Supercritical Fluid Chromatography System Research Articles

Supercritical Fluid Chromatographic Detection by use of a Parallel Flow Restrictor

In supercritical fluid chromatography (SFC), the role of the flow restrictor is not only to maintain supercritical conditions throughout the column but also to provide the necessary interface between the column and the detector. In the previous paper,1 a new type of flow restrictor called parallel flow restrictor was introduced. At that time, the parallel flow restrictor was used only for the flow control. In this paper, the parallel flow restrictor was used not only for the flow control but also for the interface to the second detector. A supercritical fluid chromatographic system with a combination of two detectors based on physically different principles, flame ionization and UV absorption, was used.

Supercritical fluid chromatography and extraction of Fe(III) with hydroxamic acids

Representative aliphatic and aromatic mono-hydroxamic acids are shown to be separable by supercritical fluid chromatography (SFC) using methanol modified CO 2 on a diol column. Evidence for ligand contamination by Fe(III) from the SFC system is provided, as the ligands are detected as Fe(III) chelates at 420 nm. The ligands and chelates studied were octanohydroxamic acid (OHA), Fe(OHA) 3, benzohydroxamic acid (BHA), Fe(BHA) 3, heptanohydroxamic acid (HHA), Fe(HHA) 3, and a newly synthesised hydroxamic acid, perfluorooctanohydroxamic acid (PFOHA). When the ligands were examined using unmodified supercritical CO 2 (SFCO 2) for their ability to extract Fe(III) from solid supports by supercritical fluid extraction (SFE), the fluorinated hydroxamic acid showed enhanced performance and solubility.

Solubilities of the Fat-Soluble Vitamins A, D, E, and K in Supercritical Carbon Dioxide

Solubilities of eight different species of the fat-soluble vitamins A, D, E, and K in supercritical carbon dioxide were measured at (313, 333, and 353) K and over a pressure range of 20 MPa to 35 MPa. Solubilities have been determined by an analytical method using the direct coupling of an equilibrium cell to a supercritical fluid chromatographic system with UV detection. The solubilities of all fat-soluble vitamins in supercritical carbon dioxide under the conditions investigated are in the range of 10 g/kg, except for β-carotene (provitamin A), which is 3 orders of magnitude less soluble. With increasing molecular mass of the vitamin, its solubility in supercritical carbon dioxide decreases. At constant temperature, the solubility of all substances increases with increasing density. At constant density, a rise of temperature results in an increase in solubility. This is caused by the increasing vapor pressure of the solid.

Design and Optimization of a Corona Discharge Ion Source for Supercritical Fluid Chromatography Time-of-Flight Mass Spectrometry

The interfacing of capillary column supercritical fluid chromatography (SFC) to time-of-flight mass spectrometry (TOFMS) through atmospheric pressure chemical ionization (APCI) was investigated. An ion source chamber and a new, flexible, and efficient transfer line from the SFC to the TOFMS system were designed to accommodate the requirements of this study. Ionization of analytes was performed using a corona discharge needle. The interface was equipped with two multiple-axis translation stages for positioning of the transfer line tip and the discharge needle inside the ion chamber. The investigations were oriented toward the optimization of parameters which have a strong effect on the intensity and stability of the analyte signal, including background stability, corona discharge needle positioning in the ion source, transfer line tip and discharge needle relative positioning, curtain gas and makeup gas flow interactions, ion chamber temperature, and elution pressure of analytes from the SFC system.

Supercritical fluid chromatography of paclitaxel

The analysis of paclitaxel and related compounds was investigated using supercritical fluid chromatography (SFC). The separation of paclitaxel and five related taxanes was compared on two SFC instruments. The typical analysis time was 20 min on system I and 4 min on system II. Based on this, SFC system II was selected for further studies and a separation of paclitaxel from fifteen of its impurities or degradation products was achieved in about 35 min.

Coupled Packed SFC and Capillary GC for the Quantitative Analysis of Complex Petroleum Fractions

Packed-column supercritical fluid chromatography (SFC) is coupled to capillary gas chromatography (GC) and applied to the analysis of complex petroleum fractions. The SFC system employs an electronically controlled back pressure regulator to allow independent control of flow and pressure. The SFC eluant is split after the stationary phase column with a fraction directed to a flame-ionization detector with a fused-silica restrictor. The remainder of the eluant passes through an ultraviolet detector after which it can be further split via a three-way valve to allow selected fractions to be «cut» into the GC split injector where they can be cryofocused onto the GC column

Supercritical fluid chromatography—finding a place in the chromatographers' arsenal?

AbstractIn the mid‐ to late 1980s, supercritical fluid chromatography (SFC) was ‘reborn’ as a technique for the 1990s. Supercritical fluids have physical properties (viscosity, diffusivity and density) intermediate between those of licuids and gases. Analyte solubilities are similar to those in some liquid chromatography solvents and the gas‐like properties of supercritical fluids make higher resolution or shorter analysis times possible.Applications and experience with a home‐built SFC system, as well as methods developed elsewhere, are described. The successes and limitations of the technique are reviewed together with details of the instrumentation.Areas in which SFC may become the procedure of choice include multi‐residue methods, non‐polar analyses, micro‐preparative uses and for difficult extractions. The advances in GC and HPLC technology, however, lead us to believe that SFC will remain a specialist technique, appealing only to a minority of analysts.

Trapping efficiency and solute focusing in on‐line supercritical fluid extraction/capillary supercritical fluid chromatography

AbstractAn on‐line supercritical fluid extraction/capillary supercritical fluid chromatography system was developed using a capillary trap with stationary phase and a linear restrictor. With the system, samples can be injected into either the supercritical fluid chromatography (SFC) column or the trapping tube with the same injector, allowing rapid and accurate measurements of trapping efficiency. The self‐cooling effect due to fluid expansion drastically improved the trapping efficiency. External cooling allowed quantitative collection of n‐decane, provided that condensing of CO2 in the trap was avoided. Volatile solutes were more favorably refocused onto the SFC column at the lower column temperature. This system can also be used as a sample introduction method for volatile solutes.

Flame ionization detector responses to ethyl esters of sand eel (Ammodytes lancea) fish oil compared for different gas and supercritical fluid chromatographic systems

A fish oil fatty acid ethyl ester mixture derived from the sand eel (Ammodytes lancea) has been analysed using various capillary gas chromatography (GC) and supercritical fluid chromatography (SFC) methods and 39 components including cholesterol have been identified. The results of the analytical SFC and GC experiments are compared showing a good reproducibility within methods and a fair agreement between methods. The advantages and disadvantages of the employment of manual and autosampler split injection, splitless injection, and cold on-column injection in GC as well as the use of polar and non-polar columns in GC and SFC are discussed.

Applications of On‐Line SFE/SFC in Environmental Analysis

AbstractPolycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorinated Pesticides (OCPs) on different absorbents were extracted and analyzed by a directly coupled supercritical fluid extraction and supercritical fluid chromatography system (on‐line SFE/SFC). The influence of various absorbents as sample matrixes on extraction efficiencies was evaluated. In general, the extraction efficiencies were decreased if a matrix had a larger surface area and a smaller pore size. The recoveries of PAHs and PCBs were decreased in inverse proportion to their molar mass. Recoveries of OCPs containing epoxy functional groups were greater than for OCPs lacking this functional group. In conclusion, online SFE/SFC is a rapid (1‐2 h) and high recovery (70%‐100%) analytical technique.

Application of Supercritical Fluid Extraction and Chromatography to Assay Fat-Soluble Vitamins in Hydrophobic Ointment

The determination of retinol palmitate and tocopherol acetate in a hydrophobic ointment by a coupled supercritical fluid extraction (SFE) and supercritical fluid chromatography (SFC) system is described. The ointment, triturated with diatomaceous earth powder, was subjected to SFE with carbon dioxide, and the extract containing fat-soluble vitamins was trapped on a trimethylsilyl silica-gel column by reducing the fluid pressure. The trapped components were analyzed on an octadecylsilyl silica-gel column by SFC using carbon dioxide containing ethanol as a mobile phase and UV absorption monitoring at 284 nm. In this method, retinol palmitate and tocopherol acetate in preparations could be determined within ten minutes without any manual products after placing the sample into the system

Quantitative hydrocarbon group analysis of gasoline and diesel fuel by supercritical fluid chromatography

A two-dimensional supercritical fluid chromatographic system is described for the determination of saturates, alkenes and mono-, di- and tri-aromatics in gasoline and diesel fuel. Aromatics were isolated from saturates/alkenes and group separated according to the number of aromatic rings on a capillary column packed with silica of particle size 4 μm. The alkenes were separated from saturates on a 38-mm capillary column packed with a silica-based cation exchanger which had been modified in situ with silver nitrate. Elution of alkenes was facilitated by the use of a relatively high column temperature, 65°C, and operation in the back-flush mode. Carbon dioxide was used as the mobile phase. Relative standard deviations were generally in the range 0.4–20.0%. At a low content of alkenes, 0.5%, a relative standard deviation of 8.4% was achieved. The analysis time was under 8 min. The utility of the method is demonstrated by the analysis of feedstock before and after hydration.

Collision-induced dissociation mass spectrometry of nonionic surfactants following direct supercritical fluid injection

Direct injection from a capillary supercritical fluid chromatography system was used as an inlet technique for chemical ionization (CI) and low energy collision-induced dissociation (CID) mass spectrometry of a series of low volatility nonionic surfactant mixtures. Characteristic fragment ions produced by CID for various classes of nonionic surfactant molecules were found to depend greatly on the structure of the surfactant hydrophobe. This was the case even when the charge on the molecule appeared localized away from the hydrophobe. Numerous decomposition pathways are suggested by the fragment ions produced. The use of direct supercritical fluid injection as an inlet technique does not appear to influence adversely the ability to produce CID mass spectra. Direct supercritical fluid introduction allows CI to be compared with other ionization mechanisms more commonly used for multifunctional, low volatility samples.

Determination of tri- and tetra-organotin compounds by supercritical fluid chromatography with inductively coupled plasma mass spectrometric detection

Supercritical fluid chromatography (SFC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) is used for the separation and detection of tetra- and tri-organotin compound mixtures. The carbon dioxide effluent from the SFC system, using a capillary column (SB-biphenyl-30), does not require a modification in the standard ICP-MS operating conditions. Several parameters such as interface temperature, oven temperature, carbon dioxide pressure programme, mobile phase composition and column length are evaluated in order to optimize the separation conditions of several organotins. Detection limits of 0.26, 0.80, 0.57 and 0.20 pg are found for tetrabutyl tin, tributyltin chloride, triphenyltin chloride and tetraphenyltin, respectively. The relative standard deviation for five 0.05 mm3 injections containing 0.5 ng of Sn ranged from 1.3 to 3.4%.

Determination of the hold-up time and column outlet density for capillary supercritical fluid chromatography

The column hold-up time ( t u) was determined for a capillary supercritical fluid chromatographic system over a range of temperatures and densities using methane as a marker and using homologous series extrapolations. At low temperatures, t u was found to pass through a maximum with increasing density. To establish that this phenomenon is not due to a retention effect, t u was also calculated from flow-rate measurements. The measured hold-up times and Darcy's law were used to calculate the outlet densities for different inlet pressures at two temperatures.

Separation of trans/ cis- α- and β-carotenes by supercritical fluid chromatography : I. Effects of temperature, pressure and organic modifiers on the retention of carotenes

A partial separation of the isomers of α- and β-carotenes has previously been achieved by non-aqueous reversed-phase chromatography on octadecyl silica columns eluted with mixtures of hexane and polar modifiers. We show that improved results are obtained by the use of mobile phases based on liquid or supercritical carbon dioxide. Polar modifiers have similar effects on chromatographic selectivity in the non-aqueous reversed-phase and supercritical fluid chromatography systems, suggesting that the retention mechanism is the same in both cases (predominantly partition). Withthe carbon dioxide-based mobile phases, it was possible to optimize chromatographic efficiency by varying the temperature and pressure. The use of both binary and ternary mixtures was investigated.

Ion-mobility spectrometry as a detection method for packed-column supercritical fluid chromatography

Initial investigations are reported for the use of an ion-mobility spectrometer as a detector for packed-column supercritical fluid chromatography. The spectrometer was coupled to the supercritical fluid chromatography system throug a post-column split, and a small portion of the chromatographic flow was introduced directly into the ion-mobility spectrometer using either a frit restrictor or an integral restrictor. The effect of a mobile phase modifier, methanol, on the gas phase ion chemistry of the detector was studied using the reactant ions normally present in the drift tube and the response of the detector to benzoquinone and benzophenone. Separations were performed for a series of Triton X oligomers to demonstrate the various operational modes of the detector. Product ions captured for these compounds had reduced mobilities, a dimensionless measure of mobility, in the range of 1.00 to 0.405, which would make these some of the largest compounds ever introduced, individually, into an ion-mobility spectrometer.

Factors governing the analytical supercritical fluid extraction and supercritical fluid chromatographic retention of polycyclic aromatic hydrocarbons

The molecular connectivity of polycyclic aromatic hydrocarbons (PAHs) correlates well with retention data for several supercritical fluid chromatographic systems. The quantitative effect of microextractor cell geometry on supercritical fluid extraction (SFE) efficiencies of PAHs from octadecyl-bonded sorbents is compared with that seen upon varying the fluid density for the same system. Relative recoveries were increased by up to a factor of two, for coronene, by employing short broad extraction vessels, 1:1 length:I.D., compared to using long narrow vessels, 20:1 length:I.D. The average relative recovery increase was 121% with a large dependence on compound type, increasing ca. linearly with fused ring number for the PAHs studied. A similar relative recoveries increase was achievable by increasing the fluid density by 0.12 g ml −1 with a small dependence on the compound type (decreasing linearly with fused ring number).

High-pressure phase distribution isotherms for supercritical fluid chromatographic systems. 2. Binary isotherms of carbon dioxide and methanol

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh-pressure phase distribution isotherms for supercritical fluid chromatographic systems. 2. Binary isotherms of carbon dioxide and methanolJoseph R. Strubinger, Hengchang. Song, and Jon F. ParcherCite this: Anal. Chem. 1991, 63, 2, 104–108Publication Date (Print):January 15, 1991Publication History Published online1 May 2002Published inissue 15 January 1991https://doi.org/10.1021/ac00002a004RIGHTS & PERMISSIONSArticle Views325Altmetric-Citations96LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (621 KB) Get e-Alerts Get e-Alerts

High-pressure phase distribution isotherms for supercritical fluid chromatographic systems. 1. Pure carbon dioxide

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh-pressure phase distribution isotherms for supercritical fluid chromatographic systems. 1. Pure carbon dioxideJoseph R. Strubinger, Hengchang. Song, and Jon F. ParcherCite this: Anal. Chem. 1991, 63, 2, 98–103Publication Date (Print):January 15, 1991Publication History Published online1 May 2002Published inissue 15 January 1991https://doi.org/10.1021/ac00002a003RIGHTS & PERMISSIONSArticle Views261Altmetric-Citations77LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (713 KB) Get e-Alerts Get e-Alerts