A column switching high-performance liquid chromatographic technique for the determination of copper(ii), aluminium(iii) and iron(iii) as their 8-hydroxyquinolinate complexes using spectrophotometric detection at 400 nm is described. On-line preconcentration of the metal chelates was effected using a 10 x 1.5 mm i.d. pre-column packed with CI8 reversed-phase sorbent. The pre-column was mounted before the analytical column; by manual actuation of a six-port switching valve it could be switched on-line. The metal chelates were resolved by reversed-phase high-performance liquid chromatography on the analytical column following elution from the pre-column with the appropriate mobile phase. A systematic approach to this type of trace enrichment is outlined, and the results show an increase in both sensitivity and selectivity over previous methods. The linear dynamic range is from 5 ppb to 10 ppm for and from 40 ppb to 5 ppm for both Cull and Fell'. Application of the technique to waste water from a mine and to beverage samples is reported.