A flow-injection analysis of sulphate using a reaction column packed with barium chloranilate (BaCh) is described. The chloranilate ion released by the reaction is monitored at the isosbestic point (310 nm) of chloranilate. An aqueous solution of 2-propanol (60%) is used as the carrier solution at a flow-rate of 1 ml . min−1. The linear dynamic range of the detection system is approximately 2.5×10−6∼1.0×10−3 mol/l per 10 μl sample injection. The time required for a determination is only 20 s per sample injection. The method has also been applied to the amplified determination of phosphate by reaction with molybdate resulting from the decomposition of molybdophosphate (H3PO4.MoO3) extracted.