Abstract: Methadone (I) is determined in tablets and urine in the presence of other drugs after reduction on a Cd or Zn micro-column and flame AAS detection of the metal ions released. For urine, a 5 mL sample is made alkaline with NaOH and extracted with CH2Cl2. The residue from evaporation of the extract, is dissolved in water, and the solution is adjusted to pH 4.0 with 0.01 M acetic acid. Crushed tablet (200 mg) is dissolved in water by shaking for 55 min and filtering. The final solution (90 µL), at pH 3.3 to 4.3, is injected into a carrier stream of water (3.0 mL min-1) which proceeds to the reduction column (8.5 cm x 1.8 mm) and subsequently to the spectrometer. The calibration graph is rectilinear from 5 to 50 ng mL-1 of I. Recoveries from either column are quantitative, and coefficient of variation in urine (n = 3) are 1.2 to 3.0%. Sampling frequency is 150 h-1, and other drugs do not interfere.