IDENTIFICATION OF POTENTIALLY MUTAGENIC CONTAMINANTS IN THE AQUATIC ENVIRONMENT BY LIQUID-CHROMATOGRAPHIC THERMOSPRAY MASS-SPECTROMETRIC CHARACTERIZATION OF IN-VITRO DNA-ADDUCTS

Liquid chromatographic-thermospray mass spectrometric (LC-TSP-MS) char acterization of chemical adducts of DNA formed during in vitro reactio ns is proposed as an analytical technique to detect and identify those contaminants in aqueous environmental samples which have the propensi ty to be genotoxic, i.e. to covalently bond to DNA. The approach for d irect-acting chemicals includes the in vitro incubation of DNA with co ntaminated aqueous samples at 37 degrees C, pH 7.0 for 0.5 to 6 h, fol lowed by enzymatic hydrolysis of the DNA to deoxynucleosides and LC-TS P-MS analysis of the resultant solution. A series of allylic reagents was used as model reactive electrophiles in synthetic aqueous samples to demonstrate that adduct formation was linear with both contaminant concentration and electrophilic reactivity potential. The characteriza tions can also estimate the proportion of bonding to different sites o n a base, for instance, the ratio of O-6- to 7-alkylguanine (oxygen vs . nitrogen bonding) products, which is an important parameter in asses sing the genotoxicology of chemicals.