radiogravimetric analysis 

https://doi.org/10.1351/goldbook.R05104
A kind of quantitative analysis in which the activity of a precipitate is used as a measure of its mass.
Source:
PAC, 1994, 66, 2513. (Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)) on page 2524 [Terms] [Paper]