Elimination of boron memory effect in inductively coupled plasma-mass spectrometry by addition of ammonia

Boron memory effect in inductively coupled plasma-mass spectrometry is characterized theoretically and verified experimentally. The boron memory effect originates from the tendency of boron to volatilize as boric acid from the sample solution layer that covers the inside surface of the spray chamber. The skimmer, the sampler, the ion lenses, the quadrupole and other components of the mass spectrometer are not responsible for the memory effect at trace boron concentration levels. A technique to eliminate the memory effect is proposed and tested. Ammonia gas is used to convert the boron from the volatile boric acid form to the non-volatile ammonium berate. Ammonia is introduced by injecting a small volume of ammonia solution simultaneously with the sample solution. Addition of ammonia is effective in completely eliminating the boron memory effect and reducing boron signals to blank levels instantaneously (within 20 s) in a conventional concentric nebulizer-double pass spray chamber arrangement. (C) 1999 Elsevier Science B.V. All rights reserved.