A novel method of the determination of boron in the presence of a little methanol by discoloring spectrophotometry in pharmaceutical and biological samples

It is the first time that boron is determined in the presence of a little methanol by discoloring spectrophotometry in this paper. A russety product can be formed by the reaction between glycine (Gly) and sodium 1,2-naphthoquinone-4-sulfonate (NQS) in alkaline solution. When boron is added to the solution, the system will be discolored, and the addition of a little methanol will improve the discoloration. Beer's law is obeyed in the range of boron concentrations of 0.86-43.24 μg ml⁻¹ at the maximal discoloring wavelength of 382 nm. The equation of linear regression is A = −0.07581-86.79186C (mol l⁻¹), with a linearly correlation coefficient of 0.9979. The detection limit is 0.80 μg ml⁻¹ and R.S.D. is 4.2%. The method is successfully applied to the determination of boron in pharmaceutical and biological samples. The average recoveries are in the range of 98.2-104.1%. Analytical results obtained with this novel method are satisfactory.