Determination of boron isotopic composition in natural samples by thermal ionization mass spectrometry

Thermal ionization mass spectrometry has been used for the determination of isotopic composition of boron in natural samples, like water, with an impr oved degree of accuracy and precision. After concentration and separation b oron is treated with an excess of sodium hydroxide in order to convert it c ompletely to sodium metaborate. The excess of sodium hydroxide present in t he sample causes problems in the isotopic analysis. This excess is neutrali zed with 0.1M nitric acid on the filament while loading the sample by a spe cial technique. This procedure improves the precision and accuracy of the a nalysis to a large extent.