NCJ Number
51786
Journal
Journal of Forensic Sciences Volume: 23 Issue: 4 Dated: (OCTOBER 1978) Pages: 643-661
Date Published
1978
Length
19 pages
Annotation
THIN-LAYER CHROMATOGRAPHY (TLC) IS USED TO SEPARATE WAX PRODUCTS USED IN PENCILS AND TO INVESTIGATE THE EFFECTS OF CLAYS, RESINS, AND OTHER ORGANIC FILLERS AND BINDING AGENTS IN PAPER ON IDENTIFICATION OF PENCIL TYPES.
Abstract
THE PENCIL LEADS USED BY THE 17 MAJOR PENCIL MANUFACTURERS IN THE UNITED STATES WERE SUBJECTED TO A SERIES OF TESTS TO ANALYZE THEIR CHEMICAL AND PHYSICAL CHARACTERISTICS. THE PURPOSE WAS TO DETERMINE THE FEASIBILITY OF IDENTIFYING A SPECIFIC TYPE OF PENCIL AS THE INSTRUMENT USED IN A PIECE OF WRITING. FOLLOWING AN OVERVIEW OF THE PENCIL MANUFACTURING PROCESS, THE WAXES AND CLAYS USED TO BIND THE GRAPHITE IN A PENCIL LEAD ARE DESCRIBED. TLC WAS CHOSEN FOR THE ANALYSIS BECAUSE OF ITS ABILITY TO EFFECTIVELY DIFFERENTIATE WAX PRODUCTS USING ONLY MICROGRAM AMOUNTS OF SAMPLE. THE EXPERIMENTAL TECHNIQUE USED IS DESCRIBED IN DETAIL. TYPICAL X-RAY SPECTRUMS OBTAINED BY THE ANALYSES ARE ILLUSTRATED. THE INTERACTION OF VARIOUS FILLERS AND COATINGS IN PAPER ON THESE SPECTRUMS WAS ALSO EXAMINED. IT WAS FOUND THAT THE TLC TECHNIQUE SUCCESSFULLY DIFFERENTIATED VARIOUS MANUFACTURERS' PENCIL LEADS AND THAT THE PROCEDURE WAS BOTH PRACTICAL AND RELIABLE. HOWEVER, IT WAS IMPOSSIBLE TO LIFT SUFFICIENT LEAD FROM A SAMPLE OF WRITING ON PAPER TO PERMIT IDENTIFICATION. THE CONTAMINATING PAPER COMPONENTS SERIOUSLY INTERFERED WITH THE TLC IDENTIFICATION. IT IS SUGGESTED THAT MORE SENSITIVE TECHNIQUES, SUCH AS LIQUID CHROMATOGRAPHY, GAS-LIQUID CHROMATOGRAPHY, OR OTHER MICROSCOPY TECHNIQUES, BE INVESTIGATED FOR THIS PURPOSE. THE POSSIBILITY OF USING TRACE ELEMENTS TO DIFFERENTIATE AMONG WRITING SPECIMENS ON PAPER IS BRIEFLY DISCUSSED. SUPPORTING DATA AND REFERENCES ARE PROVIDED. (GLR)