Application of pressure assisted electrokinetic injection technique in the measurements of DNA oligonucleotides and their adducts using capillary electrophoresis-mass spectrometry

The identification and measurement of negatively charged DNA oligonucleotides and their benzoa]pyrene-7,8,9,10-tetrahydro-7,8-dihydrodiol-9,10-epoxide (BPDE) adducts by capillary zone electrophoresis (CZE) hyphenated mass spectrometry (MS) system using an on-line enrichment technique, the constant pressure assisted electrokinetic injection (PAEKI), is described here. With optimized PAEKI conditions, an on-line sample concentration power of 300-800 times could be reached for both single-stranded (ss) and double-stranded (ds) oligonucleotides during a 90-s PAEKI injection. The detection limits using single quadrupole MS in the scan mode were 0.01-0.03 microM for ss and 0.04-0.08 microM for ds oligonucleotides, respectively. The relative standard deviations at 1 microM of oligonucleotides were from 7.6 to 15.8%. A dynamic linear calibration range of about two orders of magnitude were observed. Good mass spectra of oligonucleotides and BPDE-oligonucleotide adducts at low micromolar levels could be obtained using single quadrupole MS which could be a helpful tool in DNA adducts studies.