This article reports the use of solid phase spectrophotometry associated with flow injection technique for simultaneous determination of zinc and nickel with 1-(2-thiazolylazo)-2-naphthol (TAN) immobilized on a C18 bonded silica support in the concentration range from 0.30 to 1.0 μg mL −1 of both ions. The multicomponent analysis was implemented using the absorbance signals in different intervals of time in a flow injection analysis peak for each sample solution inserted into the analytical path. A partial least squares (PLS) algorithm for model construction was developed in QuickBasic 4.5 as a subrotine in order to assemble it in a data acquisition program, permitting the concentration estimation in real time. The proposed method was successfully applied to nickel and zinc determination in synthetic mixtures with analytical throughput of 43 samples per hour. The results obtained with the proposed method were compared with Inductively Coupled Plasma Atomic E Mission Spectrometry (ICP-AES) data, and the results agreed with 95% confidence level. © 2000 John Wiley & Sons, Inc. Lab Robotics and Automation 12:305–311, 2000