ABSTRACT
Once the analyst has prepared an aqueous solution representative of the metal or alloy sample, several options present themselves, nearly all of them involving some form of chemistry. The chemistry involved in preconcentration, separation, masking, and measurement is usually complex. Preconcentration, although a widely used term with a well-defined meaning, is actually a semantic redundancy. In concentrating the analyte by solvent evaporation one is usually also concentrating sample matrix components and dissolution medium components, and sometimes separation medium components as well. Group separations are extremely useful to remove a major amount of the sample matrix from the analyte. Perhaps the most generally useful class of group separations are precipitations, and especially in the case of trace analysis, coprecipitations. A classic example of the use of coprecipitation to preconcentrate a group of trace elements is the collection of antimony, bismuth, thallium, and tin in a manganese dioxide precipitate.
