title: A feasible method for indirect quantification of L-T4in drugs by iodine determination.
abstract: In this work, a method combining microwave-induced combustion (MIC) for sample preparation of commercial levothyroxine sodium (L-T4) drugs (L-T4: 25-200µg/tablet), and potentiometry with ion selective electrode (ISE) for iodine determination and subsequent indirect quantification of L-T4was proposed. The type and concentration of the absorbing solution were evaluated to select the most suitable conditions for this study. Using the MIC method, it was possible to use solutions as diluted as 150mmolL-1(NH4)2CO3(for samples containing 25-200µg of L-T4/tablet) for I absorption. In these conditions, recoveries for L-T4were between 99% and 101%, and relative standard deviations were lower than 10%. The limit of detection for L-T4was 11.2µg/tablet, which is almost two times lower than the minimum concentration of L-T4in commercially available drugs. Thus, the MIC was suitable for the digestion of several L-T4drugs for subsequent I determination by ISE and indirect quantification of L-T4. Furthermore, the proposed method presents high throughput with low reagent consumption and consequently lower waste generation, making it suitable for routine determination of L-T4in drugs. From the obtained results, it was possible to observe that one of the analyzed samples is not in agreement with the limits established by the United States Pharmacopeia, indicating the importance of the drug quality control. The United States Pharmacopeia establishes that each tablet must contain between 90% and 110% of the amount of active substance declared by the manufacturer.
authors.affiliation: Centro de Ciências Químicas, Farmacêuticas e de Alimentos, Universidade Federal de Pelotas, Campus Capão do Leão, 96160 000, Capão do Leão, Brazil. Electronic address: marcia.mesko@pq.cnpq.br.
authors.forename: Marcia Foster
authors.initials: MF
authors.lastname: Mesko
authors.affiliation: Centro de Ciências Químicas, Farmacêuticas e de Alimentos, Universidade Federal de Pelotas, Campus Capão do Leão, 96160 000, Capão do Leão, Brazil.
authors.forename: Alessandra Cortes
authors.initials: AC
authors.lastname: Teotonio
authors.affiliation: Centro de Ciências Químicas, Farmacêuticas e de Alimentos, Universidade Federal de Pelotas, Campus Capão do Leão, 96160 000, Capão do Leão, Brazil.
authors.forename: Dirce Taina
authors.initials: DT
authors.lastname: Teixeira Oliveira
authors.affiliation: Centro de Ciências Químicas, Farmacêuticas e de Alimentos, Universidade Federal de Pelotas, Campus Capão do Leão, 96160 000, Capão do Leão, Brazil.
authors.forename: Diogo La
authors.initials: D
authors.lastname: Rosa Novo
authors.affiliation: Centro de Ciências Químicas, Farmacêuticas e de Alimentos, Universidade Federal de Pelotas, Campus Capão do Leão, 96160 000, Capão do Leão, Brazil.
authors.forename: Vanize Caldeira
authors.initials: VC
authors.lastname: Costa
mesh_terms: D053000:Analytic Sample Preparation Methods / Q000379:methods*; D004566:Electrodes; D005240:Feasibility Studies; D007455:Iodine / Q000032:analysis*; D057230:Limit of Detection; D008872:Microwaves; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D013974:Thyroxine / Q000032:analysis*
chemical_list: D004364:Pharmaceutical Preparations; D007455:Iodine; D013974:Thyroxine
keywords: Drug analysis; Iodine determination; Ion selective electrode; Microwave-induced combustion; Sample preparation; Sodium levothyroxine determination