Limits of elemental chemical analysis with small samples

Abstract

Chemical methods of analysis, especially titrimetric and photometric, lend themselves to the accurate quantitative determination of elements in small samples of their compounds. Even today these methods still have their place beside the more modern “instrumental” methods. Several orders of magnitude exist between the statistically-calculated smallest sample that can be used with the microchemical method and that used in practice to obtain accurate results. There are several reasons for this difference, which are discussed. Errors arising in the grinding and weighing of the sample, chemical separation stages and in the method of determination are discussed, and examples with organic and inorganic materials given.

The lower limit of determination by classical micro-analytical methods has been lowered by adjusting the solution concentrations and techniques of trace analysis usually used. It was shown that in some specific cases this approach enabled a quantitative determination of the element in samples of a few micrograms to be made with a precision of about 1 per cent.

Further work is reported in which fluorimetric and gas-chromatographic techniques are used for determining elements present in nanogram amounts.