2. Experimental
2.1. Materials and chemicals
All chemicals were analytical-reagent grade and all solutions
were prepared with doubly distilled deionized water (DDW). The
thermoseparating triblock copolymer L44 [(PEO)10(PPO)23(PEO)10,
molar mass 2200 g mol1] was produced by Haian Petrochemical
Plant (Haian, China). Two buffer solution, sodium tetraborate–
sodium hydroxide (Na2B4O710H2O–NaOH), citric acid-disodium
hydrogen phosphate sodium (C6H8O7-Na2HPO4) and Pb(NO3)2 used
in this experiment were all obtained from Sinopharm Chemical
Reagent Co. Ltd (Shanghai, China).
A stock standard solution of Pb(II) was prepared by an appropriate
amount of Pb(NO3)2 into a 100 mL flask and diluting with DDW.
Working solutions of Pb(II) were made daily by suitable dilution of
the stock solutions with DDW.