APPLICATION OF GAS-CHROMATOGRAPHY ELECTRON-CAPTURE NEGATIVE CHEMICAL-IONIZATION HIGH-RESOLUTION MASS-SPECTROMETRY FOR ANALYSIS OF DNA AND PROTEIN ADDUCTS

The analytical potential of gas chromatography/electron capture negati ve chemical ionization high-resolution mass spectrometry (HRMS) for ch aracterization and quantitation of DNA and hemoglobin adducts was demo nstrated using three model compounds: N-2,3-ethenoguanine (EG), 7-(2-h ydroxyethyl)guanine (7-HEG), and N-(2-hydroxyethyl)valine (HEV). At a resolving power of 10 000, the signal-to-noise (S/N) ratios obtained f rom quantitative selected ion monitoring (SIM) experiments using biolo gical samples were comparable to or better than existing unit mass res olution experiments due to the reduction of chemical noise from the us e of narrower mass windows. The specificity gained by HRMS was essenti al for quantitation of ultratrace amounts near the limit of detection since coeluting interferences of the analyte or internal standard can lead to inaccurate measurement of response factors. The limit of detec tion (LOD) was 100 amol (S/N = 5) using a pure standard of TTB2-EG. Th e LOD for complete assays using spiked samples was 500 amol (S/N = 5) for EG and 600 amol (S/N = 5) injected for 7-HEG. The standard deviati on (SD) for the HRMS quantitative measurements was typically less than 10%. The SD for the complete biological assays as determined by spiki ng replicate samples was less than 15%. This method has adequate sensi tivity and specificity to accurately measure DNA and protein adducts a s low as endogenous concentrations in rodent and human tissues.