Abstract:
Factors affecting the detennination of PAHs by capillary GC/MS were
studied. The effect of the initial column temperature and the injection solvent on
the peak areas and heights of sixteen PAHs, considered as priority pollutants,
USillg crosslinked methyl silicone (DB!) and 5% diphenyl, 94% dimethyl, 1%
vinyl polysiloxane (DBS) columns was examined. The possibility of using high
boiling point alcohols especially butanol, pentanol, cyclopentanol, and hexanol as
injection solvents was investigated.
Studies were carried out to optimize the initial column temperature for
each of the alcohols. It was found that the optimum initial column temperature is
dependent on the solvent employed. The peak areas and heights of the PAHs are
enhanced when the initial column temperature is 10-20 c above the boiling point
of the solvent using DB5 column, and the same or 10 C above the boiling point of
the solvent using DB1 column. Comparing the peak signals of the PAHs using the
alcohols, p-xylene, n-octane, and nonane as injection solvents, hexanol gave the
greatest peak areas and heights of the PAHs particularly the late-eluted peaks. The
detection limits were at low pg levels, ranging from 6.0 pg for fluorene t9 83.6
pg for benzo(a)pyrene.
The effect of the initial column temperature on the peak shape and the
separation efficiency of the PARs was also studied using DB1 and DB5 columns.
Fronting or splitting of the peaks was obseIVed at very low initial column
temperature. When high initial column temperature was used, tailing of the peaks
appeared. Great difference between DB! and.DB5 columns in the range of the
initial column temperature in which symmetrical.peaks of PAHs can be obtained is observed. Wider ranges were shown using DB5 column. Resolution of the
closely-eluted PAHs was also affected by the initial column temperature
depending on the stationary phase employed. In the case of DB5, only the earlyeluted
PAHs were affected; whereas, with DB1, all PAHs were affected.
An analytical procedure utilizing solid phase extraction with bonded phase
silica (C8) cartridges combined with GC/MS was developed to analyze PAHs in
water as an alternative method to those based on the extraction with organic
solvent. This simple procedure involved passing a 50 ml of spiked water sample
through C8 bonded phase silica cartridges at 10 ml/min, dried by passing a gentle
flow of nitrogen at 20 ml/min for 30 sec, and eluting the trapped PAHs with
500 Jll of p-xylene at 0.3 ml/min. The recoveries of PAHs were greater than
80%, with less than 10% relative standard deviations of nine determinations. No
major contaminants were present that could interfere with the recognition of
PAHs. It was also found that these bonded phase silica cartridges can be re-used
for the extraction of PAHs from water.
