[ RadSafe ] Gross Alpha questions

[Michael E. Kitto]

Gross alpha activity can be determined by measuring planchets on
gas-proportional counters.  We have a limit of 100 mg (5 mg/cm2) of
precipitate on the planchet.  Does anyone have a method of estimating the
maximum volume of a water sample that can be evaporated to stay below this
limit without "trial and error" or pre-evaporation of small aliquot ?  For
example, will a conductivity meter or turbidity measurement provide an
estimate of the amount of dissolved solids?  I am looking to develop a
correlation of the measured precipitate (dissolved solids) with a (yet to
be determined) parameter.  Thanks in advance, Mike Kitto