Handling and detection of 25 amol of near-infrared dye deoxynucleotide conjugates by capillary electrophoresis with laser-induced fluorescence detection

Near-infrared dyes are attractive as labeling reagents to enhance sensitivity in trace analysis largely because background fluorescence is low in this spectral region. Here we demonstrate, towards a goal of detecting DNA adducts in small biological samples, that some near-infrared (IR) dye-labeled deoxynucleotides can be separated and detected with high sensitivity by capillary electrophoresis (CE)–laser-induced fluorescence detection (LIF) in a realistic way (handling detection limit of 25 amol) for near-IR dye-labeled deoxynucleotides. This detection limit is achieved by polarity-switching injection of 2.0 μl from a volume of 5.0 μl, in which the compounds are 5·10 −12 mol/l in 50% aqueous methanol. Although the adenine and cytosine-containing conjugates co-migrated, the other three (guanine, N 2-ethylguanine and thymine) were resolved.