A highly versatile stable optical sensor based on 4-decyloxy-2-(2-pyridylazo)-1-naphthol in Nafion for the determination of copper

A new optical chemical sensor based on the recently synthesized azo dye, 4-decyloxy-2-(2-pyridylazo)-1-naphthol (DPAN), immobilised in Nafion membranes is reported. The sensing membranes cast onto glass substrates and integrated into a flow-through measuring cell were homogeneous, transparent, mechanically stable and showed no evidence of reagent leaching. The DPAN/Nafion sensor was used for the determination of Cu(II) which forms a blue coloured complex with DPAN. The main parameters of the computer controlled flow system incorporating the flow-through optical sensor, a multi-port selection valve and a peristaltic pump were optimized. The duration of the time during which the sample was aspirated into the flow system governed the sensitivity and working range of the Cu(II) determination thus making the system easily adaptable to a wide range of Cu(II) concentrations in the samples analyzed. The copper content in solutions obtained after dissolving turnings of certified aluminium bronze and bronze standards was determined using 90 s aspiration time while a 600 s aspiration time was required for the determination of the Cu(II) concentration in tap water. Satisfactory agreement with atomic absorption spectroscopy (AAS) results and the bronze standards specifications was obtained in all cases.