A PVC-membrane bulk optode for gallium(III) ion determination

An optical probe responsive to gallium(III) ion has been developed. The gallium sensing system was prepared by incorporating 4-(p-nitrophenyl azo)-pyrocatechol (NAP) as ionophore in a plasticized PVC membrane containing tributylphosphate (TBP) as plasticizer. The sensing membrane in contact with gallium ion at pH 3.5, changes color from yellow-brown to pink-brown. Under optimum conditions, the proposed membrane displayed a linear range of 5–83 μM with a limit of detection of 4 μM. The response time of the membrane was within 10–15 min depending on the concentration of Ga3+ ions. The selectivity of the probe towards gallium determination was found to be very good. Experimental results showed that the probe could be used as an effective tool in analyzing the gallium content of water samples.