The effect of solvent grade on thin layer chromatographic analysis of writing inks. (September 2016)

• Record Type: Journal Article
• Authors: Barker, Julia; Ramotowski, Robert; Nwokoye, Jennie
• Is Part Of: Forensic science international. Volume 266(2016)
• Page Start: 139
• Page End: 147
• Publication Date: 2016-09
• Subjects: Forensic science -- Questioned documents -- Ink analysis -- Thin layer chromatography -- Solvent system I -- Solvent system II; Medical jurisprudence -- Periodicals; Chemistry, Forensic -- Periodicals; Forensic Medicine -- Periodicals; Médecine légale -- Périodiques; Chimie légale -- Périodiques; Gerechtelijke geneeskunde; Gerechtelijke chemie; Gerechtelijke psychiatrie; Chemistry, Forensic; Medical jurisprudence; Electronic journals; Periodicals; Electronic journals; 614.1
• DOI: 10.1016/j.forsciint.2016.05.003
• Languages: English
• ISSNs: 0379-0738

Abstract

Highlights: A total of 50 blue and black inks were analyzed using thin layer chromatography. Two solvent systems consisting of three different solvents were evaluated. A total of 24 different combinations for each solvent system were compared. The grades and manufacturers of solvents in solvent system I and solvent system II must be consistent. Abstract: The effects on the separation of writing ink dyes and the repeatability of the R f values from using different grades of chemicals used in solvent system I (SSI) and solvent system II (SSII) for thin-layer chromatographic (TLC) ink analysis were studied. Solvent system I consists of a 70:35:30 mixture of ethyl acetate, ethanol, and water. Solvent system II consists of a 50:10:15 mixture of ethanol, water, and n-butanol. Since 1991, the ASTM International Guideline E 1422 has recommended that the purity of solvents should be "reagent grade" and that water quality should be "distilled or equivalent." A total of 25 blue and 25 black inks were selected for analysis. Thirteen of each color ink were ballpoint and the remainder were non-ballpoint. The observations show that there is a solvent grade effect on both the separation and clarity of the ink dyes and the repeatability of their R f values. These results indicate that the grades and manufacturers of solvents used in solvent systems for thin-layer chromatography must be consistent. This is especially critical for searching TLC plates against those from a large ink library in casework. Overall, the combination of solvents that produced the best results for solvent system I consisted of denatured ethanol, HPLC grade water, and ACS grade ethyl acetate. There was no consensus for the best combination of solvent grades for solvent system II; however, it was shown that different grades did have an effect on the separation of ink components.