Abstract: The color reaction between lead and non-water-soluble reagent, tetraphenylporphyri (TPP) was studied in this research. Effects of some factors such as pH, temperature and reaction time, coexistent ion on the formation and stability of TPP-comples were investigated by spectrophotometric method. The optimal reaction conditions were confirmed, and a new method established for determining lead content in food. Results showed that with presence of hydroxylamine hydrochloride, stable comples could form by reaction between tetraphenylporphyrin (TPP) and lead with the complex ration 1:1 in alkaline medium (pH12), and the reaction could complete in boiling water within 20 minutes. The maximum absorption wavelength of the complex is 466 nm. As lead content in 0～1μg/ml range, the measured curve was linear and obeyed Beer’s alw. The satisfactory results were obtained when the method was used to determine trace lead in preserved egg.

Key words: lead, preserved egg, tetraphenylporphyrin(TPP), spectrophotometric method