Supercritical flow chromatography

Raynor et al separated additives in complex mixtures by capillery supercritical flow chromatography and deposited the separated products in potassium bromide discs prior to measurement of their infrared spectra by FTIR spectroscopy. Supercritical flow chromatography coupled with F.T. infrared spectroscopy (SFC-FTIR) has been used to provide quantitative information on and characterization of a range of polymeric surfactants. Bartle et al and Chester also investigated this technique. 

Blestos produced time of flight secondary ion mass spectra of thick films of poly(dimethylsiloxane) and fluorocarbon polymers containing additives in the range m/z up to 4500. The spectra obtained were characteristic of the polymer and its additives or any surface contamination. 

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In preparative liquid-carbon-dioxide-based supercritical flow chromatography (SFC), smaller particles in the 5-10 /tm range are used due to the decreased viscosity of the mobile phase. The pore size of the particles should be large enough to allow the molecules to readily diffuse into and out of the pores. In reversed-phase HPLC, longer alkyl chains provide better load- ability because of the higher volume of interaction be-... 

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). 

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