Electrostatic Sample Nebulization for Improved Sample Vaporization in the Split/Splitless Gas Chromatography Inlet

摘要

The split/splitless inlet system has basically the same fundamental drawbacks it had when it was introduced: poor repeatability of the injected amount of sample and discrimination of high-boiling analytes. Hot needle injection improves the repeatability of the sample transfer but suffers from in-needle discrimination. Injection with a fast autosampler, resulting in minimal heating of the needle, solves this problem but usually requires a glass wool packing in the inlet liner to assist in vaporization of the sample. As glass wool has been reported to cause degradation of labile analytes, it cannot be applied as a general remedy for improving incomplete vaporization. In this paper, a novel concept, based on electrostatic nebulization of the injected sample, is presented. The resulting fine droplets promote a more effective heat transfer and a rapid vaporization. Evaluation of the electrospray inlet in the split mode, using a straight, empty glass liner and a cold needle, showed an improvement in peak area repeatability by about 1 order of magnitude, compared with the results obtained when no electrostatic field was applied. Splitless injection of a series of hydrocarbons up to C_(28) in the electrospray inlet with an empty, tapered liner, using a cold needle, showed no measurable analyte discrimination. The relative standard deviation in terms of area count for the largest hydrocarbon (C_(28)) was <1.5percent, compared to approx30percent for injections where no high voltage was applied.