Elemental heterogeneity observations in float glass samples via LA-ICP-MS thickness profiling

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) was used to determine elemental profiles of float glass samples by means of closely-spaced (100-250 mu m apart) spot ablations through the thickness of the glass. Five examples with anomalous elemental profiles displaying significant heterogeneity, notably for the elements Ce and Zr, are presented. The heterogeneities may be attributed to the common glass manufacturing flaws called reams, and have been found to extend laterally over at least a few centimeters. The detection of two very similar Ce profiles in the outer and inner panes of a laminated vehicle windshield indicates that elemental heterogeneities might in fact extend much farther laterally. All of the observed heterogeneities have the potential to cause a Type I error (false exclusion) based on a four standard deviation criterion, if the corresponding comparison sample is not adequately characterized. It is recommended that comparison samples be analyzed by distributing the ablation spots evenly through the thickness of the glass in order to detect elemental heterogeneities.