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Gas-Liquid Partition Chromatography: The Separation and Micro-Estimation of Volatile Fatty Acids from Formic Acid to Dodecanoic Acid

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... GC utilizing columns with liquid stationary phase is known as gaseliquid chromatography (GLC) and as partition GC [24]. This is the most frequently used type of GC by far and the subject of primary attention in this chapter. ...
... The equilibrium of a solute distribution between two phases (stationary liquid polymer phase and mobile gas phase in partition GC) can be described by the distribution constant [2,20] ( partition constant [3e5, 7,8,24,25]): ...
... of the gas is frequently used in GC as a single gas velocity measure. It relates to the gas outlet velocity (u o ) as [2,4,6,24]: ...
Chapter
This chapter provides up-to-date theory of analytical gas chromatography (GC)—a technique of separation of components of mixtures (samples) with the purpose of obtaining information about their molecular composition. The theory presented here is designed to address such issues as the effect of column dimensions, carrier gas type and flow rate, temperature programming, and other factors on duration of analysis, the number of peaks that can be resolved, detection limits, and the trade-offs between these performance factors. To get simple and insightful mathematical descriptions of these relations, simplicity of the basic models becomes more important than their accuracy. As a general trend, this chapter favors simplicity over unnecessary accuracy. The secondary factors complicating the models are typically ignored. The chapter starts with the review of relevant theoretical information regarding interaction of organic compounds with liquid polymers, properties of ideal gases, and flow of ideal gases. This information is then used as a basis for addressing such core issues of GC theory as formation of retention times and other parameters of eluting solutes; formation of peak spacing and factors affecting reversal of peak order; and formation of peak widths. This material is used then as the basis for the study of the column optimization—the optimal flow rate, optimal heating rate, and optimal trade-off between a column separation performance, analysis time, and detection limit. The study of the optimization is preceded by the review of the column performance metrics and by formulations of optimization goals.
... In their publications from 1952, James and Martin both suggested a comprehensive theory for gas liquid partition chromatography based on the plate concept (see below), and demonstrated experimentally the separation of volatile acids and bases. [30,31] Detection and quantitation were carried out by titration of the eluted analytes with an automatic recording burette. ...
... However, the fact of the different axial flow velocity will not be further discussed here, as under the usual operation conditions it is a factor of minor significance. If being of interest, pressure-dependent velocities can be calculated and accounted for by appropriate correction factors as described by James and Martin [31] or retrieved from the literature. ...
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This contribution covers the major historic milestones of the evolution of gas chromatography (GC) from its beginnings to its current status as one of the most powerful analytical separation techniques, and demonstrates simultaneously how this technique has enabled and continuously improved the analysis of organic binding media in objects of cultural heritage. After an introduction into the basics of chromatography , the development of GC is traced from its emergence in the late 1800s as a mere preparative technique through a period of relative stagnation into the mid of the 20 th century. Then, the 1950s are covered by highlighting the major advances in theory and technology within this decade, all of which contributed to firmly consolidate the status of GC as a modern analytical separation technique. From there the maturing of GC is followed through the 1960s up to the present days, a period being marked by the transition from packed to capillary columns; the essential adaptation of injection and detection devices; the replacement of glass by fused silica as column material; major progresses in stationary phase chemistry; and, finally, the advent of the hyphenation of GC with mass spectrometric detection devices. Throughout this survey, examples of applications of contemporary GC techniques to binding media analysis are discussed to provide an illustrative historic record of the continuous improvements achieved. The account will be closed with critical reflections on GC's current relevance to and future role in the analysis of binding media in objects of cultural heritage.
... Analytical science in recent years has progressed spectacularly with the discovery of new separation methods, (Sahingil D. et al., 2019;Sivananthan M. et al., 2013). It is an important and integral components of analytical science because few instrumental methods can be directly used for quantitative analysis on account of the presence of interfering substances (Agrawal et al., 2006;James et al., 1952), Plant phytoconstituents as a source of medicinal actives have been reported in literature, since ancient times (Tewari D. et al., 2012;Tosun G. et al., 2012). Many plants are used as folk medicines to infectious diseases (Jan AK et al., 2019;Moghtader M. et al., 2016). ...
... The separation of compounds from a complex mixture (with posterior identification and quantification) leads to detailed understanding of the complexity of molecules inducing sensorial responses during food consumption. From a historical perspective, development of liquid chromatography dates back to 1941 and gas chromatography to 1952 (James and Martin, 1952;Martin and Synge, 1941). ...
Chapter
Sensory analysis is one of the core pillars of food science. The advances made in the last century greatly assisted in the study and production of foods. From a historical perspective, sensory analysis has gradually grown from an intrinsic concept of food to be stablished as a solid and have a central role in food science area. The area of meat and meat products is a relevant sector for sensory analysis application due to the core role played by these foods in the nutrition of mankind. This chapter presents the historical events of sensory analysis and meat science, the main concepts involved in sensory perception, and the current challenges in meat and meat product area that have meaningful connections with sensory analysis.
... Since that time, progress in the instrumental documentation and quantification of odors has been a slow and laborious process. The first step forward was the introduction of gas chromatography (GC), a powerful analytical chemistry technique that was first formalized by James and Martin in 1952 [5]. GC was quickly adopted to separate the individual compounds in complex odor mixtures with each detected compound appearing as a single peak in the analysis [6] [7]. ...
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The human olfactory system remains one of the most challenging biological systems to replicate. Humans use it without thinking, where it can equally offer protection from harm and bring enjoyment in equal measure. It is the system’s ability to detect and analyze complex odors, without the need for specialized infra-structure, that is the envy of many scientists. The field of artificial olfaction has recruited and stimulated interdisciplinary research and commercial development for several applications that include malodor measurement, medical diagnostics, food and beverage quality, environment and security. Over the last century, innovative engineers and scientists have been focused on solving a range of problems associated with measurement and control of odor. The IEEE Sensors Journal has published Special Issues on olfaction in 2002 and 2012. Here we continue that coverage. In this article, we summarize early work in the 20th Century that served as the foundation upon which we have been building our odor-monitoring instrumental and measurement systems. We then examine the current state of the art that has been achieved over the last two decades as we have transitioned into the 21st Century. Much has been accomplished, but great progress is needed in sensor technology, system design, product manufacture and performance standards. In the final section, we predict levels of performance and ubiquitous applications that will be realized during in the mid to late 21st Century.
... Chromatography is one of the most commonly applied technologies in the downstream processing of biomoecules (Carta & Jungbauer, 2010). In chromatographic field, model-based studies have emerged since 1940s (Martin & Synge, 1941;James & Martin, 1952;Wilson, 1940;DeVault, 1943;Craig, 1944) and, hitherto, extensive papers have been published (Guiochon et al., 2006;Antos & Seidel-Morgenstern, 2001;Aumann & Morbidelli, 2007;Hahn et al., 2014;Leweke & von Lieres, 2016). Identification of model parameters in model calibration step (i.e., parameter estimation) is inevitable in the framework of model-based studies, to further exploit models. ...
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Uncertainties from experiments and models render multi-modal difficulties in model calibrations. Bayesian inference and \textsc{mcmc} algorithm have been applied to obtain posterior distributions of model parameters upon uncertainty. However, multi-modality leads to difficulty in convergence criterion of parallel \textsc{mcmc} sampling chains. The commonly applied $\widehat{R}$ diagnostic does not behave well when multiple sampling chains are evolving to different modes. Both partitional and hierarchical clustering methods has been combined to the traditional $\widehat{R}$ diagnostic to deal with sampling of target distributions that are rough and multi-modal. It is observed that the distributions of binding parameters and pore diffusion of particle parameters are multi-modal. Therefore, the steric mass-action model used to describe ion-exchange effects of the model protein, lysozyme, on the \textsc{sp} Sepharose \textsc{ff} stationary phase might not be fully capable in certain experimental conditions, as model uncertainty from steric mass-action would result in multi-modality.
... Here, tR represents the retention time and tM is the dead time, which is usually experimentally calculated by using an unretained methane gas probe. Fa represents the volumetric flow rate, T represents the column temperature, Ta represents the ambient temperature, and j represents the James-Martin gas compressibility correction factor, which can be calculated from Equation (2) [45]: ...
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The desire to customize the properties of a material through complete control over both its chemical and architectural structure has created a constant and persistent need for efficient and convenient characterization techniques. Inverse gas chromatography (IGC) is considered a useful characterization method for probing the material’s surface properties, like its enthalpies of adsorption, which are the key stimulus components for their adsorption performance. Here, we conclusively review the significance of a less common application of the IGC technique for the physicochemical characterization of metal-organic frameworks (MOFs), which are an innovative subclass of porous materials with matchless properties in terms of structure design and properties. This review focuses on the fundamental theory and instrumentation of IGC as well as its most significant applications in the field of MOF characterization to shed more light on this unique technique.
... By applying the Martin-James gas compression correction factor j [28], the flow rate, F tm , through the column is given by: ...
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An electronic pressure control unit, coupled with a small built-in compressed air chamber, is applied to a field-portable gas chromatograph to precisely adjust the column head pressure with an accuracy of < 0.04% relative standard deviation. This system features a repetitive refill design of ambient air as the carrier gas through the use of a small diaphragm pump, thereby eliminating the need for external gas supplies or disposable cylinders. The flow rate of the separation column determined from the consumption rate of the air chamber matches exactly with the results of holdup time measurements of an unretained peak, as well as theoretical flow calculations within a 2% relative standard deviation. Mixtures of aromatic volatile organic compounds were then analyzed to demonstrate the performance of the built-in chamber-coupled electronic pressure control system. A 30 m × 0.28 mm × 1.0 μm capillary column operated at an isothermal temperature of 70 ℃ and an inlet pressure of 12 psig above atmospheric pressure provided a peak capacity of 60 with an analysis time of < 10 min for a vapor mixture of benzene, toluene, ethylbenzene, and o-xylene. The measurement cycle, including sample collection, injection, separation, and detection required a total time of only 15 min. The relative standard deviations of the retention time and the peak intensity variation during 40 h of operation were < 0.19% and < 0.74%, respectively, demonstrating the reproducibility and long-term stability of this process for continuous measurements. Such temperature programming of the constant head pressure and control of the flow rate ultimately allows faster analysis with very little peak broadening of the long retention peaks.
... A ce jour, il existe différentes techniques de mesures « on-line », les deux principales étant : la chromatographie en phase gazeuse (CPG) (James and Martin, 1952) et par spectrométrie de masse à transfert de protons (PTR-MS) (Hansel et al., 1995;Badjagbo et al., 2007). ...
Thesis
L’ozone et ses précurseurs gazeux, les oxydes d’azote (NOx) et les Composés atmosphériques majeurs. Les concentrations en ozone sont gouvernées par les émissions de ses précurseurs, sa production et sa consommation photochimique, les phénomènes de transport atmosphérique et de dépôt. Réduire efficacement les niveaux d’ozone pour atténuer ses effets néfastes sur la qualité de l’air, le climat et l’environnement, implique une bonne représentation de l’ensemble de ces facteurs. Pourtant ces derniers sont encore entachés d’incertitudes parmi lesquelles celles relatives aux émissions des COV, aux transformations chimiques de ces derniers et à la relation complexe et non linéaire entre l’ozone et ses précurseurs. Organiques Volatils (COV), restent encore aujourd’hui des polluants Dans ce contexte, ces travaux de thèse ont eu un double objectif : (1) mieux comprendre les sources d’émission des COV anthropiques et (2) mieux comprendre leur devenir ainsi que ceux des photo-oxydants à partir des observations collectées dans trois régions contrastées du globe : les moyennes latitudes Nord (Paris), le Bassin de la Méditerranée et l’Afrique de l’Ouest. Les observations in-situ de surface et aéroportées des campagnes internationales MEGAPOLI, ChArMEx et DACCIWA avec l’ATR-42 français de Safire ont été analysées par une approche source-récepteur et la mise en œuvre de métriques originales ou communément utilisées. Les sources urbaines des COV ont d’abord été évaluées pour la mégapole d’Istanbul grâce à la mise en œuvre du modèle multivarié PMF (Positive Matrix Factorization) et des rapports à l’émission appliqués aux données en COV de la campagne TRANSEMED, composante de ChArMEx. Les résultats montrent que le trafic n’apparaît pas comme la source dominante à Istanbul avec une contribution d’environ 16% contrairement aux autres villes de la Méditerranée de l’Est et que les inventaires globaux sous-estiment largement les émissions des COV. Le système ozone-NOy-COV a ensuite été caractérisé et comparé dans les panaches de couche limite des trois régions d’intérêt à partir de l’évaluation de l’état photo stationnaire, des régimes chimiques, de la réactivité potentielle des COV mesurés par le spectromètre de masse à transfert de protons (PTR-MS) embarqué et de la production de photo-oxydants au cours du transport. L’état photo-stationnaire est atteint aux abords des panaches avec un rapport de Leighton proche de l’unité. Aux moyennes latitudes, le régime chimique de production d’ozone dans les panaches est sensible aux COV tandis qu’en Afrique de l’Ouest les deux régimes coexistent (NOx ou COV-sensible). La distribution des COV dans les panaches est relativement homogène dans les trois régions, dominée par les COV oxygénés à hauteur de 70%. En pondérant par la réactivité, les COV biogéniques dominent largement la réactivité vis-à-vis du radical OH et la production potentielle 9 d’ozone. La production d’oxydants (O3 +NO2) et de COV oxygénés est observée et quantifiée au cours du transport du panache parisien.
... La chromatographie en phase gazeuse (GC), développée et utilisée pour la première fois au milieu du XX ème siècle [1], a depuis connu un essor considérable compte-tenu de ses performances en matière de séparation de composés volatils. En effet, nombre de mélanges complexes issus de domaines divers et variés ont pu profiter de son pouvoir résolutif. ...
... The t N value was measured for all molecular probes at 30°C, 40°C, 50°C, 60°C, and 70°C. Additionally, Q is the flow rate measured at the column outlet using a soap-bubble flowmeter at temperature T f , T is the column temperature, and j 2 3 is the James-Martin gascompressibility correction factor [Eq. (2)] (James and Martin, 1952): ...
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Capillary column inverse gas chromatography (CCIGC) was adapted to determine the thermodynamic properties of poly (styrene-co-butadiene) rubber (SBR) and various molecules, including aliphatic alkanes (C6, C7 and C8), alicyclics (C5 and C6)), aromatics (benzene and toluene), ethanol, tetrahydrofuran and acetonitrile. Capillary column inverse gas chromatography (CCIGC) was adapted to determine the thermodynamic properties of poly (styrene-co-butadiene) rubber (SBR) and various molecules, including aliphatic alkanes (C6, C7 and C8), alicyclics (C5 and C6)), aromatics (benzene and toluene), ethanol, tetrahydrofuran and acetonitrile. The results obtained were compared with those of the literature determined by packed column (PCIGC) and by other methods. It was revealed that the values of the heat of vaporization and the Hansen solubility parameter determined by CCIGC in some cases agree well with those of the literature, while in other cases deviates significantly. The comparison of the values of the literature obtained by PCIGC determined by different authors, significant differences were also observed in certain cases. This gap is undoubtedly related to the experimental errors occurred during the support treatment and/or during the preparation of the column. The activity coefficients of the solvents at infinite dilution were calculated and compared with those obtained by fitting the non-random two-liquid and universal quasichemical models.
... The effectiveness of separative techniques, mainly chromatography, coupled with MS in the analysis of known and unknown compounds, represents a foundation in modern instrumental analytical chemistry. Amongst the available separation techniques, GC became most employed in analytical chemistry laboratories thanks to the pioneering work in 1952 of James and Martin on partition chromatography [1]. The following years were fundamental for the development of a GC-MS-based instrumentation, as well detailed by Gohlke & McLafferty [2]. ...
Article
This review article traces the history of the use of liquid chromatography coupled with mass spectrometry (LC-MS) using electron ionization (EI) from the first attempts up to the present day. At the time of the first efforts to couple LC to MS, 70 eV EI was the most common ionization technique, typically used in gas chromatography-mass spectrometry (GC-MS) and providing highly reproducible mass spectra that could be collated in libraries. Therefore, it was obvious to transport this dominant approach to the early LC-MS coupling attempts. The use of LC coupled to EI-MS is challenging mainly due to restrictions related to high-vacuum and high-temperature conditions required for the operation of EI and the need to remove the eluent carrying the analyte before entering the ion source. The authors will take readers through a journey of about 50 years, showing how through the succession of different attempts it has been possible to successfully couple LC with EI-MS, which in principle appear to be incompatible.
... A limitation in the development of detection methods for analysis before 1990 can also be excluded. The use of gas chromatography as the essential method for the detection of chemical environmental substances (Van Leeuwen and de Boer, 2008) over time was analyzed with a literature search in Web of Science with the keywords indicated in Supplementary Material, Dataset S6: An increase of articles in the year 1991 can be observed, but the method has been in use since the 1950s(James and Martin, 1952; Supplementary Material, ...
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The ongoing decline in the biomass, abundance, and species number of insects is an established fact. Persistent, bioaccumulative, and toxic chemicals (PBTs) – persistent organic pollutants (POPs) and, in the case of our study, mercury (Hg) – play an important role, but their effect on insect populations is insufficiently investigated. Here, the current state of research on PBTs related to insects is examined with a systematic literature study using Web of Science™. We investigate time trends of research intensity compared with other organisms, insect orders and chemicals analyzed, chemicals' effects on insects, and geographical aspects. We show that research intensity increased in the early 1990s, but studies on PBTs in insects are still underrepresented compared with other organisms. The taxonomic focus lies strongly on dipterans. The predominance of studies on DDT suggests its relevance in the context of disease-vector management. Phenotypic and acute effects on insects were more often investigated than genotypic and chronic effects. Laboratory-bred insects and wild-bred insects were examined equally often, pollutant exposure and analysis were conducted predominantly in the laboratory. Mostly habitats with a medium or high human impact were studied and natural and near-natural habitats are understudied. The sources of the substances are often unknown. Most studies were carried out in economically rich continents, including North America, Europe, and Australia. The numbers of publications dealing with Asia, South America, and Africa are comparatively low, although the control of vector-borne diseases with POPs is still intensively practiced there. We identify gaps in the research — among others, refined analytical methods for biomarkers and for the examination of chronic effects, combinations of field and laboratory experiments to analyze the same problem, and a global approach for the monitoring of PBTs will be needed for accelerating the dearly needed progress in the research of PBTs in insects.
Chapter
Sampling and sample preparation are challenging tasks in the analytical processes. Therefore, the design and development of efficient, easy, fast, cheap, and environmentally friendly sampling and sample preparation techniques are a crucial issue before the analysis of target compound(s). On the other hand, miniaturization is a rapidly growing trend with the novel approaches and techniques in the past years. Analytical science was also affected by this superior technology like other areas of science. A large range of new approaches such as automation and micromachining provided the reduction in the dimensions of analytical tools (i.e. sampling, separation, and detection systems) and instruments with micro‐ to nanometer scale. The aim of this chapter is to introduce sampling and sample preparation techniques and provide an overview of the latest advancements on the design and development of rapid, facile, and environmentally friendly miniaturized sampling tools.
Chapter
Spectrophotometric detection is a common method of analysis in clinical laboratories where an analyte is detected and quantified using a visible (400–800 nm) or ultraviolet wavelength (below 380 nm). Atomic absorption and emission spectroscopy and fluorescence spectroscopy also fall under this broad category of spectrophotometric detection. Chemical sensors such as ion selective electrodes and pH meters are also widely used in clinical laboratories. Ions elective electrodes are the method of choice for detecting various ions such as sodium, potassium and related electrolytes in serum or plasma. For potassium ion selective electrode, valinomycin is commonly used. In blood gas machines sensors capable of detecting hydrogen ion (pH meter) and partial pressure of oxygen during blood gas measurements are used. Another analytical method used in clinical laboratories is chromatographic method including gas chromatography, high-performance liquid chromatography, as well as liquid chromatography combined with mass spectrometry of tandem mass spectrometry. Capillary electrophoresis is also used in clinical laboratories.
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The growing global population which is estimated to hit 9 billion by 2050 is considered a time bomb considering the scarce resources at the disposal of the nations. Hence, there is a need to identify a sustainable tool that could lead to an increase in the production of food production globally. Smart monitoring using biosensors ensure that chemical and other forms of contaminants are kept at bay from compromising the quality and safety of the stored food as well as the pest and pathogens that could affect fresh agricultural produce. Biosensors are also deployed for the purpose of measuring carbohydrates, alcohol, acids. Though present techniques in chromatography like high-performance liquid chromatography, capillary electrophoresis, flow immunoanalysis, gas chromatography, and spectroscopic techniques (Ultraviolet-visible spectroscopy, nuclear magnetic resonance spectroscopy, fourier-transform infrared spectroscopy) are advantageous because they are highly responsive, reliable, and efficient for pesticide residue analysis as well as the application of immunoanalysis in plant pathogen detection, and utilization of electrophoresis for plant nucleotide evaluation. However, these techniques are time-consuming, arduous, costly, complicated, and voluminous and involve the operation of qualified technicians. Hence, the application of biosensors has been identified as a reliable technology for effective detection of pathogen and pest affecting the increase in the agricultural production as well as utilized to reduce the impact of pesticides on farmlands and on the health of the farmers and residents. Therefore, this chapter intends to provide comprehensive detail about the application of biosensors for the identification of pest and pathogens affecting the increase in agricultural production. Numerous types of biosensors with high relevance in the detection of pest and pathogen were also highlighted.
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The hydrolysis of polysorbates, e.g. induced by specific host cell proteins in biologics, is a known risk factor regarding the potential particle formation in the product over time. One of the root causes for this observation is an increase in free fatty acids (FA) within the formulation, which indicates the need for convenient monitoring of FA release. This study presents a novel UPLC-QDa based method to evaluate the content of the FAs esterified to polysorbate 20 (PS20) after hydrolysis. The presented method is label-free, i.e. independent of elaborate fluorophore-labeling and able to directly measure the ionized FAs. Furthermore, the method allows the determination of released FAs as percentage of ester bond hydrolysis and as absolute concentration expressed in ng/mL. Additionally, we describe for the first time in FA analytics the application of an isolator column, to remove trace levels of FAs present in the eluents to improve the sensitivity of the method. Lastly, the capabilities of the newly developed method are proven in case studies with three different monoclonal antibodies, which display characteristic FA release patterns in PS20-containing formulations. In summary, we developed a reliable, sensitive method for FA quantification in biologics, which could also be used as a predictive tool, considering FA solubility, regarding the formation of particles.
Chapter
Gas chromatography (GC) has been used for the analysis of wine almost since its inception. While the focus of much research (both initially and currently) has been the application of GC for the analysis of volatiles associated with aroma, many other analytes can be measured by GC, including pesticides, sugars, acids, amines, polyphenols, and organic metal-containing compounds (e.g., organic selenium). This review will discuss selected current applications of GC for analysis of wines, while emphasizing future trends and challenges and providing an update since the first edition of this volume.
Chapter
Gas chromatography (GC) is used to detect and quantify chemical warfare agent (CWA)-related compounds in a variety of matrices since the early 1950s. A general description of nerve agents, vesicants, blood and pulmonary agents, toxins, and incapacitating agents is provided in this chapter, along with issues related to GC analysis of these compounds and CWA degradation products. Specialized sample introduction methods such as solid-phase microextraction and thermal desorption of sorbent tubes are discussed, along with derivatization, retention index systems, and selective detectors. Modern methods to monitor CWA-related compounds utilize open-tubular columns and flame- or mass spectrometric-based detectors in support of the multilateral Chemical Weapons Convention, forensic efforts, public health and military force protection capabilities and to study markers for CWA exposures or metabolites found in biomedical samples. The rapid defensive detection of CWA-related analytes outside of the laboratory is important to protect the health of civilian populations and deployed military personnel, and this need has driven research and development efforts to use GC in increasingly smaller field detection devices with both element-selective and mass spectrometric detection. Important milestones in instrument development, such as restively heated low thermal mass column assemblies and very small mass spectrometers for detection of CWA-related analytes in a field setting are discussed.
Chapter
This article provides an overview of the impact of technology and column development on the evolution of gas chromatography from inception to the present day. This is not a classic history of the subject but the recollections of the authors who individually participated in several of these developments or were eyewitnesses to the impact they had on the practice of gas chromatography. An emphasis is placed on the development of wall-coated open-tubular (capillary) columns as these were the driving forces for many of the improvements in separations and instrumentation.
Chapter
Gas chromatography is a prominent technique for the separation and detection of emerging and persistent environmental contaminants. It is generally the preferred technique for the analysis of volatile and semivolatile organic compounds including polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (dioxins) and polychlorinated dibenzofurans (dioxins), organochlorine pesticides (OCPs), halogenated flame retardants, polybrominated diphenyl ethers, perfluorinated compounds (PFCs), and polycyclic aromatic hydrocarbons (PAHs). Their environmental impact assessment frequently requires high resolution separation of isomers and congeners and selective and sensitive detection, typically by mass spectrometry. This chapter describes the main approaches to extraction from typical matrices, selection of appropriate separation and confirmation techniques, and detection strategies.
Chapter
Increased use of pesticides globally has led to harmful consequences on the environment, livestock, animals, as well as humans. Hence, its detection in animal feed, vegetables, agricultural crops, milk, eggs, and meat has become a pre-requisite. Conventional techniques such as High-Performance Liquid Chromatography (HPLC), Gas Chromatography (GC), Fourier transform Infrared Spectroscopy (FTIR), Mass Spectrometry (MS), Spectrophotometry, Polarography, etc., are generally being used in detection of pesticides. Alternatively, biosensors can be employed which are cost-effective and an easy way to detect pesticides. Biosensors can be differentiated based upon its biorecognition elements ranging from antibodies to cells. This chapter gives an overview of recent advances in biosensor development for the detection of pesticides with major emphasis on electrochemical biosensors.
Chapter
Gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS) represent powerful tools for the quantitative and structural analysis of plant lipids. Here, we outline protocols for the isolation, separation, and derivatization of plant lipids for subsequent GC and GC-MS analysis. Plant lipids are extracted with organic solvents and separated according to their polarity by thin-layer chromatography or solid phase extraction. As most lipids are not volatile, the analytes are derivatized by transmethylation or trimethylsilylation to enable the transition of the molecules into the gas phase. After separation on the polymer matrix of the GC column, the analytes are detected by flame ionization or mass spectrometry. This chapter includes methods suitable for the analysis of lipid-bound or free fatty acids, long chain alcohols, and monoacylglycerols and for the determination of double bond positions in fatty acids.
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In the concrete industry, legal disputes might occur when a built structure performs worse than it was supposed to during the design phase. When dealing with underperformance of self-healing concrete (e.g., no regain of water tightness after cracking), these disputes might likely be related to questioning if healing agents were actually included in the material or not. In this study, a methodology based on Gas chromatography is proposed to detect and quantify poly-lactic acid based-healing agents in cementitious materials. The applicability of this technique for this purpose has been demonstrated on mortar and concrete powders with and without healing agents. The amount of material needed to conduct the experiment is less than 200 mg, making the technique suitable for on-site application to limit any destructive action as much as possible. The application of gas chromatography to detect and quantify healing agent inclusions in concrete has the potential to be extended to other additives, depending on their composition.
Thesis
Les BTEX est une famille de polluants très répandue en air intérieur. Ils présentent des effets nocifs sur la santé humaine à des faibles concentrations ce qui a emmené le législateur à fixer des seuils afin de limiter l'exposition des gens. L'objectif de ce travail de recherche est de développer et de mettre en place une méthode analytique sensible, précise et rapide basée sur un dispositif de mesure. Le dispositif ainsi mis en place est un chromatographe en phase gazeuse miniaturisé équipé d'un mini détecteur à photo ionisation dédié à la détection des BTEX en temps quasi-réel. Le système analytique est très portable ayant une consommation gazeuse très faible assurant une autonomie élevée sur de longues durées. Son mode de fonctionnement se base sur l'échantillonnage de l'air dans une boucle connecté à une vanne six voies. L'injection de l'échantillon sur une colonne analytique placée dans un four pour la séparation est assurée par le changement de la position de la vanne avant la détection par photo ionisation. Le nouveau dispositif miniaturisé a été déployé lors de deux campagnes intensives menées dans un collège énergétiquement performant. Cette étude a porté sur la surveillance temporelle de la concentration des polluants présents en air intérieur, y compris les BTEX. Les résultats ainsi obtenus pour les BTEX avec notre dispositif ont été comparés à ceux fournis par d'autres techniques dites techniques de référence. Ces campagnes de terrain ont permis donc de valider les performances analytiques, la robustesse et l'autonomie de cette nouvelle méthodologie.
Chapter
Chromatography is simultaneously a process, a method, and a branch of science. It may be classified in different ways; one approach distinguishes planar techniques from those involving a column. It provides both qualitative and quantitative information as well as being applicable at the ultra-trace level and preparative scale. Coverage of this monograph includes all aspects of chromatography with the exception of large-scale industrial applications. This chapter serves as an introduction to chromatography and to the rest of the monograph.
Thesis
De nombreuses études ont démontrées l'implication du microbiote intestinal dans la physiologie et la physiopathologie de l'hôte. Parmi les bactéries probiotiques, Escherichia coli Nissle 1917 a été décrite pour ses propriétés analgésiques. L'étude d'extraits lipidiques de cette bactérie par spectrométrie de masse à haute résolution a permis d'identifier le C12AsnGABA, un lipopeptide qu'elle synthétise via son ilot pks. In vivo, le C12AsnGABA est capable d'inhiber l'hypersensibilité viscérale. Ce lipopeptide bactérien possède donc des propriétés analgésiques. Afin de déterminer si le C12AsnGABA appartient à une nouvelle famille lipidique, nous avons étendu l'analyse à plusieurs espèces bactériennes et mis en place un workflow analytique de chromatographie liquide couplée à la spectrométrie de masse en tandem à haute résolution spécifique aux lipopeptides. Celui-ci, comprend plusieurs étapes interconnectées entres-elles et indispensables ayant été optimisées séparément. Vingt-trois nouveaux lipides bactériens ont ainsi pu être caractérisés. Classiquement, l'élucidation structurale de ces composés est réalisée en électrospray à l'aide de la spectrométrie de masse en tandem après de la fragmentation par dissociation induite par collision. Lors de ma thèse, nous avons combiné les modes d'activation résonnant et non résonnant afin de mettre en évidence les pertes consécutives et les pertes directes pour permettre une meilleure compréhension des mécanismes de fragmentations impliqués. Parmi les résultats obtenus, des ions fragments produits inattendus ont été découverts et ont fait l'objet d'une seconde étude. Les courbes d'évolutions des profils en fonction de l'énergie ont été réalisées et ont permis de mettre en évidence pour la première fois la présence de courbes Gaussiennes élargies et de courbes multi-composites. Ce comportement, jamais décrit auparavant, questionne sur l'origine de ces processus qui semblent être indépendant de l'instrumentation. Nous avons considéré la possibilité que deux chemins réactionnels puissent mener à la formation d'un même ion produit fragment dans le cas des courbes Gaussiennes élargies. Dans le cas des courbes composites, nous avons émis l'hypothèse que deux chemins réactionnels, le premier à basse énergie et le second à plus haute énergie menait chacun à la formation d'un ion de structure différente mais de masse identique. Par des analyses de mobilité ionique cyclique couplée à de la spectrométrie de masse et des calculs quantiques, nous avons pu confirmer nos hypothèses. Ces travaux de thèse ont permis d'identifier 23 nouveaux composés produits par le microbiote intestinal. Leur caractérisation structurale nous a permis de d'identifier des comportements de fragmentation inattendu générant des ions fragments d'acides gras jamais décrits. Nous avons démontré que deux chemins réactionnels pouvaient exister pour générer deux ions produits de même rapport masse sur charge mais de structures différentes, se traduisant par des courbes composites.
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The history of the development of extraction techniques is long and varied, linked to other scientific developments and advances. This chapter presents a list that provides a history of both the extraction techniques used and their accompanying chromatographic analytical techniques. Perhaps the birth of solid–liquid extraction can be attributed to Franz von Soxhlet whose invention of the Soxhlet extractor revolutionized the extraction of compounds from solid matrices. Whereas the birth of chromatography is often being attributed to M. Tswett. His early experimental set‐up used solid particles, packed in a column, for the separation of leaf pigments. Tswett is also attributed with coining the phrase chromatography, from the Greek chroma (colour) and graphein (to write).
Article
The boron-based ceramics namely hexagonal boron nitride (h-BN) and boron phosphate (BPO4) were synthesized and characterized by Fourier transform infrared spectroscopy and X-ray diffraction analysis. The surface properties of h-BN and BPO4 were examined by inverse gas chromatography method. The dispersive surface energy and the acidic-basic character of h-BN, and BPO4 surfaces were estimated by the retention time with probes such as n-hexane, n-heptane, n-octane, n-nonane, n-decane, acetone, ethyl acetate, dichloromethane, chloroform and tetrahydrofuran at infinite dilution region. The dispersive surface free energies calculated using both Schultz and Dorris–Gray methods, decreased linearly with increasing temperature. The specific adsorption free energy and the specific adsorption enthalpy corresponding to acid–base surface interactions were determined. By correlating with the donor and acceptor numbers of the probes, the acidic and the basic parameters of the h-BN and BPO4 were calculated. The values obtained for and parameters indicated that h-BN has a basic character, whereas BPO4 has an acidic character.
Chapter
The combined use of multidimensional gas chromatography (MDGC)—in either heart-cutting or comprehensive configuration—to mass spectrometry (MS) generates a very powerful three-dimensional platform. The potential of MDGC-MS within the context of various scenarios is herein described and highlighted; technical aspects related to such a hyphenation are also discussed. The combination of heart-cutting MDGC with MS is much more established and is characterized by no specific technical difficulties (practically the same as for GC-MS instrumentation). For such a reason, particular focus will be devoted to the combination comprehensive MDGC-MS, and on aspects related to its evolution mainly after 2010.
Article
The task of multipurpose analysis of biological samples and identification of individual compounds in them is actual for many organizations in various fields; the results of such analyses can affect lives. The most frequently used, most accurate, and highly sensitive method used for this kind of analysis is the combination of gas/liquid chromatography and high-resolution mass spectrometry. However, in some areas, it is necessary to increase the reliability of compound identification. In this paper, we present a method that combines the reaction of oxygen isotope exchange with mass spectrometry; the method allows to increase the reliability of identification of individual compounds. Oxygen isotope exchange reaction is a "selective" one, which means that not all oxygen present in the molecule can exchange, but only in certain functional groups. Thus, by the number of isotope exchanges that have occurred in this molecule, the right structural formula might be more accurately chosen. The method was tested both on pure pharmaceutical substances and on real human urine samples. In both cases, the effectiveness of the method was shown: the number of expected exchanges in known substances coincided with the experimental one, and from several possible structures of unknown substances, the correct one was chosen based on the number of isotope exchanges.
Article
This review focuses on the microextraction and determination methods of harmful substances in various complex matrices in food, herbal plants, and soil since 2011. The general characteristics of different microextraction and detection methods are introduced and compared, and some novel development and application examples are listed to show their potential in the analysis of harmful substances in complex matrices. In many cases, preliminary steps of analyte enrichment/separation are required before an analysis. Microextractions such as matrix solid-phase dispersion microextraction, headspace solid-phase microextraction, dispersive micro-solid phase extraction, etc., are considered to be a green extraction method that conforms to the principle of sustainable development and has therefore received extensive attention. In addition, common analytical methods for detecting harmful substances in various matrices are discussed, such as high-performance liquid chromatography, high-performance liquid chromatography-mass spectrometry, gas chromatography, gas chromatography-mass spectrometry, capillary electrophoresis, and capillary electrophoresis-mass spectrometry. This paper provides support and demonstration for the development of new microextraction and determination methods for harmful substances in food, herbal plants, and soil.
Chapter
Separation instruments including gas chromatography, high pressure/performance liquid chromatography, capillary electrophoresis, and ion chromatography have become a part of most of the analytical laboratories. These methods are primarily used for the separation of complex samples and quantitation of a target analyte in the sample. Some of these instruments are miniaturized in nature and can be carried to the analysis site. However, most of them are not portable. In recent years, the interest in the fabrication of portable separation instrument has been continuously increasing. This chapter provides information on the requirements for miniaturization of the most commonly used instruments. Also, it reviews attempts to construct portable hyphenated instruments.
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Chromatography is a technique that uses the difference in the partition coefficient of a compound between the stationary phase and the mobile phase to separate the mixture. The stationary phase is a solid-phase carrier that is immobilized during the separation process and its ligands loaded on the surface of the carrier. The mobile phase is a fluid that moves relative to the stationary phase during the separation process and is mainly used to carry solute molecules through the stationary phase. In the course of more than 100 years of development, chromatographic technology has formed two major branches of liquid chromatography and gas chromatography. The mobile phase of the former is liquid and the latter is gas. Liquid chromatography can be divided into normal phase chromatography, reverse-phase chromatography, ion exchange chromatography, and affinity chromatography according to the separation mechanism. In recent years, the rapid development of mixed-mode chromatography has generated considerable interest because it has a different mechanism of action and application characteristics than other chromatographic modes. This chapter will review the birth and development of chromatography focusing on mixed-mode chromatography.
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Analytical Techniques in Biosciences: From Basics to Applications presents comprehensive and up-to-date information on the various analytical techniques obtainable in bioscience research laboratories across the world. This book contains chapters that discuss the basic bioanalytical protocols and sample preparation guidelines. Commonly encountered analytical techniques, their working principles, and applications were presented. Techniques, considered in this book, include centrifugation techniques, electrophoretic techniques, chromatography, titrimetry, spectrometry, and hyphenated techniques. Subsequent chapters emphasize molecular weight determination and electroanalytical techniques, biosensors, and enzyme assay protocols. Other chapters detail microbial techniques, statistical methods, computational modeling, and immunology and immunochemistry. The book draws from experts from key institutions around the globe, who have simplified the chapters in a way that will be useful to early-stage researchers as well as advanced scientists. It is also carefully structured and integrated sequentially to aid flow, consistency, and continuity. This is a must-have reference for graduate students and researchers in the field of biosciences.
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Chromatography is a powerful technique for the separation of mixtures for both preparative and analytical purposes, to identify and quantify compounds in the mixture. Chromatography is based on two mutually immiscible phases, a stationary phase and a mobile phase. The mobile phase carries the sample through the system, and during its passage, different compounds are retained for different periods of time depending on their interactions with the stationary phase. The partition of components between the mobile and stationary phases is based on the physical and chemical properties of the components. By the correct choice of chromatographic system, different types of mixture can be separated into their individual components. The two main types of chromatography are liquid chromatography (LC) and gas chromatography (GC), depending on whether the mobile phase is a liquid or a gas. Chromatography is further divided into several subclasses based on the type of stationary phase (Fig. 4.1). In polymer science, a special type of liquid chromatography, size exclusion chromatography (SEC), is an important tool for assessing molar mass distribution. This technique is also called gel permeation chromatography (GPC). In this chapter, the principles of SEC, LC and GC, are briefly described, and their applications in the polymer field are reviewed. SEC is basically a liquid chromatographic method, but due to its special nature and importance for polymers, it is here presented under its own subtitle. Recommended introductory texts about the various chromatographic techniques are given by Poole (2003) and Vitha (2017).
Article
A triblock copolymer (PCL-PDMS-PCL) constructed from polydimethylsiloxane (PDMS) and poly(ɛ-caprolactone) (PCL) chains was synthesized and used as stationary phase for capillary gas chromatography (GC). PCL-PDMS-PCL was statically coated to the...
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Individuals living with human immunodeficiency virus type 1 (HIV-1) are often plagued by debilitating neurocognitive impairments and affective alterations;the pathophysiology underlying these deficits likely includes dopaminergic system dysfunction. The present review utilized four interrelated aims to critically examine the evidence for dopaminergic alterations following HIV-1 viral protein exposure. First, basal dopamine (DA) values are dependent upon both brain region andexperimental approach (i.e., high-performance liquid chromatography, microdialysis or fast-scan cyclic voltammetry). Second, neurochemical measurements overwhelmingly support decreased DA concentrations following chronic HIV-1 viral protein exposure. Neurocognitive impairments, including alterations in pre-attentive processes and attention, as well as apathetic behaviors, provide an additional line of evidence for dopaminergic deficits in HIV-1. Third, to date, there is no compelling evidence that combination antiretroviral therapy (cART), the primary treatment regimen for HIV-1 seropositive individuals, has any direct pharmacological action on the dopaminergic system. Fourth, the infection of microglia by HIV-1 viral proteins may mechanistically underlie the dopamine deficit observed following chronic HIV-1 viral protein exposure. An inclusive and critical evaluation of the literature, therefore, supports the fundamental conclusion that long-term HIV-1 viral protein exposure leads to a decreased dopaminergic state, which continues to persist despite the advent of cART. Thus, effective treatment of HIV-1-associated apathy/depression and neurocognitive impairments must focus on strategies for rectifying decreases in dopamine function.
Article
Green miniaturized technologies are the need of the hour which not only facilitates the downscaling of conventional analytical or bioanalytical systems but also serves as the driving force towards safeguarding our environment from toxic and harmful chemicals. Additionally, the rapid advancements in the microfabrication and nanofabrication approaches lead to a great boost in the technologies such as microfluidic devices or lab-on-a-chip (LOC). Accordingly, the present review provides a comprehensive overview of the green aspects of miniaturized systems for greener and cost-effective analytical processes including the reduction of volume of samples/solvents by employing LOC-based microextraction techniques; replacement of toxic solvents with green solvents including subcritical water, supercritical fluid, deep eutectic solvents, bioderived solvents and ionic liquids; minimization of generated waste by using microfluidic devices where lower amount of sample and solvents are utilized. The miniaturization of the overall analytical process is also discussed in terms of the miniaturization of several individual steps such as miniaturization of sample preparation techniques, analytical separation techniques, detection techniques and the automation of all these individual stages which will significantly reduce the energy requirements, risk factors and the overall cost of the analytical system. Various crucial challenges that hinder the realization of the commercialization of green miniaturized technology based LOC systems are also discussed in details along with the advancements in green miniaturized technologies which are being utilized in analytical and bioanalytical chemistry.
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O interesse por alimentos que tragam benefícios à saúde além de proporcionar sensações agradáveis está cada vez maior. Diversos são os compostos responsáveis por essas características sensoriais e são conhecidos como compostos voláteis. Diversas são os métodos de extração destes compostos de interesse onde podemos destacar a microextração em fase solida. A identificação por sua vez pode ser realizada por meio de cromatografia gasosa acoplada a um espectro de massas. Desta forma este trabalho buscou apresentar em forma de um breve referencial teórico informações a cercas destas técnicas. A busca foi realizada em bases de dados das quais foram extraídos 61 trabalhos. Assim considera-se que com avanço das exigências dos consumidores há a necessidade de explorar de forma mais detalhada os compostos presentes nas matrizes alimentares que possam contribuir para uma melhor experiência dos mesmo e a cromatografia gasosa acoplada com a espectrometria de massa torna-se uma excelente opção por ser uma técnica que fornece resultados de forma rápida, fácil.
Article
Short‐chain fatty acids (SCFAs) are produced mainly by intestinal microbiota and play an important role in many host biological processes such as immune system development, glucose and energy homeostasis, and regulation of immune response and inflammation. In addition, they participate in the regulation of anorectic hormones, which have a role in appetite control, tumor suppression, and regulating the central and peripheral nervous systems. As such, there is great interest in monitoring levels of SCFAs in various biological samples. Due to the highly hydrophilic and volatile characteristics of SCFAs, optimizing extraction and sample preparation procedures is often a central component to further improve SCFA quantification. Here, we describe a rapid and highly sensitive analytical method for measuring SCFAs in human serum and feces. Briefly, SCFAs are protected by adding sodium hydroxide, followed by a one‐step extraction (pH > 7). Then, SCFAs are quantified by gas chromatography coupled to mass spectrometry (GC‐MS) after derivatization with N‐tert‐butyldimethylsilyl‐N‐methyltrifluoroacetamide (MTBSTFA). This method demonstrates excellent sensitivity, linearity, and derivatization efficiency for simultaneous determination of 14 different SCFAs. Further, this validated method can be successfully applied to quantify SCFAs in micro‐scale biological samples. In summary, we describe efficient and advanced sample preparation and detection procedures that are critically needed for monitoring SCFA concentrations in human biological samples. © 2021 Wiley Periodicals LLC. Basic Protocol: SCFA extraction and detection from fecal and serum samples with gas chromatography−mass spectrometry
Article
The effect of a gradient of solute velocity on the chromatographic separation of closely spaced solutes is investigated by usage of a simulation. The concept of the ideal basic separation (IBS), introduced by Blumberg, is used to determine the theoretical limit of a separation without any natural or artificial gradients of features of the chromatographic medium. The IBS is the best achievable separation and can therefore be used as a baseline to which other separations can be compared to. An addition of a negative velocity gradient cannot improve the separation of closely spaced solutes. The velocity gradient is realized by adding a temperature gradient to a GC separation. The simulation confirms this theoretical limit for a range of differently strong retained solutes. In a second part controlled deviations from IBS are used to show, that a velocity gradient can be beneficial in realistic, non-IBS. The addition of a negative velocity gradient can improve e.g. the separation of broad injected solute zones or counteract a positive gradient of the mobile phase velocity caused by gas decompression along the GC column. However, the improved separation cannot exceed that of a corresponding ideal basic separation. The resolution of broadly injected solutes can be increased by up to 45% of the corresponding IBS resolution by adding a negative velocity gradient. A positive velocity gradient due to gas decompression reduces the separation by up to 6%. The added negative velocity gradient, realized by a linear temperature gradient, can compensate this resolution loss by up to 2%.
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