Abstract:

A fixed-time direct-reading ion selective electrode method was proposed for the rapid determination of borax
in yuba. Samples were acidified and fluorinated to form fluoroborate ion, which were measured by the method. Upon
acdification with 1.00 mL of 1 mol/L sulfuric acid and fluorination at 80 ℃ for 5 min with 4.00 mL of 4 mol/L hydrofluoric
acid, avrage recovery rates for spiked samples ranged from 93.04% to 104.2%, with RSD of 0.076% (n = 11). The detection
limit for fluoroborate ion was 1.12 × 10-5 mol/L. The method is cheap, simple, quick, calibration-curve-free and useful for
on-site determination with satisfying results.

Key words: ion-selective electrode (ISE), direct concentration reading, borax, yuba, fixed time method, rapid determination