Anhydrous sodium carbonate solid (analytical pure), sodium peroxide solid (analytical pure), nitric acid (analytical pure), sulfuric acid (analytical pure), hydrofluoric acid (analytical pure), high-purity argon (AR > 99.99%) and secondary deionized water for water. Boron standard solution, concentration 1 mg / ml.
Prodigy ICP inductively coupled plasma emission spectrometer (Liman leibers company, USA).
Microwave digestion instrument: Berghof speed wave four (origin: Germany).
3 Sample treatment
3.1 alkali melting method
Accurately weigh 0.100 g sample and put it into a nickel crucible containing 1.5 g anhydrous sodium carbonate, mix evenly, put it into a high-temperature furnace, from low temperature to 700 ℃, take out slightly cold, add 3 G sodium peroxide to heat to 800 ℃, melt for 10 min (shake up in three times). Take out and shake well, cool slightly, put it into a 600 ml beaker containing 100 ml hot water, and take out the frit in the crucible. Heat and boil, remove and slightly cool, add 20 ml nitric acid for acidification, heat and boil, control the volume, take it off, cool and fix the volume in a 250 ml volumetric flask. The boron content was determined by ICP-AES.
3.2 microwave digestion method
Accurately weigh 0.100 g sample into the digestion tank, add 4 ml sulfuric acid, 4 ml nitric acid and 2 ml hydrofluoric acid. When there is no bubble in the sample reaction, cover the top cover of the digestion tank and explosion-proof film, and put it in the digestion instrument.