Arizona State University Logo College of Liberal Arts and Sciences Logo
6f image #16f image #26f image #3

SIMS Analyses for Beryllium

Secondary ion mass spectrometry (SIMS, or ion microprobe) represents an extremely sensitive technique for the microanalysis of beryllium. Positive ions of beryllium are easily formed during sputtering, with Be showing a useful yield (ions detected/atom sputtered) of 0.7 (ims 3f) to 1% (ims 6f) with the instrument tuned to maximum transmission. Such high yields allow sub-ppm quantities to be detected in small volumes of sample. Just as for other SIMS analyses, one must determine if interfering species can compromise the analysis. In the case of Be, there is only one serious interference: triply-charged aluminum (27Al+++). The difference in mass between 9Be+ and this interference is 0.018 daltons (Be is heavier) requiring a mass resolving power (M/∆M, 9/0.018) of ~500. This resolving power can be achieved at very low cost to the signal of interest (maximum loss of 2x when closing the entrance slit to the mass spectrometer;(Hervig, 2002). Be does not appear to migrate under ion bombardment. In addition, beryllium is so rare in nature that contamination problems have not been observed in our lab (however, the analysis of Be-rich phases, such as phenakite or beryl might lead to a memory effect which could influence subsequent analyses). A calibration curve for Be in silicate glasses and Be minerals is shown below (Fig. 1). Matrix effects appear to be small (<20%).

Figure 1: Calibration for Be (redrawn from Hervig, 2002) illustrates the similar results obtained for Be in four different SIMS laboratories. The analysis conditions were similar in all cases. The primary beam was O- and positive secondary ions with a range of excess kinetic energy were analyzed (75 to 100 eV ions with a bandwidth of ~30-40 eV). Concentrations range from 0.004 ppm Be in San Carlos olivine (Oak Ridge National Lab analysis) to 164,000 ppm Be in phenakite (Ottolini et al., 1993). The regression uses only the data set from Ottolini et al. (1993).

Hervig, R.L. (2002) Beryllium analyses by secondary ion mass spectrometry. In E.S. Grew, Ed. Beryllium: mineralogy, petrology, and geochemistry in the Earth's crust., 50, p. 319-332. Mineralogical Society of America, Washington, D. C.
Ottolini, L., Bottazzi, P., and Vannucci, R. (1993) Quantification of lithium, beryllium, and boron in silicates by secondary ion mass spectrometry using conventional energy filtering. Anal. Chem., 65, 1960-1968.