Partial Modulation Injection for Gas Chromatography

Abstract

Partial modulation is developed and refined for one-dimensional gas chromatography (1D-GC), comprehensive two-dimensional gas chromatography (GCÃ GC), and comprehensive three-dimensional gas chromatography (GC3). Since it’s first inception, partial modulation as a technique has been relatively unstudied. In partial modulation, a small segment of the analyte concentration profile is modulated, where the first dimension, 1D, peak profile is retained while superimposing the second dimension, 2D, separation profile on top. The pulse flow valve modulator, operating in partial modulation modes, enables a large increase in chemical information density, that is the same chemical separation, or peak capacity, that is possible with current modulators can be done in a fraction (as low as every 50 ms vs > 250 ms) of the time. Coupling this modulator to an optimized GCÃ GC instrument provides an optimized GC3 instrument that can physically separate up to ~31,000 peaks in a 40 min separation, or a total of ~770 peaks separated per minute of separation run time. Additionally, the pulse flow valve can operate as an injector to a 1D-GC instrument, where it can separate similar, volatile organic compounds in very short time periods (demonstrated at 200 ms and 500 ms) with baseline resolution between all analytes. This modulation technique has readily provided analyte wb as narrow as single-digit ms, affording incredibly high peak capacities in very short modulation periods. The application of the pulse flow valve modulator, operated in the relatively un-studied partial modulation modes, has demonstrated the ability to greatly increase the physical separation between analytes in complex mixtures, which in turn can increase the scope and applicability of GC instrumentation.