Determination of Trialkyl and Triaryl Phosphates by Narrow-bore Liquid Chromatography with On-line Thermionic Detection

The potential of a previously reported on-line reversed-phase liquid chromatographythermionic detector (LC-TID) system has been further evaluated. Several trialkyl (trimethyl to tri-octyl) and triaryl (triphenyl and tri-o-cresyl) phosphates were chosen as model compounds. LC was done on an alkyl-bonded silica column with methanolwater (80:20) at a flow-rate of 35-70µl/min as eluent. The band broadening in the interface-TID unit increased with decreasing volatility of the compounds and for the relatively non-volatile compounds, the band broadening decreased with increasing eluent flow-rate. For most of the test compounds, detection limits of 40-100 pg were obtained. As an illustration of the high selectivity of the LC-TID system, the trace-level determination of two aryl phosphates in sediment samples is reported.