[Determination of seven phenolic acids in whole wheat flour by high-performance liquid chromatography]

A high-performance liquid chromatography(HPLC) method was established for the simultaneous determination of 7 phenolic acids(ferulic acid, p-coumaric acid, vanillic acid, butyric acid, p-hydroxybenzoic acid, salicylic acid, sinapic acid) in whole wheat flour, to understand further the phenolic acid substances contained in whole wheat flour and the content level.

Add 10 mL of 4% NaOH solution, 10 mL of methanol solution, and 0.4 g of sodium sulfite(antioxidant) to the whole wheat flour sample, and extract it at high temperature under ultrasonic conditions. Centrifuge the supernatant, adjust the pH 5, and then dilute it to the final volume. Use Waters Atlantis T3(4.6 mm×250 mm, 5 μm) as the chromatographic column, and determine the phenolic compounds by high-performance liquid chromatography under switching wavelength conditions, with external standard calibration.

The linear correlation coefficients(R~2) of the standard curve were all greater than 0.999. The limits of detection(LODs) of the method was 0.01-0.09 mg/100 g, and the limits of quantification(LOQs) of the method was 0.03-0.29 mg/100 g. The three-level recovery rate was 87.6%-115.7%. The precision RSDs was 2.1%-6.3%(n=6). The phenolic acid assay of 22 commercial whole wheat flours showed that ferulic acid was the highest among the seven phenolic acids(40.1 mg/100 g), followed by sinapic acid(5.8 mg/100 g).

The method has good sensitivity, precision and reproducibility, and is suitable for the determination of phenolic acids in whole wheat flour.