a flow injection system for the spectrophotometric determination of lead after preconcentration by solid phase extraction onto amberlite xad-4

An on-line flow injection analysis (FIA) system for determination of lead (II) in water samples with a preconcentration step and spectrophotometric detection was investigated. The system is based on preconcentration of lead (II) on a column packed with Amberlite XAD-4 resin and detection by means of 4-(2-pyridylazo)resorcinol (PAR)–lead complex formation with maximum absorption at 523 nm. Chemical and FIA variables influencing performance of the system were optimised. Two linear calibration curves with a range of 0.01 - 0.40 and 0.40 – 0.80 mg L-1 were obtained. The developed system allowed a throughput rate of 16 samples h-1 with a 9-fold enrichment factor and a detection limit of 7 µg L-1. Relative standard deviation for 10 replicated injections of 0.25 mg L-1 was 2.3%. Recoveries of the method were in the range of 80-94 %. The procedure was validated by analysis of lead (II) in real water samples, and the results were statistically compared with those obtained by flame atomic absorption spectrophotometry (FAAS). The results obtained both by the proposed method and by FAAS were in good agreement.