Flow injection on-line preconcentration of palladium by ion-pair adsorption in a knotted reactor coupled with electrothermal atomic absorption spectrometry

A flow injection (FI) method for the preconcentration/separation of palladium, coupled with electrothermal atomic absorption spectrometry (ETAAS), is presented. The preconcentration was performed by on-line formation of an ion-pair between the positively charged potassium complex of 1,4,7,10,13,16-hexaoxacyclooctadecane (K+18-crown-6) and the palladium thiocyanate anion (Pd(SCN)42−) and its sorption on the inner walls of a PTFE knotted reactor (KR). The elution was achieved by methanol acidified with 1% (v/v) HNO3. An enhancement factor of 29 and a sampling frequency of 14 h−1 were obtained for a preconcentration time of 90 s and a sampling flow rate of 4.4 ml min−1. The detection limit (3σ) is 16 ng l−1 and precision (RSD) for 0.4 µg l−1 Pd is 2.3%. The method was validated by recovery measurements on spiked blood and road dust samples.