Evaporative membrane modulation for comprehensive two-dimensional liquid chromatography

An evaporative membrane modulator was developed, built and evaluated to avoid loss of performance in the second dimension when coupling two-dimensional liquid chromatography systems. The automated interface reduces the volume after ¹D elution on-line by a pre-determined factor, regardless of the separation gradient. This volume reduction ensures that the injection volume in the ²D is appropriate for the second column, avoiding the detrimental effects of overloading. In addition, the fraction solvent composition is constant over the length of the separation increasing reproducibility of ²D separations. The evaporative membrane modulator was demonstrated with a 10-fold reduction, reducing the injection volume from 50 to 5 μL. A consequence of the EMM device is a reduction in the capacity of the first dimension, which is decreased by a factor of 2.4, but the peak width at half maximum was reduced by up to 22% in the second dimension. When band broadening is considered, the corrected peak capacity with the modulator was only 10% lower than that without the modulator, but with a gain in peak height of 2-3, and a decrease in retention time between subsequent peak-slices reduced from 4s to be negligible. This improves peak shape and shows potential to facilitate peak identification and quantification in more complex applications.