Chromatographic analysis resolution

In a chromatographic analysis of lemon oil a peak for limonene has a retention time of 8.36 min with a baseline width of 0.96 min. y-Terpinene elutes at 9.54 min, with a baseline width of 0.64 min. What is the resolution between the two peaks ... 

A method of resolution that makes a very few a priori assumptions is based on principal components analysis. The various forms of this approach are based on the self-modeling curve resolution developed in 1971 (55). The method requites a data matrix comprised of spectroscopic scans obtained from a two-component system in which the concentrations of the components are varying over the sample set. Such a data matrix could be obtained, for example, from a chromatographic analysis where spectroscopic scans are obtained at several points in time as an overlapped peak elutes from the column. 

A practical method for enhancing the peak capacity, and thus the resolution of analytes in multicomponent complex mixtures, can be achieved by changing the mode of the separation during the chromatographic analysis, employing a column switching system in order to optimize a separation. 

Method development remains the most challenging aspect of chiral chromatographic analysis, and the need for rapid method development is particularly acute in the pharmaceutical industry. To complicate matters, even structurally similar compounds may not be resolved under the same chromatographic conditions, or even on the same CSP. Rapid column equilibration in SFC speeds the column screening process, and automated systems accommodating multiple CSPs and modifiers now permit unattended method optimization in SFC [36]. Because more compounds are likely to be resolved with a single set of parameters in SFC than in LC, the analyst stands a greater chance of success on the first try in SFC [37]. The increased resolution obtained in SFC may also reduce the number of columns that must be evaluated to achieve the desired separation. 

Rasmussen [82] describes a gas chromatographic analysis and a method for data interpretation that he has successfully used to identify crude oil and bunker fuel spills. Samples were analysed using a Dexsil-300 support coated open tube (SCOT) column and a flame ionisation detector. The high-resolution chromatogram was mathematically treated to give GC patterns that were a characteristic of the oil and were relatively unaffected by moderate weathering. He compiled the GC patterns of 20 crude oils. Rasmussen [82] uses metal and sulfur determinations and infrared spectroscopy to complement the capillary gas chromatographic technique. 

Bush B., J.T. Snow, and S. Connor. 1983. High resolution gas chromatographic analysis of nonpolar chlorinated hydrocarbons in human milk. Jour. Assoc. Offic. Anal. Chem. 66 248-255. 

Methods have been described for determining chlorinated aliphatic hydrocarbons in soil and chemical waste disposal site samples. The latter method involves a simple hexane extraction and temperature programmed gas chromatographic analysis using electron capture detection and high resolution glass capillary columns. Combined gas chromatography-mass spectrometry was used to confirm the presence of the chlorocarbons in the samples [4],... 

The minor (R,S) diastereomer is present in the crude reaction mixture to the extent of approximately 0.9% as determined by capillary gas-liquid chromatographic analysis performed on a Hewlett-Packard 5790A gas chromatograph equipped with a Hewlett-Packard 3390A integrator and HP-1 methylsilicone gum column (25 m x 0.2 mm x 0.33 pm film thickness). The checkers found that HPLC analysis (Zorbax SB-Phenyl column 25 cm x 4.6 mm, 40 60 MeCN/0.1% aqueous phorphoric acid, 1.5 mL/min, 250 nm detection) provided satisfactory resolution of the R,R- and R,S-diastereomers. The minor diastereomer is hardly discernible by 1H NMR (500 MHz) after purification by flash chromatography. 

Zlatkis A, Ghaoui L, Wang FS, et al. 1984. Direct gas-chromatographic analysis of halogenated hydrocarbons at the part-per-trillion level. J High Resolut Chromatogr Commun 7 370-374. 

Robertson LW, Chittim B, Safe SH, et al. 1983b. Photodecomposition of a commercial polybrominated biphenyl fire retardant High-resolution gas chromatographic analysis. J Agric Food Chem 31 454-457. 

Derivative formation prior to chromatographic analysis has been used successfully. An unidentified component of urine was found which had a retention time very close to that of pregnanediol and which could not be separated from it by thin layer chromatography. The trimethylsilyl ether derivatives and the tri-fluoroacetate derivatives of the two compounds would not provide resolution only the acetate derivatives could be separated. 

N Nimura, T. Kinoshita. o-Phthalaldehyde-A -acetyl-t.-cystcine as a chiral derivatization reagent for liquid chromatographic optical resolution of amino acid enantiomers and its application to conventional amino acid analysis. J Chromatogr 352 169-177, 1986. 

The quality of chromatographic separation depends on the composition of the stationary phase of the column and the instrument settings. The temperature regime of the oven the flow rate of the mobile phase gas through the column the temperature of the injection port—all of these factors influence compound retention time and peak resolution. The reduction in the chromatographic analysis time may adversely affect compound resolution. Because commercial laboratories always balance a need for a sufficient resolution with a need to perform analysis within the shortest possible period of time, the quality of chromatographic resolution is often traded for the speed of analysis. 

The concepts of retention time and peak resolution form the very basis of chromatographic analysis. They also are the technique s worst limitations. The qualitative and quantitative uncertainty of chromatographic determinations originates from the following factors ... 

Patterson DG Jr, Hampton L, Lapeza Cr Jr, et al. 1987a. High-resolution gas chromatographic/high-resolution mass spectrometric analysis of human serum on a whole-weight and lipid basis for... 

Rimmer DA, Johnson PD, Brown RH (1996) Determination of phenoxy add herbicides in vegetation, utilising high-resolution gel permeation chromatographic clean-up and methylation with trimethylsilyldiazomethane prior gas chromatographic analysis with mass-selective detection. J Chromatogr A 755 245-250... 

This procedure applies both to the assay of flavor chemicals and to the quantitation of minor components in flavor chemicals. Analysts following this procedure and performing the test should obtain sufficient resolution of major and even trace components of a mixture to calculate accurately the concentration of the desired component should be familiar with the general principles, usual techniques, and instrumental variables normally met in gas chromatographic analysis and should pay particular attention to the following ... 

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