The system can also be used to measure glucose in other fluids, such as cell culture medium. Use of enzymes other than glucose oxidase (e.g., cholesterol oxidase, lactate oxidase, or D- 3-hydroxybutyrate dehydrogenase15) will enable the measure- ment of other metabolites, (e.g., cholesterol, lactate, or D-3- hydroxybutyrate, respectively), making this system versatile for general clinical applications. It also has the potential for multiplexed analyses. The analytical platform can be adapted for checking water quality using anodic stripping voltammetry,