Hindawi Publishing Corporation International Journal of Analytical Chemistry Volume 2012, Article ID 546282, 7 pages doi:10.1155/2012/546282 Research Article Sensitive Determination of Terazosin in Pharmaceutical Formulations and Biological Samples by Ionic-Liquid Microextraction Prior to Spectrofluorimetry Mohsen Zeeb 1, 2 and Mahdi Sadeghi 1 1 Agricultural, Medical and Industrial Research School, Nuclear Science and Technology Research Institute, P.O. Box 31485/498, Karaj, Iran 2 Department of Analytical Chemistry, Faculty of Chemistry, University College of Science, University of Tehran, P.O. Box 14155-6455,Tehran, Iran Correspondence should be addressed to Mahdi Sadeghi, mahdisadeghi2003@yahoo.com Received 10 September 2011; Accepted 2 November 2011 Academic Editor: P. Haglund Copyright © 2012 M. Zeeb and M. Sadeghi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. An efficient and environmentally friendly sample preparation method based on the application of hydrophobic 1-Hexylpyridinium hexafluorophosphate [Hpy][PF 6 ] ionic liquid (IL) as a microextraction solvent was proposed to preconcentrate terazosin. The performance of the microextraction method was improved by introducing a common ion of pyridinium IL into the sample solution. Due to the presence of the common ion, the solubility of IL significantly decreased. As a result, the phase separation successfully occurred even at high ionic strength, and the volume of the settled IL-phase was not influenced by variations in the ionic strength (up to 30% w/v). After preconcentration step, the enriched phase was introduced to the spectrofluorimeter for the determination of terazosin. The obtained results revealed that this system did not suffer from the limitations of that in conventional ionic-liquid microextraction. Under optimum experimental conditions, the proposed method provided a limit of detection (LOD) of 0.027 μgL −1 and a relative standard deviation (R.S.D.) of 2.4%. The present method was successfully applied to terazosin determination in actual pharmaceutical formulations and biological samples. Considering the large variety of ionic liquids, the proposed microextraction method earns many merits, and will present a wide application in the future. 1. Introduction Terazosin is a selective potent α 1 adreno-receptor antagonist. It is an effective drug for hypertension and benign prostatic hyperplasia [1, 2]. The needs of monitoring trace levels of terazosin in treated patients with initiate or chronic treatment routine in chronic regimen, especially in renal impairment cases, are necessary. To prevent excess employed dosage, it is critical to develop the sensitive and accurate techniques for its quantitative analysis. Several analytical methods have been developed for the measurement of terazosin in bulk, pharmaceuticals, or biological fluids [3–8]. Sample preparation is a critical step to isolate the analytes of interest from the sample matrix as well as to increase the concentration of analytes prior to their determination, especially when their levels are lower than the detection limit of analytical techniques. Liquid-liquid extraction (LLE) and solid-phase extraction (SPE) have been widely used as basic, simple, and adaptable methods for sample preconcentration. However, some drawbacks such as the use of large amount of hazardous organic solvents, and the employment of multistep procedures associated with the high risk of analyte losses make LLE and SPE tedious, expensive, and environmentally unfriendly. In recent years, reduction or complete removal of hazardous organic sol- vents in sample pretreatment techniques has received great attention. For this goal, many microextraction methods such as dispersive liquid-liquid microextraction (DLLME) [9– 12], single-drop microextraction (SDME) [13–15], stir bar sorptive extraction [16], and so forth, have been developed to reduce the amount of toxic solvents. In some of these procedures, however, the use of toxic materials like benzene,