The article shows the possibility of using sodium 4-amino-5-hydroxy-3 - ((e) - (4-nitrophenyl) diazenyl) - 6 - ((e) -phenyldiazenyl) naphthalene2,7-isulfonate, immobilized on polyacrylonitrile fiber PPD, as a reagent for the determination of lead ions. The optimal conditions for immobilization and complexation were found.