1
|
Gaida M, Stefanuto PH, Focant JF. Theoretical modeling and machine learning-based data processing workflows in comprehensive two-dimensional gas chromatography-A review. J Chromatogr A 2023; 1711:464467. [PMID: 37871505 DOI: 10.1016/j.chroma.2023.464467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Revised: 10/15/2023] [Accepted: 10/17/2023] [Indexed: 10/25/2023]
Abstract
In recent years, comprehensive two-dimensional gas chromatography (GC × GC) has been gradually gaining prominence as a preferred method for the analysis of complex samples due to its higher peak capacity and resolution power compared to conventional gas chromatography (GC). Nonetheless, to fully benefit from the capabilities of GC × GC, a holistic approach to method development and data processing is essential for a successful and informative analysis. Method development enables the fine-tuning of the chromatographic separation, resulting in high-quality data. While generating such data is pivotal, it does not necessarily guarantee that meaningful information will be extracted from it. To this end, the first part of this manuscript reviews the importance of theoretical modeling in achieving good optimization of the separation conditions, ultimately improving the quality of the chromatographic separation. Multiple theoretical modeling approaches are discussed, with a special focus on thermodynamic-based modeling. The second part of this review highlights the importance of establishing robust data processing workflows, with a special emphasis on the use of advanced data processing tools such as, Machine Learning (ML) algorithms. Three widely used ML algorithms are discussed: Random Forest (RF), Support Vector Machine (SVM), and Partial Least Square-Discriminate Analysis (PLS-DA), highlighting their role in discovery-based analysis.
Collapse
Affiliation(s)
- Meriem Gaida
- Organic and Biological Analytical Chemistry Group (OBiAChem), MolSys Research Unit, Liège University, Belgium
| | - Pierre-Hugues Stefanuto
- Organic and Biological Analytical Chemistry Group (OBiAChem), MolSys Research Unit, Liège University, Belgium
| | - Jean-François Focant
- Organic and Biological Analytical Chemistry Group (OBiAChem), MolSys Research Unit, Liège University, Belgium
| |
Collapse
|
2
|
Boegelsack N, Sandau C, McMartin DW, Withey JM, O'Sullivan G. Development of retention time indices for comprehensive multidimensional gas chromatography and application to ignitable liquid residue mapping in wildfire investigations. J Chromatogr A 2020; 1635:461717. [PMID: 33254004 DOI: 10.1016/j.chroma.2020.461717] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 11/07/2020] [Accepted: 11/09/2020] [Indexed: 01/07/2023]
Abstract
In this study, we introduce a simple three-step workflow for a universally applicable RI system, to be used in GC×GC analysis of ignitable liquid residue (ILR) for arson investigations. The proposed RI system applies a combination of two well-established GC RI systems: non-isothermal Kovats (K) index in the first dimension and Lee (L) index in the second dimension. The proposed KLI RI system showed very good correlations when compared with predicted values and existing RI systems (r2 = 0.97 in first dimension, r2 = 0.99 in second dimension) and was valid for a wide range of analyte concentrations and operational settings (coefficient of variance (CV) < 1% in first dimension, < 10% in second dimension). Using the KLI RI, an ILR classification contour map was created to assist with the identification of ILR types within ASTM E1618. The contour map was successfully applied to neat fuels and a fire scene sample, highlighting the application to wildfire investigation. Standardizing the RI process and establishing acceptable error margins allows the exploration and comparison of comprehensive data generated from GC×GC analysis of ILRs regardless of location, time, or system, further enhancing comprehensive and tenable chemometric analyses of samples. Overall, the KLI workflow was inexpensive, quick to apply, and user-friendly with its simple 3-step design.
Collapse
Affiliation(s)
- Nadin Boegelsack
- Department of Earth and Environmental Sciences, Mount Royal University, 4825 Mount Royal Gate SW, Calgary, AB Canada, T3E 6K6; Department of Civil, Geological and Environmental Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK Canada, S7N 5A9.
| | - Court Sandau
- Department of Earth and Environmental Sciences, Mount Royal University, 4825 Mount Royal Gate SW, Calgary, AB Canada, T3E 6K6; Chemistry Matters Inc., 104-1240 Kensington Rd NW Suite 405, Calgary, AB Canada, T2N 3P7
| | - Dena W McMartin
- Department of Civil, Geological and Environmental Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK Canada, S7N 5A9
| | - Jonathan M Withey
- Department of Chemistry and Physics, Mount Royal University, 4825 Mount Royal Gate SW, Calgary, AB Canada, T3E 6K6
| | - Gwen O'Sullivan
- Department of Earth and Environmental Sciences, Mount Royal University, 4825 Mount Royal Gate SW, Calgary, AB Canada, T3E 6K6
| |
Collapse
|
3
|
Comparison of allelopathic effects of two typical invasive plants: Mikania micrantha and Ipomoea cairica in Hainan island. Sci Rep 2020; 10:11332. [PMID: 32647288 PMCID: PMC7347892 DOI: 10.1038/s41598-020-68234-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 05/08/2020] [Indexed: 11/08/2022] Open
Abstract
Mikania micrantha and Ipomoea cairica are two invasive plants widely distribute and seriously damage in Hainan island. In this study, the leaves extracts of two weeds were collected and determined for their allelopathic potentials on Chrysanthemum coronarium. The phytotoxicity bioassay showed that when the extract concentration was 50 and 100 mg/ml, the inhibited effects of M. micrantha on growth of C. coronarium were greater than by I. cairica. However, when the extract concertation at 400 mg/ml, the opposite inhibited effects were observed. We speculated this phenomenon was caused by different allelopathic compounds. Therefore, using gas chromatography-mass spectrometry, 19 and 23 compounds were identified respectively, benzoic acid and cinnamic acid were the main components in the two leaves extracts, which were selected to carry out the further bioassays. Subsequent bioassay results showed the effects of two allelochemicals on morphological index and chlorophyll content and POD activity were all negative to C. coronarium, whereas the content of MDA and activity of SOD, CAT represented adverse changes. Moreover, the inhibitions by cinnamic acid were generally greater than those by benzoic acid. Thus, the phenolic acids played the most crucial roles in the allelopathic effccts of M. micrantha and I. cairica leaves extracts.
Collapse
|
4
|
Jaramillo R, Dorman FL. Thermodynamic modeling of comprehensive two dimensional gas chromatography isovolatility curves for second dimension retention indices based analyte identification. J Chromatogr A 2020; 1622:461111. [DOI: 10.1016/j.chroma.2020.461111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 04/02/2020] [Accepted: 04/03/2020] [Indexed: 10/24/2022]
|
5
|
Jiang M. Facile Approach for Calculation of Second Dimensional Retention Indices in Comprehensive Two Dimensional Gas Chromatography with Single Injection. Anal Chem 2019; 91:4085-4091. [DOI: 10.1021/acs.analchem.8b05717] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ming Jiang
- School of Pharmacy, Tongji Medical College, Huazhong University of Science & Technology, #13 Hangkong Road, Wuhan, Hubei 430030, PR China
| |
Collapse
|
6
|
Regression algorithm for calculating second-dimension retention indices in comprehensive two-dimensional gas chromatography. J Chromatogr A 2018; 1569:178-185. [DOI: 10.1016/j.chroma.2018.07.038] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 06/21/2018] [Accepted: 07/06/2018] [Indexed: 11/21/2022]
|
7
|
Prodhan MAI, Sleman AA, Kim S, McClain C, Zhang X. Generalization of Reference System for Calculating the Second Dimension Retention Index in GC × GC–MS. JOURNAL OF ANALYSIS AND TESTING 2018. [DOI: 10.1007/s41664-018-0074-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
8
|
Prodhan MAI, Yin X, Kim S, McClain C, Zhang X. Surface fitting for calculating the second dimension retention index in comprehensive two-dimensional gas chromatography mass spectrometry. J Chromatogr A 2018; 1539:62-70. [PMID: 29395161 PMCID: PMC5826898 DOI: 10.1016/j.chroma.2018.01.049] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 01/22/2018] [Accepted: 01/23/2018] [Indexed: 11/21/2022]
Abstract
Comprehensive two-dimensional gas chromatography mass spectrometry (GC × GC-MS) has been widely used for analysis of volatile compounds. However, the second dimension retention index (I) of each compound is not widely used to aid compound identification owing to the limited accuracy of I calculation. We report a surface fitting approach to the calculation of I using n-alkanes (C7-C30) as references, where the second dimension retention time (2tR) and the second dimension column temperature (2Te) formed the X-Y plane and the I was the Z-axis to form the I surface. Compared to the conventional approach for calculating I using isovolatility curves, the surface fitting approach eliminated the construction of isovolatility curves for the reference compounds and gives better reproducibility. The goodness of the proposed surface fitting achieved R2 = 0.9999 and RMSE = 6.1 retention index units (iu). Ten-fold cross validation demonstrated the surface fitting approach had a good predictability with average R2 = 0.9999 and RMSE = 6.6 iu. The developed method was also applied to calculate the second dimension retention indices of compound standards in two commercial mixtures MegaMix A and MegaMix B. The mean standard deviation of the calculated I was only 1.6 iu for compounds in MegaMix A and 3.4 iu for compounds in MegaMix B. Compared with the literature results, the small value of standard deviation in the calculated retention index using surface fitting method shows that the surface fitting method has less measurement variability than the conventional isovolatility curve approach.
Collapse
Affiliation(s)
- Md Aminul Islam Prodhan
- Department of Chemistry, University of Louisville, Louisville, KY 40208, USA; University of Louisville Alcohol Research Center, Louisville, KY 40208, USA; University of Louisville Hepatobiology & Toxicology Program, Louisville, KY 40208, USA; Center for Regulatory and Environmental Analytical Metabolomics, University of Louisville, Louisville, KY 40208, USA
| | - Xinmin Yin
- Department of Chemistry, University of Louisville, Louisville, KY 40208, USA; University of Louisville Alcohol Research Center, Louisville, KY 40208, USA; University of Louisville Hepatobiology & Toxicology Program, Louisville, KY 40208, USA; Center for Regulatory and Environmental Analytical Metabolomics, University of Louisville, Louisville, KY 40208, USA
| | - Seongho Kim
- Biostatistics Core, Karmanos Cancer Institute, Department of Oncology, School of Medicine, Wayne State University, Detroit, MI 48201, USA
| | - Craig McClain
- University of Louisville Alcohol Research Center, Louisville, KY 40208, USA; University of Louisville Hepatobiology & Toxicology Program, Louisville, KY 40208, USA; Department of Pharmacology & Toxicology, University of Louisville, Louisville, KY 40208, USA; Department of Medicine, University of Louisville, Louisville, KY 40208, USA; Robley Rex Louisville VAMC, Louisville, KY 40292, USA
| | - Xiang Zhang
- Department of Chemistry, University of Louisville, Louisville, KY 40208, USA; University of Louisville Alcohol Research Center, Louisville, KY 40208, USA; University of Louisville Hepatobiology & Toxicology Program, Louisville, KY 40208, USA; Center for Regulatory and Environmental Analytical Metabolomics, University of Louisville, Louisville, KY 40208, USA; Department of Pharmacology & Toxicology, University of Louisville, Louisville, KY 40208, USA.
| |
Collapse
|
9
|
A regression model for calculating the second dimension retention index in comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry. J Chromatogr A 2016; 1451:127-134. [DOI: 10.1016/j.chroma.2016.04.068] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 04/21/2016] [Accepted: 04/25/2016] [Indexed: 11/22/2022]
|
10
|
Savareear B, Jacobs MR, Shellie RA. Multiplexed dual first-dimension comprehensive two-dimensional gas chromatography–mass spectrometry with contra-directional thermal modulation. J Chromatogr A 2014; 1365:183-90. [DOI: 10.1016/j.chroma.2014.09.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 09/03/2014] [Accepted: 09/05/2014] [Indexed: 10/24/2022]
|
11
|
Chin ST, Eyres GT, Marriott PJ. System Design for Integrated Comprehensive and Multidimensional Gas Chromatography with Mass Spectrometry and Olfactometry. Anal Chem 2012; 84:9154-62. [DOI: 10.1021/ac301847y] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sung-Tong Chin
- Centre for Green Chemistry,
School of Chemistry, Monash University,
Wellington Road, Clayton, VIC 3800, Australia
| | - Graham T. Eyres
- CSIRO Animal, Food and Health Sciences, PO Box 52, North Ryde, NSW 1670,
Australia
| | - Philip J. Marriott
- Centre for Green Chemistry,
School of Chemistry, Monash University,
Wellington Road, Clayton, VIC 3800, Australia
| |
Collapse
|
12
|
Meinert C, Meierhenrich UJ. Die umfassende zweidimensionale Gaschromatographie - eine neue Dimension für analytische Trennwissenschaften. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201200842] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
13
|
Meinert C, Meierhenrich UJ. A New Dimension in Separation Science: Comprehensive Two-Dimensional Gas Chromatography. Angew Chem Int Ed Engl 2012; 51:10460-70. [DOI: 10.1002/anie.201200842] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 04/12/2012] [Indexed: 11/11/2022]
|
14
|
|
15
|
Retention indices in comprehensive two-dimensional gas chromatography. Anal Bioanal Chem 2011; 401:2351-60. [DOI: 10.1007/s00216-011-5247-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 07/05/2011] [Accepted: 07/06/2011] [Indexed: 10/17/2022]
|
16
|
Zhao Y, Zhang J, Wang B, Kim SH, Fang A, Bogdanov B, Zhou Z, McClain C, Zhang X. A method of calculating the second dimension retention index in comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry. J Chromatogr A 2011; 1218:2577-83. [PMID: 21429495 DOI: 10.1016/j.chroma.2011.02.072] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2010] [Revised: 02/26/2011] [Accepted: 02/28/2011] [Indexed: 10/18/2022]
Abstract
A method was developed to calculate the second dimension retention index of comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC/TOF-MS) data using n-alkanes as reference compounds. The retention times of the C(7)-C(31) alkanes acquired during 24 isothermal experiments cover the 0-6s retention time area in the second dimension retention time space, which makes it possible to calculate the retention indices of target compounds from the corresponding retention time values without the extension of the retention space of the reference compounds. An empirical function was proposed to show the relationship among the second dimension retention time, the temperature of the second dimension column, and the carbon number of the n-alkanes. The proposed function is able to extend the second dimension retention time beyond the reference n-alkanes by increasing the carbon number. The extension of carbon numbers in reference n-alkanes up to two more carbon atoms introduces <10 retention index units (iu) of deviation. The effectiveness of using the proposed method was demonstrated by analyzing a mixture of compound standards in temperature programmed experiments using 6 different initial column temperatures. The standard deviation of the calculated retention index values of the compound standards fluctuated from 1 to 12 iu with a mean standard deviation of 5 iu.
Collapse
Affiliation(s)
- Yaping Zhao
- Department of Chemistry, University of Louisville, Louisville, KY 40292, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Solvation parameter model of comprehensive two-dimensional gas chromatography separations. J Chromatogr A 2009; 1216:1650-7. [DOI: 10.1016/j.chroma.2008.07.060] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 07/20/2008] [Accepted: 07/22/2008] [Indexed: 11/18/2022]
|
18
|
Reichenbach SE. Chapter 4 Data Acquisition, Visualization, and Analysis. COMPREHENSIVE ANALYTICAL CHEMISTRY 2009. [DOI: 10.1016/s0166-526x(09)05504-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
19
|
Zellner BD, Bicchi C, Dugo P, Rubiolo P, Dugo G, Mondello L. Linear retention indices in gas chromatographic analysis: a review. FLAVOUR FRAG J 2008. [DOI: 10.1002/ffj.1887] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
20
|
Comparative study of Eucalyptus dunnii volatile oil composition using retention indices and comprehensive two-dimensional gas chromatography coupled to time-of-flight and quadrupole mass spectrometry. J Chromatogr A 2008; 1200:34-42. [DOI: 10.1016/j.chroma.2008.05.070] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Revised: 05/21/2008] [Accepted: 05/26/2008] [Indexed: 11/23/2022]
|
21
|
Bieri S, Marriott PJ. Dual-Injection System with Multiple Injections for Determining Bidimensional Retention Indexes in Comprehensive Two-Dimensional Gas Chromatography. Anal Chem 2008; 80:760-8. [DOI: 10.1021/ac071367q] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stefan Bieri
- School of Applied Sciences, RMIT University, G.P.O. Box 2476V, Melbourne, Victoria, 3001, Australia
| | - Philip J. Marriott
- School of Applied Sciences, RMIT University, G.P.O. Box 2476V, Melbourne, Victoria, 3001, Australia
| |
Collapse
|
22
|
Seeley JV, Seeley SK. Model for predicting comprehensive two-dimensional gas chromatography retention times. J Chromatogr A 2007; 1172:72-83. [DOI: 10.1016/j.chroma.2007.09.058] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Revised: 09/20/2007] [Accepted: 09/25/2007] [Indexed: 10/22/2022]
|
23
|
Pierce KM, Hoggard JC, Mohler RE, Synovec RE. Recent advancements in comprehensive two-dimensional separations with chemometrics. J Chromatogr A 2007; 1184:341-52. [PMID: 17697686 DOI: 10.1016/j.chroma.2007.07.059] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 07/17/2007] [Accepted: 07/18/2007] [Indexed: 11/30/2022]
Abstract
Comprehensive two-dimensional (2D) separations provide the analyst with a tremendous amount of complex data. In order to glean useful information from this complex data, advancements in commercially available software that implement chemometrics are currently available and continue to evolve. Future advancements will no doubt involve commercializing (or adapting) specialized, in-house chemometric techniques that are currently found only in the hands of technical experts and researchers in industry, government, and academia. In order to make timely advancements, future commercialization of novel chemometric techniques should involve collaborations among instrument software manufacturers, professional programmers, technical experts, and researchers. During the last decade, this field has seen a steady advancement from single analyte target analysis to comprehensive non-target analysis of entire multidimensional sample profiles (involving sample classification and/or data mining for discovery-based sample comparisons). The advancements in instrumentation and chemometric software tools have a tremendous impact in various applications: fuels, food, environmental, pharmaceuticals, metabolomics, etc. Most of the development has been for software to apply with gas chromatography-based instrumentation, such as comprehensive two-dimensional gas chromatography (GC x GC) and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC x GC-TOF-MS). More recently there have been notable advancements in liquid-phase instrumentation as well.
Collapse
Affiliation(s)
- Karisa M Pierce
- Department of Chemistry, Box 351700, University of Washington, Seattle, WA 98195-1700 USA
| | | | | | | |
Collapse
|
24
|
Mondello L, Casilli A, Tranchida PQ, Lo Presti M, Dugo P, Dugo G. Comprehensive gas chromatography coupled to mass spectrometry for the separation of pesticides in a very complex matrix. Anal Bioanal Chem 2007; 389:1755-63. [PMID: 17589835 DOI: 10.1007/s00216-007-1412-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 05/18/2007] [Accepted: 05/31/2007] [Indexed: 11/28/2022]
Abstract
The present research is focused on the development of a comprehensive two-dimensional gas chromatography-rapid scanning quadrupole mass spectrometric (GC x GC-qMS) methodology for the analysis of trace-amount pesticides contained in a complex real-world sample. Reliable peak assignment was carried out by using a recently developed, dedicated pesticide MS library (for comprehensive GC analysis), characterized by a twin-filter search procedure, the first based on a minimum degree of spectral similarity and the second on the interactive use of linear retention indices (LRI). The library was constructed by subjecting mixtures of commonly used pesticides to GC x GC-qMS analysis and then deriving their pure mass spectra and LRI values. In order to verify the effectiveness of the approach, a pesticide-contaminated red grapefruit extract was analysed. The certainty of peak assignment was attained by exploiting both the enhanced separation power of dual-oven GC x GC and the highly effective search procedure.
Collapse
Affiliation(s)
- Luigi Mondello
- Dipartimento Farmaco-chimico, Facoltà di Farmacia, Università di Messina, viale Annunziata, 98168 Messina, Italy.
| | | | | | | | | | | |
Collapse
|
25
|
Zhu S, Lu X, Qiu Y, Pang T, Kong H, Wu C, Xu G. Determination of retention indices in constant inlet pressure mode and conversion among different column temperature conditions in comprehensive two-dimensional gas chromatography. J Chromatogr A 2007; 1150:28-36. [PMID: 17010352 DOI: 10.1016/j.chroma.2006.09.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 08/25/2006] [Accepted: 09/08/2006] [Indexed: 10/24/2022]
Abstract
A method to determine the second dimensional real retention time, dead times on both dimensions and retention indices in constant inlet pressure mode was developed in comprehensive two-dimensional gas chromatography. At the same time, the conversion of GC x GC retention indices among different column temperature conditions were also conducted based on some thermodynamics parameters. The calculation accuracies are better than 1.0 retention index unit. Furthermore, a retention index database was developed and used to identify the compounds in a cigarette essential oil sample. It showed that identification by the database was of close agreement with by time-of-flight mass spectrometry, and some isomers could also be distinguished based on the retention index database.
Collapse
Affiliation(s)
- Shukui Zhu
- National Chromatographic R&A Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | | | | | | | | | | | | |
Collapse
|
26
|
Pang T, Zhu S, Lu X, Xu G. Identification of unknown compounds on the basis of retention index data in comprehensive two-dimensional gas chromatography. J Sep Sci 2007; 30:868-74. [PMID: 17536732 DOI: 10.1002/jssc.200600471] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The identification of unknown compounds in complex samples is very difficult. Comprehensive two-dimensional gas chromatography (GC x GC) provides very good resolution and improved identification reliability. Mass spectrometry is a powerful identification tool and retention index data are another good approach to this end. In this study, a second-order polynomial was used to calculate retention index data based on n-alkanes beyond the region of the 'isovolatile' curve in GC x GC, and the results in the 2nd dimension were validated by using the same stationary phase column in one-dimensional GC. To test the usefulness of the method, volatile compounds in a tobacco leaf extract fraction were analyzed using GC x GC, and 60 compounds were identified on the basis of their retention indices.
Collapse
Affiliation(s)
- Tao Pang
- National Chromatographic R&A Center, Dalian Institute of Chemical Physics, The Chinese Academy of Sciences, Dalian, China
| | | | | | | |
Collapse
|
27
|
Tranchida PQ, Casilli A, Dugo P, Dugo G, Mondello L. Generation of Improved Gas Linear Velocities in a Comprehensive Two-Dimensional Gas Chromatography System. Anal Chem 2007; 79:2266-75. [PMID: 17288460 DOI: 10.1021/ac0618066] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A comprehensive two-dimensional gas chromatography (GC x GC) system (for convenience defined as "split flow" GC x GC), which may be operated at improved gas linear velocities in both dimensions, has been developed. The setup is formed of an apolar 30 m x 0.25 mm i.d. column connected, by means of a Y press fit, to a detector-linked 1 m x 0.1 mm i.d. polar analytical column, which passes through the (cryogenic) modulator, and to a 0.3 m x 0.1 mm i.d. retention gap, which is connected to a manually operated split valve. The latter enables the regulation of gas flows through the second analytical column [e.g., 60:40 (FID) ratio, 50:50 ratio, 40:60 (FID) ratio, etc.], in order to generate the most appropriate gas linear velocity, which is related to each specific analysis. In the pre-sent investigation, two sets of traditional and split flow GC x GC analyses were carried out on a cod liver oil fatty acid methyl ester sample by using the same temperature programs [180-250 degrees C at (a) 3 degrees C/min and at (b) 1.3 degrees C/min] and at an average first-dimension linear velocity of approximately 35.0 cm/s; thus, primary column retention times (and therefore elution temperatures) were essentially maintained. The second-dimension linear velocity was calculated to be approximately 333 cm/s in the traditional applications, while it was split valve-regulated until the most appropriate values [(a) approximately 213 cm/s; (b) approximately 264 cm/s] were attained in the alternative applications. Substantial improvements were observed and measured in the chromatography along the y-axis, while the contour plot chemical class structure was maintained.
Collapse
Affiliation(s)
- Peter Quinto Tranchida
- Dipartimento Farmaco-Chimico, Facoltà di Farmacia, Università di Messina, viale Annunziata, 98168-Messina, Italy
| | | | | | | | | |
Collapse
|
28
|
Bieri S, Marriott PJ. Generating Multiple Independent Retention Index Data in Dual-secondary Column Comprehensive Two-dimensional Gas Chromatography. Anal Chem 2006; 78:8089-97. [PMID: 17134144 DOI: 10.1021/ac060869l] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A method producing simultaneously three retention indexes for compounds has been developed for comprehensive two-dimensional gas chromatography by using a dual secondary column approach (GC x 2GC). For this purpose, the primary flow of the first dimension column was equally diverted into two secondary microbore columns of identical geometry by means of a three-way flow splitter positioned after the longitudinally modulated cryogenic system. This configuration produced a pair of comprehensive two-dimensional chromatograms and generated retention data on three different stationary phases in a single run. First dimension retention indexes were determined on a polar SolGel-Wax column under linear programmed-temperature conditions according to the van den Dool approach using primary alcohol homologues as the reference scale. Calculation of pseudoisothermal retention indexes in both second dimensions was performed on low-polarity 5% phenyl equivalent polysilphenylene/siloxane (BPX5) and 14% cyanopropylphenyl/86% dimethylpolysiloxane (BP10) columns. To construct a retention correlation map in the second dimension separation space upon which KovAts indexes can be derived, two methods exploiting "isovolatility" relationships of alkanes were developed. The first involved 15 sequential headspace samplings of selected n-alkanes by solid-phase microextraction (SPME), with each sampling followed by their injection into the GC at predetermined times during the chromatographic run. The second method extended the second dimension retention map and consisted of repetitive introduction of SPME-sampled alkane mixtures at various isothermal conditions incremented over the temperature program range. Calculated second dimension retention indexes were compared with experimental values obtained in conventional one-dimensional GC. A case study mixture including 24 suspected allergens (i.e., fragrance ingredients) was used to demonstrate the feasibility and potential of retention index information in comprehensive 2D-GC.
Collapse
Affiliation(s)
- Stefan Bieri
- School of Applied Sciences, RMIT University, G.P.O. Box 2476V, Melbourne, Victoria 3001, Australia
| | | |
Collapse
|
29
|
Adahchour M, Beens J, Vreuls R, Brinkman U. Recent developments in comprehensive two-dimensional gas chromatography (GC×GC). Trends Analyt Chem 2006. [DOI: 10.1016/j.trac.2006.03.002] [Citation(s) in RCA: 227] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
30
|
Arey JS, Nelson RK, Xu L, Reddy CM. Using Comprehensive Two-Dimensional Gas Chromatography Retention Indices To Estimate Environmental Partitioning Properties for a Complete Set of Diesel Fuel Hydrocarbons. Anal Chem 2005; 77:7172-82. [PMID: 16285663 DOI: 10.1021/ac051051n] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Comprehensive two-dimensional gas chromatography (GCxGC) provides nearly complete composition data for some complex mixtures such as petroleum hydrocarbons. However, the potential wealth of physical property information contained in the corresponding two-dimensional chromatograms is largely untapped. We developed a simple but robust method to estimate GCxGC retention indices for diesel-range hydrocarbons. By exploiting n-alkanes as reference solutes in both dimensions, calculated retention indices were insensitive to uncertainty in the enthalpy of gas-stationary-phase transfer for a suite of representative diesel components. We used the resulting two-dimensional retention indices to estimate the liquid vapor pressures, aqueous solubilities, air-water partition coefficients, octanol-water partition coefficients, and vaporization enthalpies of a nearly complete set of diesel fuel hydrocarbons. Partitioning properties were typically estimated within a factor of 2; this is not as accurate as some previous estimation or measurement methods. However, these relationships may allow powerful and incisive analysis of phase-transfer processes affecting petroleum hydrocarbon mixtures in the environment. For example, GCxGC retention data might be used to quantitatively deconvolve the effects of water washing and evaporation on environmentally released diesel fuels.
Collapse
Affiliation(s)
- J Samuel Arey
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Massachusetts 02543, USA.
| | | | | | | |
Collapse
|
31
|
Ryan D, Morrison P, Marriott P. Orthogonality considerations in comprehensive two-dimensional gas chromatography. J Chromatogr A 2005; 1071:47-53. [PMID: 15865172 DOI: 10.1016/j.chroma.2004.09.020] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
This study explores separation orthogonality with respect to comprehensive two-dimensional gas chromatography (GC x GC) for a range of different column polarities in the first dimension (1D), with two second dimension (2D) column types. Systematic variation in the net polarity of the first dimension allows the effect of column phase relative polarity on analyte retention in both the first and second dimensions to be evaluated. First dimension polarity manipulation significantly affects elution temperature (T(e)) of the analytes. This alters the magnitude of retention on the second dimension, and the extent of utility of separation space. By use of retention factor/temperature data in single column experiments, along with 1D T(e) data, retention on the 2D column can be estimated. This allows the two-dimensional separation to be predicted, and compared with experimental data. Predicted GC x GC peak positions corresponded favourably with the experimentally derived chromatograms, yielding a simple approach for predicting two-dimensional separations, using unique column set combinations.
Collapse
Affiliation(s)
- Danielle Ryan
- School of Applied Sciences, RMIT University, G.P.O. Box 2476V, Melbourne, Vic. 3001, Australia
| | | | | |
Collapse
|
32
|
Marriott PJ, Massil T, Hügel H. Molecular structure retention relationships in comprehensive two-dimensional gas chromatography. J Sep Sci 2004; 27:1273-84. [PMID: 15587276 DOI: 10.1002/jssc.200401917] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Comprehensive two-dimensional gas chromatography (GC x GC) offers new opportunities to develop relationships between molecular structure and retentions in the two dimensional (2D) separation space defined by the GC x GC retention in each dimension. Whereas single dimension GC provides only one retention property for a solute, and hence the specific relationship between retention and chemical property is not readily apparent or derivable, the 2D presentation of compounds in GC x GC provides a subtle and exquisite correlation of chemical property and retention unlike any other GC experiment. The 'orthogonality' of the two separation dimensions is intimately related to the manner in which different separation mechanisms, available through use of two dissimilar phases, are accessible to the different chemical compounds or classes in a sample mixture, and indeed the specific chemical classes present in the sample. The GC x GC experiment now permits various processes such as chemical decompositions, molecular interconversions, various non-linear chromatography effects, and processes such as slow reversible interactions that may arise with stationary phases or in the injector or column couplings, to be identified and further investigated. Here, we briefly review implementation of the GC x GC method, consider the molecular selectivity of GC x GC, and highlight a selection of molecular processes that can be probed by using GC x GC.
Collapse
Affiliation(s)
- Philip J Marriott
- Australian Centre for Research on Separation Science, School of Applied Sciences, RMIT University, Melbourne 3001, Australia.
| | | | | |
Collapse
|