Silicon Selective Non-Doped Hydrogen Atmosphere Flame Ionization Detector for Gas Chromatography

A commercial flame ionization detector was converted to a gas chromatographic detector selective for silicon-containing compounds by simply interchanging the oxygen and hydrogen inlets so that the flame burned in a hydrogen atmosphere. The optimal configuration of various detector geometries was found to be a narrow cylindrical tube with the collector electrode positioned more than 10 cm from the flame. This configuration eliminated peak tailing which is prevalent in other designs. Helium was shown to be the carrier gas of choice since nitrogen reduced the sensitivity of the detector to siliconcontaining compounds, but not lo hydrocarbon compounds. The calibration curve for tetraethylsilane proved to be linear for about three orders of magnitude with a minimum detectable amount of 4 ng and a selectivity over decane of 2600. This corresponds to a silicon to carbon selectivity better than 1 X lo4. The advantage of a silicon selective detector is demonstrated by comparing a chromatographic tracing of a mixture of n-alkanes and silylated n-alcohols to that of the same mixture obtained with a standard flame ionization detector. Three-microgram peaks of the silylated alcohols could easily be detected with the silicon selective detector while 3 qg of each alkane gave no response.