Two-dimensional separation techniques using 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.

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

Monitoring of pesticide residues in Riyadh dates by SFE, MSE, SFC, and GC techniques

BackgroundLipidomics studies require rapid separations with accurate and reliable quantification results to further elucidate the role of lipids in biological processes and their biological functions. Supercritical fluid chromatography (SFC), in particular, can provide this rapid and high-resolution separation. The combination with trapped ion mobility spectrometry (TIMS) has not yet been applied, although the post-ionization separation method in combination with liquid chromatography or imaging techniques has already proven itself in resolving isomeric and isobaric lipids and preventing false identifications. However, a multidimensional separation method should not only allow confident identification but also provide quantitative results to substantiate studies with absolute concentrations. ResultsA SFC method was developed and the hyphenation of SFC and TIMS was further explored towards the separation of different isobaric overlaps. Furthermore, lipid identification was performed using mass spectrometry (MS) and parallel accumulation serial fragmentation (PASEF) MS/MS experiments in addition to retention time and collision cross section (CCS). Quantification was further investigated with short TIMS ramps and performed based on the ion mobility signal of lipids, since TIMS increases the sensitivity by noise filtering. The final method was, as an exemplary study, applied to investigate the function of different ceramide synthases (CerS) in the nematode and model organism Caenorhabditis elegans (C. elegans). Loss of three known CerS hyl-1, hyl-2 and lagr-1 demonstrated different influences on and alterations in the sphingolipidome. SignificanceThis method describes for the first time the combination of SFC and TIMS-MS/MS, which enables a fast and sensitive quantification of lipids. The results of the application to C. elegans samples prove the functionality of the method and support research on the metabolism of sphingolipids in nematodes.

Recent developments in supercritical fluid chromatography – mass spectrometry: Is it a viable option for analysis of complex samples?

Multidimensional separations in the pharmaceutical arena

Reversed-phase liquid chromatography coupled to high-resolution mass spectrometry (RP-LC-HRMS) is the standard for nontarget screening (NTS) of environmental samples but lacks retention of highly polar contaminants. We compared 12 chromatographic methods across four platforms, RP-LC, anion chromatography (IC), supercritical fluid chromatography (SFC), and hydrophilic interaction chromatography (HILIC), using 127 environmentally relevant compounds (logDpH7.4 -5.6 to 6.6). Compounds were analyzed in solvent and for a polar subset, in groundwater enriched by vacuum evaporation. Data were collected across four laboratories using 5 RP-LC-, 3 HILIC-, 2 SFC-, and 2 IC-HRMS setups. Feature detection with standard tools yielded more false negatives for SFC and IC. To enable a fair and method-agnostic comparison, an extracted ion chromatogram (EIC)-based workflow was used. Of the 127 compounds, 125 were detected by at least one platform. For logDpH7.4 > 0, RP-LC covered ∼90%, followed by SFC (∼70%), while IC and HILIC each covered <30%. For very polar compounds (logDpH7.4 < 0), coverage dropped across all platforms. SFC and HILIC detected up to 60% of polar analytes; IC performed better in negative ionization mode, consistent with anion-exchange separation. Detection frequency declined with polarity, reflecting analytical limitations. Combining RP-LC with either SFC or HILIC increased coverage to 94%. In spiked groundwater, coverage was lower (73%) due to matrix effects and losses during vacuum enrichment. Peak widths were narrowest for SFC (∼2.5 s) and RP-LC (∼4 s) and broadest for HILIC (∼7 s) and IC (∼17 s). Retention times showed limited cross-platform correlation while ionization efficiency was consistent, except for SFC. As no single method provided full coverage, combining RP-LC with one complementary platform (SFC, HILIC, or IC) is required to extend chemical space in environmental NTS.

Retention studies in supercritical fluid chromatography

Chiral separation of selected proline derivatives using a polysaccharide-type stationary phase by supercritical fluid chromatography and comparison with high-performance liquid chromatography

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

The development of the hyphenation of high-performance liquid chromatography (HPLC) and other chromatographic methods (supercritical fluid chromato-graphy (SFC), gel-permeation chromatography (GPC), gas chromatography (GC) and capillary electrophoresis (CE)) with nuclear magnetic resonance (NMR) is reviewed. The focus is not only on application (e.g. pharmaceutical chemistry, food chemistry, polymer analysis, fuel chemistry), but also on technical improvements (e.g. flow rate, flow cell, probe, solvent suppression). The increasing importance and overwhelming analytical possibilities of on-line coupling of HPLC with NMR is demonstrated. The literature up to March 1995 is considered.

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

Development of a supercritical fluid chromatography method with ultraviolet and mass spectrometry detection for the characterization of biomass fast pyrolysis bio oils

Enantiomeric pairs of triticonazole have been successfully separated by supercritical fluid chromatography coupled with a tris(3,5-dimethylphenylcarbamoyl) cellulose-coated chiral stationary phase in this work. The effects of co-solvent, dissolution solvent, flow rate, backpressure, and column temperature have been studied in detail with respect to retention, selectivity, and resolution of triticonazole. As indicated, the co-solvents mostly affected the retention factors and resolution, due to the different molecular structure and polarity. In addition, the dissolution solvents, namely, chloromethanes and alcohols, have been also important for enantioseparation because of the different interaction with stationary phase. Higher flow rate and backpressure led to faster elution of the triticonazole molecules, and the change of column temperature showed slight effect on the resolution of triticonazole racemate. Moreover, a comparative separation experiment between supercritical fluid chromatography and high performance liquid chromatography revealed that chiral supercritical fluid chromatography gave the 3.5 times value of Rs /tR2 than high performance liquid chromatography, which demonstrated that supercritical fluid chromatography had much higher separation efficiency.

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.