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Supercritical Fluid Chromatography (supercritical + fluid_chromatography)
Selected AbstractsDynamic control of split flow in packed column supercritical fluid chromatography using dual resistively heated restrictorsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2009Jian Jun Li Abstract Remote control of the vent/detector split flow ratio in packed column supercritical fluid chromatography (pSFC) with flame ionization detector (FID) is demonstrated using a dual heated restrictor method. Restrictors stemming from a Tee at the separation column outlet were, respectively, fixed into an FID and a vent port, and their individual temperatures were controlled using resistively heated wires. Subsequently, both system pressure and split flow could be manipulated. For example, for applied restrictor temperatures examined up to 600°C, corresponding vent/FID split flow ratios between 2 and 7 were observed depending on the port heated. As well, column pressures around 16,23 MPa were also achievable over the same range. Conversely, isobaric altering of the split flow ratio was possible when opposing positive and negative temperature gradients were applied at the two restrictors. Under these conditions, the system pressure varied less than 1% RSD over a 10 min period. As an application, the method was used to establish stable detector operation in the analysis of n -alkanes under pSFC-FID conditions that initiated flame instability. Results indicate that this technique could be a relatively simple and inexpensive means of controlling system pressure and detector split flow ratios in pSFC-FID. [source] Highly sensitive and accurate profiling of carotenoids by supercritical fluid chromatography coupled with mass spectrometryJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2009Atsuki Matsubara Abstract We attempted to establish a high-speed and high-resolution profiling method for a carotenoid mixture as a highly selective and highly sensitive detection method; the analysis was carried out by supercritical fluid chromatography (SFC) coupled with mass spectrometry (MS). When an octadecyl-bonded silica (ODS) particle-packed column was used for separation, seven carotenoids including structural isomers were successfully separated within 15 min. This result indicated not only improved separation but also improved throughput compared to the separation and throughput in RP-HPLC. The use of a monolithic ODS column resulted in additional improvement in both the resolution and the throughput; the analysis time was reduced to 4 min by increasing the flow rate. Furthermore, carotenoids in biological samples containing the complex matrices were separated effectively by using several monolithic columns whose back pressure was very low. The mass spectrometer allowed us to perform a more sensitive analysis than UV detection; the detection limit of each carotenoid was 50 pg or below. This is the first report of carotenoid analysis carried out by SFC-MS. The profiling method developed in this study will be a powerful tool for carrying out accurate profiling of biological samples. [source] Pharmaceutical analysis by supercritical fluid chromatography: Optimization of the mobile phase composition on a 2-ethylpyridine columnJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2008Claudio Brunelli Abstract The separation of neutral, acidic, and basic pharmaceuticals with diverse physicochemical properties by packed column supercritical fluid chromatography (pSFC) on a 2-ethylpyridine column (25 cm×4.6 mm id, 3 ,m particles) is presented. The optimization strategy involved separations at 100% methanol (MeOH) and at 50% MeOH/50% ACN while keeping the peak symmetry additives formic acid (FA) and isopropylamine (IPA) at constant levels of 0.25% v/v. By plotting the adjusted retention times as a function of the MeOH/ACN ratio, an optimal modifier ratio composition of 65% MeOH/35% ACN was found. The total set of 26 neutral, acidic, and basic pharmaceuticals was analyzed and the optimal composition experimentally verified. This mobile phase composition is currently used in pharmaceutical method development and open-access generic screening environments. [source] Semipreparative chiral supercritical fluid chromatography in the fractionation of lansoprazole and two related antiulcer drugs enantiomersJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2008Laura Toribio Abstract The semipreparative chiral separation of lansoprazole and two related compounds (pantoprazole and rabeprazole) using supercritical fluid chromatography (SFC) is presented in this work. Different loads were evaluated in order to obtain high enantiomeric purities and production rates. The volumes injected were 1, 2 and 4 mL. The concentrations of the racemic mixtures were 3 and 6 g/L for lansoprazole and 1.5 g/L for pantoprazole and rabeprazole. In all the cases, the recoveries, for a purity higher than 99.9%, were better for the second eluted enantiomer than for the first one. This fact conditioned the production rate of the first eluted enantiomer that, considering a fixed purity, was always lower than that obtained for the other one. In the case of lansoprazole it was possible to obtain 0.025 and 0.090 mg/min of the first and second eluted enantiomer, respectively, with an enantiomeric purity of 99.9%. For rabeprazole enantiomers 0.037 and 0.062 mg/min, and in the case of pantoprazole the results were better (0.062 and 0.122 mg/min) due to the higher resolution. [source] gAn improved interface for universal acoustic flame detection in modified supercritical fluid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2008Christine Mah Abstract A novel method of interfacing the acoustic flame detector (AFD) with modified supercritical fluid chromatography (SFC) is presented. By applying resistive heating directly to the burner region between the restrictor outlet and the acoustic flame, infrequent severe noise, baseline drifting, and peak deformations that can occasionally be observed with the AFD are eliminated. For example, by increasing the interface temperature only a few hundred degrees Celsius, such sporadic noise in the detector can be reduced nearly ten-fold resulting in smooth stable operation of the AFD. Further, for various levels of methanol modified supercritical carbon dioxide mobile phase examined, the interface was observed to reduce detector noise in each to a common minimal range near 10,25 Hz when an appropriate temperature was achieved. The method is simply assembled, inexpensive to construct, and robust in its daily operation. Overall, the heated interface developed and presented facilitates reliable AFD operation in modified SFC, and supports further exploration and implementation of this sensor as an alternative universal detector in separations requiring an organic cosolvent in the mobile phase. [source] Chiral separation of omeprazole and several related benzimidazoles using supercritical fluid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2004M. Jesús del Nozal Abstract A study of the enantiomeric separation of omeprazole and several related benzimidazoles, using supercritical fluid chromatography (SFC), on the amylose based column Chiralpak AD is presented in this work. The effect of the organic modifier as well as temperature on the retention and enantioresolution was investigated. Alcohol-type modifiers provided the best results, allowing the enantiomeric separation of all the compounds studied with resolutions that were in most cases higher than 2, and analysis times lower than 10 minutes. An investigation of the temperature effect revealed that the isoelution temperature was below the working temperature range in only two cases, and hence it was better to work at the highest temperature permitted. [source] Determination of conjugated dienes in petroleum products by supercritical fluid chromatography and ultraviolet detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2003Flávio Cortiñas Albuquerque Abstract A method for determining total conjugated dienes in petroleum products, such as catalytic or thermal cracking fractions, using supercritical fluid chromatography (SFC) is presented. The separation is carried out in one or two silica columns and with CO2 as mobile phase. The conditions of analysis are the same as used in group-type analysis of diesel fuels by SFC (ASTM D 5186 standard method), except that UV detection at 240 nm is used. Hydrocarbons with two conjugated double bonds are the only substances eluting in the retention time range of the non-aromatics that appreciably absorb UV radiation at this wavelength. This was confirmed by analyzing standards of olefins, isolated diolefins, and conjugated diolefins. Results are reported in mol L,1 of 1,3-pentadiene. Several samples of different natures, such as fluid catalytic cracking liquid products and hydrotreated cracking naphthas, were successfully analyzed. The results correlate quite well with the respective diene values as determined by UOP method 326, although the slope and intercept were specific for each type of product. [source] Solving multicomponent chiral separation challenges using a new SFC tandem column screening toolCHIRALITY, Issue 3 2007Christopher J. Welch Abstract A tool for improved tandem column chiral supercritical fluid chromatography (SFC) method development screening was prepared by modification of a commercial analytical SFC instrument with two different software-controllable, six position high-pressure column selection valves, each controlling a bank of five different columns and a pass through line. The resulting instrument, which has the ability to screen 10 different individual columns and 25 different tandem column arrangements, is a useful tool for facilitating the screening of tandem column SFC arrangements for separation of complex mixtures of stereoisomers or other multicomponent mixtures. Strategies for optimal use of the instrument are discussed, and several examples of the use of the instrument in developing tandem SFC methods for resolution of multicomponent mixtures are presented. Chirality, 2007. © 2006 Wiley-Liss, Inc. [source] Additive concentration effects on enantioselective separations in supercritical fluid chromatography,CHIRALITY, Issue 4 2003Karen W. Phinney Abstract Polar additive concentration effects in supercritical fluid chromatography were studied on chiral stationary phases having either a macrocyclic glycopeptide or a derivatized polysaccharide as the chiral selector. Two basic additives, isopropylamine and triethylamine, were incorporated into the methanol modifier at various concentrations and the effects on retention, selectivity, and resolution were monitored. Many of the analytes failed to elute from the macrocyclic glycopeptide stationary phase in the absence of an additive and the most noticeable effect of increasing additive concentration was a significant decrease in retention. On the derivatized polysaccharide stationary phase the additives had little effect on retention, but they did foster significant improvements in peak shape and resolution. Chirality 15:287,294, 2003. Published 2003 Wiley-Liss, Inc. [source] | ||||||||||