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Author: Zackery Ray Roberson Publisher: ISBN: Category : Languages : en Pages : 200
Book Description
In forensic chemistry, a quicker and more accurate analysis of a sample is always being pursued. Speedy analyses allow the analyst to provide quick turn-around times and potentially decrease back-logs that are known to be a problem in the field. Accurate analyses are paramount with the futures and lives of the accused potentially on the line. One of the most common methods of analysis in forensic chemistry laboratories is gas chromatography, chosen for the relative speed and efficiency afforded by this method. Two major routes were attempted to further improve on gas chromatography applications in forensic chemistry. The first route was to decrease separation times for analysis of ignitable liquid residues by using micro-bore wall coated open-tubular columns. Micro-bore columns are much shorter and have higher separation efficiencies than the standard columns used in forensic chemistry, allowing for faster analysis times while maintaining the expected peak separation. Typical separation times for fire debris samples are between thirty minutes and one hour, the micro-bore columns were able to achieve equivalent performance in three minutes. The reduction in analysis time was demonstrated by analysis of ignitable liquid residues from simulated fire debris exemplars. The second route looked at a relatively new detector for gas chromatography known as a vacuum ultraviolet (VUV) spectrophotometer. The VUV detector uses traditional UV and far-ultraviolet light to probe the pi and sigma bonds of the gas phase analytes as well as Rydberg traditions to produce spectra that are nearly unique to a compound. Thus far, the only spectra that were not discernable were from enantiomers, otherwise even diastereomers have been differentiated. The specificity attained with the VUV detector has achieved differentiation of compounds that mass spectrometry, the most common detection method for chromatography in forensic chemistry labs, has difficulty distinguishing. This specificity has been demonstrated herein by analyzing various classes of drugs of abuse and applicability to "real world" samples has been demonstrated by analysis of de-identified seized samples
Author: Zackery Ray Roberson Publisher: ISBN: Category : Languages : en Pages : 200
Book Description
In forensic chemistry, a quicker and more accurate analysis of a sample is always being pursued. Speedy analyses allow the analyst to provide quick turn-around times and potentially decrease back-logs that are known to be a problem in the field. Accurate analyses are paramount with the futures and lives of the accused potentially on the line. One of the most common methods of analysis in forensic chemistry laboratories is gas chromatography, chosen for the relative speed and efficiency afforded by this method. Two major routes were attempted to further improve on gas chromatography applications in forensic chemistry. The first route was to decrease separation times for analysis of ignitable liquid residues by using micro-bore wall coated open-tubular columns. Micro-bore columns are much shorter and have higher separation efficiencies than the standard columns used in forensic chemistry, allowing for faster analysis times while maintaining the expected peak separation. Typical separation times for fire debris samples are between thirty minutes and one hour, the micro-bore columns were able to achieve equivalent performance in three minutes. The reduction in analysis time was demonstrated by analysis of ignitable liquid residues from simulated fire debris exemplars. The second route looked at a relatively new detector for gas chromatography known as a vacuum ultraviolet (VUV) spectrophotometer. The VUV detector uses traditional UV and far-ultraviolet light to probe the pi and sigma bonds of the gas phase analytes as well as Rydberg traditions to produce spectra that are nearly unique to a compound. Thus far, the only spectra that were not discernable were from enantiomers, otherwise even diastereomers have been differentiated. The specificity attained with the VUV detector has achieved differentiation of compounds that mass spectrometry, the most common detection method for chromatography in forensic chemistry labs, has difficulty distinguishing. This specificity has been demonstrated herein by analyzing various classes of drugs of abuse and applicability to "real world" samples has been demonstrated by analysis of de-identified seized samples
Author: Ashur Rael Publisher: ISBN: Category : Languages : en Pages : 262
Book Description
In the area of forensic chemistry, improved or new analysis methods are continually being investigated. One common and powerful technique used in forensic chemistry is wall-coated open-tubular column (WCOT) gas chromatography with electron ionization single quadrupole mass spectrometry (GC-MS). Improvements to and effectiveness of alternatives to this instrumental platform were explored in an array of parallel inquiries. The areas studied included the column for the chromatographic separation, the universal detection method employed, and the fragmentation method used to enhance molecular identification. Superfine-micropacked capillary (SFμPC) columns may provide an alternative to commercial packed GC columns and WCOT GC columns that combines the benefits of the larger sample capacity of packed columns and the benefits of the excellent separation capabilities and mass spectrometry (MS) flow rate compatibility of WCOT columns. SFμPC columns suffer from high inlet pressure requirements and prior reported work has required specialized instrumentation for their use. Fabrication of and chromatography with SFμPC GC columns was successfully achieved with typical GC-MS instrumentation and within the flow rate limit of a MS. Additionally, the use of higher viscosity carrier gasses was demonstrated to reduce the required inlet pressure for SFμPC GC columns. Recently, a new vacuum ultraviolet spectrometer (VUV) universal detector has been commercialized for GC. The ability of VUV detectors to acquire absorbance spectra from 125 nm to 430 nm poses a potential alternative to MS. As such, GC-VUV provides an exciting potential alternative approach to achieving excellent quantitative and qualitative analysis across a wide range of analytes. The performance of VUV and MS detectors for forensic analysis in terms of quantitative and qualitative analysis was compared. Analysis of alkylbenzenes in ignitable liquids was explored, which can be important evidence from suspected arson fires and are difficult to differentiate with MS. The VUV detector was found to have superior specificity and comparable sensitivity to the MS detector in scan mode. Addition of thermolysis (Th) as an orthogonal fragmentation pathway provides the opportunity to increase the differences between MS fragmentation patterns. Fragmentation has been widely established to aid in identification of molecules with MS by providing characteristic fragments at characteristic relative abundances. However, molecules with very similar structures do not result in sizable spectral differences in all cases with typical MS fragmentation techniques. A series of Th units were fabricated and integrated into GC-Th-MS instruments. Th-MS was conducted with the thermally labile nitrate esters across a range of instrumentation and thermal conditions.
Author: Xinghua Guo Publisher: BoD – Books on Demand ISBN: 9535112279 Category : Science Languages : en Pages : 226
Book Description
For decades gas chromatography has been and will remain an irreplaceable analytical technique in many research areas for both quantitative analysis and qualitative characterization/identification, which is still supplementary with HPLC. This book highlights a few areas where significant advances have been reported recently and/or a revisit of basic concepts is deserved. It provides an overview of instrumental developments, frontline and modern research as well as practical industrial applications. The topics include GC-based metabolomics in biomedical, plant and microbial research, natural products as well as characterization of aging of synthetic materials and industrial monitoring, which are contributions of several experts from different disciplines. It also contains best hand-on practices of sample preparation (derivatization) and data processing in daily research. This book is recommended to both basic and experienced researchers in gas chromatography.
Author: Fabrice Mutelet Publisher: BoD – Books on Demand ISBN: 183962602X Category : Science Languages : en Pages : 123
Book Description
Gas chromatography is one of the most used analytical techniques in the industry. It is a powerful tool with a wide range of applications. This book presents recent advances in gas chromatography, multidimensional gas chromatography, and gas chromatography mass spectrometry. It also discusses inverse gas chromatography. The main focus is the use of gas chromatography techniques to analyze petroleum fluids, biomass, and ionic liquids in medical and petrochemical industries.
Author: Nelu Grinberg Publisher: CRC Press ISBN: 1000470881 Category : Science Languages : en Pages : 209
Book Description
For six decades, scientists and researchers have relied on the Advances in Chromatography series for the most up-to date information on a wide range of developments in chromatographic methods and applications. The clear presentation of topics and vivid illustrations for which this series has become known makes the material accessible and engaging to analytical, biochemical, organic, polymer, and pharmaceutical chemists at all levels of technical skill. Key Features: Discusses the basic concepts of affinity chromatography and examines recent developments in this method and related supramolecular separation methods. Outlines the different types of gradient stationary phases and how they have been used in and benefited the field of separation science. Reviews recent trends in detectors for GC, focusing on those that are readily available and seeing wide usage. Addresses peak compression in GELC and offers the reader a plate height equation to work with that incorporates its effects.
Author: Chih-Hao Wang Publisher: ISBN: Category : Languages : en Pages : 47
Book Description
Disinfection by-products (DBPs) are a significant concern in drinking water quality. Haloacetic acids, which are generated from disinfection processes, are one of the major groups in disinfection by-products. Because they induce potential harmful effects for human health, the US government has already established regulations to control the levels of haloacetic acids in drinking water. In order to control the presence of haloacetic acids in drinking water and monitor other potential harmful compounds, an appropriate analytical method is needed. In this study, a gas chromatography (GC) method was developed for detecting haloacetic acids in water. Three different derivatization reagents were compared for sensitivity enhancement in conjunction with mass spectrometry (MS) and vacuum ultraviolet (VUV) detection. A model study was first performed using acetic acid and then the study was extended to haloacetic acids. The sensitivity of GC-MS and GCVUV had been increased after the derivatization. However, it also had many shortcomings and challenges that needed to be overcome: (1) the efficiency of derivatization was low; (2) the benzyl alcohol derivatization caused many side reactions in complex samples and generated high intensities of interference noises. Further study will need to modify the GC-MS and GCVUV methods, especially for the detection of brominated trihaloacetic acids.
Author: Walter Jennings Publisher: Elsevier ISBN: 0323141072 Category : Science Languages : en Pages : 270
Book Description
Analytical Gas Chromatography is a free-standing introduction to and guide through the rapidly progressing field of analytical gas chromatography. The book is divided into 10 chapters that cover various aspects of analytical gas chromatography, from most advantageous column type to troubleshooting. The opening chapters of the book discuss the advantages of the open tubular column over the packed column. This topic is followed by significant chapters on various variables in the gas chromatographic process, including sample injection, stationary phase, carrier gas, and installation. The effect of changes in these variables on the solution elution order is also considered. A chapter also examines the influence of instrumental design features, such as excessive or unswept volumes in the flow path; suitability of the detection mode; and speed and fidelity of the data-handling equipment. The book also presents selected methods that have been employed to achieve better results for a given gas chromatographic problem. The application areas of gas chromatographic process, including food, flavor, fragrance, petroleum- and chemical-related, environment, biology, and medicine, are also presented. The concluding chapter addresses the basic troubleshooting knowledge and considers other chromatographic problems and methods for their rectification.
Author: Colin Poole Publisher: Elsevier ISBN: 0128206772 Category : Science Languages : en Pages : 936
Book Description
Gas Chromatography, Second Edition, offers a single source of authoritative information on all aspects relating to the practice of gas chromatography. A focus on short, topic-focused chapters facilitates the identification of information that will be of immediate interest for familiar or emerging uses of gas chromatography. The book gives those working in both academia and industry the opportunity to learn, refresh and deepen their understanding of fundamental and instrumental aspects of gas chromatography and tools for the interpretation and management of chromatographic data. Users will find a consolidated guide to the selection of separation conditions and the use of auxiliary techniques. This new edition restores the contemporary character of the book with respect to those involved in advancing the technology, analyzing the data produced, or applying the technique to new application areas. New topics covered include hyphenated spectroscopic detectors, micromachined instrument platforms, derivatization and related microchemical techniques, petrochemical applications, volatile compounds in the atmosphere, and more. Includes chapters written by recognized authoritative and visionary experts in the field, thus providing an overview and focused treatments on a single topic Provides comprehensive coverage of modern gas chromatography, from theory, to methods and selected applications Places modern developments in research literature into a general context not always apparent to inexperienced users of the techniques
Author: International Symposium on Advances in Chromatography, University of Houston Publisher: ISBN: Category : Gas chromatography Languages : en Pages :
Author: Zackery Ray Roberson
Author: Zackery Ray Roberson
Author: Ashur Rael
Author: Xinghua Guo
Author: Fabrice Mutelet
Author: Nelu Grinberg
Author: Chih-Hao Wang
Author: Walter Jennings
Author: Wolfgang Bertsch
Author: Colin Poole
Author: International Symposium on Advances in Chromatography, University of Houston