Analysis of boric acid content in pickled mangoes from Municipal Shops in Sakon Nakhon Province Using UV-Visible Spectroscopy

Abstract

In the present study, quantitative analysis of boric acid in pickled mangoes has been done by using UV-VIS spectroscopy.  The samples were bought from five shops in Muang District, Sakon Nakorn province. The reaction between boric acid and curcumin yielded a rosocyanine compound (red color), absorbing light at a wavelength of 550 nm.  From the result, the standard curve between absorbance and boric acid concentration (0.02, 0.04, 0.08, 0.16 and 0.24 µg/mL) was linear, with an R² value of 0.9964 and a standard deviation ranging from 0.002-0.005. The results from pickled mangoes (five shops) indicated that the amount of boric acid ranged from 0.572 to 1.15 µg/g.  The samples from three shops contained boric acid levels of about 0.5 µg/g, which was lower than the samples from two shops (1.15 and 0.803 µg/g).  A comparison of the present results with the criteria from the Ministry of Public Health Issue 391 B.E. 2561 suggested that all pickled mangoes from these five shops were unsafe for consumers because the presence of boric acid (a prohibited substance) exceeded the criteria.