Improved sample preparation in determination of urinary metanephrines by liquid chromatography with electrochemical detection
Gupta, R.N.
Clinical Chemistry 36(3): 538-540
1990
ISSN/ISBN: 0009-9147 PMID: 2311229 Document Number: 354641
In this relatively simple procedure for extracting metanephrines from urine, after an internal standard (4-hydroxy-3-methoxybenzylamine in 1 mmol/L HCl) is added, the sample is hydrolyzed in a boiling water bath, then treated with ammonia and alumina. Excess ammonia is removed under reduced pressure and the sample is applied to a 1-mL Bond Elut SCX column, which is washed, and metanephrines and internal standard are eluted with 0.5 mmol/L sodium acetate/acetonitrile (3/1 by vol). Of this eluate, 5 .mu.L is injected onto a 15 cm .times. 4.6 mm (i.d.) column packed with 5-.mu.m octadecyl-silyl silica particles, which is eluted with a mobile phase containing tetramethylammonium perchlorate. Peaks are detected coulometrically at +0.28 V. In the resulting chromatogram, metanephrines give sharp peaks, well resolved from peaks for solvent and internal standard. There are no extraneous peaks for catechols or mono-oxygenated phenylethylamines. Results correlated well (r = 0.999, n = 13) with those by earlier described liquid-chromatography.