1-(2-pyridylazo)-2-naphthol (PAN) is a heterocyclic azo compound that forms inner, mostly reddish colored, water-insoluble chelates with many transition metal ions with metal ion-ligand ratios of 1:1 or 1:2. PAN is rather unselective but it does not form complexes with the alkali and alkaline earth metals, Ge(IV), As, Se and Te. Numerous reported techniques of pre-concentration have been considered for analyzing the role of PAN on the physiochemical outcome of the procedures. PAN been used as a chelating precipitant, flocculant, auxiliary complexing agent, as a ligand for anchoring on other supports with the purpose of introducing chelating property as well as selectivity. The role of PAN in the different techniques of pre-concentration, namely co-precipitation, membrane filtration, micro-extraction, cloud point extraction and solid phase extraction, has been investigated. PAN influences the optimum experimental parameters, namely pH, temperature, time, amount, tolerance limit, etc.
Keywords: 1-(2-pyridylazo)-2-naphthol; chelating agent; heavy metals; pre-concentration.