Silicate marine electrochemical sensor

Abstract

• Marine reagentless silicate electrochemical sensor qualification and validation. • Sensor accuracy evaluated at more than 97 % using Certified Reference Material. • Spike and recovery experiments showed between 97.9 % and 100.1 % recovery. • In situ deployment and validation in Thau lagoon (Mediterranean Sea). • Good agreements between sensor data and colorimetric analyses of discrete samples. An autonomous electrochemical sensor suitable for in situ silicate detection and monitoring in marine environments, is presented without any use of liquid reagent. This paper shows silicate sensor characteristics and figures of merit using optimized chemical and electrochemical parameters. Under controlled laboratory conditions in a 40 L tank, good calibration between 1.63 and 132.8 μmol L −1 was obtained. The limit of detection and the limit of quantification obtained are respectively LOD = 0.32 μmol L −1 and LOQ = 1.08 μmol L −1 . No bias was found while analysing Certified Reference Material (CRM) solutions i.e. natural seawaters samples with different salinities and nutrients compositions. Repeatability test showed very good reproducibility of the measurement with low overall uncertainty, cumulating systematic error and reproducibility error, of 2.4 %. Accuracies obtained with the Silicate sensor are higher than 97.4 %, 95.3 % for the smallest concentration tested, under LOQ. Spike and recovery tests were conducted with two different CRM concentrations and showed 97.9–100.1 % recovery, indicating no matrix influence in the determination of silicate concentration using electrochemical sensor and its calibration process (realised with artificial seawater solutions). In situ deployment of silicate electrochemical sensor was realized in the Thau lagoon (Mediterranean Sea) at 1.6 m depth. A good agreement between the results obtained with the sensor compared to reference colorimetric measurements made at the Marine Station of Sète (France) validates sensor’s performances.