  The conventional reverse fill/flush flow modulation for comprehensive
two-dimensional gas chromatography requires a bleed capillary column to be
connected to the outlet of the modulator channel. The purpose of this
capillary, that does not contain the stationary phase, is to provide a pressure
resistance to the modulator channel flow. In this way, the desired modulator
flow can be achieved, and channel over-filling can be avoided. Normally, the
length and the internal diameter of the bleed capillary are chosen so as to
obtain the modulator flow that is close to the flow of the first separation
column. Thus, for any chosen set of chromatographic conditions, the required
dimensions of the bleed capillary can be completely different, making the GCxGC
method development tedious and generating additional costs in consumables and
analyst time. In this work a tunable pressure source generating a suitable
backpressure was used instead of the fixed bleed capillary which has the
advantage of the possibility to freely adapt the pressure resistance and
generate the required modulator channel flow for any conditions. This set-up
has been evaluated and compared in terms of the impact on the modulation
performance to the set-up involving a fixed bleed capillary demonstrating
comparable performance.
