MultiSimplex optimisation of purge-and-trap extraction of volatile organiccompounds in soil samples

Purge-and-trap extraction and GC-FID determination of the nine volatile org anic compounds benzene, toluene, chlorobenzene, ethylbenzene, m-xylene, o-x ylene, 1,3-dichlorobenzene, 1,4-dichlorobenzene and 1,2-dichlorobenzene fro m soil samples were optimised by making use of the simplex method implement ed in the MultiSimplex computer program. The experimental variables studied were the sample heating time and temperature, the purge time, the concentr ation of sodium chloride and the cooling temperature of the trap. Optimum c onditions obtained were 7.8 min purge after sample heating at 83 degrees C for 8.4 min, a sodium chloride solution of 0.04 mol.1(-1) and the trap at a mbient temperature. The extraction yield was tested by means of repeated an alyses of different samples, obtaining recoveries ranging between 61 and 83 % and relative standard deviations between 7 and 16%.