Matrix‐assisted laser desorption time‐of‐flight mass spectrometry of oligonucleotides using 3‐hydroxypicolinic acid as an ultraviolet‐sensitive matrix

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Abstract
Matrix‐assisted laser desorption time‐of‐flight mass spectrometry has been used to produce quasimolecular ion signals from underivatized mixed‐base single‐stranded DNA oligomers ranging from 10 to 67 nucleotides in length. These results were obtained with a new matrix material, 3‐hydroxypicolinic acid (3‐hydroxypyridine‐2‐carboxylic acid)which showed significant improvement over many previously reported matrices studied in terms of mass range available, signal‐to‐noise ratio, and the ability to analyze mixed base oligomers. The desorption and simultaneous ionization was by pulsed laser light at 10 to 50 mJ/cm2, studied at 266, 308, and 355 nm. Spectra taken at 266 nm provided the smallest amounts of doubly charged and dimer ions—characteristics desirable for DNA sequencing by this technology. Negative‐ion spectra were uniformly superior to positive‐ion spectra. This new matrix also is quite effective for molecular weight determinations of peptides and proteins in both positive‐ and negative‐ion modes.