Analysis of 5-methoxytryptamine in brain by gas chromatography mass spectrometry.

A quantitative gas chromatographic mass spectrometric method using a deuterated analogue as internal standard were developed for the analysis of 5-methoxytryptamine in brain. The internal standard was synthesized in two steps and possessed high isotopic purity. The analytical procedure involves the addition of the internal standard to the homogenizing medium containing the tissue, followed by homogenization, extraction with chloroform and derivatization with pentafluoropropionic anhydride. The identification and quantitation of 5-methoxytryptamine is based on monitoring the ions at m/z 306, 319 and 482 for the pentafluoropropionyl derivative of 5-methoxytryptamine and m/z 308, 322 and 486 for the internal standard. Using this procedure 5-methoxytryptamine was identified and quantitated in the sheep pineal gland. The mean 5-methoxytryptamine level (N = 12) was 545 +/- 180 pmol g-1.