Advanced Chemometric Techniques for the Analysis of Complex Samples Using One- and Two-dimensional Gas Chromatography Coupled with Time-of-flight Mass Spectrometry PDF Download
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Author: Brooke C. Reaser
Publisher:
ISBN:
Category :
Languages : en
Pages : 172
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Book Description
Gas chromatography is a powerful separation technique that alone, and when coupled with mass spectrometric detection, can provide detailed information regarding the chemical composition of complex mixtures. Advanced chemometric algorithms are often applied to the data generated from these gas chromatographic separations in order to glean additional meaningful information from large and complex data sets. This dissertation presents several research investigations conducted on the development, optimization, application and study of several chemometric algorithms applied to one- and two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (TOFMS). The two-dimensional mass cluster method and principal component analysis (PCA) were applied to a non-targeted investigation of the stable-isotope incorporation of metabolites present in the metabolome of the methylotrophic bacteria Methylobacterium extorquens AM1 using gas chromatography time-of-flight mass spectrometry (GC-TOFMS). The area under the curve (AUC) of receiver operating characteristic (ROC) curves were used as quantitative metrics for the optimization of the tile-based Fisher ratio method using diesel fuel spiked with native and non-native analytes using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC – TOFMS). This optimized algorithm was then applied to a process analytical chemistry (PAC) investigation into the source of catalyst yield reduction in an industrial polymerization plant. Finally, a GC-TOFMS simulation-based study determined the chemometric limit of resolution for deconvoluting analytes using multivariate curve resolution alternating least squares (MCR-ALS) and compared the results to expected theory surrounding the probability of peak overlap.
Author: Brooke C. Reaser
Publisher:
ISBN:
Category :
Languages : en
Pages : 172
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Book Description
Gas chromatography is a powerful separation technique that alone, and when coupled with mass spectrometric detection, can provide detailed information regarding the chemical composition of complex mixtures. Advanced chemometric algorithms are often applied to the data generated from these gas chromatographic separations in order to glean additional meaningful information from large and complex data sets. This dissertation presents several research investigations conducted on the development, optimization, application and study of several chemometric algorithms applied to one- and two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (TOFMS). The two-dimensional mass cluster method and principal component analysis (PCA) were applied to a non-targeted investigation of the stable-isotope incorporation of metabolites present in the metabolome of the methylotrophic bacteria Methylobacterium extorquens AM1 using gas chromatography time-of-flight mass spectrometry (GC-TOFMS). The area under the curve (AUC) of receiver operating characteristic (ROC) curves were used as quantitative metrics for the optimization of the tile-based Fisher ratio method using diesel fuel spiked with native and non-native analytes using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC – TOFMS). This optimized algorithm was then applied to a process analytical chemistry (PAC) investigation into the source of catalyst yield reduction in an industrial polymerization plant. Finally, a GC-TOFMS simulation-based study determined the chemometric limit of resolution for deconvoluting analytes using multivariate curve resolution alternating least squares (MCR-ALS) and compared the results to expected theory surrounding the probability of peak overlap.
Author: Sarah Elizabeth Prebihalo
Publisher:
ISBN:
Category :
Languages : en
Pages : 151
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Book Description
Comprehensive two-dimensional gas chromatography (GCxGC) coupled with time-of-flight mass spectrometry (TOFMS) is a powerful analytical technique capable of separating complex mixtures, providing valuable information about the chemical composition of samples. However, the inherent data density associated with three-dimensional data provides a unique challenge to analytical chemists. As a result, significant effort has been invested in utilizing advanced chemometrics to glean meaningful information about samples from large and complex data sets. Herein, this dissertation introduces several investigations conducted on optimizing separation conditions to be amenable to chemometric deconvolution algorithms as well as the development, study, and application of advanced chemometric techniques applied to GCxGC-TOFMS data. To begin, the metric trilinear deviation ratio (TDR) is utilized to study the impact of experimental parameters such as column selection and modulation period, PM, on the quantitative accuracy of parallel factor analysis (PARAFAC) deconvolution. TDR scales with increasing change in second dimension retention time, delta2tR, associated with pseudo-isothermal conditions on the second dimension, 2D, and quantitative accuracy decreases as TDR increases. Two column sets were utilized with varying film thickness on the first column, 1D, and each column set was studied using two PM for a total of 4 experiments. It was reported that using 1D columns with larger film thicknesses allows the analyst to employ a shorter PM, in turn lowering the delta2tR, leading to higher quantitative accuracy. Many GCxGC-TOFMS studies relate to identifying class distinguishing analytes and can be tedious when performed manually. Fortunately, the use of discovery-based chemometric tools such as principal component analysis (PCA) and Fisher ratio (F-ratio) analysis has increased in popularity as less time-intensive and automated techniques for untargeted analyses. To begin, this dissertation will investigate mass channel purity obtained via the tile-based F-ratio algorithm using diesel fuel spiked with non-native analytes using GCxGC-TOFMS. The F-ratio algorithm, considered a supervised discovery technique because class membership is known a priori, was first used to "discover" the spiked non-native analytes. Then, using a novel signal ratio (S-ratio) algorithm, the mass channel selectivity information output by the F-ratio method was studied using three statistical metrics: null distribution analysis, p-value, and lack-of-fit (LOF). The result of this investigation revealed that a mass channel has a high likelihood of being pure when its p-value and LOF are sufficiently low. Finally, F-ratio analysis was applied to a dataset including patients with an anterior cruciate ligament (ACL) injury to discover potential biomarkers of post-traumatic osteoarthritis (PTOA) post-injury. Standard F-ratios are calculated by the between class variance divided by the sum of the within-class variance, scaling up as the between class variance increases and the within-class variance remains sufficiently small. However, many biological studies involve significant biological variance (~30%) that may not be associated with disease state or injury severity, etc. Herein, the standard tile-based F-ratio algorithm was modified to use only the within-class variance associated with control samples. It was expected that the control class contained less within-class variance relative to the patient class, due to the expectation that some patient samples would be associated with increased severity of injury or the presence of coexisting conditions. Hit lists (metabolites discovered via F-ratio) from standard F-ratio and control-normalized F-ratio were studied and directly compared to establish a comprehensive metabolome of potential biomarkers for PTOA development post ACL injury. Reported in this dissertation is a discussion on the complementary nature of standard and control-normalized F-ratio, followed by demonstration of class distinguishing metabolites via PCA.
Author: Christopher E. Freye
Publisher:
ISBN:
Category :
Languages : en
Pages : 320
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Book Description
A combination of four instrumental systems and five chemometric methods are shown to improve the efficiency and resolving power (i.e. peak capacity/ peak capacity production) of multi-dimensional gas chromatography (MDGC) as well as provide straightforward, easily interpretable chemical information. Implementation of a high speed pulse flow valve for two-dimensional gas chromatography (GC × GC) is shown to provide ultra-fast modulation with modulation periods (P[subscript]M) as short as 50 ms. Using a commercially available pulse flow valve, this injection technique performs a combination of vacancy chromatography and frontal analysis, whereby each pulse disturbance in the analyte concentration profile as it exits the first column (1D) results in data that is readily converted into a second separation (2D). A three-step process converts the raw data into a format analogous to a GC × GC separation, incorporating signal differentiation, baseline correction and conversion to a GC × GC chromatogram representation. For a P[subscript]M of 250 ms, the apparent peak width on the 2D, 2W[subscript]b, ranged from 12 to 45 ms producing a 2D peak capacity, 2n[subscript]c, of ~ 10, and the total peak capacity, n[subscript]c,2[subscript]D, was 4300 or a peak capacity production of 650 peaks/min. Next, the use of a high temperature diaphragm valve as a modulator for GC × GC facilitated separation temperatures up to 325 °C. Previous diaphragm valve technology limited use to 175 °C if the valve was mounted in the oven or to 265 °C if the valve was face mounted on the outside of the oven. A 44-component mixture was evaluated and the diaphragm valve created narrow, reproducible peaks on the 2D dimension leading to a peak capacity production of 300 peaks/min and had minimal retention time shifting on the 1D and 2D dimensions. In addition, the high temperature diaphragm valve was shown to increase the detection sensitivity by ~8 times compared to one-dimensional gas chromatography due to zone compression. Furthermore, the high temperature diaphragm valve was proven to be compatible with time-of-flight mass spectrometry (TOFMS). Finally a combination of the high temperature diaphragm valve and pulse flow valve yielded a three-dimensional gas chromatography system (GC3) that had a peak capacity production of 1000 peaks/min which is a ~5 times increase in efficiency compared to other GC3 systems. Investigation of novel chemometric techniques for the analysis of GC × GC is shown to be beneficial in extracting useful chemical information from complicated samples. Kerosene-based rocket fuels were analyzed via a GC × GC – FID system that implemented a high temperature diaphragm valve as a modulator. Using leave-one-out cross validation (LOOCV), the summed GC × GC – FID signal of three compound-class selective 2D regions (alkanes, cycloalkanes, and aromatics) was regressed against previously measured ASTM derived values. Additionally, a more detailed partial least squares (PLS) analysis was performed on compound classes (n-alkanes, iso-alkanes, mono-, di-, and tri-cycloalkanes, and aromatics) as well as the physical properties previously determined by ASTM methods (such as net heat of combustion, hydrogen content, density, kinematic viscosity, sustained boiling temperature and vapor rise temperature). The resulting models had low root mean square errors of cross validation (RMSECV) and had similar outcomes to previously reported results using a GC × GC – TOFMS. Using the information gained from the study, a more extensive study of predicting four physical properties (e.g., viscosity, heat of combustion, hydrogen content, and density) was undertaken using 74 different kerosene-based fuels. Highly reliable PLS models were developed that related chemical composition obtained via GC × GC – TOFMS to fuel properties obtained via ASTM methods. The PLS prediction of the four physical properties (e.g., viscosity, heat of combustion, hydrogen content, and density) had relatively low errors of RMSECV values of 0.0434, 38.1, 0.112, and 0.0037, respectively. Investigation of the linear regression vectors (LRVs) indicate the relationship between the chemical composition and physical properties enabling the chemical compositions of fuels to be altered to meet certain industrial specifications. Using a similar fuel set comprised of 36 kerosene-based fuels, the thermal stability was evaluated using a novel instrument, CRAFTI (Compact Rapid Assessment of Fuel Thermal Integrity). Using a chemometrics-based feature discovery algorithim, the chemical information obtained via GC × GC – TOFMS was correlated to the thermal integrity data. Certain forms of carbon that were deposited within the test article of the CRAFTI instrument were found to strongly correlate with increased backpressure and some of the more prevalent compounds were identified. Next, tile-based Fisher ratio (F-ratio) analysis was applied to tandem ionization time-of-flight mass spectrometry (TI – TOFMS) in order to enhance discovery-based analyses. A hard ionization energy (70 eV) and soft ionization energy (14 eV) were collected concurrently, and the discovery of 12 analytes spiked in diesel fuel was shown to be improved when the two ionization energies were used in tandem resulting in a higher discovery rate while also lowering the number of false positives. Using parallel factor analysis (PARAFAC) the analytes that were “discovered” were deconvoluted in order to obtain their identification via match values. Lastly, the limit of detection (LOD) and limit of quantification (LOQ) were improved by a novel integration method. Signal to noise (S/N) enhancement was theoretically studied using simulations and both the LOD and LOQ can be lowered by a factor of 3. When compared to the two-step, a commonly applied method for quantifying one-dimensional and two-dimensional, the integration method resulted in more accurate and precise measurements at low S/N.
Author: Lourdes Ramos
Publisher: Elsevier
ISBN: 008093269X
Category : Science
Languages : en
Pages : 324
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Book Description
The book reviews the basic concepts and highlights the most relevant advances and developments that have taken place in the field of comprehensive two dimensional gas chromatography (GC x GC) since its introduction in 1991. The several instrumental and technical approaches assayed and developed during these seventeen years and that have contributed to the development of this powerful separation technique and to its increasing application in many areas is explained and comprehensively illustrated through a number of chapters devoted these specific topics. More specialized aspects of the technique, including theoretical aspects, modelization of the chromatographic process, software developments, and alternative couplings is also covered. Finally, special attention is paid to data treatment, for both qualitative and quantitative analysis. This book will be a practical resource that will explain from basic to specialized concepts of GC x GC and will show the current state-of-the-art and discuss future trends of this technique. - Outlines basic concepts and principles of GCxGC technique for non-specialists to apply the technique to their research - Provides detailed descriptions of recent technical advances and serves as an instructional guide in latest applications in GCxGC - Sets the scene for possible future development and alternative new applications of technique
Author: Michal Holcapek
Publisher: Elsevier
ISBN: 0128117338
Category : Technology & Engineering
Languages : en
Pages : 522
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Book Description
Handbook of Advanced Chromatography /Mass Spectrometry Techniques is a compendium of new and advanced analytical techniques that have been developed in recent years for analysis of all types of molecules in a variety of complex matrices, from foods to fuel to pharmaceuticals and more. Focusing on areas that are becoming widely used or growing rapidly, this is a comprehensive volume that describes both theoretical and practical aspects of advanced methods for analysis. Written by authors who have published the foundational works in the field, the chapters have an emphasis on lipids, but reach a broader audience by including advanced analytical techniques applied to a variety of fields. Handbook of Advanced Chromatography / Mass Spectrometry Techniques is the ideal reference for those just entering the analytical fields covered, but also for those experienced analysts who want a combination of an overview of the techniques plus specific and pragmatic details not often covered in journal reports. The authors provide, in one source, a synthesis of knowledge that is scattered across a multitude of literature articles. The combination of pragmatic hints and tips with theoretical concepts and demonstrated applications provides both breadth and depth to produce a valuable and enduring reference manual. It is well suited for advanced analytical instrumentation students as well as for analysts seeking additional knowledge or a deeper understanding of familiar techniques. - Includes UHPLC, HILIC, nano-liquid chromatographic separations, two-dimensional LC-MS (LCxLC), multiple parallel MS, 2D-GC (GCxGC) methodologies for lipids analysis, and more - Contains both practical and theoretical knowledge, providing core understanding for implementing modern chromatographic and mass spectrometric techniques - Presents chapters on the most popular and fastest-growing new techniques being implemented in diverse areas of research
Author:
Publisher: Newnes
ISBN: 0444626247
Category : Science
Languages : en
Pages : 525
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Book Description
Gas chromatography mass spectrometry (GC-MS) has been the technique of choice of analytical scientists for many years. The latest developments in instrumentation, including tandem mass spectrometry (MS-MS) and time-of-flight (TOF) detectors, have opened up and broadened the scope of environmental analytical chemistry. This book summarizes the major advances and relevant applications of GC-MS techniques over the last 10 years, with chapters by leading authors in the field of environmental chemistry. The authors are drawn from academia, industry and government. The book is organized in three main parts. Part I covers applications of basic GC-MS to solve environmental-related problems. Part II focuses on GC-MS-MS instrumentation for the analyses of a broad range of analysis in environmental samples (pesticides, persistent organic pollutants, endocrine disruptors, etc.). Part III covers the use of more advanced GC-MS techniques using low- and high-resolution mass spectrometry for many applications related to the environment, food and industry. - Summarizes the major advances of GC-MS techniques in the last decade - Presents relevant applications of GC-MS techniques - Covers academic, industrial and governmental sectors
Author: Amanda Elizabeth Moses Sinha
Publisher:
ISBN:
Category : Gas chromatography
Languages : en
Pages : 410
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Book Description
Author:
Publisher: Academic Press
ISBN: 0128137460
Category : Science
Languages : en
Pages : 332
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Book Description
Basic Multidimensional Gas Chromatography is aimed at the next generation of multidimensional gas chromatography users who will require basic training in the fundamentals of both GC and GCxGC. This book fills the current need for an inexpensive, straightforward guidebook to get new users started. It will help new users determine when to add or purchase a multidimensional system and teach them to optimize and maximize the capability of each system. Readers will also learn to select specific modes for each portion of a multidimensional analysis. This ideal resource is a concise, hard-hitting text that provides the facts needed to get users up and running. Provides a comprehensive and fundamental introduction to multidimensional gas chromatography Assists readers in determining when to add or purchase a multidimensional system Explains how a given system can be used to its maximum capacity and how users should choose specific modes for different portions of multidimensional analysis
Author: Ahmed Mohamed Mostafa
Publisher:
ISBN:
Category :
Languages : en
Pages : 282
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Book Description
Comprehensive two-dimensional gas chromatography (GCxGC) is among the most powerful methods used to separate complex samples. Two columns of different selectivities are coupled in series through a special interface (modulator). The main role of the modulator is to trap and/or sample the primary column effluent and inject it into the secondary column. This results in an enhanced sensitivity, increased peak capacity and structured chromatograms. Practically all thermal modulators in use today are equipped with two trapping stages to prevent problems related to analyte breakthrough, which makes their design more complicated. In this work, The sensitivity of GCxGC coupled to two different detectors, time-of-flight mass spectrometer (GCxGC-TOFMS) and flame ionization detector (GCxGC-FID) was compared to the sensitivity of conventional one-dimensional gas chromatography (GC-TOFMS and GC-FID) by determining the limits of detection (LOD) for a series of different compounds such as n-alkanes and alcohols using both approaches. Different modulation periods were used for GCxGC ranging from 2 to 8 seconds. In addition, different types of inlet ferrules were used to study their effect on both systems. In general, the LODs in GCxGC were lower by at least an order of magnitude. A new liquid nitrogen-based single-stage cryogenic modulator was developed and characterized. In addition, a new liquid nitrogen delivery system was developed. Band breakthrough was prevented using changes in the carrier gas viscosity with temperature to reduce the carrier gas flow during desorption. Injection band widths for n-alkanes of 30-40 ms at half height were obtained. Most importantly, even the solvent peak could be perfectly modulated, which is impossible with any commercially available thermal modulator. Moreover, the newly developed liquid nitrogen supply system reduced liquid nitrogen consumption to ~30 L per day versus 50-100 L per day for commercially available modulators. Evaluation of the newly developed system for the GCxGC separation of some real samples such as regular gasoline and diesel fuel showed that the analytical performance of this single-stage modulator rivals that of the more complicated dual-stage designs. The technique was tested in various applications. Headspace solid phase microextraction in combination with GCxGC coupled to time-of-flight mass spectrometry (HS-SPME-GCxGC-TOFMS) were used for the detailed investigation of the impact of malolactic fermentation (MLF) using three commercial Oenococcus oeni strains on the volatile composition of Pinotage wines. The technique was also applied for the characterization of Pinotage wine volatiles and blue honeysuckle berries volatiles.
Author: Imma Ferrer
Publisher: John Wiley & Sons
ISBN: 047042995X
Category : Science
Languages : en
Pages : 281
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Book Description
Time of flight mass spectrometry identifies the elements of a compound by subjecting a sample of ions to a strong electrical field. Illuminating emerging analytical techniques in high-resolution mass spectrometry, Liquid Chromatography Time-of-Flight Mass Spectrometry shows readers how to analyze unknown and emerging contaminants—such as antibiotics, steroids, analgesics—using advanced mass spectrometry techniques. The text combines theoretical discussion with concrete examples, making it suitable for analytical chemists, environmental chemists, organic chemists, medicinal chemists, university research chemists, and graduate and post-doctorate students.
