Green Separation Techniques for -Omics Platforms: Supercritical Fluid Chromatography

New psychoactive substances represent serious social and health problem as tens of new compounds are detected in Europe annually. They often show structural proximity or even isomerism, which complicates their analysis. Two methods based on ultra high performance supercritical fluid chromatography and ultra high performance liquid chromatography with mass spectrometric detection were validated and compared. A simple dilute-filter-and-shoot protocol utilizing propan-2-ol or methanol for supercritical fluid or liquid chromatography, respectively, was proposed to detect and quantify 15 cathinones and phenethylamines in human urine. Both methods offered fast separation (<3min) and short total analysis time. Precision was well <15% with a few exceptions in liquid chromatography. Limits of detection in urine ranged from 0.01 to 2.3ng/mL, except for cathinone (5ng/mL) in supercritical fluid chromatography. Nevertheless, this technique distinguished all analytes including four pairs of isomers, while liquid chromatography was unable to resolve fluoromethcathinone regioisomers. Concerning matrix effects and recoveries, supercritical fluid chromatography produced more uniform results for different compounds and at different concentration levels. This work demonstrates the performance and reliability of supercritical fluid chromatography and corroborates its applicability as an alternative tool for analysis of new psychoactive substances in biological matrixes.

Retention studies in supercritical fluid chromatography

Contribution of supercritical fluid chromatography to serially coupling columns for chiral and achiral separations

An integral restrictor interface with jet separator for coupling capillary column supercritical fluid extraction – supercritical fluid chromatography with high resolution mass spectrometry (SFE‐SFC‐MS) has been built and used for the analysis of a fatty acid ester, and of polymer additives with a wide range of masses. The mobile phase used was supercritical carbon dioxide; a flame ionization detector (FID) was used in parallel with the mass spectrometer. Different SFC‐MS interface operating conditions, e.g. temperature, restrictor position, flow rate, and sample transfer conditions were optimized to obtain good sensitivity and separation for these applications. In addition, the sensitivity of measurements performed with the direct insertion probe and by SFC‐MS interface have been compared.

This paper presents a review of the literature covering separations of enantiomers achieved with supercritical fluids. Supercritical fluid chromatography (SFC) is the main technique represented but chiral extraction (chiral SFE) and simulated moving bed (SMB) are also present. First of all, a historical view of the technique is presented. Then stationary phases, mobile phases and operating conditions are discussed, with a particular focus on the effect of operating parameters on the resolution. Detection issues are presented. The interest of SFC for screening methods and for the preparative scale is demonstrated. Comparison with other chromatographic techniques, namely gaseous-phase chromatography (GC) and high-performance liquid chromatography (HPLC) is provided. While the pharmaceutical industry is the principal application area of enantioselective separations, other examples with agrochemicals or fragrances are also presented. Foreword: This article focuses on main developments in the field of chiral separations with supercritical fluid chromatography and related techniques, as well as representative applications. It is not intended to be a comprehensive review of all papers published on the topic of chiral separations with supercritical fluids. However, it is believed that the publications mentioned here are representative of the evolution of the technique over more than 25 years of use. Several excellent reviews covering other aspects of chiral separations and/or supercritical fluid chromatography are also mentioned where appropriate. Keywords: Chiral resolution, chiral stationary phases, enantiomer separation, packed column, simulated moving bed, supercritical fluid chromatography.

Application of supercritical fluid chromatography to the analysis of liquid-crystal mixtures

Plate height theory for compressible mobile phase fluids and its application to gas, liquid and supercritical fluid chromatography

Ultra-high performance supercritical fluid chromatography hyphenated to atmospheric pressure chemical ionization high resolution mass spectrometry for the characterization of fast pyrolysis bio-oils

A high pressure vessel equipped with continuous magnetic stirring has been interfaced directly online with supercritical fluid chromatography (SFC). The interface consists of an oven housing a recirculation pump that maintains a constant flow of supercritical fluid solution from the vessel through a sample injection valve for online SFC analysis. The method involves increasing the vessel pressure in controlled steps to produce a series of progressively more saturated supercritical fluid carbon dioxide solutions for online SFC solubility measurements. The integrated static solubility system provides a convenient means to ensure equilibrium is established prior to performing online SFC solubility measurements and also facilitates a self-validation accuracy check procedure. For nifedipine, solubility data was obtained at 333.15 and 353.15 K through the pressure range from 12.5 to 27.5 MPa using 2.5 MPa steps. For quinine, solubility data was obtained at 323.15 and 343.15 K through the pressure range from 12....

Recent developments in preparative-scale supercritical fluid- and liquid chromatography for chiral separations

In supercritical fluid chromatography (SFC) compressed gases in the region of their critical temperature are used as mobile phases. SFC has important advantages over gas chromatography (GC) for the separation of low‐volatile or thermally unstable substances. Like high pressure liquid chromatography (HPLC) and gel chromatography, it is used for various special applications and preparative separations, e.g. in the petroleum industry and in the separation of oligomers. SFC is of great interest in fundamental research on fluid extraction and for the determination of the physicochemical properties of fluid systems. In this contribution the most important physicochemical, methodological, and instrumental principles of SFC are summarized; characteristic physicochemical applications are the determination of capacity ratios, partition coefficients, partial molar volumes, interaction second virial coefficients, and difusion coefficients.

Supercritical fluid chromatography (SFC) serves as a high resolution chromatographic technique for the analysis of high molecular mass solutes that are beyond the volatility range of gas chromatography (GC). Multidimensional SFC is a relatively new technique which is growing at a rapid pace. SFC also serves as a high resolution chromatographic technique for the analysis of high molecular mass solutes that are beyond the volatility range of GC. SFC instrumentation has some similarities to both LC and GC. A syringe or reciprocating pump delivers the SFC mobile phase as a liquid to the injection valve. SFC is often applied to the analysis of high molecular mass samples such as fossil fuels, but such samples generally become more complex with increasing molecular mass because the number of possible isomers increases. In SFC, more than one of the operating parameters can be varied simultaneously; for example, the temperature may be continuously increased during a density/pressure program.

Characterization of a solventless injection interface for supercritical fluid chromatography

High performance liquid chromatography (HPLC) employing chiral stationary phases (CSPs) is the most popular and effective method for the separation of enantiomers. In this dissertation, the first chapter is an overview of chiral stationary phases for HPLC, which includes the structures, separation mechanisms, and applications of a variety of chiral stationary phases. The use of some chiral stationary phases in SFC also is discussed. The next three chapters present the enantiomeric separations of chiral furans, isochromenes, and polycycles on cyclodextrin-based chiral stationary phases. The performance of chiral stationary phases for the separation of these analytes was compared. The effect of the mobile phase compositions and structures of the analytes on the chiral recognitions were discussed. Chapter 5 through chapter 7 focuses mainly on the development and evaluation of new synthetic polymeric chiral stationary phases. First, the enantiomeric separation abilities of a new polymeric chiral stationary phase based on the monomer N,N’-(1S,2S)-1,2cyclohexanediyl-bis-2-propenamide was screened with 200 racemic samples. The enantiomeric separations obtained were optimized. The mobile phase compositions and a mobile phase additive (trifluoroacetic acid) were evaluated and the chiral recognition mechanism was discussed. The new CSP showed high sample loading capacity. Then, we developed two new synthetic polymeric CSPs with two other monomers, which are polymerible derivatives of trans-1,2-diphenylethylenediamine and trans-9,10-dihydro-9,10ethanoanthracene-(11S,12S)-11,12-dicarboxylic acid. The two new CSPs also showed enantiomeric selectivities for a variety of chiral compounds and high sample loading capacity. The three new synthetic polymeric CSPs are complementary to each other. Chapter 8 is a study on the use of the new synthetic polymeric CSPs with supercritical fluid eluents. The new CSPs also can separate many compounds using supercritical fluid chromatography (SFC). They showed high stabilities under SFC conditions. Compared with HPLC, SFC provides much faster separations due to the high flow rates. For some analytes, better enantiomeric separations were observed with SFC due to the better separation efficiencies.

High-resolution separation systems are essential for the analysis of complex mixtures in a wide variety of application areas. To increase resolution, multidimensional chromatographic techniques have been one key solution. Supercritical fluid chromatography provides a unique opportunity in these multidimensional separations based on its potential for high solvent compatibility, rapid duty cycles, and orthogonality to other separation modes. This review focuses on two-dimensional chromatography methods from the past decade that use supercritical fluid chromatography because of these advantages. Valving schemes and modulation strategies used to interface supercritical fluid chromatography with other liquid chromatography and gas chromatography techniques are described. Particular applications of multidimensional separations using supercritical fluid chromatography for the analysis of oils and chiral separations of pharmaceutical compounds are highlighted. Limitations of and a potential trajectory for supercritical fluid chromatography in this field are also discussed.