RESUMO
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.
