Computerized capillary gas chromatographic analysis of hydrocarbon mixtures in workplace air

The quantitative composition of white spirit vapours in workplace air may differ considerably from the solvent being used, although all components are the same. By calculating the hygienic effect from the threshold limit value (NGV) of each component, a more reliable estimate is obtained of the occupational hazard than by using the NGV for white spirit. In this method the analyses were performed by on-column injection onto a temperature-programmed capillary column. Retention indices based on n-paraffins and isooctane were calculated using spline functions. Index tables were established for different hydrocarbon mixtures. The validity of the retention indices was found to be satisfactory, depending on the stability of the column and the possibility of optimizing the indices when replacing one column by another of the same type and dimensions. Comparisons were made with alternative methods for determining the concentration of white spirit vapours in air samples. A polar column was used to check the total content of aromatics.