Otimização de metodologia de análise de ácido graxo trans (C18:1 9t) por eletroferese capilar em amostras alimentícias

Abstract

A different method for determination of total trans fatty acids expressed as elaidic acid by capillary zone electrophoresis (CZE) under indirect UV detection at 224 nm within an analysis time of 8 min was developed. The optimized running electrolyte includes 15.0 mmol L-1 KH2PO4/Na2HPO4 buffer (pH ∼ 6,8), 4.0 mmol L-1 SDBS, 8.0 mmol L-1 Brij 35, 45% v/v ACN, 8% v/v methanol and 1.5% v/v n-octanol. Baseline separation of the critical pair C18:1-9t / C18-9cis with a resolution higher than 1.5 was achieved. The optimum capillary electrophoresis (CE) conditions for the background electrolyte were established with the support of Raman spectroscopy and experiments of a 32 factorial design were used to better level of Brij 35 and noctanol determination. Following optimization electrolyte system was made calibration curve using C15:0 as the internal standard and, after certification where no lack of fit within proposed model the response factor (RF) was calculated and applied to total trans fatty acid (TTFA) analysis in a hydrogenated vegetable fat (HVF), margarine, spreadable cheese and strawberry cookies samples by CE. The CZE method was compared with the American Oil Chemists’ Society (AOCS) official method by gas chromatography (GC) to hydrogenated vegetable fat samples using independent sample t-student test for six genuine replicates and no significant difference was found within 95% confidence interval. The results obtained were satisfactory, indicating that the optimized methodology by CE can be useful for TTFA analysis in different matrix foods presenting as advantages short analysis time, no derivatization step in sample preparation, no specific separation columns and low cost.