As part of a study using ⁷Be and ¹⁰Be isotopes to examine the exchange of air between the stratosphere and troposphere and vertical mixing in the troposphere, a series of air filters were obtained from the radiological monitoring network operated by Health Canada.  The polypropylene filters from these high volume samplers were first compressed for ⁷Be analysis with a high purity germanium detector, then halved and one half was sent to IsoTrace for ¹⁰Be analysis.

This paper will describe the measurements of ¹⁰Be extracted from these filters using the method outlined by X-L Zhao et al [1] in which the ¹⁰Be is analysed in the spectrometer in the form of BeF^–.  The use of this ion greatly reduced the interference from ¹⁰B as a result of the instability of BF^–.  The compound BaBeF₄, mixed with silver powder was used as target material. 

The compressed filter was first shredded and then soaked in HCl to which BeF₂ was added as carrier.  Following alternating periods of heating and agitation, the aqueous portion was collected, heated to dryness and then re-dissolved in HCl and centrifuged to remove unwanted material trapped by the filter. Alkali was added to the supernatant to obtain a precipitate at pH 14.  This precipitate was discarded and the pH of the supernatant was then adjusted to pH 8 to obtain a precipitate of Be(OH)₂.  After dissolving the Be(OH)₂, BaBeF₄ was precipitated in the presence of CsF and BaCl₂∙2H₂O. This procedure has several advantages: 1) safety, as the production of BeO and the use of concentrated HF are unnecessary, 2) the use of ion exchange methods is not required, and 3) normal laboratory glassware (borosilicate glass) can be used for much of the procedure because of the ability of the BeF^– method to separate the ¹⁰Be from ¹⁰B.

The AMS measurement was carried out using the General Ionex 834 ion source at IsoTrace which provides less ion current than higher power sources.  However, the filters, each monitoring 18,000 m³ of air (1 day exposure) provided sufficient ¹⁰Be for these preliminary measurements.  This method also will permit the analysis of ⁷Be in recently obtained filters and will lead to investigations of carrier-free methods for the analysis of both beryllium isotopes.

1. X. -L. Zhao, A. E. Litherland, J. P. Doupé and W. E. Kieser, The potential for AMS analysis of ¹⁰Be using BeF^-  Nucl. Instr and Methods B223 (2004) 199-204