sion of 0.01% can be achieved, and it may be possible to achieve accuracies this good in special cases.

The coulometric principle can be applied in many different ways to determine specific substances. The most obvious and direct way is to electrolyze a sample of known volume at constant potential. However, coulometry can also be applied in titrations at constant current, employing a reagent that is oxidized or reduced in the process. Coulometry may also be employed in titrations by coulometric generation of reagent. Examples include the determination of CO₂ by reaction with ethanolamine, with subsequent titration with coulometrically generated base. Another coulometric reagent generation is for determination of SO₂ by coulometrically generated iodine. Coulometric titration is now the method of choice for determination of TCO₂ in seawater (Johnson et al., 1987). Finally, it can be used for the generation of standards, particularly for substances that are difficult to prepare and store, and for in situ calibration. Coulometry may also be used for detection in liquid chromatography and flow injection analysis.

New electrochemical techniques can be applied directly to presently employed amperometric methods to optimize the potential-time waveform and current sampling scheme. For example, steady-state amperometric measurements at constant potential may be converted to pulsed operation with synchronous sampling of current in a way that improves performance but is transparent to the user. Optimal sampling schemes for individual methods can be developed through laboratory research. This type of development is exemplified by the Endeco^® pulsed oxygen sensor. For remote operation, as from buoys, improvement in performance of computers should make it possible to convert amperometric techniques to voltammetric techniques. Determining the voltammetric response (which might consist of 150 data points per concentration measurement) provides better statistical definition of the current-concentration relationship. Knowledge of the voltammetric response could also provide the ability to compensate directly for changes in the properties of the reaction being used to determine concentration. This approach is presently practical in a laboratory research setting and, assuming further improvements in technology of computers, should be possible in oceanographic applications in the near future. Again, this type of development could be made transparent to the user.

The size, shape, and material of the electrode can be tailored to the application. Problems of response time, for example, often can be solved by using a smaller electrode. The use of new electrode materials, including possibilities for modification of the electrode surfaces, could lead to new measurement capabilities. This emphasizes the importance of the development of polymers, new materials, and recognition chemistry, as discussed in the section on new chemistry. Size, shape, and choice of material all present new technical opportunities that can be applied now, but also present many