A novel spot test based on digital images for determination of methanol in biodiesel

Autor(es)

Soares, Samara ^[1] ; Torres, Ketheny G. ^[2] ; Pimentel, Eduardo L. ^[1] ; Martelli, Patricia B. ^[2] ; Rocha, Fabio R. P. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Ctr Nucl Energy Agr, Ave Centenario 303, BR-13416000 Piracicaba, SP - Brazil

^[2] Univ Fed Sao Joao del Rei, Praca Dom Helvecio 74, BR-36301160 Sao Joao Del Rei, MG - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Talanta; v. 195, p. 229-235, APR 1 2019.
• Citações Web of Science: 3

Resumo

Methanol is used in transesterification reaction for biodiesel production, being an important quality parameter to evaluate the purity of the final product. Methanol concentrations higher than 0.20% (m/m) reduce the biofuel efficiency. The Brazilian, United States, and European standards recommend the reference method based on gas chromatography with flame ionization detection, which involves a time-consuming procedure and requires high cost equipment. In this work, it is proposed a simple and low cost spot test based on digital images acquired with a smartphone camera for the determination of methanol in biodiesel. The procedure was based on the oxidation of methanol to formaldehyde and subsequent reaction with Schiff reagent, resulting in a violet product. Analytical signals were based on the reflected radiation measured on the G channel (RGB system), which refers to the complementary color of the reaction product. Linear responses were obtained within 20-500 mg kg(-1) and 500-2000 mg kg(-1) methanol for 600 and 150 mu L of sample aqueous extracts, respectively. The coefficient of variation (n = 10) and the limit of detection (99.7% confidence level) were estimated as 4.8% and 10 mg kg(-1) (600 mu L of sample), respectively. The procedure requires only 75 mu g of potassium permanganate, 6 mg of oxalic acid, and 1.5 mg of p-rosaniline and generates ca. 1.2 mL of residue per determination. The results agreed with those obtained by the reference procedure at the 95% confidence level, demonstrating that the proposed method is an alternative for routine analysis of the biofuel. (AU)

• Processo FAPESP: 18/07687-5 - Avaliação de estratégias de calibração, imagens digitais e análises em fluxo para o controle de qualidade de biodiesel
• Beneficiário: Samara Soares
• Modalidade de apoio: Bolsas no Brasil - Doutorado