Quantitation of Urinary 7-Methyladenine by Gas Chromatography-Mass Spectrometry Using Isotopically Labeled Internal Standards

✍ Scribed by H.G. Mandel; J.J. Kusmierz; B.F. Dickens; L.W. Anderson

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 555 KB
• Volume: 217
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1006/abio.1994.1121

✦ Synopsis

We have developed a procedure for isolating and quantifying 7 -methyladenine from rat urine following the administration to the rat of methylating agents, such as dimethylnitrosamine. Urinary 7-methyladenine and its trideutero isomer, added as an internal standard, were precipitated with silver nitrate, the precipitate was extracted with (\mathrm{HCl}), and the extract was further purified by (\mathrm{C}_{18})-Sep-Pak chromatography. The recovered 7 -methyladenine was then derivatized with pentafluorobenzyl bromide at alkaline (\mathrm{pH}) for analysis by gas chromatography-mass spectrometry, indicating a bis(pentafluorobenzyl) conjugate, (m / z 509). The mass spectrum of this derivative shows a major fragmentation ion at (m / z 328) (and 331 for the trideutero derivative) resulting from the loss of one pentafluorobenzyl group. Levels of urinary 7 -methyladenine above (150 \mathrm{pg}) could be detected from the ratio of the gas chromatography peak areas for these ions, using selective-ion monitoring. The method was selective for the 7 -methyl isomer. The procedures developed for the syntheses of deuterated and tritiated 7 -methyladenine, which were required for these studies, are also described. (c) 1994 Academic Press, Inc.