Abstract: The color reaction of lead and non-water soluble reagent meso-tetrakis (4-nitryl) porphyrin (TNPP) was studied for propolis assay with spectrophotometric method. The effects of temperature, pH and time etc. on stability of this complex were assayed. An excellent method that can be used to determine the lead in food or medicine has been ascertained. The experimental results indicated that in the presence of hydroxylamine hydrochloride, with ortho-dinitrogenous ptenanthrene,NH4SCN and seignette saltat as masking agents, meso-tetrakis-(4-nitryl) porphyrin and lead can produce light yellow complex. This response can be produced completly by being heated in 50 ℃ water baths for 20 minutes. A stable l:1 (M:L) complex forms. The Soret band of the complex is at 673 nm. Beer’s law is obeyed in the range between 0～10 μg of lead per ml with r=0.9865. In order to achieve the lead ions enrichment, this experiment can be carried into effect through traditional ashing digest method. It is easy to operate and the repeatability is good, so it can be use for the determination of plumbous trace amount in the medicines. The result is satisfactory. This method has also been used to determine the trace of lead in food with satisfactory results.

Key words: lead, meso-tetrakis (4-nitryl) porphyrin, spectrophotometric method