Applications Gas chromatography is a physical separation method in where volatile mixtures are separated. It can be used in many different fields such as pharmaceuticals, cosmetics and even environmental toxins. Since the samples have to be volatile, human breathe, blood, saliva and other secretions containing large amounts of organic volatiles can be easily analyzed using GC. Knowing the amount of which compound is in a given sample gives a huge advantage in studying the effects of human health and of the environment as well. Air samples can be analyzed using GC. Most of the time, air quality control units use GC coupled with FID in order to determine the components of a given air sample. Although other detectors are useful as well, FID is the most appropriate because of its sensitivity and resolution and also because it can detect very small molecules as well. GC/MS is also another useful method which can determine the components of a given mixture using the retention times and the abundance of the samples. This method be applied to many pharmaceutical applications such as identifying the amount of chemicals in drugs. Moreover, cosmetic manufacturers also use this method to effectively measure how much of each chemical is used for their products. Equations “Height equivalent to a theoretical plate” (HETP) use to calculate the flow rate by usingthe total number of theoretical plates (N) and column length (L). Some application, HETP concepts is used in industrial practice to convert number of theoretical plates to packing height. HETP can be calculate with the Van Deemter equation, which is given by HETP=A+Bυ+Cv(1)(1)HETP=A+Bυ+Cv HETP= A + \dfrac{B}{υ} + Cv \tag{1} Where A and B and C are constants and v is the linear velocity (carrier flow rate). A is the "Eddy-Diffusion" term and causes the broadening of the solute band. B is the "Longitudinal diffusion" term whereby the concentration of the analyte, in which diffuses out from the center to the edges.This causes the broadering of the analyte band. C is the "Resistance to Mass Transfer " term and causes the band of the analyte broader. HETP=LN(2)(2)HETP=LN HETP= \dfrac{L}{N} \tag{2} L is the length of the column, where N is the number of theoretical plates, tR is the retention time, and ω is the width of the elution peak at its base. N=16(tRω)2(3)(3)N=16(tRω)2 N= 16 \left (\dfrac{tR}{ω} \right)^2 \tag{3} In which, the more plates give a better resolution and more efficiency. Resolution can be determined by   R=2[(tR)B–(tR)AWA+WB](4)(4)R=2[(tR)B–(tR)AWA+WB]R= 2\left[ \dfrac{(tR)B – (tR)A}{ WA +WB}\right] \tag{4} A relationship between the plates and resolution is giving by, R=(N)1/2/4)(α−1α)(1+K′BK′B)(5)(5)R=(N)1/2/4)(α−1α)(1+K′BK′B) R= (N)1/2 /4) ( \alpha -\dfrac{1}{\alpha}) ( 1+ \dfrac{K’B}{ K’B}) \tag{5} Where the selectivity, a, and k' is the capacity factors take places of the two solutes. The selectivity and capacity factors can be control by improving separation, such as changing mobile/ stationary phase composition, column temperature and use a special chemical effect. References Skoog, D. A.; Holler, F. J.; Crouch, S. R. Principles of Instrumental Analysis. Sixth Edition, Thomson Brooks/Cole, USA, 2007. Krugers, J. Instrumentation in Gas Chromatography. Centrex Publishing Company-Eindhoven, Netherlands, 1968. Hubschmann, H. Handbook of GC/MS: Fundamentals and Applications. Wiley-VCH Verlag, Germany, 2001. Scott, R. P. W. Chromatographic Detectors: Design, Function, and Operation. Marcel Dekker, Inc., USA, 1996. J.N. Driscoll. REview of Photoionization Detection in Gas Chromatography: The first Decade. Journal of CHromatographic Science , Vol 23. November 1985. 488-492. Boer, H. , "Vapour phase Chromatography", ed. Desty, D. H., 169 (Butterworths Sci. Pub., London, 1957). Dimbat, M. , Porter, P. E. , and Stross, F. H. , Anal. Chem., 28, 290 (1956). | Article | ISI | ChemPort | Contributors Kyaw Thet (UC Davis), Nancy Woo (UC Davis) /*<![CDATA[*/ $(function() { if(!window['autoDefinitionList']){ window['autoDefinitionList'] = true; $('dl').find('dt').on('click', function() { $(this).next().toggle('350'); }); } });/*]]>*/ /*<![CDATA[*/ var front = "auto"; if(front=="auto"){ front = "Gas Chromatography"; if(front.includes(":")){ front = front.split(":")[0]; if(front.includes(".")){ front = front.split("."); front = front.map((int)=>int.includes("0")?parseInt(int,10):int).join("."); } front+="."; } else { front = ""; } } front = front.replace(/_/g," "); MathJaxConfig = { TeX: { equationNumbers: { autoNumber: "all", formatNumber: function (n) { if(false){ return front + (Number(n)+false); } else{return front + n; } } }, macros: { PageIndex: ["{"+front+" #1}",1], test: ["{"+front+" #1}",1] }, Macros: { PageIndex: ["{"+front+" #1}",1], test: ["{"+front+" #1}",1] }, SVG: { linebreaks: { automatic: true } } } }; MathJax.Hub.Config(MathJaxConfig); MathJax.Hub.Register.StartupHook("End", ()=>{if(activateBeeLine)activateBeeLine()}); /*]]>*/ /*<![CDATA[*/window.addEventListener('load', function(){$('iframe').iFrameResize({warningTimeout:0, scrolling: 'omit'});})/*]]>*/ Back to top Chromatography High Performance Liquid Chromatography Recommended articles There are no recommended articles. 3.1: Principles of Gas ChromatographyNowadays, gas chromatography is a mature technique, widely used worldwide for the analysis of almost every type of organic compound, even those that a...10.23: ChromatographyChromatography is an efficient way for chemists to separate and analyze mixtures. 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