethylbenzene, and xylene mixture, under programmed operating temperatures.
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A Binder Jet Printed, Stainless Steel Preconcentrator as an In-Line Injector of Volatile Organic Compounds. SENSORS 2019; 19:s19122748. [PMID: 31248098 PMCID: PMC6630219 DOI: 10.3390/s19122748] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 06/11/2019] [Accepted: 06/17/2019] [Indexed: 11/17/2022]
Abstract
A conventional approach to making miniature or microscale gas chromatography (GC) components relies on silicon as a base material and MEMS fabrication as manufacturing processes. However, these devices often fail in medium-to-high temperature applications due to a lack of robust fluidic interconnects and a high-yield bonding process. This paper explores the feasibility of using metal additive manufacturing (AM), which is also known as metal 3D printing, as an alternative platform to produce small-scale microfluidic devices that can operate at a temperature higher than that which polymers can withstand. Binder jet printing (BJP), one of the metal AM processes, was utilized to make stainless steel (SS) preconcentrators (PCs) with submillimeter internal features. PCs can increase the concentration of gaseous analytes or serve as an inline injector for GC or gas sensor applications. Normally, parts printed by BJP are highly porous and thus often infiltrated with low melting point metal. By adding to SS316 powder sintering additives such as boron nitride (BN), which reduces the liquidus line temperature, we produce near full-density SS PCs at sintering temperatures much lower than the SS melting temperature, and importantly without any measurable shape distortion. Conversely, the SS PC without BN remains porous after the sintering process and unsuitable for fluidic applications. Since the SS parts, unlike Si, are compatible with machining, they can be modified to work with commercial compression fitting. The PC structures as well as the connection with the fitting are leak-free with relatively high operating pressures. A flexible membrane heater along with a resistance-temperature detector is integrated with the SS PCs for thermal desorption. The proof-of-concept experiment demonstrates that the SS PC can preconcentrate and inject 0.6% headspace toluene to enhance the detector's response.
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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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Soo JC, Gyung Lee E, LeBouf RF, Kashon ML, Chisholm W, Harper M. Evaluation of a portable gas chromatograph with photoionization detector under variations of VOC concentration, temperature, and relative humidity. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2018; 15:351-360. [PMID: 29333991 PMCID: PMC6379918 DOI: 10.1080/15459624.2018.1426860] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The objective of this present study was to evaluate the performance of a portable gas chromatograph-photoionization detector (GC-PID), under various test conditions to determine if it could be used in occupational settings. A mixture of 7 volatile organic compounds (VOCs)-acetone, ethylbenzene, methyl isobutyl ketone, toluene, m-xylene, p-xylene, and o-xylene-was selected because its components are commonly present in paint manufacturing industries. A full-factorial combination of 4 concentration levels (exposure scenarios) of VOC mixtures, 3 different temperatures (25°C, 30°C, and 35°C), and 3 relative humidities (RHs; 25%, 50%, and 75%) was conducted in a full-size controlled environmental chamber. Three repetitions were conducted for each test condition allowing for estimation of accuracy. Time-weighted average exposure data were collected using solid sorbent tubes (Anasorb 747, SKC Inc.) as the reference sampling medium. Calibration curves of Frog-4000 using the dry gases showed R2 > 0.99 for all analytes except for toluene (R2 = 0.97). Frog-4000 estimates within a test condition showed good consistency for the performance of repeated measurement. However, there was ∼41-64% reduction in the analysis of polar acetone with 75% RH relative to collection at 25% RH. Although Frog-4000 results correlated well with solid sorbent tubes (r = 0.808-0.993, except for toluene) most of the combinations regardless of analyte did not meet the <25% accuracy criterion recommended by NIOSH. The effect of chromatographic co-elution can be seen with m, p-xylene when the results are compared to the sorbent tube sampling technique with GC-flame ionization detector. The results indicated an effect of humidity on the quantification of the polar compounds that might be attributed to the pre-concentrator placed in the selected GC-PID. Further investigation may resolve the humidity effect on sorbent trap with micro GC pre-concentrator when water vapor is present. Although this instrument does not fulfill the accuracy criterion specified in the NIOSH technical report No. 2012-162, it can be used as a screening tool for range finding monitoring with dry gases calibration in the occupational setting rather than compliance monitoring.
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Affiliation(s)
- Jhy-Charm Soo
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, West Virginia
| | - Eun Gyung Lee
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, West Virginia
| | - Ryan F. LeBouf
- Respiratory Health Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, West Virginia
| | - Michael L. Kashon
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, West Virginia
| | - William Chisholm
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, West Virginia
| | - Martin Harper
- Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Morgantown, West Virginia
- Department of Environmental Engineering Sciences, University of Florida, Gainesville, Florida
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11
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Zhou MD, Akbar M, Myrick AJ, Xia Y, Khan WJ, Gao X, Baker TC, Zheng SY. Chopper-modulated gas chromatography electroantennography enabled using high-temperature MEMS flow control device. MICROSYSTEMS & NANOENGINEERING 2017; 3:17062. [PMID: 31057886 PMCID: PMC6444993 DOI: 10.1038/micronano.2017.62] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 07/07/2017] [Accepted: 07/26/2017] [Indexed: 06/09/2023]
Abstract
We report the design, fabrication and characterization of a microelectromechanical systems (MEMS) flow control device for gas chromatography (GC) with the capability of sustaining high-temperature environments. We further demonstrate the use of this new device in a novel MEMS chopper-modulated gas chromatography-electroantennography (MEMS-GC-EAG) system to identify specific volatile organic compounds (VOCs) at extremely low concentrations. The device integrates four pneumatically actuated microvalves constructed via thermocompression bonding of the polyimide membrane between two glass substrates with microstructures. The overall size of the device is 32 mm×32 mm, and it is packaged in a 50 mm×50 mm aluminum housing that provides access to the fluidic connections and allows thermal control. The characterization reveals that each microvalve in the flow control chip provides an ON to OFF ratio as high as 1000:1. The device can operate reliably for more than 1 million switching cycles at a working temperature of 300 °C. Using the MEMS-GC-EAG system, we demonstrate the successful detection of cis-11-hexadecenal with a concentration as low as 1 pg at a demodulation frequency of 2 Hz by using an antenna harvested from the male Helicoverpa Virescens moth. In addition, 1 μg of a green leafy volatile (GLV) is barely detected using the conventional GC-EAG, while MEMS-GC-EAG can readily detect the same amount of GLV, with an improvement in the signal-to-noise ratio (SNR) of ~22 times. We expect that the flow control device presented in this report will allow researchers to explore new applications and make new discoveries in entomology and other fields that require high-temperature flow control at the microscale.
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Affiliation(s)
- Ming-Da Zhou
- Micro & Nano Integrated Biosystem (MINIBio) Laboratory, Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, USA
| | - Muhammad Akbar
- Micro & Nano Integrated Biosystem (MINIBio) Laboratory, Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, USA
| | - Andrew J. Myrick
- Micro & Nano Integrated Biosystem (MINIBio) Laboratory, Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Entomology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Yiqiu Xia
- Micro & Nano Integrated Biosystem (MINIBio) Laboratory, Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, USA
| | - Waleed J. Khan
- Micro & Nano Integrated Biosystem (MINIBio) Laboratory, Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Electrical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Xiang Gao
- Micro & Nano Integrated Biosystem (MINIBio) Laboratory, Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
| | - Thomas C. Baker
- Department of Entomology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Si-Yang Zheng
- Micro & Nano Integrated Biosystem (MINIBio) Laboratory, Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
- Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Electrical Engineering, The Pennsylvania State University, University Park, PA 16802, USA
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12
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Van Den Houwe K, Evrard C, Van Loco J, Lynen F, Van Hoeck E. Use of Tenax® films to demonstrate the migration of chemical contaminants from cardboard into dry food. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2017; 34:1261-1269. [DOI: 10.1080/19440049.2017.1326067] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- K. Van Den Houwe
- Department of Food, Medicines and Consumer Safety, Scientific Institute of Public Health, Brussels, Belgium
| | - C. Evrard
- Department of Food, Medicines and Consumer Safety, Scientific Institute of Public Health, Brussels, Belgium
| | - J. Van Loco
- Department of Food, Medicines and Consumer Safety, Scientific Institute of Public Health, Brussels, Belgium
| | - F. Lynen
- Department of Organic and Macromolecular Chemistry, Ghent University, Ghent, Belgium
| | - E. Van Hoeck
- Department of Food, Medicines and Consumer Safety, Scientific Institute of Public Health, Brussels, Belgium
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13
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Akbar M, Narayanan S, Restaino M, Agah M. A purge and trap integrated microGC platform for chemical identification in aqueous samples. Analyst 2015; 139:3384-92. [PMID: 24837988 DOI: 10.1039/c4an00254g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The majority of current micro-scale gas chromatography (μGC) systems focus on air sampling to detect volatile organic compounds (VOCs). However, purging the VOCs from a water sample using microsystems is an unchartered territory. Various organic compounds used in everyday life find their way to water bodies. Some of these water organic compounds (WOCs) persist or degrade slowly, threatening not just human existence but also aquatic life. This article reports the first micro-purge extractor (μPE) chip and its integration with a micro-scale gas chromatography (μGC) system for the extraction and analysis of water organic compounds (WOCs) from aqueous samples. The 2 cm × 3 cm μPE chip contains two inlet and outlet ports and an etched cavity sealed with a Pyrex cover. The aqueous sample is introduced from the top inlet port while a pure inert gas is supplied from the side inlet to purge WOCs from the μPE chip. The outlets are assigned for draining water from the chip and for directing purged WOCs to the micro-thermal preconcentrator (μTPC). The trapped compounds are desorbed from the μTPC by resistive heating using the on-chip heater and temperature sensor, are separated by a 2 m long, 80 μm wide, and 250 μm deep polydimethylsiloxane (OV-1) coated μGC separation column, and are identified using a micro-thermal conductivity detector (μTCD) monolithically integrated with the column. Our experiments indicate that the combined system is capable of providing rapid chromatographic separation (<1.5 min) for quaternary WOCs namely toluene, tetrachloroethylene (PCE), chlorobenzene and ethylbenzene with a minimum detection concentration of 500 parts-per-billion (ppb) in aqueous samples. The proposed method is a promising development towards the future realization of a miniaturized system for sensitive, on-site and real-time field analysis of organic contaminants in water.
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Affiliation(s)
- Muhammad Akbar
- VT MEMS Lab, Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA.
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Haghighi F, Talebpour Z, Sanati-Nezhad A. Through the years with on-a-chip gas chromatography: a review. LAB ON A CHIP 2015; 15:2559-2575. [PMID: 25994317 DOI: 10.1039/c5lc00283d] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In recent years, the need for measurement and detection of samples in situ or with very small volume and low concentration (low and sub-parts per billion) is a cause for miniaturizing systems via microelectromechanical system (MEMS) technology. Gas chromatography (GC) is a common technique that is widely used for separating and measuring semi-volatile and volatile compounds. Conventional GCs are bulky and cannot be used for in situ analysis, hence in the past decades many studies have been reported with the aim of designing and developing chip-based GC. The focus of this review is to follow and investigate the development and the achievements in the field of chip-based GC and its components from the beginning up to the present.
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Affiliation(s)
- F Haghighi
- Chromatographic and Separation Laboratory, Department of Chemistry, Faculty of Physics and Chemistry, Alzahra University, Vanak, Tehran, Iran.
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15
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Akbar M, Shakeel H, Agah M. GC-on-chip: integrated column and photoionization detector. LAB ON A CHIP 2015; 15:1748-1758. [PMID: 25673367 DOI: 10.1039/c4lc01461h] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This paper reports a unique GC-on-chip module comprising a monolithically integrated semi-packed micro separation column (μSC) and a highly sensitive micro helium discharge photoionization detector (μDPID). While semi-packed μSC with atomic layer deposited (ALD) alumina as a stationary phase provides high separation performance, the μDPID implemented for the first time in a silicon-glass architecture inherits the desirable features of being universal, non-destructive, low power consumption (1.4 mW), and responsive. The integrated chip is 1.5 cm × 3 cm in size and requires a two-mask fabrication process. Monolithic integration alleviates the need for transfer lines between the column and the detector which improves the performance of the individual components with overall reduced fabrication and implementation costs. The chip is capable of operating under the isothermal as well as temperature and flow programming conditions to achieve rapid chromatographic analysis. The chip performance was investigated with two samples: 1) a multi-analyte gas mixture consisting of eight compounds ranging from 98 °C to 174 °C in boiling point and 2) a mixture containing higher alkanes (C9-C12). Our experiments indicate that the chip is capable of providing rapid chromatographic separation and detection of these compounds (<1 min) through the optimization of flow and temperature programming conditions. The GC-on-chip demonstrated a minimum detection limit of ~10 pg which is on a par with the widely used destructive flame ionization detector (FID).
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Affiliation(s)
- M Akbar
- VT MEMS Lab, Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA.
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