A SIMS METHOD FOR BE-10/BE-9 RATIO MEASUREMENT IN ENVIRONMENTAL MATERIALS

A new SIMS based technique for measurement of Be-10/Be-9 ratios in a variety of environmental materials is reported. Be samples are chemically preconcentrated and isotopically analysed using a VG ISOLAB-120 SIMS instrument by sputtering Be from a Ta target using a primary beam of 0(+) ions. Potential interferences (BeH+)-Be-9 and B-10(+) on Be-10 are reduced to negligible or manageable proportions by the use of the instrument's mass resolving power and abundance sensitivity, and sputtering Be+ at approximate to 1000 degrees C under which condition the total contribution from (BeH+)-Be-9 and B-10(+) is reduced to < 1 c.p.s. The repeatability of measurement has been assessed using Oak Ridge National Laboratory (ORNL) dilutions with Be-10/Be-9 ratios between 10(-2) and 10(-9) and instrumental mass discrimination evaluated using boron reference material, NIST SRM-951. The mass discrimination is estimated to be 4 +/- 1% u(-1) at mass 10 and the repeatability of Be-10/Be-9 ratio measurement is 4% (one standard deviation).