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Thamatam N, Ahn J, Chowdhury M, Sharma A, Gupta P, Marr LC, Nazhandali L, Agah M. A MEMS-enabled portable gas chromatography injection system for trace analysis. Anal Chim Acta 2023; 1261:341209. [PMID: 37147055 DOI: 10.1016/j.aca.2023.341209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 03/18/2023] [Accepted: 04/10/2023] [Indexed: 05/07/2023]
Abstract
Growing concerns about environmental conditions, public health, and disease diagnostics have led to the rapid development of portable sampling techniques to characterize trace-level volatile organic compounds (VOCs) from various sources. A MEMS-based micropreconcentrator (μPC) is one such approach that drastically reduces the size, weight, and power constraints offering greater sampling flexibility in many applications. However, the adoption of μPCs on a commercial scale is hindered by a lack of thermal desorption units (TDUs) that easily integrate μPCs with gas chromatography (GC) systems equipped with a flame ionization detector (FID) or a mass spectrometer (MS). Here, we report a highly versatile μPC-based, single-stage autosampler-injection unit for traditional, portable, and micro-GCs. The system uses μPCs packaged in 3D-printed swappable cartridges and is based on a highly modular interfacing architecture that allows easy-to-remove, gas-tight fluidic, and detachable electrical connections (FEMI). This study describes the FEMI architecture and demonstrates the FEMI-Autosampler (FEMI-AS) prototype (9.5 cm × 10 cm x 20 cm, ≈500 gms). The system was integrated with GC-FID, and the performance was investigated using synthetic gas samples and ambient air. The results were contrasted with the sorbent tube sampling technique using TD-GC-MS. FEMI-AS could generate sharp injection plugs (≈240 ms) and detect analytes with concentrations <15 ppb within 20 s and <100 ppt within 20 min of sampling time. With more than 30 detected trace-level compounds from ambient air, the demonstrated FEMI-AS, and the FEMI architecture significantly accelerate the adoption of μPCs on a broader scale.
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Affiliation(s)
- Nipun Thamatam
- VT MEMS Lab, The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, United States
| | - Jeonghyeon Ahn
- VT MEMS Lab, The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, United States; Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, United States
| | - Mustahsin Chowdhury
- VT MEMS Lab, The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, United States
| | - Arjun Sharma
- CESCA, The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, United States
| | - Poonam Gupta
- CESCA, The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, United States
| | - Linsey C Marr
- Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, United States
| | - Leyla Nazhandali
- CESCA, The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, United States
| | - Masoud Agah
- VT MEMS Lab, The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, United States.
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Micropreconcentrators: Recent Progress in Designs and Applications. SENSORS 2022; 22:s22041327. [PMID: 35214229 PMCID: PMC8963072 DOI: 10.3390/s22041327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/31/2022] [Accepted: 02/04/2022] [Indexed: 02/04/2023]
Abstract
The detection of chemicals is a fundamental issue of modern civilisation, however existing methods do not always achieve the desired sensitivity. Preconcentrators, which are devices that allow increasing the concentration of the intended analyte via e.g., adsorption/desorption, are one of the solutions for increasing the sensitivity of chemical detection. The increased detection sensitivity granted by preconcentration can be used to miniaturise detection instruments, granting them portability. The primary goal of this review is to report on and briefly explain the most relevant recent developments related to the design and applications of preconcentrators. The key design elements of preconcentrators and the emerging area of liquid-phase preconcentrators are briefly discussed, with the most significant applications of these devices being highlighted.
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Prestage J, Day C, Husheer SL, Winter WT, Ho WO, Saffell JR, Hutter T. Selective Detection of Volatile Organics in a Mixture Using a Photoionization Detector and Thermal Desorption from a Nanoporous Preconcentrator. ACS Sens 2022; 7:304-311. [PMID: 34958564 DOI: 10.1021/acssensors.1c02344] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The selective detection of individual hazardous volatile organic compounds (VOCs) within a mixture is of great importance in industrial contexts due to environmental and health concerns. Achieving this with inexpensive, portable detectors continues to be a significant challenge. Here, a novel thermal separator system coupled with a photoionization detector has been developed, and its ability to selectively detect the VOCs isopropanol and 1-octene from a mixture of the two has been studied. The system includes a nanoporous silica preconcentrator in conjunction with a commercially available photoionization detector (PID). The PID is a broadband total VOC sensor with little selectivity; however, when used in conjunction with our thermal desorption approach, selective VOC detection within a mixture can be achieved. VOCs are adsorbed in the nanoporous silica over a 5 min period at 5 °C before being desorbed by heating at a fixed rate to 70 °C and detected by the PID. Different VOCs desorb at different times/temperatures, and mathematical analysis of the set of PID responses over time enabled the contributions from isopropanol and 1-octene to be separated. The concentrations of each compound individually could be measured in a mixture with limits of detection less than 10 ppbv and linearity errors less than 1%. Demonstration of a separation of a mixture of chemically similar compounds, benzene and o-xylene, is also provided.
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Affiliation(s)
| | - Coco Day
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | | | | | - Wah O. Ho
- Alphasense Ltd., Sensor Technology House, 300 Avenue West, Skyline 120,
Great Notley, Essex CM77 7AA, U.K
| | - John R. Saffell
- SensorHut Ltd., Vision Park, Cambridge CB24 9ZR, U.K
- Alphasense Ltd., Sensor Technology House, 300 Avenue West, Skyline 120,
Great Notley, Essex CM77 7AA, U.K
| | - Tanya Hutter
- SensorHut Ltd., Vision Park, Cambridge CB24 9ZR, U.K
- Materials Science and Engineering Program and Texas Materials Institute, The University of Texas at Austin, 204 E. Dean Keeton Street, Austin, Texas 78712, United States
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
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Abstract
We address multi-walled carbon nanotubes (MWCNTs) for structural health monitoring in adhesive bonds, such as in building structures. MWCNT-loaded composites are employed to sense strain changes under tension load using an AC impedance measurement setup. Different weight percentages of 1, 1.5, 2 and 3 wt % MWCNTs are added to the base epoxy resin using different dispersion times, i.e., 5, 10, and 15 min. The equivalent parallel resistance of the specimens is first measured by applying an alternating voltage at different frequencies. To determine the mechanical as well as sensory properties, the specimens are then subjected to a tensile test with concurrent impedance measurement at a fixed pre-chosen frequency. Using alternating voltage, a higher sensitivity of the impedance reading can be achieved. Employing these sensors in buildings and combining the readings of a network of such devices can significantly improve the buildings’ safety. Additionally, networks of such sensors can be used to identify necessary maintenance actions and locations.
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Rydosz A. Sensors for Enhanced Detection of Acetone as a Potential Tool for Noninvasive Diabetes Monitoring. SENSORS 2018; 18:s18072298. [PMID: 30012960 PMCID: PMC6068483 DOI: 10.3390/s18072298] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2018] [Revised: 07/03/2018] [Accepted: 07/16/2018] [Indexed: 01/17/2023]
Abstract
Measurement of blood-borne volatile organic compounds (VOCs) occurring in human exhaled breath as a result of metabolic changes or pathological disorders is a promising tool for noninvasive medical diagnosis, such as exhaled acetone measurements in terms of diabetes monitoring. The conventional methods for exhaled breath analysis are based on spectrometry techniques, however, the development of gas sensors has made them more and more attractive from a medical point of view. This review focuses on the latest achievements in gas sensors for exhaled acetone detection. Several different methods and techniques are presented and discussed as well.
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Affiliation(s)
- Artur Rydosz
- Department of Electronics, AGH University of Science and Technology, 30-059 Krakow, Poland.
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