Urinary sulfur compounds in Down syndrome.

internal standard (leucinol) was added. Separation was performed on a C18 Zorbax (Agilent Technologies) column [15 3 0.46 cm (i.d.)] using the following mobile phase: 450 mL/L acetonitrile in sodium acetate buffer (0.5 g/L) adjusted to a final pH of 6.1 with glacial acetic acid. The flow rate was 1.2 mL/min. The wavelengths for excitation and emission were 338 and 445 nm, respectively. The patients’ urine samples were found to contain 887 and 1340 mg/L heptaminol, respectively. Lastly, heptaminol was added to drug-free urine specimens to determine the response of the AxSYM FPIA assay for amphetamines. The results are presented Table 1. Because the cutoff concentration was 500 mg/L, urine specimens were positive for heptaminol concentrations $750 000 mg/L. In conclusion, heptaminol exhibits cross-reactivity (;0.06%) with the AxSYM FPIA Amphetamine/Methamphetamine II assay, but gives false-positive results only with high urine concentrations of heptaminol.