A system and method to improve the accuracy of the measure of constituent element(s) in a sample containing domains potentially including the constituent element(s) are described herein. For each domain, the volume of the domain is estimated and the concentration of the constituent element(s) in the domain is determined using LIBS. When all the domains have been analyzed, the volumetric concentration of the domains is summed and divided by the total volume of the sample. Accordingly, by limiting the concentration analysis to separate domains, it is possible to improve the accuracy of the concentration analysis.