**Abstract**

The development of an analytical methodology commonly includes sampling and sample pretreatment-preparation. The sample preparation step should provide the analytes (pesticides, heavy metals, drugs, dyes…etc.) in an adequate medium (typically aqueous or non-aqueous solution) to be detected and/or quantified. It is, therefore, necessary to ensure that the sample is homogeneous and free of interferents, as long as the preparation step is the most significant source of error in the analytical method development and is the most time-consuming step especially when solid samples are analyzed. Given its importance, this preparation step has a fundamental importance in the overall analytical method development, mainly when electroanalytical methods are applied. In this chapter, the steps involved in preparing samples for electrochemical analysis will be described in detail. Specifically, we will be focusing on the sample preparation techniques for the electrochemical analysis of pesticides and heavy metals, in environmental and food samples. For non-electrochemical readers, a brief introduction to the most commonly used electroanalytical methods will be described.

**Keywords:** electrochemistry, pesticides, heavy metals, samples preparation, environment, food
