140,174 research outputs found

    Analytical Chemistry

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    Exam paper for the first semester (Department of Applied Physics and Engineering Mathematics, National Diploma: Analytical Chemistry

    Countercurrent chromatography in analytical chemistry (IUPAC technical report)

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    © 2009 IUPACCountercurrent chromatography (CCC) is a generic term covering all forms of liquid-liquid chromatography that use a support-free liquid stationary phase held in place by a simple centrifugal or complex centrifugal force field. Biphasic liquid systems are used with one liquid phase being the stationary phase and the other being the mobile phase. Although initiated almost 30 years ago, CCC lacked reliable columns. This is changing now, and the newly designed centrifuges appearing on the market make excellent CCC columns. This review focuses on the advantages of a liquid stationary phase and addresses the chromatographic theory of CCC. The main difference with classical liquid chromatography (LC) is the variable volume of the stationary phase. There are mainly two different ways to obtain a liquid stationary phase using centrifugal forces, the hydrostatic way and the hydrodynamic way. These two kinds of CCC columns are described and compared. The reported applications of CCC in analytical chemistry and comparison with other separation and enrichment methods show that the technique can be successfully used in the analysis of plants and other natural products, for the separation of biochemicals and pharmaceuticals, for the separation of alkaloids from medical herbs, in food analysis, etc. On the basis of the studies of the last two decades, recommendations are also given for the application of CCC in trace inorganic analysis and in radioanalytical chemistry

    Analytical and applied chemistry: A compilation

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    Analytical chemistry and chemical processes and applied chemistry are presented. The reporting source is given for the dissemination of information

    Chemometrics in Analytical Chemistry

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    Over the last two decades, chemometrics has carved out a firm niche in the field of analytical chemistry. This term was supposedly coined by the Swedish Physical Organic Chemist S.Wold in 1972.Together with the Americal Analy-tical Chemist B.R.KowaLski, Wold formed the International Chemometrics Society. Subsequently, there have been seve-ral major reviews 11-71, ACS symposia'8'91, a National Bureau of Standards Conference (10 a NATO School I'll a series of monographs 1121 and several textbooks 113.141. Acceptace of chemometrics as a growing discipline has also been emphasized by 115,161 two international journals dev-oted to chemometrics

    Analytical chemistry of lanthanides

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    The work described in this thesis consists of nine chapters.The first chapter is a general introduction, where lanthanide elements and their application are presented. Candoluminescence is defined as a type of solid state luminescence excited by hydrogen-based flame, and its relation to similar phenomena are clarified. A detailed historical review of candoluminescence of the lanthanides and its theoretical aspects are reported. Also a general introduction on vidicon detectors is given.In chapter two instrumental developments for monitoring candoluminescence spectra and intensities and methods of improving the reproducibility of candoluminescence measurements are reported. Automated matrix introducing and matrix making devices are described, and methods for wavelength calibration of the Optical Spectrum Analyzer are reported.Chapters three and four describe the candoluminescence of terbium and europium respectively. Terbium gives a characteristic green emission in MgO and rare earth oxides (Y₂O₃, La₂0₃, Gd₂O₃ and Lu₂O₃ ) coated on CaO matrices. It was possible to determine 0.1 - 50 ng of terbium in Gd₂O₃ coated matrices with a 0.01 ng detection limit and 2.5% relative standard deviation (r.s.d.).Europium was a new activator for the above rare earth oxides coated on CaO matrices in which it gives a red emission. It was possible to determine 0.1 - 15 ng of europium in such a matrix with a detection limit of 0.05 ng and 2.6% r.s.d.In chapter five a general introduction for fluorescence analysis and flow injection analysis (FIA), their principles, instrumentation and applications for lanthanides determination are given. Chapter six describes a flow injection spectrofluorimetric method for determination of cerium(lll) (1-100 ng ml¯¹ ) based on its native fluorescence in an acidic carrier stream. Cerium(lV) can similarly be determined by incorporating a zinc reductor minicolumn into the system. Splitting the injection sample so that only part passes through the reductor, and the remainder by-passes it, allows total cerium and cerium(lll) to be detected from the two sequential fluorescence peaks obtained.Chapter seven describes a very selective flow injection method for determination of 0.5 - 4 µg m¯¹ europium. A zinc reductor minicolumn is used for reduction of europium(lll) to europium(ll), which is indirectly detected either spectrofluorimetrically by reaction with cerium(lV), and measurement of the cerium(lll) produced, or spectrophotometrically by reaction with iron(lll), and determination, with 1,10-phenanthroline, of the iron(ll) formed.Chapter eight describes a sensitive and selective flow injection spectrofluorimetric method for samarium, terbium and europium determinations. The method utilizes the formation of energy-transfer complexes between the lanthanide ions and hexafluoracetylacetone.Finally in chapter nine, some general conclusions are drawn, and possible areas of future research are suggested

    Derivatization in Analytical Chemistry

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    Derivatization is one of the most widely used sample pretreatment techniques in Analytical Chemistry and Chemical Analysis. Reagent-based or reagent-less schemes offer improved detectability of target compounds, modification of the chromatographic properties and/or the stabilization of sensitive compounds until analysis. Either coupled with separation techniques or as a “stand alone” analytical procedure, derivatization offers endless possibilities in all aspects of analytical applications

    Truth in Judging: Supreme Court Opinions As Legislative Drafting

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    The first thesis this Article postulates is that the history of food and drug regulation during the past twenty centuries has been the history of the development of analytical chemistry, not the history of the development of law and regulation. Statutory law during this period has remained relatively static, while general understanding of analytical chemistry has leapt ahead with unparalleled achievement. Increased scientific enlightenment, largely achieved through analytical chemistry, has produced every important advance in food and drug regulation. Indeed, the overwhelming success of the field of analytical chemistry has created entire scientific disciplines as well as improvement in government regulation of food and drugs. The second thesis this Article presents is that the very nature of food and drug regulation requires that analytical chemistry will retain its central regulatory significance for the foreseeable future. The task that must be accomplished by analytical chemistry, in short, is far from completed, and stretches into the indefinite future. Before pursuing these two theses, it is necessary to dispose of one subsidiary matter. The past few years has witnessed intense debate concerning the scope of the term analytical chemistry. AOAC has, for example, discussed changing its name because of concern that the present title is not sufficiently broad to reflect the comprehensive purposes of the scientific field it represents. The plain meaning of the words themselves, however, quite adequately describes the scope of scientific inquiry represented by this field. Chemistry is defined as [t]he science of the composition, structure, properties, and reactions of matter. Analysis, as it relates to chemistry, is defined as [s]eparation of a substance into constituents or the determination of its composition. \u27 This Article approaches the subject of analytical chemistry in this comprehensive context

    The Importance of Analytical Chemistry to Food and Drug Regulation

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    The first thesis this Article postulates is that the history of food and drug regulation during the past twenty centuries has been the history of the development of analytical chemistry, not the history of the development of law and regulation. Statutory law during this period has remained relatively static, while general under-standing of analytical chemistry has leapt ahead with unparalleled achievement. Increased scientific enlightenment, largely achieved through analytical chemistry, has produced every important advance in food and drug regulation. Indeed, the overwhelming success of the field of analytical chemistry has created entire scientific disciplines as well as improvement in government regulation of food and drugs. The second thesis this Article presents is that the very nature of food and drug regulation requires that analytical chemistry will retain its central regulatory significance for the foreseeable future.The task that must be accomplished by analytical chemistry, in short, is far from completed, and stretches into the indefinite future. Before pursuing these two theses, it is necessary to dispose of one subsidiary matter. The past few years has witnessed intense debate concerning the scope of the term analytical chemistry. AOAC has, for example, discussed changing its name because of concern that the present title is not sufficiently broad to reflect the comprehensive purposes of the scientific field it represents. The plain meaning of the words themselves, however, quite adequately describes the scope of scientific inquiry represented by this field.Chemistry is defined as [t]he science of the composition, structure, properties, and reactions of matter. Analysis, as it relates to chemistry, is defined as [s]eparation of a substance into constituents or the determination of its composition. \u27 This Article approaches the subject of analytical chemistry in this comprehensive context
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