Analytical Sciences

Separation of Parabens on a Zirconia-Based Stationary Phase in Superheated Water Chromatography

Takashi YARITA,* Yoshie AOYAGI,* Haruka SASAI,** Atsuko NISHIGAKI,** and Masami SHIBUKAWA***

*National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Umezono, Tsukuba 305-8563, Japan
**Faculty of Science, Toho University, Miyama, Funabashi 274-8510, Japan
***Graduate School of Science and Engineering, Saitama University, Sakura, Saitama 338-8570, Japan

A superheated water chromatography (SWC) method for the separation of alkyl esters of 4-hydroxybenzoic acid (parabens) using a zirconia-based stationary phase was developed and applied to real sample analysis. First, the SWC system was optimized in terms of the proper length of the preheating coil for establishing thermal equilibration of the mobile phase entering the column at the oven temperature. Next, the effect of the column temperature on the retention was investigated at 100 – 180°C. The elution time for all parabens decreased with increasing column temperature, and linear relationships between ln k and 1/T were obtained. At higher column temperatures, the elution time was further shortened because of the increased mobile-phase flow rate. Nevertheless, the loss of column efficiency at the higher flow rates was not significant. The application of the present method to the analysis of commercial lotions was then demonstrated. The quantification results obtained from SWC showed good agreement with those from a conventional HPLC method.

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