Determination of seventeen major and trace elements in new float glass standards for use in forensic comparisons using laser ablation inductively coupled plasma mass spectrometry.

Consensus concentration values for seventeen (17) major and trace elements typically present in soda-lime glass manufactured using the "float " process and used in the quantitative analysis and forensic comparison of glass samples were determined using laser ablation (LA) micro sampling coupled to inductively coupled plasma mass spectrometry (ICP-MS). This is the first reporting of the chemical characterization of a new set of float glass intended for use as matrix-matched calibration standards in the forensic analysis and comparison of glass by LA-ICP-MS using a standard test method (ASTM E2927-16e1). Three Corning Float Glass Standards (CFGS) were manufactured at low, medium, and high concentrations of 32 elements typically encountered in float glass samples as found in forensic casework. This work describes an international collaboration among seven (7) laboratories to evaluate the homogeneity of the three glass materials and reports the consensus concentrations values of 17 elements at three concentration levels. Eight (8) sets of independent results from LA-ICP-MS analysis using the standard test method of analysis and one set of micro-X-ray Fluorescence Spectrometry (μXRF) data (using method ASTM E2926-17) resulted in typically <3% relative standard deviation (RSD) within each lab and < 5% RSDs among all labs participating in the study for the concentration ranges using sampling spots between 50 μm - 100 μm in diameter. These results suggest that the new calibration standards are homogeneous for most elements at the small sampling volumes (~ 90 μm deep by ~80 μm in diameter) reported and show excellent agreement among the different participating labs. Consensus concentration values are determined using a previously reported calibration standard (FGS 2) and checked with a NIST 1831 SRM®. A collaboration with National Institute of Standards and Technology (NIST) scientists to certify these glasses as SRMs, including the certification of the quantitative analysis of the minor and trace element content, for future distribution by NIST is ongoing.