The flow system was configured in two steps as shown in Fig. 1.In the first step (Fig. 1a), the 0.1 mol L1 HNO3 solution eluted the analytes (from the RACNT) through the TS-FF-AAS at 0.75 mL min1. At the same time, the sample loop was filled with 2 mL of standard/sample. In the second step (Fig. 1b), the injector was commuted and a phosphate buffer carrier solution(0.01 mol L1, pH¼5.7) led the sample through the RACNTs column at a 0.75 mL min1 flow rate. The proteins were excluded to the waste and monitored at 240 nm in a UV–vis spectrophotometer and the Pb2þ was retained in the RACNTs' core.Afterwards, the system returned to position “a” and the analyte was eluted and led to the detector. A conditioning loop was used to eliminate the acidic residues from the column before the sample extraction.