Xem 1-20 trên 197 kết quả Gas chromatography
  • MODERN PRACTICE OF GAS CHROMATOGRAPHY .MODERN PRACTICE OF GAS CHROMATOGRAPHY FOURTH EDITION Edited by Robert L. Grob, Ph.D. Professor Emeritus, Analytical Chemistry, Villanova University Eugene F. Barry, Ph.D. Professor of Chemistry, University of Massachusetts Lowell A JOHN WILEY & SONS, INC. PUBLICATION .Copyright  2004 by John Wiley & Sons, Inc. All rights reserved. Published by John Wiley & Sons, Inc., Hoboken, New Jersey. Published simultaneously in Canada.

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  • Gas chromatography – chromatography using a gas as the mobile phase and a solid/liquid as a stationary phase – In GC, the analytes migrate in the gas phase, so their boiling point plays a role – GC is generally applicable to compounds with masses up to about 500 Da and with ~60 torr vapor pressure at room temp (polar functional groups are trouble) Supercritical fluid chromatography – chromatography using a supercritical fluid as the mobile phase and a solid/liquid as a stationary phase – In SFC, the analytes are solvated in the supercritical fluid – SFC is applicable to a much ...

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  • This book presents a critical review of various chromatography techniques for a limited number of processes. Most techniques are illustrated by examples. The processes described are necessarily limited to those which appear to the authors to have the greatest validity and practical use. Wherever possible, we have included recommendations delineating the best techniques for analyzing each sample. Recommended techniques are often illustrated by detailed examples.

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  • Gas Chromatography Mass Spectometry (viết tắt là GC-MS hoặc GCMS, tạm dịch là Phương pháp Sắc ký khí kết hợp với Khối phổ) là một phương pháp mạnh mẽ với độ nhạy cao được sử dụng trong các nghiên cứu về thành phần các chất trong không khí. Bản chất GC-MS, đúng như tên gọi của nó, là sự kết hợp của Sắc ký khí (Gas Chromatography) và Khối phổ (Mass Spectometry).

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  • Gas chromatography has been and it still is, one of the key tools in analytical techniques in many of the advanced research carried out over the globe. This technique has contributed tremendously and was once the main technique in the analysis of specific compounds like volatile compounds, certain pesticides, pharmaceuticals and petroleum products. The advance of this technique has resulted in several tandem instruments with application of other techniques to enhance the results obtained by gas chromatography.

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  • Chromatography was gained more importance initially after discovered in the preparative chromatography using large amount of the sample for the separation all components properly and collect each in their pure forms. Recently analytical chromatography found many application areas. The purpose of preparative Analytical chromatography is done normally with smaller amounts of material and is for measuring the relative proportions of analytes in a mixture after discovered some detectors which need very low amount of the analyte and have proper detection limits....

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  • ● Adsorption chromatography • The stationary phase is an adsorbent (like silica gel or any other silica-based packing) • The separation is based on repeated adsorption-desorption steps. ● Normal-phase chromatography • The stationary bed is strongly polar in nature (e.g., silica gel), and the mobile phase is nonpolar (such as n-hexane or tetrahydrofuran). • Polar samples are retained on the polar surface of the column packing longer than less polar materials.

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  • Trigeneration. The combination of gas engines with absorption chillers is an optimal solution for generating air conditioning and/or refrigeration. The waste heat from the mixture intercooler, the engin oil, the engine cooling water, and the exhaust gas serves as drive energy for the chillers. Combining a cogeneration plant unit with an absorption refrigeration system allows utilization of seasonal excess heat for cooling.

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  • Critics of the flares in the Niger-Delta have said that the Nigerian government puts profit ahead of the environmental safety and the welfare of its citizens. The harmful effects of gas flaring and inability of the oil companies and government to quantify the resultants effects of gas flaring on the environment has led to strain relationship between the oil producing companies and the people of Niger-Delta Area of Nigeria.

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  • Ionic methods of separation have been used since the industrial revolution in Europe to reduce hardness of water. In the mid-nineteenth century, British researchers treated various clays with ammonium sulfate or carbonate in solution to release calcium. In the early twentieth century, zeolite columns were used to remove interfering calcium and magnesium ions from solutions to permit determination of sulfate. Ionic separation procedures were used in the Manhattan project to purify and concentrate radioactive materials needed to make atom bombs.

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  • Employers in English-speaking countries are increasingly requiring evidence from non-English speaking background professionals seeking employment in fields for which they are academically qualified that they can demonstrate a high level of proficiency in English, such as is represented by an IELTS band score of 7.0. The purpose of this study was to investigate the likelihood of non-English speaking background undergraduate students who had met the English language proficiency requirements for study at an Australian university on the basis of an Overall score of 6.

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  • Statistical analysis has also meant that no generalisation regarding the kind of student least likely to improve (or likely to regress) can be reliably made. Nevertheless, it is interesting to consider the characteristics of each of the individuals who did regress in their IELTS Test results. Table 12 gives data relating to the six students whose IELTS Test results in Test 2 were lower than in Test 1. Five of the six students who regressed were studying Nursing and four were of East or South Asian language background. Four were in the older age group and four had an...

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  • In another recent study by our group (Gürlek et al. 2009) similar salivary ICTP levels were detected in smoker, non-smoker and ex-smoker patient groups with similar clinical periodontal findings. Smoking status was confirmed by salivary cotinine analysis but there was no clinically healthy control group in that study and the number of teeth present, average probing depths and attachment levels were all similar in the three study groups. There were no significant differences in saliva ICTP concentrations between the smoker and non-smoker patient groups.

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  • GSMS là một trong những phương pháp sắc ký hiện đại nhất hiện nay với độ nhạy và độ đặc hiệu cao, được sử dụng trong các nghiên cứu và phân tích kết hợp.

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  • Over 25 years ago, Horvath and Melander, in their fundamental work [1], discussed the reason behind the explosive popularity of reversed-phase liquid chromatography (RPLC) for analytical separations. It was estimated that about 80–90% of all analytical separations were performed in RPLC mode, and the authors noted that “the variation of eluent composition alone extends both retention and selectivity in HPLC [high-performance liquid chromatography] over an extremely broad range.

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  • A text/reference regarding the structure and function of components used in perfume development and the process of developing perfumes. Covers gas chromatography, mass spectrometry and a host of other analytical techniques; the esthetics and techniques of perfume development; the manifold and ever-changing safety-related requirements of countries and customers; concerns about the environmental impact of materials and impurities which affect the perfumer's work.

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  • Since the middle of last century, the use of organic synthetic pesticides became a widespread practice, in order to better prevent, control and destroy pests. Despite their usefulness in the increment of food production, the extensive use of pesticides during production, processing, storage, transport or marketing of agricultural commodities can led to environmental contamination and to the presence of residues in food.

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  • Bacteria are non-chlorophyllated unicellular organisms that reproduce by fission and do not present nuclear envelope. Gram´s stain is a staining technique used to classify bacteria based on the different characteristic of their cell walls. Gram-positive or Gram-negative bacteria are determined by the amount and location of peptidoglycan in the cell wall, exhibiting different chemical compositions and structures, cell-wall permeabilities, physiologies, metabolisms, and pathogenicities.

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  • Flow cytometry is a technology that simultaneously measures and analyses multiple physical characteristics of single particles, usually cells, as they flow in a fluid stream through a beam of light. The properties measured include a particle’s relative size (represented by forward angle light scatter), relative granularity or internal complexity (represented by right-angle scatter), and relative fluorescence intensity.

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