Determination of Oceanic Carbon Dioxide Using a Carbonate-Selective Electrode (original) (raw)

Potentiometric properties of the PVC membrane-based electrodes prepared with molecular tweezer-type neutral carriers, 3,12-bis(TFAB)CA and deoxy-3,12-bis(TFAB)-CA, and trifluoroacetyl-p-decylbenzene (TFADB) were measured in buffered electrolytes (0.1 M Tris-H 2 SO 4 , pH 8.6 and 8.0) and artificial seawater. It was observed that the deoxy-3,12-bis(TFAB)CA-based electrode provides greatly enhanced carbonate selectivity over chloride (log K CO 3 2-,Cl-POT ∼-6) and other minor anions present in seawater. Thus, we explored the possibility of applying this new carbonate-selective electrode for direct determination of oceanic carbon dioxide. The total carbon dioxide (TCO 2) level in surface Yellow Sea water was determined with the deoxy-3,12-bis(TFAB)CA-based electrode, Severinghaustype CO 2 gas sensor, and the traditional potentiometric titration methods. The results showed that the carbonateselective electrode provides accurate oceanic TCO 2 determination comparable to that obtainable with the other two methods. The analytical procedure based on a carbonate-selective electrode is clearly advantageous over other conventional methods: it does not require any sample pretreatment and extra reagents other than the standard calibration solutions, while providing the measured results directly and immediately.