Biosensors and Bioelectronics 21 (2006) 2283–2289 Epinephrine quantification in pharmaceutical formulations utilizing plant tissue biosensors  Fabiana S. Felix, Miyuki Yamashita, L´ ucio Angnes ∗ Departamento de Qu´ ımica Fundamental, Instituto de Qu´ ımica, Universidade de S˜ ao Paulo, Av. Prof. Lineu Prestes, 748, 05508-900 S˜ ao Paulo, SP, Brazil Received 9 August 2005; received in revised form 26 October 2005; accepted 31 October 2005 Available online 15 December 2005 Abstract A plant tissue biosensor associated with flow injection analysis is proposed to determine epinephrine in pharmaceutical samples. The polyphenol oxidase enzymes present in the fibers of a palm tree fruits (Livistona chinensis), catalyses the oxidation of epinephrine to epinephrinequinone as a primary product. This product is then electrochemically reduced (at -0.10 V versus Ag/AgCl sat ) on the biosensor surface and the resulting current is used for the quantification of epinephrine. The biosensor provides a linear response for epinephrine in the concentration range from 5.0 × 10 -5 to 3.5 × 10 -4 mol l -1 . The limit of detection estimated for this interval was 1.5 × 10 -5 mol l -1 and the correlation coefficient of 0.998, working under a flow rate of 2.0 ml min -1 and using a sample loop of 100 l. The repeatability (R.S.D. for 10 consecutive determinations of a 3.0 × 10 -4 mol l -1 epinephrine solution) was 3.1%. The results obtained by the method here proposed were compared with the official UV spectrophotometric procedure and also using a plant tissue reactor. The responses obtained with the proposed strategies were in good agreement with both ways of analyses, whereas the values obtained by the official spectrophotometric method was strongly affected by benzoic acid, present in the formulation of pharmaceutical product utilized for inhalation. Such favorable results obtained with the carbon paste biosensor or utilizing the bioreactor, joined with the simplicity of its preparation turns these procedures very attractive for epinephrine quantification in pharmaceutical products. © 2005 Elsevier B.V. All rights reserved. Keywords: Epinephrine; Biosensor; Polyphenol oxidase; Pharmaceutical products; Amperometric detection; Tissue biosensors 1. Introduction Epinephrine or adrenaline [1-(3,4-dihydroxyphenyl)-2- methyloamino-ethanol] belongs to the catecholamine family and plays an important role as neurotransmitters and hormones. It is biosynthesized in the adrenal medulla and sympathetic nerve terminals, as well as is secreted by the suprarenal gland along with norepinephrine. It was first isolated in 1901 by Takamine and Aldrich, and was synthesized in 1904 by Stolz and Dalkin (Hern´ andez et al., 1998). It is used in medicine in the treatment of heart attack, bronchial asthma and cardiac surgery (Deftereos et al., 1993). Air oxidation is a major problem for epinephrine in samples. The addition of antioxidants in pharmaceutical formu-  Resume presented in the XVIII International Symposium on Electrochem- istry and Bioenergetics (Coimbra, 19–24 June, 2005). ∗ Corresponding author. Tel.: +55 11 3091 3828; fax: +55 11 3818 5579. E-mail address: luangnes@iq.usp.br (L. Angnes). lations, for example, sodium metabisulfite, serves to minimize the analyte oxidation. Several methods have been applied to determine epinephrine, such as spectrophotometry (Zhu et al., 1997; Sorouraddin et al., 1998a,b; Solich et al., 2000; Nevado et al., 1996), fluorimetry (Ca˜ nizares and Castro, 1995; Yang et al., 1997, 1998), liquid chromatography (Kawada et al., 1998; He et al., 1997; Sabbioni et al., 2004), capillary electrophoresis (Britz- Mckibbin et al., 1998, 1999; Lin et al., 2004), chemilumines- cence (Ragab et al., 2000; Michalowski and Halaburda, 2001), electrochemiluminescence (Zheng et al., 2001; Li et al., 2002), amperometry (Garrido et al., 1997; Ni et al., 1999), biamperom- etry (Mateo and Kojlo, 1997) and piezoelectric detection (Mo et al., 1999). However, some of these methods are very expensive or complicated and need extraction or derivatization. Biosen- sors developed using plant tissue materials in combination with transducers offer a good alternative compared with biosensors based on isolated enzymes (Leite et al., 2003; Bezerra et al., 2003; Caruso et al., 1999) as well as others analytical tech- niques for catecholamines determination. These biosensors have 0956-5663/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2005.10.025