The determination of boron in aluminium-magnesium alloys

An etched 0.5 g aluminium sample is spiked with a standard solution of boron enriched in B (1.202 10 at.B/g B = 88.06 at.%), and dissolved in 2 ml concentrated nitric acid (suprapur) at 70 C under addition of 1 ml hydrochloric acid (suprapur) every 10 to 15 minutes in order to prevent excessive foaming. After addition of 6 ml hydrochloric acid a clear solution is obtained. To this solution 10 g methanol (purified by distillation over a mixture of sodium hydroxide and mannite) is added, and boron is distilled at 95°C in the form of trimethyl borate. After dilution to 20 ml with water and addition of 2 Mg mannite, the solution is evaporated down to 0.5-1 ml at 60°C. 

25 Ml of this solution are transformed with lanthanum into lanthanum nitrate and loaded on the rhenium filament of a thermal ionization mass spectrometer. The filament is heated stepwise to 1050°C, and B0T and BOT ions are measured alternatively OO times each) using a Faraday cup. The obtained ratio s are corrected for the isotopic composition of oxygen (45). 

---