Metal speciation analysis has wide applicability and reveals how and when metals are available to engage in chemical processes. Real systems can be physically hard to reach, chemically dynamic, and sample collection and pretreatment fundamentally alter speciation. Therefore, there is great interest in in situ trace metal speciation sensors that can be integrated into on-site, portable analysis devices. Electrochemistry is an attractive method since the sensing component can be fashioned into a submersible probe. In this review, we define a set of criteria that an electrochemical approach must conform to for in situ metal analysis and review methods that closely follow these criteria. As an emerging technique, fast-scan cyclic voltammetry is introduced. Next design and material of analysis probes is detailed, followed by a discussion of portable instrumentation. Finally, studies that show promise towards a portable, in situ metal analysis device are showcased and ongoing analytical challenges are outlined. To read the rest of the article click here.