Electrospray ionization coupled with low energy collision induced dissociation (CID) in an ion trap mass spectrometer was used to examine the fragmentation patterns of the [M + Na](+) of eight pairs of heptapeptides containing α- or β-Asp residues in second and sixth amino acid positions, respectively. Selective cleavages at the peptide backbone C-terminal to two Asp residues were observed, which generated a series of C-terminal y(5) ions and N-terminal b(6) ions. Two typical ions: [y5 + Na - H]+ and [b6 + Na + OH]+, produced by α-Asp containing peptides were noted to be much more abundant than those of the peptides with β-Asp, which could be used for distinction of the isomers in Asp2 and Asp6, respectively. In addition, a series of internal ions generated by simultaneous cleavages at Asp residues were detected. Competitive reactions of carboxylic groups occurred between Asp6 side chain and C-terminus. Formation mechanisms of most product ions are proposed. The results obtained in this work are significant since low energy CID has been demonstrated to be effective for the distinction of Asp isomers.

This paper researched on the adsorption kinetics and thermodynamics of the typical components of petroleum hydrocarbon-benzene, naphthalene, phenanthrene and their mixed solution on the typical media-the medium sand from the aquifer in an oil contaminated field, with a self-made rotary adsorption device. The result showed that the adsorption of the three adsorbates on the media follows the Henry adsorption model, no matter when they are separated or mixed. The adsorption capacity order of benzene, naphthalene and phenanthrene on the medium sand is phenanthrene> naphthalene>benzene, when they are separated or mixed. Comparing with the adsorption capacity when the adsorbates are single, benzene and naphthalene in the mixed solution shows stronger adsorption capacity, while phenanthrene carries on less adsorption capacity.

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Through the column simulation experiments, this paper researched on the naphthalene migration in the typical aquifer media-gravel sand and coarse sand in a petroleum contaminated field. The research also quantified the retardation of the two medium to the important petroleum component-naphthalene, by giving the retardation parameter after the chlorine breakthrough experiment. The results showed that the migration of naphthalene in the medium is not only influenced by the convection and the dispersion, but also the adsorption and the biodegradation, which is much stronger in the coarse sand than it is in the gravel sand.