Instrumental analysis has continuously evolved in the last decades and determination of trace elements is becoming a routine task in analytical laboratories. Inductively coupled plasmas with argon gas are successfully applied for measurements of emission lines (ICP OES) and isotopes (ICP-MS) for most elements of periodic table. However, a laboratory must have full control of analytical blanks and sample preparation for obtaining accurate results. In this book we discuss how to control contaminations and modern strategies for microwave-assisted sample preparation. Discussions comprehend digestions with diluted acid solutions, microwave-assisted evaporation, microwave vessels with inserts, vapor phase microwave digestion, and single reaction vessel. Modern procedures for sample preparation fully compatible with multielement determinations are presented and experimental data are shown. Instruments and accessories for implementing these strategies are presented. The goal of the authors was to produce a readable text for practical analysts and for everyone interested in the evolution of sample preparation strategies.