The application of electro-analytical techniques to sea water analysis

Abstract

Some seven tenths of the earth's surface is occupied by sea water containing roughly three and a half per cent salts in solution. It is therefore not surprising that many sciences are applied to the study of this medium and an understanding of the chemistry of the sea is basic to all the other studies.
A knowledge of variations in salt concentration, distribution of suspended material, thermal gradients &c. is required for the
oceanographic study of translation of water masses. In ocean waters remote from the influence of tidal action, land drainage and similar disturbances, slight changes in the above-mentioned properties may be of considerable significance.
In marine biology, inter alia, a knowledge of the cheinical nature of the waters is required. In this case considerable
emphasis is laid on analysis such as the determination of phosphate, organic nitrogen, carbonaceous matter 8cc.
Within the field of fishery research and development, pollution control and marine engineering, the chemical analysis of
sea water forms an integral part of most projects.
There are many determinations common to several, if not all, the individual studies of sea water. The standard of accuracy,
or rather discrimination, to which any particular property is determined is dependent upon the application to which the result is subsequently to be put.
For instance, the determination of salinity (see page 4'E in the oceanographic study of current distribution requires values
quoted to at least.i. 500 parts per million (p.p.m.). For fishery development work applied to the cultivation of shellfish however, salinity values quoted to ± 5000 p.p.m. would be satisfactory.
Certain parameters, frequently involved in sea water studies, are considerably influenced by the apparatus and method used for sasnpling (see page 26). Accuracy is thus often limited by sampling rather than analytical technique.
The complexity of the problem of general water analysis may be seen by examining Table 1 below. This table is not intended as an exhaustive list of analytical methods nor of their applications to water analysis. It is intended as a brief indication of the range of analytical techniques required for general water studies. frequently, with sea water analysis, large numbers of sampies require analysing on a routine basis. Sometimes, due to the need for further samples on a successive tidal cycle, or perhaps deteriorating weather conditions in the open sea, a rather tight time limit for completion of analysis is imposed.
It is in cases such as this that some electroanalytical techniques are particularly suitable although there are also many
other applications where these methods have replaced older methods by virtue of improved accuracy and speed.
Whitnac$ 7 sums up the position nicely in his paper "The application of cathode ray polarography in the field of oceanography" in which he states:- "Present day research on the physical, chemical and biological phenomena of the deep ocean has placed new requirements on the methods of analysis that are needed in support of this work. Modern electroanalytical methods appear to have the desired range of precision, reproducibility and sensitivity that will be required,
plus the feature of using the basic principles in direct reading instrumentation with digital recording of data."