Flame supercritical fluid chromatography

An on-line supercritical fluid chromatography-capillary gas chromatography (SFC-GC) technique has been demonstrated for the direct transfer of SFC fractions from a packed column SFC system to a GC system. This technique has been applied in the analysis of industrial samples such as aviation fuel (24). This type of coupled technique is sometimes more advantageous than the traditional LC-GC coupled technique since SFC is compatible with GC, because most supercritical fluids decompress into gases at GC conditions and are not detected by flame-ionization detection. The use of solvent evaporation techniques are not necessary. SFC, in the same way as LC, can be used to preseparate a sample into classes of compounds where the individual components can then be analyzed and quantified by GC. The supercritical fluid sample effluent is decompressed through a restrictor directly into a capillary GC injection port. In addition, this technique allows selective or multi-step heart-cutting of various sample peaks as they elute from the supercritical fluid... 

Figure 12.20 SFC-GC analysis of a sample of aviation fuel (a) SFC separation into two peaks (b and c) coixesponding GC ttaces of the respective peaks (flame-ionization detection used throughout). Reprinted from Journal of High Resolution Chromatography, 10, J. M. Levy et ah, On-line multidimensional supercritical fluid chromatography/capillary gas chromatography , pp. 337-341, 1987, with permission from Wiley-VCH.

The amount detected by this system (0.3pg on column) was below the level which could have been determined using a flame ionization detector. Initial indications show that the photoionization detector may be a very useful detector for people who wish to get to lower levels on the supercritical fluid chromatography and cannot concentrate their sample. 

Trimethylsilyl derivatives of ten hydroxy- and methoxyhydroxyflavonoids have been studied by the GC-FTIR technique." " The correlation found between retention and gas-phase IR data was used in structural identification of compounds having very similar chromatographic behavior. The shift of the carbonyl frequency gave information on the presence of substitution. Some hydroxy- and methoxy-substituted flavones have been studied following carbon dioxide supercritical fluid chromatography on polymethylsiloxane capillary columns using flame ionization and FTIR detection." " " ... 

Hadj-Mahammed, M., Badjah-Hadj-Ahmed, Y., and Meklati, B.Y., Behavior of pol5nnethoxy-lated and polyhydroxylated flavones by carbon dioxide supercritical fluid chromatography with flame ionization and Fourier transform infrared detectors, Phytochem. Anal, 4, 275, 1993. 

Artemisinin 9a has been extracted from Artemisia annua L. by supercritical fluid extraction and analyzed by supercritical fluid chromatography (SFC) using a capillary column coupled with a flame ionization detector <1997JCFI(A)353>. The SFC method has also been used for the determination of artemisinin in whole blood <1995JCH(B)183>. 

Supercritical fluid chromatography provides increased speed and resolution, relative to liquid chromatography, because of increased diffusion coefficients of solutes in supercritical fluids. (However, speed and resolution are slower than those of gas chromatography.) Unlike gases, supercritical fluids can dissolve nonvolatile solutes. When the pressure on the supercritical solution is released, the solvent turns to gas. leaving the solute in the gas phase for easy detection. Carbon dioxide is the supercritical fluid of choice for chromatography because it is compatible with flame ionization and ultraviolet detectors, it has a low critical temperature. and it is nontoxic. 

Supercritical-fluid chromatography (SFC) has been demonstrated effective in the analysis of a-, / -, and iso-a-acids (54). However, few analytical laboratories have SFC installations, so its use as an analytical tool for the analysis of hop compounds is extremely limited. Interestingly, SFC and GC provide the opportunity to move away from the problems associated with differential response factors, because these methods rely on flame ionization detection. 

Karlsson et al. reported the supercritical fluid chromatography of methaqualone, cotinine, and reclopride, among other compounds, using capillary columns of different polarities [19]. Detection was either thermionic nitrogen-phosphorus or flame ionization. Supercritical nitrous oxide was used as the mobile phase. The detection limits obtained were in the range of 2-4 ppm and the precision was in the range of 3-12%. 

Edder et al. reported the capillary supercritical fluid chromatography of basic drugs of abuse, namely nicotine, caffeine, methadone, cocaine, imipramine, codeine, diazepam, morphine, benzoylecgonine, papverine, narcotine, and strychnine [25]. They compared the separation of these drugs on DBS and DB wax columns. The chromatographic conditions included a carbon dioxide mobile phase and a flame-ionization detector. It was noted that on the DBS column, all peaks other than methadone and cocaine were separated. With the exception of benzoylecgonine and papaverine, all other peaks were separated on a DB wax column. A reproducibility of less than 5% was obtained with an internal standard method. The detection limits obtained were within 10-50 ppm on both the columns. A linearity of >0.99 was obtained for methadone, codeine, and morphine in the concentration range 10-1000 ppm. 

Chester, T. L. (1984). Capillary supercritical-fluid chromatography with flame-ionization detection reduction of detection artifacts and extension of detectable molecular weight range. J. Chromatogr. 299 424-431. 

Fjeldsted, J.C., Kong, R.C., and Lee, M.L. 1983. Capillary supercritical-fluid chromatography with conventional flame detectors. Journal of Chromatography, 279 449-55. 

France, J.E., Snyder, J.M., and King, J.W. 1991. Packed-microbe supercritical fluid chromatography with flame ionization detection of abused vegetable oils. Journal of Chromatography, 540 271-8. 

Vela, N.P., Caruso, J.A. Comparison of flame ionization and inductively coupled plasma mass spectrometry for the detection of organometallics separated by capillary supercritical-fluid chromatography. J. Chromatogr. 641, 337-345 (1993)... 

SFC-FID Supercritical fluid chromatography flame ionization detection... 

Supercritical fluid chromatography is compatible with both HPLC and GC detectors. As a result, optical detectors, flame detectors and spectroscopic detectors can be used. The FID is the most common detector used. However, the mobile phase composition, column type and flow rate must be taken into account when the detector is selected. Some care must also be taken such that the detector components are capable of withstanding the high pressures of SFC. 

Supercritical fluid chromatography, SFC a super critical fluid is produced when a gas, e.g. carbon dioxide is maintained above its critical pressure (73 atm) and temperature (3rC). The super critical fluid is used as the mobile phase with GC like capillary columns or HPLC reverse phase columns and a flame ionisation or flame photometric detector. 

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