Nutrient Detection Sensors in Seawater Based on ISI Web of Science Database

Abstract

Marine ecosystem is increasingly deteriorating. In order to assess anthropogenic influence and instigate appropriate remedial actions, it is still of great significance to develop the technology of sensors applied for nutrient detection (e.g., nitrate, phosphate, and silicate) in seawater. This brief review shows an important direction for the development of nutrient detection sensors in seawater and also the limitations and challenges based on data from the ISI Web of Science database. Being different from previous review papers, in this short critical review paper (1) we unified the unit of limit of detection (LOD) for making the comparison within different researches possible; (2) only the literatures focusing on the technological development of sensors in seawater were used; and (3) not only the detection methods but also the detected analytes and publication years were discussed to supply more valuable information for the development of nutrient sensors applied in seawater. In total, 109 literatures were collected with regard to technological development. The quantity of literatures has increased most during 2011-2020. For analytes, literatures related to nitrate, phosphate, ammonium, and phosphate will continue to increase with more accurate data. For detection methods, spectrophotometry, colorimetry, fluorimetry, and electrochemistry are the most widely used sensors. LODs show thousands of orders. In general, there are lower LOD to nitrite and ammonium and fluorimetry method. Now, for analytes, $\text{nitrate}\left(1.0983\right)>\text{silicate}\left(0.5495\right)>\text{phosphate}\left(0.4823\right)>\text{ammonium}\left(0.1324\right)>\text{nitrite}\left(0.0568\right)$ . For detection methods, $\text{microfluidics}\left(1.7617\right)>\text{electrochemistry}\left(1.2607\right)>\text{colorimetry}\left(0.4462\right)>\text{spectrophotometry}\left(0.2941\right)>\text{fluorimetry}\left(0.0558\right)$ . This result indicated that the development level of detection methods is closer for nitrate, nitrite, phosphate, and silicate. For ammonium, spectrophotometry has significantly lower LOD than electrochemistry ( $p<0.05$ ), and fluorimetry also has significantly lower LOD than electrochemistry ( $p<0.05$ ). Our results imply that sensors with accurate LOD should be developed in the future. In addition, more detection methods should be considered by future sensors.