Analysis of ascorbic acid content in various fruits and vegetables by spectrofluorimetric methods

Ascorbic acid (AA) is one of the most important vitamin for human nutrition that is supplied by fruits and vegetables. In this study, a simple and sensitive fluorimetric method determination of ascorbic acid was used in 25 different samples of fruits and vegetables. This method is based on the condensation reaction of AA with o-phenylenediamine (OPDA) in the absence of the oxidant. The fluorescence intensity is measured at excitation and emission wavelengths of 330nm and 430nm, respectively. The effect of pH and OPDA concentration on fluorescence intensity of the system was examined. Optimum pH was between 9.4 and 9.5, and optimal concentration of OPDA was 0.05% (w/v). Under optimal conditions, a linear relationship is obtained between the fluorescence intensity and the concentration of AA in the range 1–10 micro g/mL. The regression coefficient was 0.9999. The content of AA were found between 3 and 60mg/100g of fresh fruits and between 17 and 50mg/100g of fresh vegetables. The detection limit (3σ) was found to be 0.20 micro g/mL of AA (σ from 4 determination of 5 micro g/mL). A relative standard deviation of 1.0% was recorded for 4 measurements of 5 micro g/mL standard AA solution. Limit of quantification AA was 0.68 micro g/mL. The results obtained with this method are comparable with the results obtained by other methods [1]. Presented method seems to be useful in the nutritional analytical practice.

References: 1. Eitenmiller RR, Ye L, Landen WO (2008) Vitamin analysis for the health and food sciences, CRC press