A reversed-flow differential flow modulator for comprehensive two-dimensional gas chromatography

A simple and reliable differential flow modulator has been demonstrated which reverses the flow during the flush step. The modulator is constructed with commercially available capillary flow technology tees which simplifies the apparatus and permits wide range of column dimensions to be used because the modulator volume is adjustable. Using a reverse flush arrangement the tailing of the peak at the base (baseline rise between modulations) is reduced 10–20 fold as compared to forward flush modulation. This is most easily observed for peaks overloaded in the first dimension. Excellent reproducibility (<2% RSD) of area measurements has been demonstrated with a complex fragrance sample as well as the capacity to handle significant overloading without loss of resolution in the second dimension. Further demonstrating the flexibility of this modulator, separation of C1–6 alkanes and olefins are demonstrated with two porous layer open tubular columns.