Quantitative determination of DNA adducts using liquid chromatography/electrospray ionization mass spectrometry and liquid chromatography/high-resolution inductively coupled plasma mass spectrometry This contribution is dedicated to the memory of Professor Wilhelm Richter.

Abstract

The quantitative determination of nucleotides from DNA modified by styrene oxide is described using a combination of inductively coupled plasma high-resolution mass spectrometry (ICP-HRMS) and electrospray ionization mass spectrometry (ESI-MS), both interfaced to reversed-phase high-performance liquid chromatography (HPLC). LC/ICP-MS (resolution >1500 to discriminate against 15N16O+ and 14N16OH+) was employed to determine quantitatively the content of modified nucleotides in standard solutions based on the signal of phosphorus; phosphoric acid served as an internal standard. By means of the standard addition technique the sensitivity of the LC/ESI-MS approach was subsequently determined. Since a comparison of UV, ICP and ESI-MS data suggested that in ESI-MS the ionization efficiency of the adducts is identical within the error limits, quantitative determination of all adducts is possible. For LC/ESI-MS with single ion monitoring, the detection limit for styrene oxide adducts of nucleotides was determined to be 20 pg absolute or 14 modified in 108 unmodified nucleotides in a 5 μg DNA sample, which comes close to the best methods available for the detection of chemical modifications in DNA Copyright © 1999 John Wiley & Sons, Ltd.