DISCRIMINATION AND CLASSIFICATION OF SMALL FRAGMENTS OF WINDOW AND NON-WINDOW GLASSES USING ENERGY DISPERSIVE X-RAY FLUORESCENCE SPECTROMETRY

• NCJ Number: 52539
• Author(s): R J DUDLEY; C R HOWDEN; T J TAYLOR; K W SMALLDON
• Date Published: 1978
• Length: 13 pages
• Corporate Author: Great Britain Home Office Central Research Establishment
• Publication Format: Document
• Language: English
• Country: United Kingdom
• Note: DISTRIBUTION LIMITED TO AUTHORIZED LAW ENFORCEMENT AGENCIES

Annotation

FIFTY PAIRS OF WINDOW-NONWINDOW GLASS (SAMPLES IN EACH PAIR BEING MATCHED IN REFRACTIVENESS) WERE ANALYZED USING ENERGY-DISPERSIVE X-RAY FLUORESCENCE SPECTROMETRY.

Abstract

THE MEASUREMENT OF THE REFRACTIVE INDEXES OF GLASS FRAGMENTS AND THE COMPARISON OF THEIR DENSITIES ARE ROUTINE OPERATIONS IN MOST FORENSIC SCIENCE LABORATORIES. ENERGY-DISPERSIVE X-RAY FLUORESCENCE SPECTROMETRY IS A MULTIELEMENT TECHNIQUE THAT OFFERS RAPID NONDESTRUCTIVE ANALYSIS. THE DISCRIMINATING POWER OF THE TECHNIQUE WAS INVESTIGATED FOR 200-MICROGRAM FRAGMENTS OF WINDOW AND NONWINDOW GLASS. THE REFRACTIVE INDEX FOR EACH SAMPLE WAS DETERMINED BY OBSERVING THE BECKE LINE IN SODIUM LIGHT USING A PREVIOUSLY CALIBRATED SILICONE OIL AS THE IMMERSION MEDIUM. TO ENABLE A CLASSIFICATION SCHEME TO BE DEVISED, 50 PAIRS OF GLASS WERE EVALUATED. THE RANGE OF THE REFRACTIVE INDEX IN THE SAMPLES WAS CONDITIONED BY THE AVAILABILITY OF SUITABLE SAMPLES. GLASS FRAGMENTS WERE DISTRIBUTED FAIRLY EVENLY THROUGHOUT THE REFRACTIVE INDEX RANGE. IN ORDER TO ASSESS WITHIN-SAMPLE VARIATION, 20 DIFFERENT GLASS SAMPLES WERE EXAMINED IN DUPLICATE. THE CLASSIFICATION OF GLASS USING THE X-RAY FLUORESCENCE TECHNIQUE DEPENDED ON THE EXISTENCE OF SIGNIFICANT DIFFERENCES BETWEEN FREQUENCY DISTRIBUTIONS OF ELEMENTAL RATIOS BETWEEN THE TWO POPULATIONS OF GLASS SAMPLES (WINDOW AND NONWINDOW). IT WAS DEMONSTRATED THAT X-RAY FLUORESCENCE HAS CONSIDERABLE POTENTIAL FOR THE DISCRIMINATION OF DIFFERENT GLASS FRAGMENTS WITH THE SAME REFRACTIVE INDEX AND THAT DATA FROM APPLICATIONS OF THE TECHNIQUE CAN BE USED TO CLASSIFY UNKNOWN GLASS TYPES. OTHER METHODS OF ANALYSIS, SUCH AS ATOMIC ABSORPTION SPECTROPHOTOMETRY AND SPARK SOURCE MASS SPECTROMETRY, OFFER GOOD DISCRIMINATION AND CLASSIFICATION BUT ARE BOTH COMPARATIVELY VERY SLOW AND ALSO DESTRUCTIVE. THE USE OF THE X-RAY FLUORESCENCE TECHNIQUE FOR CLASSIFICATION IS ILLUSTRATED BY REFERENCE TO GLASS FRAGMENTS RECOVERED FROM A SUSPECT IN A BREAK-IN CASE. SUPPORTING DATA AND REFERENCES ARE INCLUDED. AN APPENDIX LISTS PEAK AREAS RATIOED TO CALCIUM FOR THE 50 PAIRS OF GLASS SAMPLES. (DEP)