A spreadsheet method for 90Sr and 89Sr interpretation

A spreadsheet method of handling multiple data points is described for the interpretation of "radiostrontium" analyses. The method uses up to 10 or more counts on one sample, starting 1 d after the chemical separation. The unreliable "day-0" count on a relatively low activity sample is not used since it introduces too many uncertainties. The count data for each sample are compared against a spreadsheet-calculated matrix of ingrowth/decay curves from 0 to 100% 90Sr and at the analytical count intervals between about 24 to 650 h after the chemical separation to determine the best fit of the data set. This fit occurs where the decay/ingrowth characteristics of the sample, as defined by the changing counts, most closely match those of the matrix for all of the data points. At this fit, the 89Sr and 90Sr percentages are defined, and the best estimate of the "time-0" counts is calculated using all of the counts. Secondary separations and analyses are not required.