In this thesis, the possibility of the application of liquid anion exchanger in three phase hollow fiber-based liquid microextraction for the direct extraction and preconcentration of some inorganic anions in biological and water samples was evaluated. In this method an aqueous acceptor phase is used for the extraction of analytes that can be injected only to high performance liquid chromatograghy and capillary electrophoresis.In this technique, octanol containing a liquid anion exchanger (trioctylamine) was used as extractant. Parameters affecting the extraction efficiency such as extracting solvent, liquid anion exchanger amount, type of acid, concentration of acid in sample and acceptor phase, salt concentration, stirring rate, extraction time and temperature were studied and optimized. The best extraction efficiency was achieved utilizing % 2.5 v/v trioctylamine in octanol, NaOH 0.065 M as an acceptor phase, H3PO4 0.001 M, without salt addition, 700 rpm stirring rate and 20 min extraction time at 35? C. Since hollow fiber is low cost, Then it was disposed after a single extraction that eliminated the possibility of carry over effects. The limit of detection and linear dynamic range were ranged 0.002-0.061 and 0.01-40 µg/ml, respectively. various real water samples were analyzed by the method and recoveries were from 75 to 112 %.