Optimization of Separations Using Short Capillary Columns in Supercritical Fluid Chromatography (original) (raw)
Related papers
Bioanalytical application of multidimensional open tubular column supercritical fluid chromatography
Chromatographia, 1993
On-line multidimensional open tubular column supercritical fluid chromatography (SFC/SFC) using either a flow-switching or a rotary valve-switching interface has been applied to bioanalytical problems. These include the analysis of (a) cholesterol in dried egg yolk, (b) retinoic acids in rat serum, and (c) a digitalis-like factor in peritoneal dialysate from hypertensive patients. A solvent vent injection technique was incorporated in the system, allowing single or multiple volumes of extract (up to 2.0 laL each) to be injected into an uncoated, but deactivated, length of capillary precolumn without flooding of the analytical column. For flow-switching, a well-deactivated, glasslined offset-cross with a small dead volume was placed between the primary and the secondary column. With a rotary valve-switching interface, a cold trap was employed for refocusing analytes at low pressure from single or multiple fractional cuts after being transferred to the second dimension.
Fatty acid analysis on short glass capillary columns
Journal of Agricultural and Food Chemistry, 1980
Analyses of fatty acid methyl esters (FAME) were compared on loo-, lo-, and 2-m glass capillary columns coated with SP2340. The accuracy and precision for the analysis of FAME standards were comparable for all three columns. When actual food samples were chromatographed, the 100-m column gave superior resolution of the many positional and geometric isomers in hydrogenated vegetable oils and ruminant animal fats; however, analysis times were 90-135 min/sample. The 10-m column was adequate for quantitation of major fatty acids, but some minor acids were not detected. Analysis time ranged from 5 to 30 min depending on the sample and the chromatographic conditions. Low resolution made the 2-m column undesirable, even though the major fatty acids could be separated in less than 3.5 min. Quantitative data from the analysis of peanut oil, rapeseed oil, shortening, cod liver oil, pork, beef, and beef liver samples on 100-and 10-m columns are compared, and the characteristics of the three columns are discussed.
Journal of chromatography, 1988
Unless special precautions are taken, injection of untreated biological samples onto a reversed-phase high-performance liquid chromatography (HPLC) column causes column clogging. This results in increasing pressure drop, peak broadening, variation of retention times, etc. To avoid clogging and rapid deterioration of the analytical column, a sample preparation step is needed to remove the proteins (e.g., precipitation followed by extraction of the compound(s) of interest into a protein-free sample). Although such multi-step preparation techniques are time-consuming, they still attract much of the practical attention of analysts.
Electrophoresis, 2000
A rapid and direct method for immobilizing conventional high performance liquid chromatography (HPLC) packing material inside fritless capillaries has been developed. Due to the simple composition of the entrapment matrix (tetraethoxysilane, alkyltriethoxysilane, ethanol and water), straightforward manufacturing procedure and modest equipment requirement, the method can readily be transferred to any laboratory and easily automated. The entrapment procedure has minimal influence on the structure and chromatographic properties of the original reverse-phase sorbent. Various immobilization solutions have been tested, and a comparison between columns entrapped with different immobilization mixtures and conventional packed capillaries is presented. High effficiency separations were obtained using tert-butyl-triethoxysilane entrapped columns in both capillary electrochromatography (reduced plate heights of 1.1±1.4 were measured) and microliquid chromatography (reduced plate heights of 2.2±2.6 were observed) formats. Elimination of frits, stabilization of the packed bed and on-thefly customization of column length render mechanically robust columns that are remarkably stable over time, from which manufacturing imperfections can be removed easily.*
Analytical Chemistry, 1992
Llquld samples were Introduced Into an open tubular column wpercrltlcal fluld chromatograph (SFC) udng a short packed caplllary column as a solute focurlng devlce after a typlcal sample loop valve Injector. The packlng materlals were held lndde the caplllary by porous ceramlc frlts. Excess solvent was vented Into the atmosphere through the packed caplllary. Slnce the exit end of the packed caplllary column was at atmosplwrk pressure, a denslty gradlent was established along the length of the column and solutes preclpltated at the polnt where the dendty dropped below the carbon dloxlde solvating density for these compounds. The solutes were then backflushed from the precolumn Into the analytlcal column wlth wpercrltlcal COS. Thls method made lt pomlble to Inject rdatlvdy large volumes (1-3 pL) Into a 50-pm4.d. open tubular wpercrltlcal fluld chromatography column wlthout floodlng the column wlth the solvent. The reproduclblllty of thls InJectlon method was compared wlth other lnjectlon methods used wlth SFC; the relatlve standard devlatlon (five measurements) of peak areas of n-hexadecane was 5.5 %.
Journal of Chromatography A, 2006
A method is proposed for the comprehensive characterization and comparison of columns in the high-performance liquid chromatographic (HPLC) and capillary electrochromatographic (CEC) modes. Using this approach, column parameters such as the number of plates, the eddydiffusion and mass-transfer contributions to peak broadening, the permeability, and the analysis time are incorporated in a single graph and a comparison in terms of efficiency and speed is obtained. The chromatographic performance of silica-based and polymer-based monolithic capillary columns is discussed and a comparison is made with the performance of packed columns. Also, the potential of ultra-high-pressure liquid chromatography is discussed in this context. In the HPLC mode, the best results were obtained with silica monoliths; in the CEC mode, the low-density methacrylate-ester-based monoliths showed the best performance.
Instrumental aspects of capillary supercritical fluid chromatography
Analytical Chemistry, 1982
The bask Instrument components requlred for caplllary supercrltlcal fluld chromatography include a high-pressure pump with pressure programmer, a small-volume sample Inlet system, a constant temperature oven, and a small-volume detector. The major stresses applied to the hstrumentatlon are the hlgh pressures and temperatures required to maintain the mobile phase at or above Its crltlcal polnt. Of the dlfferent sample introductlon systems studied, spllt Injection presently appears to be the most effectlve. By use of the described hstrumentatlon, a plate helght of 0.30 mm was obtalned for pyrene ( k = 0.50) on a 100-hm caplllary column contalnlng a bonded poly(methylphenylslloxane) statlonary phase.