Metrological characteristics of lead determination in rare earth phosphates by electron probe microanalysis

An equation for the calculation of the detection limit c _lim is presented. Relations for the limit of detection c _lim, limit of determination c _min, and relative error V of analyte determination are derived. The performance characteristics of lead determination in rare earth phosphates on a JXA-8100 microanalyzer are found. Under the typical conditions of the determination of monazite age (15 kV, probe current of 250 nA, count time in the positions of the line and background 400 s each) c _min using the 2σ-criterion is 0.006 wt % for an ordinary spectrometer and 0.004 wt % for a high-aperture one. In the simultaneous registration of lead by the scheme ”two ordinary plus one high-aperture channel,” c _min is reduced to 0.003%. For c _min = 0.006%, the acceptable error of age estimates V of 1–3 relative percent is attained at c _lim = 0.3-0.08%, respectively. As was found, the lowest capacity of microanalyzers for geochronology needs is 0.02–0.03% of PbO. Equations of constraints for the performance characteristics of methods ensure the revelation of the necessary conditions of analysis and compliance with them.