Analytica Chimica Acta 538 (2005) 77–84 Determination of triamterene in pharmaceutical formulations and of triamterene and its main metabolite hydroxytriamterene sulfate in urine using solid-phase and aqueous solution luminescence G.A. Iba ˜ nez a , G.M. Escandar a,∗ , A. Espinosa Mansilla b , A. Mu ˜ noz de la Pe ˜ na b,∗∗ a Departamento de Qu´ ımica Anal´ ıtica, Facultad de Ciencias Bioqu´ ımicas y Farmac´ euticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina b Departamento de Qu´ ımica Anal´ ıtica, Universidad de Extremadura, Av. de Elvas s/n, 06071 Badajoz, Spain Received 18 November 2004; received in revised form 26 January 2005 Available online 19 March 2005 Abstract Solid-phase extraction (SPE) (reversed-phase and mixed-mode) and nylon membranes were investigated as solid matrices for obtaining fluorescence signals from adsorbed triamterene (TA). Although a significant emission was found in all investigated surfaces, solid-phase extraction systems yielded the best results. The analytical figures of merit obtained under the best experimental conditions, using nonpo- lar/strong cation mixed phase MP1 discs and 5 ml of extracting sample, were: linear calibration range from 1.7 to 21 ng ml -1 (the lowest value corresponds to the quantitation limit), relative standard deviation, 1.3% (n = 5) at a level of 12.7 ng ml -1 , and limit of detection, 0.6 ng ml -1 (calculated according to Clayton’s definition, taking into account false positive and false negative errors). An approach for the spectrofluo- rimetric determination of triamterene in pharmaceutical formulations was successfully applied. In addition, a simple and rapid method for the separation and fluorimetric determination of triamterene and its main metabolite (hydroxytriamterene sulfate) in urine was developed and rendered very satisfactory results, requiring in this case the use of reversed-phase C18 solid-phase extraction. © 2005 Elsevier B.V. All rights reserved. Keywords: Room temperature fluorimetry; Solid-phase extraction; Triamterene; Hydroxytriamterene sulfate 1. Introduction Triamterene (TA), 2,4,7-triamino-6-phenylpteridine (Fig. 1), is a diuretic drug belonging to the potassium- sparing diuretic family [1]. It is generally administered together with other, more powerful, diuretics such as derivatives of anthranilic acid and thiazide, with the purpose of reducing their potassium-wasting effects [2]. After oral administration, TA is absorbed and metabolized by hydroxylation and subsequent immediate conjugation rendering its main metabolite hydroxytriamterene sulfate (STA; Fig. 1) [3]. STA is pharmacologically active and ∗ Corresponding author. Tel.: +34 143 72650; fax: +34 143 72650. ∗∗ Co-corresponding author. E-mail address: gescanda@fbioyf.unr.edu.ar (G.M. Escandar). therefore its determination is as important as that for TA. TA has been included, by the International Olympic Com- mittee, in the list of forbidden drugs [4]. The prohibition is principally due to two factors: (1) the drug allows for a rapid decrease of the corporal weight (an important factor in sports where weight categories are involved) and (2) it conceals the ingestion of other proscribed agents, because the profuse amount of eliminated liquid reduces their concentration in urine. Different methods have been applied for TA determination in pharmaceutical preparations and biological fluids, includ- ing spectrophotometry, chromatography (with spectropho- tometric, spectrofluorimetric and amperometric detection), spectrofluorimetry, and capillary electrophoresis [5–12]. Re- cently, a determination of TA by transient retention in a 0003-2670/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2005.02.001