Liquid-liquid microextraction in sequential injection analysis for the direct spectrophotometric determination of acid number in biodiesel

Autor(es)

Batista, Alex D. ^[1] ; Amais, Renata S. ^[1] ; Rocha, Fabio R. P. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Ctr Energia Nucl Agr, BR-13400970 Piracicaba, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Microchemical Journal; v. 124, p. 55-59, JAN 2016.
• Citações Web of Science: 10

Resumo

Sequential injection analysis (SIA) is used here for acid number determination in biodiesel exploiting liquid-liquid microextraction and spectrophotometric detection. Free fatty acids (FFA) from biodiesel are partially extracted to an aqueous bromocresol green (BCG) aliquot placed in between two aliquots of biodiesel without any pretreatment. Microextraction is favored by using holding coils and transmission lines made of Teflon due to the formation of biodiesel film in the tube walls. Detection was performed in a glass tube coupled to a fiber-optic spectrophotometer and analytical signals were related to the discoloration of the BCG after FFA microextraction. A linear response was observed up to 0.6 mg KOH g(-1), with detection limit, coefficient of variation, and sampling rate estimated at 0.0074 mg KOH g(-1) 2.9% (n = 10) and 12 h(-1), respectively. The procedure is a fast, reliable, and mechanized alternative for acid number determination, which requires only 250 mu L of sample, 10 mu g BCG and 500 mu L. of ethanol. A reference procedure based on visual titration was used for comparison and results agreed at the 95% confidence level. (C) 2015 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 13/26857-5 - Teores totais e análise de especiação química de As, Cr e Se usando colunas monolíticas a baixa pressão e técnicas com plasma acoplado indutivamente
• Beneficiário: Renata Stábile Amais
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 14/19115-5 - Desenvolvimento e aplicação de um sistema de cromatografia bidimensional por injeção sequencial
• Beneficiário: Alex Domingues Batista
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado