Chiang Mai Journal of Science

     A sequential injection analysis incorporated with spectrophotometric method was developed for determination of lead, based on reaction of dithizone with lead producing pink complex and absorbance of the complex was measured at 515 nm. The analytical parameters of the system were optimized by univariate method such as reagent concentration, fl ow rate of reagent and injection volume. Linear calibration curve over the range of 0.02-0.08 mg L^-1 and 0.1-2.0 mg L^-1 lead was obtained. The detection limit of lead was 0.012 mg L^-1. The relative standard deviations for fi ve replicate injections was 0.77-1.54% for intra-day and 0.86-1.80% for inter-day. The recovery of 98.75-101.20% was achieved with sample throughput of 45 samples per hour. The proposed method has been applied to the determination of lead in vegetable samples. The obtained results were in good agreement with those obtained by the ICP-MS standard method, verifi ed by the student t-test at the 95% confi dence level.