Determination of Homovanillic Acid and Vanillylmandelic Acid in Neuroblastoma Screening by Stable Isotope Dilution GC-MS

A method for the quantitative determination of homovanillic acid (HVA) and vanillylmandelic acid (VMA), two metabolites of catecholamines, is presented. The assay is based on gas chromatography/electron impact mass spectrometry. The preparation of 13C‐labeled VMA from [13C6]vanillin is described. Together with purchased deuterated HVA the 13C‐labeled VMA is used as an internal standard in stable isotope dilution GC/MS. The method involves elution from soaked filter‐papers, determination of creatinine content, extraction of HVA and VMA from eluted and urinary samples and derivatization to the di‐and tri(trimethylsilyl) derivatives, respectively. The detection limits were found to be 4.0 pg for HVA and 0.8 pg for VMA. The method was applied to the routine determination of urinary HVA and VMA in a range from 5 to 100 ng HVA and VMA per μg creatinine. The lower limits of pathological concentrations are set at 35 ng μg‐1 creatinine for HVA and to 20 ng μg‐1 creatinine for VMA, which are in close correlation with the values from other methods, but with the main advantage of reducing the amount of questionable or elevated results from 6.7% (high‐performance liquid chromatography (HPLC) alone) to 0.9% (HPLC and GC/MS). © 1997 by John Wiley & Sons, Ltd.