Simple and Rapid Determination of Trace Boron in Viarious Sodium Chloride with Flow Injection System Utilizing In-line Preconcentrarion/Separation Coupled with Fluorimetric Detection

Abstract

A silnple and rapid method is presented for the determination of boron at ppb to sub-ppm levels in sodium chloride, in which in-line preconcentration/separation is directly coupled with spectrofluorimetric detection in a flow injection system. Boron in the buffered sample solution at pH 10 was adsorbed on a small Sephadex G-25 gel column and desorbed with a small volume of 0.10mol/l HCl, which allowed effective preconcentration/separation of boron from a large excesss of NaCl matrix and other coexisting elements. Boron was detected by measuring the fluorescence intensity due to its complex formation with chromotropic acid (1,8-dihidroxy-3, 6-naphthalenedisulphonic acid). Various parameters affecting analytical sensitivity and precision were investigated, and optimal conditions and manifold configurations were established. A linear calibration using a 5 m sample loop was obtained for boron in the range of 0-15 ppb. The relative standard deviation was 1.8% for 5.0 ppb boron solution and the estimated limit of detection was ca.0.2 ppb. The limit of detemlination defined as five times the limit of detection is ca.6 ppb in sodium chloride when 3mol/l sodium chloride solution is applied for analysis. The present FIA system is rapid and simple and can be readily applied to determine boron at sub-ppm to several tens of ppb levels in various salt samples. Only 9 min is required for analytical measurement after sample injection and no complicated manual operation is involved.