Flow supercritical fluid chromatography

In the first section, the mechanisms involved in size exclusion chromatography are discussed this is an area where additional understanding and clarification still are needed. Data treatment with respect to statistical reliability of the data along with corrections for instrumental broadening is still a valid concern. Instrumental advances in the automation of multiple detectors and the developm.ent of a pressure-programmed, controlled-flow supercritical fluid chromatograph are presented. 

The separation and estimation of diloxanide furoate and metronidazole in solid dosage forms was reported by Bhoir et al., using packed column supercritical fluid chromatography [38], A JASCO Cig colunm (10 pm particle size, 25 cm x 4 mm) was used at 40°C, with an injection volume of 20 pL. The mobile phase consisted of 26% methanol in CO2 (flow rate of 2 mL/min), and operated at a pressure of 17.6 MPa. When detected on the basis of its ultraviolet absorbance at 230 nm, the retention time for the drug was 1.6 minutes. The linear region of the calibration graph was reported to be 20-70 pg/mL. 

Higher-throughput analysis was achieved by utilizing shorter columns at higher flow rates.4 Supercritical fluid chromatography (SFC)/MS has... 

This article treats the benefits, possibilities and drawbacks of supercritical fluid chromatography (SFC) and supercritical fluid extraction (SFE) coupled to nuclear magnetic resonance spectroscopy. After a general overview and consideration of the motivation for such techniques, the design of high-pressure flow probes, as well as the principle experimental set-ups, are described. By means of several applications and comparison to HPLC-NMR, the utility of these hyphenated techniques is demonstrated. 

Biermanns et al. reported the chiral resolution of /3-blockers, including propranolol, metoprolol, and atenolol using packed-column supercritical fluid chromatography [38]. A Chiracel OD column with a mobile phase of 30% methanol with 0.5% isopropylamine in carbon dioxide was used for the separation. A baseline separation of isomers was obtained in less than 5 min at a mobile-phase flow rate of 2 ml/min. While keeping the column outlet pressure constant, the flow rate was increased to 4 ml/min and it was noted that, although the retention was reduced, the resolution remained the same. Both R- and S-propranolol gave linear responses from 0.25-2500 ppm with a correlation coefficient of >0.9999. The detection limit was approximately 250 ppb for a S/N ratio of 3. The reproducibility for both R- and S-propranolol was less than 1.5%. It was also noted that 0.09% R-propranolol can be quantitated in the presence of 2500 ppm of S-Propranolol. 

It is also possible to employ detectors with solutions flowing over a static mercury drop electrode or a carbon fiber microelectrode, or to use flow-through electrodes, with the electrode simply an open tube or porous matrix. The latter can offer complete electrolysis, namely, coulometric detection. The extremely small dimensions of ultramicroelectrodes (discussed in Section 4.5.4) offer the advantages of flow-rate independence (and hence a low noise level) and operation in nonconductive mobile phases (such as those of normal-phase chromatography or supercritical fluid chromatography). 

The checkers determined enantiomeric purity by supercritical fluid chromatography (SFC) using a Chiralpak AD (4.6 x 250 mm) column. Eluent carbon dioxide (300 Bar) modifier methanol (24%) flow rate 1.5 mL/min detection UV (210 nm). Retention times were as follows "diphenylcyclopentanone (3.9 min) (R)-diphenylcyclopentanol (5.9 min) (S)-diphenylcyclopentanol (10.4 min). 

Many important developments have been made during the last few years but are not yet commercially available. Specifically, there is an active interest in electrospray and continuous flow fast atom bombardment (FAB) for peptides. Applications using supercritical fluid chromatography (SFC) in combination with MB1 and DLI have been slow but continue to attract interest. The current work in capillary zone electrophoresis (with... 

This chapter treats several separation methods that are not readily classified, including supercritical fluid chromatography, paper chromatography, capillary electrophoresis, capillary electrochromatography, and field-flow fractionation. The use of CE for DNA sequencing is the subject of a feature in the electrophoresis section of this chapter. 

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