Investigations into the extraction and the determination of polycyclic aromatic hydrocarbons (PAHs) from water by solid-phase extraction and capillary gas chromatography/ mass spectrometry

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.

Mass spectrometric studies on aryltin compounds and alkali halides /

The fragmentation behavior of aryltin compounds [(p-ThAnis)nSnPh4.n (n=l-4); (p-ThAnis)3SnX (X=C1, Br, I); (o-CH30C6H4)3SnCl; Ph3Sn(o-pyr)] have been studied comparatively under EI and FAB ionization modes. Alkali halides were run under FAB mode. For the aryltin compounds, the effect of ligand type on the spectra have been explored in both EI and FAB modes. The fragmentation mechanisms have been examined with linked scans, such as fragment ion scans (B/E) and parent ion scans (B^/E). Ab Initio molecular orbital calculations were used to determine the structures of the fragments by comparing their relative stabilities. In the EI MS studies, negative ion EI mode has also been used for some of the aryltin compounds, to examine the possible ion molecule reactions under low pressures at 70eV. In the positive ion FAB MS studies, matrix optimization experiments have been carried out. Negative ion FAB experiments of all the compounds have been done in two different ways. Finally, the comparison of the two methods, EI MS and FAB MS, have been made.For alkali halides, the studies focused on the FAB MS behavior under different conditions. The intensities of cluster ions were reported, and the anomalies in the intensity distribution was also discussed.