Examining the conditions to achieve successful fraction transfer in two-dimensional supercritical fluid chromatography.

In this study, the optimization of the conditions necessary to ensure successful fraction transfer in two-dimensional supercritical fluid chromatography (2D-SFC) were examined. Particular attention was placed on the influence of instrumental parameters, including the addition of valves, tubes, and loop volumes, on the chromatographic performance in both dimensions. The impact of these modifications on retention times, gradient delays and peak shape was evaluated. While the first dimension remained unaffected, a slight broadening of the peaks was observed in the second dimension, which did not significantly compromise resolution. Optimizing the loop volume revealed no benefit in reducing the loop dimensions, as dividing the peaks into several fractions did not improve resolution. Furthermore, combining different proportions of CO2 and methanol between the two dimensions showed that most combinations guaranteed satisfactory performance on polar and non-polar columns. Only the cases where the methanol proportion was greatly different between the first and second dimensions, yielded unsatisfactory peak shapes, but these are quite unlikely in normal SFC operation. Finally, these results provide indications of the operational limits of 2D-SFC systems to guarantee stable and efficient performance.