Hydrotrophic solubilization is an advance method for spectroscopic determination. Although there are some practical problems in enhancement of solubility by hydrotrophic solubilization but in this book we have tried to explain the phenomena of hydrotrophic solubilization & gives the comparison with I.P. methods. This textbook covers sampling techniques, handling interferents, optimizing methods, analyzing data, validating data, and ensuring that data are collected under a state of statistical control. In preparing this textbook, We have tried to find a more appropriate balance between theory and practice, between "classical" and "modern" methods of analysis, between analyzing samples and collecting and preparing samples for analysis, and between analytical methods and data analysis. Valuable suggestions are invited from dear students and professionals.