Analytical Sciences

Micro-organic Ion-associate Phase Extraction via in situ Fresh Phase Formation for the Preconcentration and Determination of Di(2-ethylhexyl)phthalate in River Water by HPLC

Noriko HATA,  Erini YUWATINI, Kaori ANDO, Mika YAMADA, Issei KASAHARA, and Shigeru TAGUCHI

Department of Environmental Biology and Chemistry, Faculty of Science, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

A high-enrichment method was proposed for the HPLC determination of trace di(2-ethylhexyl)phthalate (DEHP) in environmental water. A micro-organic ion-associate phase (IAP) was formed in situ from an aqueous sample by adding 4-trifluoromethylanilinium ion and dodecylbenzenesulfonate ions. Centrifugation of the solution led to the isolation of a liquid organic phase containing DEHP at the bottom of the centrifuge tube. The volume of the phase formed was less than 30 μL. DEHP was extracted into the IAP quantitatively during phase formation. After discarding the aqueous phase, the ion associate was dissolved with 50 μL of 2-methoxyethanol, and DEHP in the concentrate was determined by HPLC with an ultra-violet (UV) diode-array detector. DEHP in the concentrations range from 0.8 to 78 μg L^-1 was determined with good precision. The recovery tests for DEHP added to some river water were satisfactory. The detection limit of DEHP, defined as 3-times the standard deviation of the blank signals, was 0.07 μg L^-1 (n = 3). The present method is very simple, and was applied to the determination of DEHP in the river water samples collected around Toyama City, Japan.

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