A novel method of separation that uses water as a stationary phase in capillary
gas chromatography (GC) is presented. Through applying a water phase to the
interior walls of a stainless steel capillary, good separations were obtained for
a large variety of analytes in this format. It was found that carrier gas
humidification and backpressure were key factors in promoting stable operation
over time at various temperatures. For example, with these measures in place, the
retention time of an acetone test analyte was found to reduce by only 44s after
100min of operation at a column temperature of 100°C. In terms of efficiency,
under optimum conditions the method produced about 20,000 plates for an acetone
test analyte on a 250μm i.d.×30m column. Overall, retention on the stationary
phase generally increased with analyte water solubility and polarity, but was
relatively little correlated with analyte volatility. Conversely, non-polar
analytes were essentially unretained in the system. These features were applied
to the direct analysis of different polar analytes in both aqueous and organic
samples. Results suggest that this approach could provide an interesting
alternative tool in capillary GC separations.