This book exhibits the excellent performance of the carrier based HF-LPME technique for the analysis and extraction of trace level of HCTZ with the concentrations of µg L-1, from water and biological samples. After extraction, analytes are analysed by HPLC-UV. This method provides high PFs for the target analyte, along with an excellent clean-up capability without any loss of micro-extract. There is no carry-over effects because each fiber is used only once. The whole operation is very convenient to handle because the receiving phase is protected by the hollow fiber. In addition, the equipment needed is very simple and inexpensive and the proposed method can be easily used in chemical and biological laboratories.