Pub Date : 2021-08-05DOI: 10.5772/intechopen.98614
Diana M. Hernandez-Baez, A. Reid, A. Chapoy, B. Tohidi, R. Bounaceur, F. Montel
This chapter provides an insight into the reactive transport in a capillary column which heavy-oil hydrocarbons undergo when analysed by high temperature gas chromatography (HTGC), and their implications on characterisation outcomes, namely thermal cracking of the injected sample; and incomplete or non-elution of heavy components from the column, by using a coupled Thermo-Hydro-Chemical (THC) multiphysics modelling approach. For this purpose, a computational coupled THC, multicomponent, multi-physics model is developed, accounting for: multiphase equilibrium using an in-house, extended thermodynamics distribution factors dataset, up to nC98H198; transport and fluid flow in COMSOL and MATLAB; and chemical reactions using kinetics and mechanisms of the thermal cracking, in CHEMKIN. The determination of the former extended dataset is presented using two complementary HTGC modes: i) High-Efficiency mode, with a long column operated at low flow rate; and ii) true SimDist mode, with a short column operated at high flow rate and elution up to nC100H202.
{"title":"Reactive Transport and Its Implications on Heavy Oil HTGC Analysis. A Coupled Thermo-Hydro-Chemical (THC) Multiphysics Modelling Approach","authors":"Diana M. Hernandez-Baez, A. Reid, A. Chapoy, B. Tohidi, R. Bounaceur, F. Montel","doi":"10.5772/intechopen.98614","DOIUrl":"https://doi.org/10.5772/intechopen.98614","url":null,"abstract":"This chapter provides an insight into the reactive transport in a capillary column which heavy-oil hydrocarbons undergo when analysed by high temperature gas chromatography (HTGC), and their implications on characterisation outcomes, namely thermal cracking of the injected sample; and incomplete or non-elution of heavy components from the column, by using a coupled Thermo-Hydro-Chemical (THC) multiphysics modelling approach. For this purpose, a computational coupled THC, multicomponent, multi-physics model is developed, accounting for: multiphase equilibrium using an in-house, extended thermodynamics distribution factors dataset, up to nC98H198; transport and fluid flow in COMSOL and MATLAB; and chemical reactions using kinetics and mechanisms of the thermal cracking, in CHEMKIN. The determination of the former extended dataset is presented using two complementary HTGC modes: i) High-Efficiency mode, with a long column operated at low flow rate; and ii) true SimDist mode, with a short column operated at high flow rate and elution up to nC100H202.","PeriodicalId":378756,"journal":{"name":"Recent Advances in Gas Chromatography [Working Title]","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133895243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-09DOI: 10.5772/intechopen.94903
M. García-Valverde, V. S. D. Medina, V. Codesido, Jesús Hidalgo-García, C. Ferreiro-Vera
In the last decades, cannabinoids, the active constituents of Cannabis sativa L., have been attracting a strong interest, regarding the health effects associated with the use of Cannabis and Cannabis-derived products. The progressive legalization of this species in several countries has prompted an increasing concern about the characterization and quantification of cannabinoids in diverse chemotypes of the plant, as well as the obtained final products. Therewith, Process and Product Quality Assurance (PPQA) becomes a mandatory practise to verify the Good Manufacturing Practices (GMP). Gas chromatography is one of the most used techniques in this sense due to its high attainable resolution. However, sample complexity and the thermal lability of cannabinoids hinder the analysis. In this chapter, a fully description of the recent advances in the Cannabis sativa L. analysis by gas chromatography will be presented, including different approaches that have come up to solve the obstacles encountered.
{"title":"Exploring the Mysteries of Cannabis through Gas Chromatography","authors":"M. García-Valverde, V. S. D. Medina, V. Codesido, Jesús Hidalgo-García, C. Ferreiro-Vera","doi":"10.5772/intechopen.94903","DOIUrl":"https://doi.org/10.5772/intechopen.94903","url":null,"abstract":"In the last decades, cannabinoids, the active constituents of Cannabis sativa L., have been attracting a strong interest, regarding the health effects associated with the use of Cannabis and Cannabis-derived products. The progressive legalization of this species in several countries has prompted an increasing concern about the characterization and quantification of cannabinoids in diverse chemotypes of the plant, as well as the obtained final products. Therewith, Process and Product Quality Assurance (PPQA) becomes a mandatory practise to verify the Good Manufacturing Practices (GMP). Gas chromatography is one of the most used techniques in this sense due to its high attainable resolution. However, sample complexity and the thermal lability of cannabinoids hinder the analysis. In this chapter, a fully description of the recent advances in the Cannabis sativa L. analysis by gas chromatography will be presented, including different approaches that have come up to solve the obstacles encountered.","PeriodicalId":378756,"journal":{"name":"Recent Advances in Gas Chromatography [Working Title]","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132722787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-20DOI: 10.5772/intechopen.94229
I. Zenkevich
The processes of thermal decomposition of analytes in gas chromatographic (GC) columns are classified and two new examples of them are considered in details. First of them is monomolecular decomposition of monoalkyl esters of benzene-1, 2-dicarboxylic (phthalic) acid (monoalkyl phthalates). This process has the analogy in chemical reactions in solutions and it may be responsible for the toxicity of phthalates. The second example is decomposition of non-substituted hydrazones of both aliphatic and aromatic carbonyl compounds. The analytes of the second sub-group present the first example of bimolecular (second order) decomposition in a GC column: two molecules of hydrazones form stable azines and hydrazine. Besides that this process presents the particular interest, because it is accompanied by secondary chemical reactions not in an injector, but within GC column, when a by-product of decomposition is involved into secondary interaction with other constituents of the samples. It was confirmed, that visual images of all these decomposition processes on the chromatograms are rather identical and coincide with the manifestations of interconversion of isomers or tautomers. The most often expressed features of chromatographic profiles in such cases are the presence of peaks of an initial analyte and a product of its decomposition or isomerization, connected with more or less expressed diffused “plateau” or “train” between them. The decomposition processes during sample preparation prior to chromatographic separation or in the heated injector of GC instrument are not accompanied by such features. Despite of the rather “exotic” character of the examples considered, the knowledge of them seems to be useful for better revealing the analogous situations in chromatographic practice. Thermal instability of analytes is the principal restriction of GC separation of reactive compounds and we cannot eliminate it for objective reasons. However, in some cases we can evaluate the temperature limits of chromatographic columns, which should not be exceeded during GC separation of instable compounds. The simplest (low boiling) homologs of thermally unstable compounds are often characterized by “normal” boiling point at atmospheric pressure (T b, °C) without decomposition, that means the possibility of their GC analysis unambiguously. Therefore, we can select such T b values as GC and/or GC–MS temperature limit (T lim) for other members of series of thermally unstable homologs. If GC separation is carried out not in isothermal, but in temperature programming conditions, so-called retention temperature (T R) of unstable analytes should not exceed the evaluated T lim value.
{"title":"Features and New Examples of Gas Chromatographic Separation of Thermally Unstable Analytes","authors":"I. Zenkevich","doi":"10.5772/intechopen.94229","DOIUrl":"https://doi.org/10.5772/intechopen.94229","url":null,"abstract":"The processes of thermal decomposition of analytes in gas chromatographic (GC) columns are classified and two new examples of them are considered in details. First of them is monomolecular decomposition of monoalkyl esters of benzene-1, 2-dicarboxylic (phthalic) acid (monoalkyl phthalates). This process has the analogy in chemical reactions in solutions and it may be responsible for the toxicity of phthalates. The second example is decomposition of non-substituted hydrazones of both aliphatic and aromatic carbonyl compounds. The analytes of the second sub-group present the first example of bimolecular (second order) decomposition in a GC column: two molecules of hydrazones form stable azines and hydrazine. Besides that this process presents the particular interest, because it is accompanied by secondary chemical reactions not in an injector, but within GC column, when a by-product of decomposition is involved into secondary interaction with other constituents of the samples. It was confirmed, that visual images of all these decomposition processes on the chromatograms are rather identical and coincide with the manifestations of interconversion of isomers or tautomers. The most often expressed features of chromatographic profiles in such cases are the presence of peaks of an initial analyte and a product of its decomposition or isomerization, connected with more or less expressed diffused “plateau” or “train” between them. The decomposition processes during sample preparation prior to chromatographic separation or in the heated injector of GC instrument are not accompanied by such features. Despite of the rather “exotic” character of the examples considered, the knowledge of them seems to be useful for better revealing the analogous situations in chromatographic practice. Thermal instability of analytes is the principal restriction of GC separation of reactive compounds and we cannot eliminate it for objective reasons. However, in some cases we can evaluate the temperature limits of chromatographic columns, which should not be exceeded during GC separation of instable compounds. The simplest (low boiling) homologs of thermally unstable compounds are often characterized by “normal” boiling point at atmospheric pressure (T\u0000b, °C) without decomposition, that means the possibility of their GC analysis unambiguously. Therefore, we can select such T\u0000b values as GC and/or GC–MS temperature limit (T\u0000lim) for other members of series of thermally unstable homologs. If GC separation is carried out not in isothermal, but in temperature programming conditions, so-called retention temperature (T\u0000R) of unstable analytes should not exceed the evaluated T\u0000lim value.","PeriodicalId":378756,"journal":{"name":"Recent Advances in Gas Chromatography [Working Title]","volume":"165 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125971387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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