I. INTRODUCTION Chemical speciation may be defined as the determination of the individual concentrations of the various chemical forms of an element which together make up the total concentration of that element in a sample. The next decade will certainly see a blossoming of interest from chemists, biochemists, and biologists in techniques for chemical speciation. This is because it is becoming more and more apparent that both bioavailability and toxicity are critically dependent on the chemical form of the substance under test. Measurement of the total concentration of a nutrient or a trace element provides very little information about the bioavailability of the substance, since many vitamins and essential elements are now known to exist in a variety of chemical forms, the assimilability of which vary greatly.1–3 For example, niacin and folic acid exist in some foods in bound forms which are unavailable to many species,4 and the same is true of a whole range of essential metals, including iron, zinc, co...

Chemical speciation in natural waters

Reduction of ionic species by fulvic acid

The theoretical basis of trace metal complexing capacity of natural waters and the analytical methods used to measure it are reviewed. The current literature on this subject is also reviewed, in an attempt to draw out the most important features relating to the validity of the methods used and the nature of the metal‐binding ligands and complexes formed.

James W. Dillard

Papers

Evaluation of micromolar compleximetric titrations for the determination of the complexing capacity of natural waters