Using electronic pressure programming to reduce the decomposition of labile compounds during splitless injection



A split/splitless capillary injection port has been developed for electronic pressure programming (EPP) in gas chromatography. The inlet may be operated in several modes: constant pressure, constant flow, vacuum compensation (for gas chromatography–mass spectrometry (GC-MS)), pressure-programmed, or a combination mode enabling a pressure program to be followed by constant flow. A pressure-programming technique has been tried which uses high pressure (high column flow rate) at the time of injection followed by reduction in inlet pressure to a value required for normal chromatography. Sample is swept rapidly from the inlet and into the column, reducing contact with the hot, active inlet surfaces which cause sample decomposition. The decomposition of endrin and 4,4′-DDT, two labile pesticides, can be substantially reduced using this technique and modest improvements were also observed with the carbamate pesticide carbaryl.