[Study on method for benzene and its homologues in indoor air monitored by portable gas chromatography].

OBJECTIVE: To set up a method for the low concentration of benzene and its homologues (toluene, ethylbenzene and xylene, BTEX) in indoor air monitored simultaneously by portable gas chromatography (GC).

METHODS: The target gas of individual benzene and its homologues was prepared in Tedlar bag by liquid standard solution. The air samples were collected with the on- board sampling pump and preconcentrated on a sorbent tube, then thermally desorbed into capillary column and detected by MAID detector to determine the retention time. Retention time was used to confirm the target compound. The mix calibration gas of benzene and its homologues was prepared by liquid external standard method. Peak area was used to determine the amount of mixture.

RESULTS: The benzene and its homologues were separated very well in the selected analysis parameter. The analytical period was less than 15 min. The concentration ranges that could be determined were 0.018-0.879 mg/m3 of benzene, and 0.035-1.299 mg/m3 of toluene, and 0.035-1.300 mg/m3 of ethylbenzene, and 0.035-1.320 mg/m3 of m, p-xylene, and 0.035-1.296 mg/m3 of o-xylene, respectively. The minimum detectable concentration of benzene, toluene, m, p-xylene and o-xylene were 7.5, 11.5, 28.8, 30.3 and 30.6 microg/m3 respectively. The relative deviations between this method and standard method were less than 13.9% and 20.0% in laboratory and in filed study, respectively. In the precision experiment, the relative standard deviations of BTEX were less than 8.4% in different concentrations within one day and one week.

CONCLUSION: This method which has high sensitivity and precision, and strong anti-interference ability could be used to detect the low concentration of benzene and its homologues in indoor air.