In an era of interdisciplinary harmonization, analytical sciences, particularly analytical chemistry has emerged to be among fore runner and virtually become a backbone of all branches of science and that of industries too. Analysis is a continuing process right from raw material stage to final products. Analytical measurements and outcome of the measurements in the form of final results could be the basis on which economic, ecological, environmental, geological, biological, high-tech materials, medical, food and legal matters decisions are made which are essential in our day to day life and also in trade, production and development, in monitoring and protection of human and environmental health. This is related to Quality Management System thereby directly related to analyst and analytical data. Modern analytical techniques play a vital role and form the lifeline in achieving technological excellence worldwide. With the rapid advancement of analytical instrumentation technologies, modern analytical techniques have formed an integral part of quality assurance along with research in industries, academic and research institutions. Analytical chemistry has been important since the early days of chemistry, providing methods for determining which elements and chemicals are present in the object in question. During this period significant analytical contributions to chemistry include the development of systematic elemental analysis by Justus von Liebig and systematized organic analysis based on the specific reactions of functional groups. This encyclopaedia analyses various aspects of this subject. The encyclopaedia will be highly useful to students and teachers.