title: Fast quantification of α-lipoic acid in biological samples and dietary supplements using batch injection analysis with amperometric detection.
abstract: Batch injection analysis (BIA) with amperometric detection, using a pyrolytic graphite electrode modified with cobalt phthalocyanine (PG/CoPc), was employed for determination of α-lipoic acid (ALA) in pharmaceutical product and in synthetic urine samples. The proposed BIA method is based on the application of a potential of +0.9V vs. Ag/AgCl, KCl sat, enabling quantification of ALA over a concentration range from 1.3×10(-6) to 1.0×10(-4)molL(-1), with a detection limit of 1.5×10(-8)molL(-1). A sampling rate of 180 injections per hour was attained and measurements of the reproducibility of successive injections (100µmolL(-1) ALA on the same electrode) showed a RSD of 2.11% for 40 successive injections. The new sensor was utilised for ALA quantification in a dietary pharmaceutical supplement and in synthetic urine and the results obtained for both samples were compared with parallel analysis using high performance liquid chromatography (HPLC), the method recommended by the United States Pharmacopeia. The results obtained were similar (at a 95% confidence level) and in the case of the synthetic urine sample (prepared with a known amount of ALA) the recovery was situated between 98.0% and 102.6%.
authors.affiliation: Departamento de Química, Universidade Federal do Maranhão, Avenida dos Portugueses, 1966, CEP 65080-805, São Luís, MA, Brazil.
authors.forename: Laise Nayra Dos
authors.initials: LN
authors.lastname: Santos Pereira
authors.affiliation: Departamento de Química, Universidade Federal do Maranhão, Avenida dos Portugueses, 1966, CEP 65080-805, São Luís, MA, Brazil.
authors.forename: Iranaldo Santos
authors.initials: IS
authors.lastname: da Silva
authors.affiliation: Departamento de Química, Universidade Federal do Maranhão, Avenida dos Portugueses, 1966, CEP 65080-805, São Luís, MA, Brazil.
authors.forename: Thaylan Pinheiro
authors.initials: TP
authors.lastname: Araújo
authors.affiliation: Departamento de Química, Universidade Federal do Maranhão, Avenida dos Portugueses, 1966, CEP 65080-805, São Luís, MA, Brazil; Instituto Nacional de Ciência e Tecnologia de Bioanalítica, Caixa Postal 6154, CEP 13083-970 Campinas, SP, Brazil.
authors.forename: Auro Atsushi
authors.initials: AA
authors.lastname: Tanaka
authors.affiliation: Instituto de Química, Universidade de São Paulo, Avenida Prof. Lineu Prestes, 748, CEP 05599-970 São Paulo, SP, Brazil. Electronic address: luangnes@iq.usp.br.
authors.forename: Lúcio
authors.initials: L
authors.lastname: Angnes
mesh_terms: D019587:Dietary Supplements / Q000032:analysis*; D004566:Electrodes; D006108:Graphite; D015203:Reproducibility of Results; D008063:Thioctic Acid
chemical_list: D008063:Thioctic Acid; D006108:Graphite
keywords: Batch injection analysis; Cobalt phthalocyanine; Dietary supplement; Synthetic urine; α-lipoic acid