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Wang W, Chen H, Zhu W, Gong Z, Yin H, Gao C, Zhu A, Wang D. A two-staged adsorption/thermal desorption GC/MS online system for monitoring volatile organic compounds. ENVIRONMENTAL MONITORING AND ASSESSMENT 2023; 195:869. [PMID: 37347444 DOI: 10.1007/s10661-023-11431-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 05/27/2023] [Indexed: 06/23/2023]
Abstract
Real-time online monitoring of volatile organic compounds (VOCs) in ambient air is crucial for timely and effective human health protection. Here, we developed an innovative, automated two-staged adsorption/thermal desorption gas chromatography/mass spectrometry (GC/MS) system for real-time online monitoring of 117 regulated volatile organic compounds (VOCs). This system comprised a sampling unit, water management trap, two-staged adsorption/thermal desorption unit, thermoelectric coolers (TECs), and a commercial GC/MS system. By implementing a micro-purge-and-trap (MP & T) step and a two-staged adsorption/thermal desorption unit, the presence of interfering substances was effectively minimized. The utilization of a heart-cutting GC, combined with a single MS detector, facilitated the precise separation and detection of 117 C2-C12 VOCs, while circumventing the identification and coelution challenges commonly associated with traditional GC-FID or GC-FID/MS methods. The performance of our newly developed online system was meticulously optimized and evaluated using standard gas mixtures. Under optimal conditions, we achieved impressive results, with R2 values ≥ 0.9946 for the standard linear curves of all 117 VOCs, demonstrating a precision (RSD) ranging from 0.2% to 6.4%. When applied in the field monitoring, the concentration drifts for 10 ppbv standard gas mixtures were 0.01-5.64% within 24 h. Our study developed a system for online monitoring of 117 atmospheric VOCs with relatively high accuracy and robustness.
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Affiliation(s)
- Wenjun Wang
- School of Leisure Tourism, Chengdu Agricultural College, Chengdu, 611130, China
| | - Huan Chen
- Biogeochemistry & Environmental Quality Research Group, Clemson University, Clemson, SC, 29442, USA
| | - Wei Zhu
- Sichuan Branch, Shimadzu (China) Co., LTD, Chengdu, 610031, China
| | - Zhengjun Gong
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 611756, China.
- State-Province Joint Engineering Laboratory of Spatial Information Technology of High-Speed Rail Safety, Chengdu, 610756, China.
| | - Hui Yin
- Sichuan Shengshi Technology Co., LTD, Chengdu, 610031, China
| | - Chao Gao
- Hebei Sailhero Environmental Protection High-Tech Co., LTD, Shijiazhuang, 050035, China
| | - Anni Zhu
- School of Leisure Tourism, Chengdu Agricultural College, Chengdu, 611130, China
| | - Dongmei Wang
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 611756, China
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Liu Z, Liu C, He Z, Mu Y, Zhang C, Zhang Y, Liu P, Wang Y, Liu J. Evaluation of offline sampling for atmospheric C3-C11 non-methane hydrocarbons. J Environ Sci (China) 2022; 113:132-140. [PMID: 34963523 DOI: 10.1016/j.jes.2021.05.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 05/08/2021] [Accepted: 05/14/2021] [Indexed: 06/14/2023]
Abstract
The concentration variation of C3-C11 non-methane hydrocarbons (NMHCs) collected in several types of commercial flexible bags and adsorption tubes was systematically investigated using a gas chromatography-flame ionization detector (GC-FID) system. The percentage loss of each NMHC in the polyvinyl fluoride (PVF) bags was less than 5% during a 7-hr storage period; significant NMHCs loss was detected in aluminum foil composite film and fluorinated ethylene propylene bags. The thermal desorption efficiency of NMHCs for adsorption tubes filled Carbopack B and Carboxen1000 sorbents was greater than 95% at 300℃, and the loss of NMHCs in the adsorption tubes during 20-days storage at 4℃ was less than 8%. The thermal desorption efficiency for C11 NMHCs in the adsorption tube filled with Carbograph 1 and Carbosieve SⅢ absorbents was less than 40% at 300℃, and pyrolysis of the absorbents at 330℃ interfered significantly with the measurements of some alkenes. The loss of alkenes was significant when NMHCs were sampled by cryo-enrichment at -90℃ in the presence of O3 for the online NMHC measurements, and negligible for enrichment using adsorption tubes at 25℃. Although O3 scrubbers have been widely used to eliminate the influence of O3 on NMHC measurements, the loss of NMHCs with carbon numbers greater than 8 was more than 10%. Therefore, PVF bags and adsorption tubes filled Carbopack B and Carboxen1000 sorbents were recommended for the sampling of atmospheric NMHCs.
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Affiliation(s)
- Zhiguo Liu
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chengtang Liu
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Center for Excellence in Urban Atmospheric Environment, Institute of Regional Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhouming He
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Center for Excellence in Urban Atmospheric Environment, Institute of Regional Environment, Chinese Academy of Sciences, Xiamen 361021, China
| | - Yujing Mu
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Center for Excellence in Urban Atmospheric Environment, Institute of Regional Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chenglong Zhang
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Center for Excellence in Urban Atmospheric Environment, Institute of Regional Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuanyuan Zhang
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Center for Excellence in Urban Atmospheric Environment, Institute of Regional Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pengfei Liu
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Center for Excellence in Urban Atmospheric Environment, Institute of Regional Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuzheng Wang
- 3Clear Science & Technology Co., Ltd, Beijing 100029, China
| | - Junfeng Liu
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Center for Excellence in Urban Atmospheric Environment, Institute of Regional Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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3
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Fanizza C, De Berardis B, Ietto F, Soggiu ME, Schirò R, Inglessis M, Ferdinandi M, Incoronato F. Analysis of major pollutants and physico-chemical characteristics of PM2.5 at an urban site in Rome. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 616-617:1457-1468. [PMID: 29074245 DOI: 10.1016/j.scitotenv.2017.10.168] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/27/2017] [Accepted: 10/16/2017] [Indexed: 06/07/2023]
Abstract
Air quality data from a one year study at an urban roadside location in Rome are reported for major pollutants. Continuous concentration data of carbon monoxide, ozone, nitrogen dioxide, aromatic hydrocarbons and natural radioactivity were measured in the urban air of Rome from January 2016 to January 2017. Moreover, PM2.5 mass concentration and physico-chemical characteristics of single constituent particles are herein reported. Gaseous pollutants, except ozone, and PM2.5 showed maximum concentrations in December due to high atmospheric stability. O3 and NO2 trend analysis showed photochemical smog episodes in June and September. In September, during a photochemical smog episode the aromatic hydrocarbons contribution to ozone formation was experimentally proven. Pearson's coefficient among aromatic hydrocarbons and the ratio Toluene/Benzene (T/B) showed that pollutants were under the influence of vehicular traffic. Physico-chemical characterization of PM2.5 single particles, carried out by field emission scanning electron microscope combined with energy dispersive X-ray spectroscopy, displayed the presence of particle diversity from natural and anthropogenic origin. Four principal components in the PM2.5 were identified: carbonaceous particles, Ca-sulphates, soil dust and building structure particles, metal particles. The principal source of carbonaceous particles in this urban area consists of the motor vehicle exhausts and the heating systems in winter. Traces of S and sometimes S, Na, K were detected on varying percentages of carbonaceous particles. These data suggested that the carbonaceous particles act as vehicles for strong acids, prevalently H2SO4 and alkaline metal sulphates. A Saharan dust contribution to PM2.5 was found in different periods. Metal particles included iron oxide particles, metals oxide particles and Fe-rich metal compounds. The identification of chemical composition of individual particles provide useful information to determine their origin and formation processes.
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Affiliation(s)
- Carla Fanizza
- INAIL, DITSIPIA - Via R. Ferruzzi 38-40, 00143 Rome, Italy.
| | - Barbara De Berardis
- Italian National Institute of Health (ISS), Centre of Innovative Technologies in Public Health, Viale Regina Elena 299, 00161 Rome, Italy
| | - Federica Ietto
- INAIL, DITSIPIA - Via R. Ferruzzi 38-40, 00143 Rome, Italy
| | - Maria Eleonora Soggiu
- Italian National Institute of Health (ISS), Department of Environmental and Health, Viale Regina Elena 299, 00161 Rome, Italy
| | - Roberto Schirò
- INAIL, DITSIPIA - Via R. Ferruzzi 38-40, 00143 Rome, Italy
| | - Marco Inglessis
- Italian National Institute of Health (ISS), Department of Environmental and Health, Viale Regina Elena 299, 00161 Rome, Italy
| | - Marcello Ferdinandi
- Italian National Institute of Health (ISS), Department of Environmental and Health, Viale Regina Elena 299, 00161 Rome, Italy
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Ou-Yang CF, Hua HC, Chou YC, Teng MK, Liu WT, Wang JL. Two-dimensional gas chromatography with electron capture detection for the analysis of atmospheric ozone depleting halocarbons. J Chromatogr A 2017; 1499:158-164. [DOI: 10.1016/j.chroma.2017.04.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 03/27/2017] [Accepted: 04/02/2017] [Indexed: 12/01/2022]
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Characterization of thermal desorption with the Deans-switch technique in gas chromatographic analysis of volatile organic compounds. J Chromatogr A 2016; 1462:107-14. [PMID: 27492597 DOI: 10.1016/j.chroma.2016.07.070] [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: 05/05/2016] [Revised: 07/26/2016] [Accepted: 07/26/2016] [Indexed: 11/23/2022]
Abstract
This study presents a novel application based on the Deans-switch cutting technique to characterize the thermal-desorption (TD) properties for gas chromatographic (GC) analysis of ambient volatile organic compounds (VOCs). Flash-heating of the sorbent bed at high temperatures to desorb trapped VOCs to GC may easily produce severe asymmetric or tailing GC peaks affecting resolution and sensitivity if care is not taken to optimize the TD conditions. The TD peak without GC separation was first examined for the quality of the TD peak by analyzing a standard gas mixture from C2 to C12 at ppb level. The Deans switch was later applied in two different stages. First, it was used to cut the trailing tail of the TD peak, which, although significantly improved the GC peak symmetry, led to more loss of the higher boiling compounds than the low boiling ones, thus suggesting compound discrimination. Subsequently, the Deans switch was used to dissect the TD peak into six 30s slices in series, and an uneven distribution in composition between the slices were found. A progressive decrease in low boiling compounds and increase in higher boiling ones across the slices indicated severe inhomogeneity in the TD profile. This finding provided a clear evidence to answer the discrimination problem found with the tail cutting approach to improve peak symmetry. Through the use of the innovated slicing method based on the Deans-switch cutting technique, optimization of TD injection for highly resolved, symmetric and non-discriminated GC peaks can now be more quantitatively assessed and guided.
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Ou-Yang CF, Liao WC, Wang PC, Fan GJ, Hsiao CC, Chuang MT, Chang CC, Lin NH, Wang JL. Construction of a cryogen-free thermal desorption gas chromatographic system with off-the-shelf components for monitoring ambient volatile organic compounds. J Sep Sci 2016; 39:1489-99. [DOI: 10.1002/jssc.201501336] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 01/25/2016] [Accepted: 02/15/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Chang-Feng Ou-Yang
- Department of Chemistry; National Central University; Taoyuan Taiwan
- Department of Atmospheric Sciences; National Central University; Taoyuan Taiwan
| | - Wei-Cheng Liao
- Department of Chemistry; National Central University; Taoyuan Taiwan
| | - Pei-Chieh Wang
- Department of Chemistry; National Central University; Taoyuan Taiwan
| | - Gang-Jei Fan
- Department of Chemistry; National Central University; Taoyuan Taiwan
| | - Chien-Cheng Hsiao
- Department of Chemistry; National Central University; Taoyuan Taiwan
| | - Ming-Tung Chuang
- Graduate Institute of Energy Engineering; National Central University; Taoyuan Taiwan
| | - Chih-Chung Chang
- Research Center for Environmental Changes; Academia Sinica; Taipei Taiwan
| | - Neng-Huei Lin
- Department of Atmospheric Sciences; National Central University; Taoyuan Taiwan
| | - Jia-Lin Wang
- Department of Chemistry; National Central University; Taoyuan Taiwan
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7
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Liu C, Mu Y, Zhang C, Zhang Z, Zhang Y, Liu J, Sheng J, Quan J. Development of gas chromatography-flame ionization detection system with a single column and liquid nitrogen-free for measuring atmospheric C2–C12 hydrocarbons. J Chromatogr A 2016; 1427:134-41. [DOI: 10.1016/j.chroma.2015.11.060] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 11/17/2015] [Accepted: 11/18/2015] [Indexed: 10/22/2022]
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8
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Liao WC, Ou-Yang CF, Wang CH, Chang CC, Wang JL. Two-dimensional gas chromatographic analysis of ambient light hydrocarbons. J Chromatogr A 2013; 1294:122-9. [DOI: 10.1016/j.chroma.2013.04.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 04/03/2013] [Accepted: 04/04/2013] [Indexed: 11/29/2022]
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9
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Wang JL, Chang CC, Lee KZ. In-line sampling with gas chromatography-mass spectrometry to monitor ambient volatile organic compounds. J Chromatogr A 2012; 1248:161-8. [PMID: 22717034 DOI: 10.1016/j.chroma.2012.05.091] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 05/22/2012] [Accepted: 05/25/2012] [Indexed: 11/25/2022]
Abstract
An existing GC-MS/FID method coupling with the cryogenic trapping was improved to perform continuous field monitoring of 106 VOCs, covering a wide range of volatilities and polarities (C(2)-C(11) NMHCs, ≥C(1) halocarbons, toxic chlorinated compounds, ethers, some esters and ketones). Cryogenic enrichment was employed from the standpoints of higher signal-to-noise ratio, less carry-over and better protection of thermally labile compounds than chemical sorbent enrichment. However, cryogen consumption is large and creates a great logistical burden for field deployment. As a result, a new in-line sampling manifold was designed and incorporated into the system to separate the sampling from trapping during enrichment of ambient VOCs, which gave rise to two major advantages: (1) the sampling is performed by a pre-evacuated flask, which does not need cryogen when filling a sample, so that the sampling time can be extended to yield better sample representation (approximately one hour was chosen for the sampling time for hourly data resolution in this study) and (2) because the cryo-trapping only takes a short time period (3 min in this study), the consumption of cryogen is greatly reduced (4 L liquid nitrogen per sample for conventional cryo-trapping vs. 0.6L for the new method). The robustness of the automated GC-MS/FID coupling with in-line sampling for the 106 target compounds was assessed with a set of quality assurance criteria of system blank, wall effect, precision, linearity, detection limit and field test to support the field applicability of the method. The configuration of the proposed in-line sampling apparatus is simple and rugged, which can be easily built and connected with any GC or GC-MS and readily deployed in the field to perform high-quality continuous measurements of more than 106 VOCs.
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Affiliation(s)
- Jia-Lin Wang
- Department of Chemistry, National Central University, Chungli 320, Taiwan
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10
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Full-range analysis of ambient volatile organic compounds by a new trapping method and gas chromatography/mass spectrometry. J Chromatogr A 2011; 1218:5733-42. [DOI: 10.1016/j.chroma.2011.06.067] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 06/13/2011] [Accepted: 06/16/2011] [Indexed: 11/21/2022]
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11
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Peng H, Wang J, Shen Z, Wu D, Guan Y. A cryogen-free refrigerating preconcentration device for the measurement of C2 to C4 hydrocarbons in ambient air. Analyst 2011; 136:586-90. [DOI: 10.1039/c0an00563k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Su YC, Kao HM, Wang JL. Mesoporous silicate MCM-48 as an enrichment medium for ambient volatile organic compound analysis. J Chromatogr A 2010; 1217:5643-51. [DOI: 10.1016/j.chroma.2010.06.065] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 06/14/2010] [Accepted: 06/24/2010] [Indexed: 10/19/2022]
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13
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Wang CH, Chiang SW, Wang JL. Simultaneous analysis of atmospheric halocarbons and non-methane hydrocarbons using two-dimensional gas chromatography. J Chromatogr A 2010; 1217:353-8. [DOI: 10.1016/j.chroma.2009.11.053] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Revised: 11/17/2009] [Accepted: 11/17/2009] [Indexed: 11/25/2022]
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14
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Yuan Z, Lau AKH, Shao M, Louie PKK, Liu SC, Zhu T. Source analysis of volatile organic compounds by positive matrix factorization in urban and rural environments in Beijing. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jd011190] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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15
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Shao M, Lu S, Liu Y, Xie X, Chang C, Huang S, Chen Z. Volatile organic compounds measured in summer in Beijing and their role in ground‐level ozone formation. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jd010863] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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16
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Su YC, Chang CC, Wang JL. Construction of an automated gas chromatography/mass spectrometry system for the analysis of ambient volatile organic compounds with on-line internal standard calibration. J Chromatogr A 2008; 1201:134-40. [DOI: 10.1016/j.chroma.2008.03.071] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2008] [Revised: 03/13/2008] [Accepted: 03/14/2008] [Indexed: 11/29/2022]
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17
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Su H, Cheng YF, Shao M, Gao DF, Yu ZY, Zeng LM, Slanina J, Zhang YH, Wiedensohler A. Nitrous acid (HONO) and its daytime sources at a rural site during the 2004 PRIDE-PRD experiment in China. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007jd009060] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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18
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Tsai DH, Wang JL, Wang CH, Chan CC. A study of ground-level ozone pollution, ozone precursors and subtropical meteorological conditions in central Taiwan. ACTA ACUST UNITED AC 2008; 10:109-18. [DOI: 10.1039/b714479b] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Huang H, Liang M, Zhang X, Zhang C, Shen Z, Zhang W. Simultaneous determination of nine flavonoids and qualitative evaluation ofHerba Epimedii by high performance liquid chromatography with ultraviolet detection. J Sep Sci 2007; 30:3207-13. [DOI: 10.1002/jssc.200700262] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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20
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Quantitative in silico analysis of the selectivity of graphitic carbon synthesized by different methods. Anal Bioanal Chem 2007; 390:369-75. [DOI: 10.1007/s00216-007-1675-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Revised: 09/30/2007] [Accepted: 10/04/2007] [Indexed: 10/22/2022]
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21
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Wang CH, Chang CC, Wang JL. Devising an adjustable splitter for dual-column gas chromatography. J Chromatogr A 2007; 1163:298-303. [PMID: 17651745 DOI: 10.1016/j.chroma.2007.06.070] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 06/12/2007] [Accepted: 06/19/2007] [Indexed: 10/23/2022]
Abstract
A flow controlled adjustable splitter was configured from a Deans switch and employed in an automated dual column gas chromatographic (GC) system for analyzing mono-aromatic compounds. Volatile organic compounds (VOCs), thermally desorbed from the sorbent trap, were split by the adjustable splitter onto two columns of different phases for separation and then detection by flame ionization detection (FID). Unlike regular splitters in which the split ratio is passively determined by the diameter and/or length of the connecting columns or tubing, the split ratio in our adjustable splitter is controlled by the auxiliary flow in the Deans switch. The auxiliary flow serves as a gas plug on either side of the column for decreasing the sample flow in one transfer line, but increasing the flow in the other. By adjusting the auxiliary flow and therefore the size of the gas plug, the split ratio can be easily varied and favorable to the side of no auxiliary gas. As an illustration, two columns, DB-1 and Cyclodex-B, were employed in this study for separating benzene, toluene, ethylbenzene, xylenes, denoted as BTEX, in particular the structural isomers of o-, m-, p-xylenes. This configuration demonstrates that BTEX cannot be fully separated with either column, but can be deconvoluted by simple algebra if dual columns are used with a splitter. The applicability of the proposed concept was tested by analyzing a gas standard containing BTEX at different split ratios and with various sample sizes, all leading to a constant ratio of m-xylene versus p-xylene.
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Affiliation(s)
- Chieh-Heng Wang
- Department of Chemistry, National Central University, Chungli 320, Taiwan
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22
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Tanner D, Helmig D, Hueber J, Goldan P. Gas chromatography system for the automated, unattended, and cryogen-free monitoring of C2 to C6 non-methane hydrocarbons in the remote troposphere. J Chromatogr A 2006; 1111:76-88. [PMID: 16497314 DOI: 10.1016/j.chroma.2006.01.100] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Revised: 01/23/2006] [Accepted: 01/24/2006] [Indexed: 11/22/2022]
Abstract
An unattended, automated, on-line, cryogen-free, remotely controlled gas chromatography (GC) system was developed and has been deployed for more than 1 year for the continuous determination of C(2) to C(6) hydrocarbons at an observatory located at 2225 m elevation, on the summit caldera of an inactive volcano on the island of Pico, Azores. The GC instrument is tailored to the measurement challenges at this remote and high altitude site. All consumable gases are prepared in situ. Total power use remains below 700 W at all times. Sample collection and analysis is performed without use of cryogen. Hydrocarbons are concentrated on a one-stage trapping/injection system consisting of a Peltier-cooled multi-bed solid adsorbent trap. Analytes are detected after thermal desorption and separation on an alumina-PLOT (porous-layer open tubular) column by flame ionization detection (FID). Sample focusing, desorption, separation and detection parameters were thoroughly investigated to ensure quantitative collection and subsequent injection onto the GC system. GC operation is controlled remotely and data are downloaded daily. Sample volumes (600 and 3000 ml) are alternated for analysis of C(2) to C(3) and C(3) to C(6) hydrocarbons, respectively. Detection limits are in the low parts per trillion by volume (pptv) range, sufficient for quantification of the compounds of interest at their central North Atlantic lower free troposphere background concentrations.
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Affiliation(s)
- David Tanner
- Institute of Arctic and Alpine Research, University of Colorado at Boulder, 80309-0450, USA
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Wu TM, Wu GR, Kao HM, Wang JL. Using mesoporous silica MCM-41 for in-line enrichment of atmospheric volatile organic compounds. J Chromatogr A 2006; 1105:168-75. [PMID: 16209870 DOI: 10.1016/j.chroma.2005.09.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Revised: 09/12/2005] [Accepted: 09/13/2005] [Indexed: 11/15/2022]
Abstract
A mesoporous silica MCM-41 with pore size of 29A was synthesized and assessed for its applicability as a sorbent for in-line trapping of volatile organic compounds (VOCs) from air samples. Several commercially available microporous carbon molecular sieves, i.e., Carbosieve SIII, Carboxen 1000, Carboxen 1003, and Carbotrap purchased from Supelco, were employed to form either single sorbent traps or multi-sorbent traps for comparing adsorption properties with those of the silica MCM-41. A standard gas mixture containing more than 50 target compounds with size varying from C(2) to C(12) was adsorbed by these sorbents and the per carbon response of flame ionization detection (FID) for the target compounds was calculated for obtaining the adsorption profiles. While the multi-carbon sorbents show very uniform adsorption ability across the entire carbon range from C(3) to C(12), the mesoporous silica MCM-41, however, shows little sorption for smaller molecules from C(3) to C(7), but exhibit comparable sorption ability for C(8)-C(12) compounds. Desorption at various temperatures indicates that C(8)-C(12) compounds once trapped can be easily released at moderate temperatures of about 150 degrees C, whereas for carbon sorbents the desorption temperatures for sufficient recovery need to go beyond 300 degrees C due to much tighter hold-up in the microporous structure. Sorption ability for MCM-41 is also reflected on linearity. Compounds with sufficient sorption as suggested by the adequate per carbon response also exhibit excellent precision and linearity with R(2) close to unity, an important requirement for quantitative analysis of ambient VOCs.
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Affiliation(s)
- Tung-Min Wu
- Department of Chemistry, National Central University, Chungli 320, Taiwan
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Wang CH, Chang CC, Wang JL. Peak tailoring concept in gas chromatographic analysis of volatile organic pollutants in the atmosphere. J Chromatogr A 2005; 1087:150-7. [PMID: 16130708 DOI: 10.1016/j.chroma.2005.03.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
An automated gas chromatographic system aiming at performing unattended analysis of volatile organic compounds (VOCs) was developed in laboratory. To encompass VOCs of a wide range of volatility, two different designs of enrichment and separation methods were adopted and compared with performance in analyzing ozone precursors of C3-C12. In the dual-trap dual-column design, lower boiling species (C3-C6) are enriched and separated by one set of trap and column (porous layer open tubular (PLOT)), whereas the enrichment and separation for the higher boiling species (C6-C12) are performed by the other set (wall-coated open tubular (WCOT)). Undesired peaks also inevitably appear on both chromatograms often causing annoyances. To reduce complexity of both the apparatus and the resulting chromatograms, the heart-cut technique was adopted as a base for developing a system, which only uses one trap and one flame ionization detector for constructing two-dimensional GC with PLOT and DB-1. Methods were developed to allow the auxiliary flow pressure in the heart-cut device to be programmed to create dual effects, which not only can perform regular heart-cut actions but can also temporally hold up species in the precolumn for prescribed time intervals. Because it is characteristic for PLOT chromatograms to have reproducible blank retention time windows, segments of a DB-1 trace are produced by the auxiliary flow program aligning perfectly in time with the gaps of the PLOT trace. Subsequently, the two column flows are merged and channeled into single flame ionization detector to produce a very condensed "tailored" chromatogram which is equivalent to overlaying a PLOT and a DB-1 chromatogram on top of each other, except that no peaks are overlapped. This innovative "peak tailoring" concept based on the heart-cut technique is simple in design, easy to build, and extremely rugged for long-term continuous operation as fewer moving parts are involved, which is beneficial for deploying in remote monitoring stations.
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Affiliation(s)
- Chieh-Heng Wang
- Department of Chemistry, National Central University, Chungli 320, Taiwan
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