Statistical and practical considerations of limits of detection in X-ray spectrometry

Abstract

Five formulae have been derived statistically to enable the limits of detection in X-ray spectrometry to be calculated. The formulae have been tested experimentally on eleven elements over the atomic number range 11 to 82 on three spectrometers, in one matrix of high and one of low massadsorption coefficient and under a variety of instrumental conditions. The formulae 0·80 N^1/2_bm^–1 and 1·09 s_cm^–1, the latter based on a curve-fitting approach, gave agreeing best limits of detection. Minimum values for the limits were found under optimum experimental conditions to fall in the first transition series and can be as low as 1 p.p.m. in lanthanum oxide media and 0·02 p.p.m. in cellulose acetate. Theoretical and experimental factors that influence the limits of detection are examined and discussed.