Gas Chromatography

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● Gas Chromatography

نوع زبان: انگلیسی حجم: 1.9 مگا بایت
نوع فایل: اسلاید پاورپوینت تعداد اسلایدها: 39 صفحه
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گروه موضوعی: زمان استخراج مطلب: 2019/06/05 11:43:27

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., chromatography, column, phase, component, mobile, stationary, tsvet, a, sample, gas, base,

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عبارات پرتکرار و مهم در این اسلاید عبارتند از: ., chromatography, column, phase, component, mobile, stationary, tsvet, a, sample, gas, base,

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مشاهده محتوای متنیِ این اسلاید ppt

gas chromatography invention of chromatography mikhail tswett russian botanist ۱۸۷۲ ۱۹۱۹ mikhail tswett invented chromatography in ۱۹ ۱ during his research on plant pigments. he used the technique to separate various plant pigments such as chlorophylls xanthophylls and carotenoids. http wiki mikhail tsvet the method was described on ۳ december ۱۹ ۱ at the xi congress of naturalists and physicians xi съезд естествоиспытателей и врачей in st. petersburg. the first printed description was in ۱۹ ۳ in the proceedings of the warsaw society of naturalists biology section. he first used the term chromatography in print in ۱۹ ۶ in his two papers about chlorophyll in the german botanical journal berichte der deutschen botanischen gesellschaft. in ۱۹ ۷ he demonstrated his chromatogaph for the german botanical society. tsvet s work was ignored for several decades because of diverse reasons the tragic events in russia at the beginning of the ۲ th century the fact that tsvet originally published only in russian what made his results inaccessible to western scientists and an article denying tsvet s findings. willstater and stoll tried to repeat tsvet s experiments but because they used an aggressive adsorbent what destroys the chlorophyll s were not able to do so. they published their results and tsvet s chromatography method went into oblivion. it was recollected ۱ years after his death thanks to german scientist edgar lederer and austrian biochemist richard kuhn and the work of martin and synge. original chromatography experiment later start a glass column is filled with powdered limestone caco۳ . end a series of colored bands is seen to form corresponding to the different pigments in the original plant extract. these bands were later determined to be chlorophylls xanthophylls and carotenoids. an etoh extract of leaf pigments is applied to the top of the column. etoh is used to flush the pigments down the column. chromatography greek chroma color and graphein writing tswett named this new technique chromatography based on the fact that it separated the components of a solution by color. common types of chromatography tswett’s technique is based on liquid chromatography. there are now several common chromatographic methods. these include paper chromatography thin layer chromatography tlc liquid chromatography lc high pressure liquid chromatography hplc ion chromatography gas chromatography gc p.۶۷۴ paper and thin layer chromatography later the solvent moves up paper by capillary action carrying mixture components at different rates. solvent solvent front how does chromatography work in all chromatographic separations the sample is transported in a mobile phase. the mobile phase can be a gas a liquid or a supercritical fluid. the mobile phase is then forced through a stationary phase held in a column or on a solid surface. the stationary phase needs to be something that does not react with the mobile phase or the sample. the sample then has the opportunity to interact with the stationary phase as it moves past it. samples that interact greatly then appear to move more slowly. samples that interact weakly then appear to move more quickly. because of this difference in rates the samples can then be separated into their components. page ۶۷۵ chromatography is based on a physical equilibrium that results when a solute is transferred between the mobile and a stationary phase. a a a a a a a a a a a a k distribution coefficient or partition ratio where cs is the molar concentration of the solute in the stationary phase and cm is the molar concentration in the mobile phase. cross section of equilibrium in a column. a are adsorbed to the stationary phase. a are traveling in the mobile phase. as a material travels through the column it assumes a gaussian concentration profile as it distributes between the stationary packing phase and the flowing mobile gas or liquid carrier phase. in a chromatography column flowing gas or liquid continuously replaces saturated mobile phase and results in movement of a through the column. column is packed with particulate stationary phase. flow flow flow flow in a mixture each component has a different distribution coefficient and thus spends a different amount of time absorbed on the solid packing phase vs being carried along with the flowing gas more volatile materials are carried through the column more rapidly than less volatile materials which results in a separation. note the first two components were not completely separated. peaks in general tend to become shorter and wider with time. if a detector is used to determine when the components elute from the column a series of gaussian peaks are obtained one for each component in the mixture that was separated by the column. theoretical plate is a term coined by martin synge. it is based on a study in which they imagined that chromatographic columns were analogous to distillation columns and made up or numerous discrete but connected narrow layers or plates. movement of the solute down the column then could be treated as a stepwise transfer. theoretical plates n measure how efficiently a column can separate a mixture into its components. this efficiency is based on the retention time of the components and the width of the peaks. the theoretical plate pp.۶۸۱ ۶۸۲ wb tr n number of theoretical plates a measure of efficiency tr is the retention time it is measured from the injection peak or zero to the intersection of the tangents. wb is the width of the base of the triangle it is measured at the intersection of the tangents with the baseline. when the retention time tr is held constant the column that produces peaks with narrower bases wb will be more efficient – have a greater …

کلمات کلیدی پرکاربرد در این اسلاید پاورپوینت: ., chromatography, column, phase, component, mobile, stationary, tsvet, a, sample, gas, base,

این فایل پاورپوینت شامل 39 اسلاید و به زبان انگلیسی و حجم آن 1.9 مگا بایت است. نوع قالب فایل ppt بوده که با این لینک قابل دانلود است. این مطلب برگرفته از سایت زیر است و مسئولیت انتشار آن با منبع اصلی می باشد که در تاریخ 2019/06/05 11:43:27 استخراج شده است.

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