Unusual PLS application for Pd(ii) sensing in extremely acidic solutions

An economic and extremely selective device for Pd(ii) determination in very acidic solutions, TazoC-Mar@ is presented. The sensor was prepared via an ion exchange technique of an azoic ligand, (2-(tetrazolylazo)-1,8 dihydroxy naphthalene-3,6,-disulphonic acid), named TazoC, on a Macroporous Strong Anion Exchange Resin, namely Marathon® (Dow Chemical-USA). The TazoC-Mar@ rapidly forms complexes with palladium(ii) ions, which give an intense blue colour to the solid phase, even at low pH. The reaction is highly selective and no other metal ions react with the device at this pH. Moreover, the quantification of Pd(ii) is reliable when applying partial least squares regression (PLS) to relate the signal to the metal ion concentration. The regression model gives a good fit and correct predictions of Pd(ii) concentrations in unknown samples. The method presented here is highly sensitive with an LOD and LOQ equal to 0.2 nM and 0.5 nM, respectively.