Developing a new method of 4-(2-pyridylazo)-resorcinol immobilization on triacetylcellulose membrane for selective determination of Ga3+ in water samples

An optical sensor responsive to gallium (III) ion has been developed. The water-soluble indicator 4-(2-pyridylazo)-resorcinol was lipophilized with N-cetyl pyridinium chloride in the form of an ion-pair (PAR-CPC) and subsequently immobilized on a triacetylcellulose membrane. Under optimum conditions the proposed membrane displayed a linear range of 1.80–25.00 μM for Ga3+ ions with a limit of detection of 0.54 μM at 503 nm. The response time of the membrane was within 8–10 min depending on the concentration of Ga3+ ion. The sensor could readily be regenerated with a hydrochloric acid solution (0.01 M) in a reversible manner and its response was reproducible (RSD = 2.5%). The optode revealed very good selectivity with respect to the considered cations including alkali, alkaline earth and transition ions. The proposed optode was applied to the determination of gallium (III) ions in water samples.