Sample preparation techniques for the determination of 4-nonylphenol in water and sediments were optimized using two-level orthogonal array design (OAD). Comparison between the use of cartridge-based solid-phase extraction and membranous disk-based extraction was made for water samples. For sediment samples, microwave-assisted solvent extraction (MASE) was employed. A comparison between MASE and classical soxhlet extraction of spiked samples was also carried out. 4-Nonylphenol was determined using high performance liquid chromatography (HPLC) coupled to both ultraviolet and fluorescence detection