Gas chromatographic determination of trace concentration of indoles in air using tenax-GC precolumn

Abstract

The gas chromatographic determination of a ppb level of 7 indoles, i.e., indole, 2-, 3-, 5-methylindole, 1, 2-, 2,3-, 2,5-dimethylindole in air was studied by the use of Tenax-GC trapping precolumn (60/80 mesh, 3 cm×8 mm i.d. glass) only or Tenax-GC trapping precolumn plus alkaline precolumn (2% NaOH on glass beads 30/60 mesh, 1 cm×8 mm i.d. glass). The conditions of Tenax-GC and alkaline precolumns were as follows: operating temperature for the trapping, room temperature (about 20°C); sampling velocity of sample air, 5.5 l/min; volume taken 50 liter. The Tenax-GC packing material trapped sample air was transfered into the analytical precolumn(14 cm×4 mm i.d. glass). The operating temperature for the injection of the trapping samples into the gas chromatograph equipped with a flame ionization detector (FID), increased from the room temperature to 280°C in 42 s. The chromatographic conditions were as follows: main column packing, 1 or 5% Silicone XE-60 on Chromosorb W-(AW, DMCS) 80/100 mesh; column size, 3 m×1 or 3 mm i.d. glass column; column temperature, 170°C; carrier gas, nitrogen, 35 or 50 ml/min. The 7 indoles were separated completely within about 14 min without tailing, except for 2, 3-and 2, 5-dimethylindole, whose peaks were overlapped. In the Tenax-GC analytical precolumn injection method the repeatabilities of the retention time and the peak area (as the counts of a digital integrator) of 29 to 570 ng of the 7 indoles were less than 2.2 and 10.9% in the coefficient of variation, respectively. The FID detector response produced a straight line relationship of the peak area or peak height with 5 to 5000 ng of the 7 indoles. The minimum detectable concentration of the 7 indoles was as low as about 0.05 ppb. The present method was applied to the determination of indoles in air of a rat house. © 1978, The Japan Society for Analytical Chemistry. All rights reserved.