Analytica Chimica Acta 405 (2000) 123–133 Optimization of the experimental parameters in the determination of rifamycin SV by adsorptive stripping voltammetry M. Asunción Alonso a , Silvia Sanllorente a , Luis A. Sarabia b , M. Julia Arcos a,∗ a Departamento de Qu´ ımica, Área de Qu´ ımica Anal´ ıtica, Facultad de Ciencias, Universidad de Burgos, Plaza Misael Bañuelos s/n, E-09001 Burgos, Spain b Departamento de Matemáticas y Computación, Facultad de Ciencias, Universidad de Burgos, Plaza Misael Bañuelos s/n, E-09001 Burgos, Spain Received 6 May 1999; received in revised form 9 August 1999; accepted 6 September 1999 Abstract A procedure for the determination of rifamycin SV by adsorptive stripping voltammetry (AdSV) has been optimized. Two different voltammetric techniques, namely differential pulse adsorptive stripping voltammetry (DPAdSV) and square wave adsorptive stripping voltammetry (SWAdSV) were used. In order to determine the most sensitive technique, an optimization of the experimental parameters was carried out for every technique using experimental design methodology. A canonical analysis of the response surface was carried out, which was adjusted to determine the optimum and the influence of the experimental factors. When this lay outside the ambit of the experiment, the optimum path method was used for the optimising process. The detection limits obtained, 3.108 × 10 −8 mol dm −3 for DPAdSV and 1.233 × 10 −8 mol dm −3 for SWAdSV, show that SWAdSV is a more sensitive technique for the analysis of rifamycin SV. Finally, this method was used to determine rifamycin SV in real samples. ©2000 Elsevier Science B.V. All rights reserved. Keywords: Rifamycin; Differential pulse adsorptive stripping voltammetry; Square wave adsorptive stripping voltammetry; Experimental design; Canonical analysis; Optimum path 1. Introduction Ansamycins are a very specific class of macrocyclic antibiotics of which the rifamycins are among the bet- ter known members. Rifamycins (A, B, C, D and E) are isolated from the fermentation broth of the bac- teria Streptomyces Mediterranei [1]. Rifamycin B is the most active of these antibiotics. Rifamycin SV is obtained by oxidation, hydrolysis and reduction of ri- ∗ Corresponding author. Tel.: +34-947-258818; fax: +34-947- 258831. E-mail address: jarcos@cid.cid.ubu.es (M.J. Arcos). famycin B. Therefore, it has a semisynthetic origin and is more powerful than rifamycin B. Rifamycins have a characteristic ring structure or chromophore spanned by an aliphatic chain and differ from one another in the type and location of the substituents on their naph- thohydroquinone ring. Fig. 1 shows how rifamycin B differs from rifamycin SV by the R group attached to the naphthohydroquinone ring. In rifamycin B this group is an oxy-acetic acid (–OCH 2 COOH) while in rifamycin SV the R group is a hydroxyl (–OH). Traditionally, rifamycin SV has been used as a chiral selector in capillary electrophoresis to resolve enantioselectively a number of chiral compounds. 0003-2670/00/$ – see front matter ©2000 Elsevier Science B.V. All rights reserved. PII:S0003-2670(99)00762-X