Determination of copper ions at the sediment-seawater interface through ion-selective microelectrode based on current pulse

The chronopotentiometric measurements based on ion-selective microelectrode (ISμE) could be a promising tool for the detection of free copper ion in seawater at the sediment-water interface with high sensitivity. In this work, an all-solid-contact copper ion-selective microelectrode (Cu²⁺-ISμE) based on platinum wire was designed for chronopotentiometric determination of copper in seawater at the sediment-water interface. The lipophilic salt ETH 500 was added into the Cu²⁺-selective membrane instead of traditional ion-exchanger, and the extraction of copper could be galvanostatically controlled. The present chronopotentiometric method shows a linear activity range of 2.5 × 10⁻⁴ - 2.5 × 10⁻⁸ M with a slope of 34.75 ± 0.5 mV/decade under the optimized conditions, and the detection limit is 5.8 × 10⁻⁹ M. Moreover, the chronopotentiometric method has a good selectivity and reproductivity. Additionally, the feasibility of the Cu²⁺-ISμE has been investigated for the measurement of the content of Cu²⁺ in the seawater samples at the sediment-water interface with a small volume (e.g., 1 mL) without any pretreatment, and the spike recovery for this method is from 92.24 % to 106.51 %. Herein, the detection of copper through the pulse current based Cu²⁺-ISμE has satisfactory results. The galvanostatic controlled technique based on ISμE has potential application in the in-situ determination of trace heavy metals in seawater.