Berger T.A.,SFC Inc
Journal of Chromatography A | Year: 2015
Analytical scale supercritical fluid chromatography (SFC) is largely a sub-discipline of high performance liquid chromatography (HPLC), in that most of the hardware and software can be used for either technique. The aspects that separate the 2 techniques stem from the use of carbon dioxide (CO2) as the main component of the mobile phase in SFC. The high compressibility and low viscosity of CO2 mean that pumps, and autosamplers designed for HPLC either need to be modified or an alternate means of dealing with compressibility needs to be found. The inclusion of a back pressure regulator and a high pressure flow cell for any UV-Vis detector are also necessary. Details of the various approaches, problems and solutions are described. Characteristics, such as adiabatic vs. isothermal compressibility, thermal gradients, and refractive index issues are dealt with in detail. © 2015 Elsevier B.V. Source
Berger T.A.,SFC Inc
Journal of Chromatography A | Year: 2011
The first systematic study of the performance of a porous shell, hydrophylic interaction liquid chromatography (HILIC) column in supercritical fluid chromatography (SFC) is presented. Observed efficiency on 2.6-μm porous shell particles exceeded all reports using UHPLC on 100-mm long columns packed with <2-μm totally porous particles. A Kinetex 4.6×150mm, 2.6μm HILIC column significantly outperformed a 3μm Luna totally porous silica of the same length and diameter. A 17 component, low molecular weight test mix, consisting of a range of small drug-like molecules was separated isocratically on each column, with similar selectivity, but the porous shell column required 1\2 the time (≈2min vs. 4min), with almost 50% higher efficiency. Even little retained compounds (k<0.5) exhibited more than 30,000 plates under some conditions. Reduced plate heights were higher than previously reported on porous shell particles in both HILIC and rHPLC, with the lowest value of 1.62. Significant fronting was sometimes observed. The cause of the fronting was not determined. The least symmetrical peaks showed the highest apparent efficiency. Pressure drop at optimum velocity (2.5ml/min) and low modifier concentrations was <60bar, and only exceeded 250bar at near double optimum flow and 65% modifier. Peak widths were mostly just over 0.01min (20Hz) wide. There was a loss of efficiency when the injection volume was increased. The chromatograph was shown to have extremely low extra-column dispersion, on the order of 5-10μL 2, which is also the lowest reported in an SFC, in spite of using standard components. This is likely due to turbulent flow in the tubing and fittings. © 2011 Elsevier B.V. Source
Berger T.A.,SFC Inc
Journal of Chromatography A | Year: 2016
The concept of peak fidelity was shown to be helpful in modeling tubing and detector cell dimensions. Connection tubing and flow cell variances were modeled to determine appropriate internal ID's, lengths, and volumes. A low dispersion plumbing configuration, based on these calculations, was assembled to replace the standard plumbing and produced the reported results. The modifications made were straightforward using commercially available parts. The full theoretical efficiency of a 3 × 100 mm column packed with 1.8 μm totally porous particles was achieved for the first time in supercritical fluid chromatography (SFC). Peak fidelity of >0.95 was maintained to below k = 2. A reduced plate height as low as 1.87 was measured. Thus, true "ultra high performance" SFC was achieved, with the results a major improvement from all previous SFC reports.Since there were no efficiency losses, none could be attributed to thermal gradients caused by the expansion of the fluid over large pressure drops, under the conditions used. Similarly, changes in diffusion coefficients caused by significant decreases in density during expansion are apparently balanced by the increase in linear velocity, keeping the ratio between the diffusion coefficient and the linear velocity a constant. Changing modifier concentration to change retention was shown to not be a significant problem. All these issues have been a concern in the past.Diffusion coefficients, and viscosity data needs to be collected at high pressures before the actual limits of SFC can be discovered. © 2016 Elsevier B.V. Source
SFC Inc | Date: 2015-02-13
An automated assay platform for determining the presence and/or amount of analytes of interest in a sample at point of care integrates microfluidic enhanced assay sites, disposable cartridge designs, a sensitive low-volume detection module, together with selected pumping and valving modules, customized control board and user friendly graphical user interface (GUI). Comparing to traditional assay platform like 96-well ELISA, the platform is capable of reducing reagent consumption, increasing assay speed, and enhancing assay performance with a sample-in-answer-out automated process. This platform also features flexibility of adapting different assay schemes for different analytes.
SFC Inc | Date: 2012-06-22
An apparatus, system, and process of converting a standard, high performance liquid chromatography (HPLC) flow path to a flow path suitable for supercritical fluid chromatography (SFC) are described. This reversible technique is applied to a variety of flow configurations including binary, high pressure solvent mixing systems and quaternary, low pressure solvent mixing systems than can be conventionally operated or automated. The technique is generally applied to the fields of supercritical fluid chromatography and high pressure liquid chromatography, but users skilled in the art will find utility for any flow system where pressurization components must be periodically applied to and removed from both ends of a flow stream in an automated manner.