Sample Preparation Methods

Abstract

This chapter discusses sample preparation methods. The preparation of many samples involves a drying stage using either freeze-drying or an oven. The relative merits and potential pitfalls of both are given. Acid dissolution methods are common methods of sample preparation. Not all samples are soluble in all acids. If nitric acid is used to “digest” a soil a significant residue remains. The “digestion” is therefore more of an aggressive leach. The importance of noting the requirements of the analysis is emphasised. This aggressive leach would give a good indication of “biologically available” rather than the total content of an analyte. Methods are given for nitric acid, aqua regia and sulfuric/nitric digestions on hotplates or hotblocks or using microwave assistance. Potential errors associated with each are provided. Alternative sample preparation methods such as fusions, sintering, dry ashing and alkaline extraction are also presented. The preparation of slurries is also discussed. If speciation analysis is to be undertaken, more gentle extraction methods are required and some of these are discussed. Preconcentration methods for analytes that are present at concentrations below that capable of being measured using the instrumentation available are discussed. This includes coprecipitation, some solid phase extractions and some liquid phase extraction methods.