Pub Date : 2019-06-13DOI: 10.1002/9780470027318.A5905.PUB3
Karen D. Ward, A. Bravenec, T. Ward
The word “chiral” is derived from the Greek word “cheir”, which means hand. Chiral molecules are molecules that are related to each other in the same way that a left hand is related to a right hand. These molecules are mirror-images of each other and are nonsuperimposable. Chiral separations have been considered among the most difficult of all separations since enantiomers have identical chemical and physical properties in an achiral environment. In this chapter we will focus on techniques used in high-performance liquid chromatography (HPLC). Most chiral separations by HPLC are accomplished via direct resolution using a chiral stationary phase (CSP). In this technique a chiral resolving agent is bound or immobilized to an appropriate support to make a CSP, and the enantiomers are resolved by the formation of temporary diastereomeric complexes between the analyte and the CSP. Various types of CSPs have been developed, including ligand exchange, protein-based, carbohydrate-based, Pirkle-type, cyclodextrin-based, and macrocyclic antibiotic-based CSPs. Ligand exchange phases are used with aqueous buffer mobile phases in which enantiomers are separated based on the differences in their charge and ionization constants. Limitations are that only ionized analytes can be separated using this technique and the copper-salt containing mobile phases used absorb in the ultraviolet (UV) region, decreasing detection sensitivity. Protein-based CSPs comprise a number of commercially available columns. These CSPs can be used in the reversed-phase mode with aqueous buffers and there are a limited number of variables to control in developing a separation method. Advantages of protein-based CSPs include low column capacity, limited solvent options and the inability to reverse the elution order of the analyte. The carbohydrate-based CSPs consist of derivatized cellulose and amylose phases and are generally used in the normal phase mode, with the exception of two derivatized phases which are conditioned for the reversed-phase mode. The main disadvantages of these phases are the limitations in pressure and solvent used since these phases are not covalently bonded but merely adsorbed on the silica. These phases may not be used with solvents of intermediate polarity, for example, methylene chloride, acetone, tetrahydrofuran, and acetonitrile. The Pirkle-type CSP typically uses nonpolar organic mobile phases such as hexane, with 2-propanol or ethanol as organic modifiers. Under these conditions, retention of the solutes decreases as the mobile phase polarity increases, following the normal phase mode behavior. The Pirkle-type columns are generally employed in separating compounds containing a π-acid or π-basic moiety, or both. The cyclodextrins can be used with either aqueous buffers or in the polar organic mode. Generally analytes separated using the cyclodextrins require formation of an inclusion complex with the cyclodextrin. Separation is most favorable when the
{"title":"Chiral Separations by High‐Performance Liquid Chromatography","authors":"Karen D. Ward, A. Bravenec, T. Ward","doi":"10.1002/9780470027318.A5905.PUB3","DOIUrl":"https://doi.org/10.1002/9780470027318.A5905.PUB3","url":null,"abstract":"The word “chiral” is derived from the Greek word “cheir”, which means hand. Chiral molecules are molecules that are related to each other in the same way that a left hand is related to a right hand. These molecules are mirror-images of each other and are nonsuperimposable. Chiral separations have been considered among the most difficult of all separations since enantiomers have identical chemical and physical properties in an achiral environment. In this chapter we will focus on techniques used in high-performance liquid chromatography (HPLC). Most chiral separations by HPLC are accomplished via direct resolution using a chiral stationary phase (CSP). In this technique a chiral resolving agent is bound or immobilized to an appropriate support to make a CSP, and the enantiomers are resolved by the formation of temporary diastereomeric complexes between the analyte and the CSP. Various types of CSPs have been developed, including ligand exchange, protein-based, carbohydrate-based, Pirkle-type, cyclodextrin-based, and macrocyclic antibiotic-based CSPs. \u0000 \u0000 \u0000 \u0000Ligand exchange phases are used with aqueous buffer mobile phases in which enantiomers are separated based on the differences in their charge and ionization constants. Limitations are that only ionized analytes can be separated using this technique and the copper-salt containing mobile phases used absorb in the ultraviolet (UV) region, decreasing detection sensitivity. Protein-based CSPs comprise a number of commercially available columns. These CSPs can be used in the reversed-phase mode with aqueous buffers and there are a limited number of variables to control in developing a separation method. Advantages of protein-based CSPs include low column capacity, limited solvent options and the inability to reverse the elution order of the analyte. The carbohydrate-based CSPs consist of derivatized cellulose and amylose phases and are generally used in the normal phase mode, with the exception of two derivatized phases which are conditioned for the reversed-phase mode. The main disadvantages of these phases are the limitations in pressure and solvent used since these phases are not covalently bonded but merely adsorbed on the silica. These phases may not be used with solvents of intermediate polarity, for example, methylene chloride, acetone, tetrahydrofuran, and acetonitrile. The Pirkle-type CSP typically uses nonpolar organic mobile phases such as hexane, with 2-propanol or ethanol as organic modifiers. Under these conditions, retention of the solutes decreases as the mobile phase polarity increases, following the normal phase mode behavior. The Pirkle-type columns are generally employed in separating compounds containing a π-acid or π-basic moiety, or both. The cyclodextrins can be used with either aqueous buffers or in the polar organic mode. Generally analytes separated using the cyclodextrins require formation of an inclusion complex with the cyclodextrin. Separation is most favorable when the","PeriodicalId":119970,"journal":{"name":"Encyclopedia of Analytical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129098049","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 : 2019-06-13DOI: 10.1002/9780470027318.A9935
X. Pang, Shilin Chen
The accurate identification of medicinal plants in relation to their purity and quality as well as safe application has become increasingly important. DNA barcoding is an established technique that uses the sequence diversity in short, standard DNA regions for species-level identification. It is primarily used to identify known species by comparing their unique barcode sequences to reference sequences in public databases, as well as to facilitate species discovery. DNA barcoding provides a more rapid, subjective, and accurate identification compared with traditional methods. Thus, it has rapidly become a widely recognized tool for species identification. Chen et al. provided a comprehensive evaluation of different DNA regions for the authentication of medicinal plants. They found that the second internal transcriber spacer (ITS2) region could be used as a universal barcode for plant authentication. The ITS2 barcode has been tested recently in a wide range of taxa. It has been proven to be effective for identifying medicinal plants. In this study, we introduce the DNA barcoding technique and determine its usage in discriminating medicinal plants, as well as its advantages and limitations. Keywords: DNA barcoding; medicinal plants; identification; ITS2; PCR condition
{"title":"Identification of Medicinal Plants Using DNA Barcoding Technique","authors":"X. Pang, Shilin Chen","doi":"10.1002/9780470027318.A9935","DOIUrl":"https://doi.org/10.1002/9780470027318.A9935","url":null,"abstract":"The accurate identification of medicinal plants in relation to their purity and quality as well as safe application has become increasingly important. DNA barcoding is an established technique that uses the sequence diversity in short, standard DNA regions for species-level identification. It is primarily used to identify known species by comparing their unique barcode sequences to reference sequences in public databases, as well as to facilitate species discovery. DNA barcoding provides a more rapid, subjective, and accurate identification compared with traditional methods. Thus, it has rapidly become a widely recognized tool for species identification. Chen et al. provided a comprehensive evaluation of different DNA regions for the authentication of medicinal plants. They found that the second internal transcriber spacer (ITS2) region could be used as a universal barcode for plant authentication. The ITS2 barcode has been tested recently in a wide range of taxa. It has been proven to be effective for identifying medicinal plants. In this study, we introduce the DNA barcoding technique and determine its usage in discriminating medicinal plants, as well as its advantages and limitations. \u0000 \u0000 \u0000Keywords: \u0000 \u0000DNA barcoding; \u0000medicinal plants; \u0000identification; \u0000ITS2; \u0000PCR condition","PeriodicalId":119970,"journal":{"name":"Encyclopedia of Analytical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133865328","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 : 2019-06-13DOI: 10.1002/9780470027318.A9668
R. Jelinek
{"title":"Polydiacetylene Bio‐ and Chemo‐Sensors","authors":"R. Jelinek","doi":"10.1002/9780470027318.A9668","DOIUrl":"https://doi.org/10.1002/9780470027318.A9668","url":null,"abstract":"","PeriodicalId":119970,"journal":{"name":"Encyclopedia of Analytical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123532042","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 : 2019-06-13DOI: 10.1002/9780470027318.A9344.PUB2
J. Snyder, L. Skewis, V. Demas, T. Lowery
Significant progress has been made over the last two decades toward the development of cutting edge diagnostics using magnetic nanoparticles (MNPs) and T2 magnetic resonance (T2MR). The MNP-based assay design, termed magnetic relaxation switch (MRSw) biosensing, has allowed for the application of T2MR to a wide range of clinical diagnostics. In MRSw assays, superparamagnetic nanoparticles (NPs) switch between dispersed and agglomerated states and affect the T2MR relaxation rate of surrounding water molecules. Sensitive T2MR relaxation measurements can be performed in complex, heterogeneous, biological samples owing to their inherently low magnetic background. MRSw assays have been designed for rapid and sensitive detection of disease biomarkers, pathogens, and cancer cells in both simulated samples and clinical studies.
{"title":"Nuclear Magnetic Resonance Nanotechnology: Applications in Clinical Diagnostics and Monitoring","authors":"J. Snyder, L. Skewis, V. Demas, T. Lowery","doi":"10.1002/9780470027318.A9344.PUB2","DOIUrl":"https://doi.org/10.1002/9780470027318.A9344.PUB2","url":null,"abstract":"Significant progress has been made over the last two decades toward the development of cutting edge diagnostics using magnetic nanoparticles (MNPs) and T2 magnetic resonance (T2MR). The MNP-based assay design, termed magnetic relaxation switch (MRSw) biosensing, has allowed for the application of T2MR to a wide range of clinical diagnostics. In MRSw assays, superparamagnetic nanoparticles (NPs) switch between dispersed and agglomerated states and affect the T2MR relaxation rate of surrounding water molecules. Sensitive T2MR relaxation measurements can be performed in complex, heterogeneous, biological samples owing to their inherently low magnetic background. MRSw assays have been designed for rapid and sensitive detection of disease biomarkers, pathogens, and cancer cells in both simulated samples and clinical studies.","PeriodicalId":119970,"journal":{"name":"Encyclopedia of Analytical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128404892","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 : 2019-06-13DOI: 10.1002/9780470027318.A5918.PUB2
B. Fried, J. Sherma
Thin-layer chromatography , Thin-layer chromatography , کتابخانه مرکزی دانشگاه علوم پزشکی تهران
{"title":"Thin‐Layer Chromatography","authors":"B. Fried, J. Sherma","doi":"10.1002/9780470027318.A5918.PUB2","DOIUrl":"https://doi.org/10.1002/9780470027318.A5918.PUB2","url":null,"abstract":"Thin-layer chromatography , Thin-layer chromatography , کتابخانه مرکزی دانشگاه علوم پزشکی تهران","PeriodicalId":119970,"journal":{"name":"Encyclopedia of Analytical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121832075","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 : 2019-03-25DOI: 10.1002/9780470027318.A0831.PUB2
W. Rasemann
Industrial sites where residuals and wastes, such as slags, ashes, dust, and sludges, have been dumped are essential parts of the environment and of the economic structure. The amount of waste produced, distributed, and deposited is constantly increasing. The wastes can contain hazardous components that pollute and endanger the environment, but they can also consist of valuable materials, which are a source of secondary raw materials. To assess the environmental risk caused by the waste or to calculate the economic benefit of dumped material, a reliable knowledge of the waste composition is required. Waste management experience has regularly shown that conflicts and lawsuits are the result if the composition of the waste materials is difficult to determine reliably. Investigations carried out by different institutions and persons, or by the same personnel under varying conditions, will often have different results. The measuring technology and the measuring methods cannot be the only reasons for that. Nowadays, it is possible to accurately determine chemical components in any natural concentration, and there is no problem in distinguishing the size and shape of particles down to the nanometer scale. The problems are created because the wastes are mixtures of particles and lumps that vary in size and shape as well as in chemical composition and physical properties. A waste dump with a varied production history and dumping conditions, with chemical reactions or physical changes occurring after dumping, will be heterogeneous as a rule. Therefore, the evaluation of any dump of industrial waste materials is quite difficult. To ensure that the results of evaluation are comparable, certain regulations of investigation must be followed. According to the delivery, the wastes are classified into material streams (stationary, moving, or free falling), heaps delivered within containers and vehicles, and free-standing heaps. As it is economically unjustifiable to investigate the entire waste dump, subsets of material (called samples) must be taken from the stream, the container, or the heap in order to determine the measurements of interest. In doing this, measuring results are obtained, which differ from the true (but unknown) waste composition. If the investigation is carried out strictly according to the rules, the differences that exist at any step of investigation (called measuring deviations or deviations caused by measurement) are random and unavoidable. The standard deviation of these measuring deviations, i.e. the square root of the respective variance, characterizes the specific uncertainty in waste characterization (called uncertainty of measurement, measuring uncertainty, measurement uncertainty, or mean deviation of the measured results from the true value) that must be accepted. The total uncertainty of a characterization procedure is calculated as the square root of the sum of the respective variances caused by the different steps of investigat
{"title":"Industrial Wastes and Waste Dumps, Sampling and Analysis","authors":"W. Rasemann","doi":"10.1002/9780470027318.A0831.PUB2","DOIUrl":"https://doi.org/10.1002/9780470027318.A0831.PUB2","url":null,"abstract":"Industrial sites where residuals and wastes, such as slags, ashes, dust, and sludges, have been dumped are essential parts of the environment and of the economic structure. The amount of waste produced, distributed, and deposited is constantly increasing. The wastes can contain hazardous components that pollute and endanger the environment, but they can also consist of valuable materials, which are a source of secondary raw materials. To assess the environmental risk caused by the waste or to calculate the economic benefit of dumped material, a reliable knowledge of the waste composition is required. Waste management experience has regularly shown that conflicts and lawsuits are the result if the composition of the waste materials is difficult to determine reliably. Investigations carried out by different institutions and persons, or by the same personnel under varying conditions, will often have different results. The measuring technology and the measuring methods cannot be the only reasons for that. Nowadays, it is possible to accurately determine chemical components in any natural concentration, and there is no problem in distinguishing the size and shape of particles down to the nanometer scale. The problems are created because the wastes are mixtures of particles and lumps that vary in size and shape as well as in chemical composition and physical properties. A waste dump with a varied production history and dumping conditions, with chemical reactions or physical changes occurring after dumping, will be heterogeneous as a rule. Therefore, the evaluation of any dump of industrial waste materials is quite difficult. To ensure that the results of evaluation are comparable, certain regulations of investigation must be followed. According to the delivery, the wastes are classified into material streams (stationary, moving, or free falling), heaps delivered within containers and vehicles, and free-standing heaps. As it is economically unjustifiable to investigate the entire waste dump, subsets of material (called samples) must be taken from the stream, the container, or the heap in order to determine the measurements of interest. In doing this, measuring results are obtained, which differ from the true (but unknown) waste composition. If the investigation is carried out strictly according to the rules, the differences that exist at any step of investigation (called measuring deviations or deviations caused by measurement) are random and unavoidable. The standard deviation of these measuring deviations, i.e. the square root of the respective variance, characterizes the specific uncertainty in waste characterization (called uncertainty of measurement, measuring uncertainty, measurement uncertainty, or mean deviation of the measured results from the true value) that must be accepted. The total uncertainty of a characterization procedure is calculated as the square root of the sum of the respective variances caused by the different steps of investigat","PeriodicalId":119970,"journal":{"name":"Encyclopedia of Analytical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130661542","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 : 2019-03-20DOI: 10.1002/9780470027318.A9918
W. Blaschek
In this chapter, basic methods for the isolation and the determination of the structure of plant oligo- and polysaccharides are described. They of course can be characterized best if isolated in high purity. Therefore, first the extraction of polysaccharides from plant material and then the separation of polysaccharides mixtures are described before presenting some important methods for the analytical characterization of polysaccharides. For details and further specific methods, the extensive literature needs to be consulted. Keywords: oligo- and polysaccharides: extraction and isolation; determination of molecular weight; colorimetric assays; hydrolysis; alditol acetates; silylation; methylation analysis; periodate oxidation; mass spectrometry; NMR spectroscopy
{"title":"Analysis of Plant Oligo‐ and Polysaccharides","authors":"W. Blaschek","doi":"10.1002/9780470027318.A9918","DOIUrl":"https://doi.org/10.1002/9780470027318.A9918","url":null,"abstract":"In this chapter, basic methods for the isolation and the determination of the structure of plant oligo- and polysaccharides are described. They of course can be characterized best if isolated in high purity. Therefore, first the extraction of polysaccharides from plant material and then the separation of polysaccharides mixtures are described before presenting some important methods for the analytical characterization of polysaccharides. For details and further specific methods, the extensive literature needs to be consulted. \u0000 \u0000 \u0000Keywords: \u0000 \u0000oligo- and polysaccharides: extraction and isolation; \u0000determination of molecular weight; \u0000colorimetric assays; \u0000hydrolysis; \u0000alditol acetates; \u0000silylation; \u0000methylation analysis; \u0000periodate oxidation; \u0000mass spectrometry; \u0000NMR spectroscopy","PeriodicalId":119970,"journal":{"name":"Encyclopedia of Analytical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134007039","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 : 2019-03-20DOI: 10.1002/9780470027318.A9921.PUB2
B. H. Oliveira
{"title":"High Pressure Liquid Chromatography Analysis of Alkaloids","authors":"B. H. Oliveira","doi":"10.1002/9780470027318.A9921.PUB2","DOIUrl":"https://doi.org/10.1002/9780470027318.A9921.PUB2","url":null,"abstract":"","PeriodicalId":119970,"journal":{"name":"Encyclopedia of Analytical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124870475","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 : 2019-03-20DOI: 10.1002/9780470027318.A9678
P. Ewart
{"title":"Multimode Absorption Spectroscopy for Multispecies Trace Gas Sensing","authors":"P. Ewart","doi":"10.1002/9780470027318.A9678","DOIUrl":"https://doi.org/10.1002/9780470027318.A9678","url":null,"abstract":"","PeriodicalId":119970,"journal":{"name":"Encyclopedia of Analytical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122310434","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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