The separation of compounds by gas chromatography is typically performed using a single analytical column. As samples become more complex, it can become difficult to separate all the compounds from each other and they can start to overlap, or co-elute. Longer or narrower columns can be used to increase resolving power, but with diminishing returns.

Comprehensive two-dimensional GC, or GCxGC, drastically increases separation power by adding a second analytical column after the first column. A modulator placed between the two columns pulses the analytes from the first column onto the second column. When the columns are orthogonal in separation power, this technique can result in an order of magnitude increase in the number of analytes that can be detected.

ARC’s solution takes advantage of stop-flow modulation to make GCxGC an attainable configuration for any analytical laboratory. It involves continually sampling the effluent from the first column into an accumulator tube and re-injecting it onto a second, smaller column with orthogonal separation. This second separation happens in the time it takes to accumulate the next sample. The pulse time is known as the modulation time