1.04 – Sample Homogenization

In environmental and food chemistry, sampling is a multistage process, which includes collection of the sample itself and a series of steps, so-called sample preparation, aimed to provide a representative measurement of the sample lot/area. Homogenization is part of the sample preparation procedure and includes mixing and blending of the sample, particle size reduction, and mass reduction. Yet because homogenization techniques are tedious and laborious, some laboratories do not incorporate it as part of their analytical protocol. Consequently, biased results can be obtained as a result of poor sample homogeneity. Diverse equipment and several procedures are available on the market, such as grinding with the common procedure based on mortar and pestle, as well as other techniques such as shearing, beating, and use of other instrumentation. Depending on the type of sample and objectives to be accomplished, the homogenization procedure should be such that it provides uniform and repeatable results, using instrumentation that is easy to clean and maintain, is adapted to hold sample sizes of variable magnitude, and, preferably, that can be automated. In this chapter, several aspects related to sample homogenization are discussed in terms of needs, available techniques, and applications for environmental and food analysis. The final objective is to provide the necessary tools to achieve homogenate samples, and especially to implicate environmental and analytical chemists in this subject so as to contribute toward obtaining more exact, precise, and comparable analytical results.