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IDENTIFICATION NEWS
1972
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A Systematic Approach to Ink Identification By Richard L. Brunelle Bureau of Alcohol, Tobacco and Firearms, U.S. Treasury Department, Washington, D. C. ,c;.. -·
w:~·Prior to 1950, inks ~nHI::e~~:ned documents were 1
j;:amined by observing the color under wavelengths ~f light ranging from ultraviolet to infrared. These ~chniques were supplemented with photography using ~lected filters. Chemical spot tests were also used to ~etect metals such as iron, copper, vanadium, and ~promium. Although these methods helped to disirriguish between many types of inks, it was not possi'to characterize the various formulations. The development of more advanced techniques for .nalyz.ing inks was slow because even the more sophis#cated analytical approaches required the destruction ;a.tsmall portions of the questioned document. How~ever, during the past few years the courts have ac~pted the practice of -removing very small samples ~r analysis. Somerford and Souder (1) analyzed fluid wHting inks by paper chromatography and their work ~hawed t•hat only a micro quantity of ink was needed J!)r the ana lysis and destruction to the document exihrined was minimal. H ~~By 1952, ballpoint inks began to appear on the ~~rket in significant numbers. Brown et al (2) showed ~~t electrophoresis can be employed to separate dye ~mponents of these inks. In their work this technique ~-s compared with paper chromatography and it was ~orted that electrophoresis could be used to sepa$te constituents not amenable to separation by ~per chromatography. Following tth·is work, numerous Jtidies comparing paper chromatography and electro!;lbresis and describing various solvent systems for !~e in the development of paper chromatograms were ~orted (3-4-5-6-7-8). ~tin 1960,. Tholl (9) ~pplied thin layer chromatography C) to mk analys1s and found the technique could ; ·- used effectively to separate dyes and other com~nents of writing ·inks. This analytical tool was found, ~·be particularly suitable for the examination of !icro-quantities of ballpoint inks and made possible ~~~ separation of dye mixtures. ~~;,MacDonald (10) showed that it was possible to !!!aracterize fountain pen inks by porous glass chroma~raphy and electrophoresis. This approach permitted arations under a much wider range of conditions n found in pap~r chromatography and el·ectrophorebecause the f1nal separations are in an optically w.,. nsparent medium which allows direct spectral tasurements on the separated chromatograms.
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Crown, et al (11) studied blue ballpoint inks and reported a scheme of analysis for the identHication of these inks by their dye compositions. This work showed that blue ballpoint inks could be divided into several distinguishable categories depending on the dyes present. Nakamura and Shimada (12) reported (TLC) of ballpoint inks on a micro scale from TLC plates prepared on microscope slides. A solvent system consisting of 50 parts of n-butanol, 10 parts ethanol and 15 parts of distilled water was found to be effective for the majority of ballpoint inks. It was further shown that four spots from a single dye such as methyl violet could be £eparated with this system. Prior to about 1966, efforts were directed towards the development of new analytical methods to compare questioned and known ink samples and very little attention was given to identifying the source of questioned inks or to establishing dates of preparation of questioned entries. The dating of inks was limited to the determination of periods of time when gross changes were made in the compositions of ink. For example, the change from oil base solvents to glycol bases provided at date pl"ior to which the glycol ballpoint inks did not exist. Early efforts to identify inks for the purpose of dating were made by Hofman (13). He collected ballpoint ink formulations from a number of manufacturers and the results of his work indicated that questioned inks can be identified and dated if a complete collectif?n of inks and their production dates are obtained. Hofman's analytical procedur-es involved paper and thin layer chromatography with various solvent systems. He also used spectrophotometry, spot tests, and the typical non-destructive tests to aid in the identification. Based on his work it was concluded that although an ink c-annot be absolutely identified, "its make or identity can be determined with a great deal of scientific certainty. Hamman (14) reported a non-destructive spectrophotometric method for identification of inks and dyes on questioned documents by analyzing the inks directly on the document without treatment. For the past several years the Internal Revenue Service has carried out considerable research in the field of ink analysis in an attempt to meet the needs of the agency in the enforcement of its laws and regulations. In many instances, the date the document was pre(Turn Page Please)
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IDENTIFICATION NEWS
pared ·is extremely important and could be the basis for establishing fraud against the government. Sinoe well established techniques for identifying inks exist and a relatively complete ink library is now available, it is possible to determine the first production date of an ink formulation. The purpose of this paper is to present a systematic approach that can be successfully used to compare and identify inks.
C. Solubility Tests
II EXPERIMENTAL The identification of questioned inks is carried out by making a comparison with known standard inks. The following approach is used: Apparatus and Equipment 1. (A) Binocular stereo microscope with 10 - lOOX magnification. (B) Magnifying glass at lOX 2. TLC Develop·ing Tank for 8x8 inch plates. 3. Ultraviolet View Box (equipped wibh long and short wave lamps). 4. Infrared Image Conversion Microscopic (minimum of lOX magnification) Leitz. 5. Spectrophotometer equipped with an attachment for scanning TLC plates. 6. Merck precoated s·ilica gel glass plates from Brinkman. 7. Analtech precoated silica gel glass plates. 8. Eastman precoated silica gel sheets without indicator. 9. Disposable Sui pipets. 10. 1 dram capped vials. 11. Syringe needle with tip cut off and filed to a blunt point (@ 0.05 mm diameter). Reagents 1. Ethyl acetate (reagent grade) 2. n-butanol (reagent grade) 3. Pyridine (reagent grade) 4. Sulfuric Acid {reagent grade) 5. Nitric Acid (reagent grade) 6. NaOH (reagent grade) 7. Hydrochloric Acid (reagent grade) 8. Ethanol (absolute) 9. Disti lied water A. Photography of the Document The document to be examined should be photographed to maintain a record of the condition of the document upon receipt. (A 1-1 black and white copy is sufficient).
D. Chemical Spots Tests
B. Visual and Microscopic Examination The ink on the document is observed visually with and without the aid of magnification to determine the type of ink used (ballpoint, fiber tip, fountain, etc.), color, and overall Hne quality of the writing. Magnification of lOX is sufficient.
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One or two plugs of ·ink are removed from the writ1 ten line with a blunted point of a hypodermic needl for use in determining the relative solubility of th questioned ink in various solvents. Fibers containin the ink are separated and the reagents absolut ethanol, ethanol-water U+l), distilled water, and pyri dine are applied to the fibers containing the ink. Th · results are observed with lOX magnification.
One or two plugs removed as in C are used to deter mine whether any color reactions occur upon additio · of the reagents of Hydrochloric Acid, Sulphuric Acid Nitric Acid and NaOH. The tests are observed a about lOX.
E. Ultraviolet and Infrared Light Examination The ink is observed under both long and short wav ultraviolet to determine whether the ink flouresces Determination of the relative opacity of the ink t infrared light involves viewing the ink through a Lei Infrared Image Convers·ion Microscope. Writing ink· show varying degrees of transparency or opacity whe viewed under ;infrared light.
F. Thin Layer Chromatography About 1 to 10 plugs of ink are removed, on the quantity of ink deposited and the type of in present. The ink is dissolved in a minimum amoun of solvent, usually about 2 drops. The salven t used t dissolve the ink .is the one determined to be the bes suitable for this purpose during the solubility test (Section C). The color of the ink solution ·is observed and r corded. The visible spectrum of the solution may als be recorded spectrophotometrica lly. The dissolved in is then spotted on an Eastman silical gel chromate gram sheet with disposable micro pipets (5 ul). Afte allowing the spots to dry, the appearance at the origi is recorded. Then, the chromatogram is developed fo 30 minutes in a solvent system of 70 parts ethy acetate, 35 parts ethanol (absolute) and 30 parts o distilled water. After 30 minutes, the chromatogram i allowed to dry and the Rf values of the various dye present or ultraviolet fluorescent spots observed ar ca leu late d. All of the inks from the standard ink library whic have similar dye compositions are selected for analysi by visually comparing the questioned (TLC) with th (TLC) of the known inks ·in the library and by referenc to the coded cards which contain the results of all o the tests carried out on the control library inks. Th standard library inks are coded according to the folloW criteria:
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l. Type of ink; 2. Color of ink; 3. Infrared opacity; 4. Type and number of dyes present, including dispersion components; and 5. Ultraviolet fluorescent components. The selected standard inks are next analyzed simul·taneously with the questioned ink by (TLC) on the same· chromatogram plate. This TLC examination is carried out on Merck precoated silica gel glass plates, using two different solvent systems. A development time of 2 hours is used for these plates. Analtech precoated silica gel glass plates can also be used, but the development time is only 30 minutes.
Solvent I 70 ethyl acetate 35 ethanol (absolute) 30 distilled water Solvent II 50 parts n-butanol 10 parts ethanol 15 parts distilled water . The Merck and Analtech plates separate the dyes into many distinguishable components and provide ·several points of comparison between questioned and ··known inks. The chromatograms are observed in visi'ble and ultraviolet l·ight for identifiable com. ponents. Tests 8, C, D, and E are next carried out on the selected standard inks and the results compared with the questioned ink.
G. Spectrophotometry The above descr·ibed (TLC) procedure together with . examinations (A-F) is usually sufficient to eliminate but perhaps 1 or 2 of the standard inks. If more . more information is needed to distinguish the standard ·o'inks, the Merck or Analtech TLC plates containing the :~¥eparated dye components of the questioned and :.~nown inks are scanned on a spectrophotometer :~~uipped with an attachment for scanning spots' on -~-~- (TLC).
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Each blue ink is usually scanned in the visible region at 550 mu, using a xenon light source and the percent Jransmiss•ion of light through each separated dye com)onent is recorded and the relative amount of each i:Q)re present with respect to the other is calculated. {'The wavelength chosen for scanning varies according ii~ th color of the ink and depends on which dyes are ~~present. A wavelength is chosen so that each dye ~~resent absorbs the light with equal intensity.
H. Other Examinations The above described procedure ·is usually sufficient to match a standard ink from the library with the questioned ink; however, wherever proprietary information from the manufacturer of the identified ink is known, it is desirable if possible to check the questioned ink for the presence of these known components. This approach can provide additional points of identification. For example, there are a variety of fatty acids, resins and viscosity adjusters added to inks and these compounds can be identified when a sufficient quantity of the questioned sample is avai 1able for analysis. In many cases, these components can readily be detected by gas liquid chromatography or by TLC. Carbon and graphite which are common dispersion ingredients in repro ballpoint inks, can be distinguished by electron diffraction techniques. Graphite will display a specific electron diffraction pattern, but carbon will not because it is not a crystalline substance. Some inks contain materials that fluoresce and have other unique compounds which help make an identification almost absolute when these materials are determined.
I. Electrophoresis The authors have not found any specia I advantages for electrophoresis over (TLC) for any of the various types of writing inks, however, when sufficient ink is available for further analysis this method can provide another means of confrirming the identification. Ill DISCUSSION
The described systematic approach to writing ink identification has been used routinely at the Internal Revenue Service Laboratory since 1968 and several hundred cases have been examined. Testimony using this technique was given in Federal courts on numerous occasions and in some instances the ink testimony was used as primary evidence. In this work the questioned inks are identified with a high degree of scientific certainty using this systematic approach. This is very much like compa-ring paint, glass, and soil and utilizing points of identification to establish statistical-ly significant comparisons. It should be recognized that it will never be possible to obtain every ink that is produced in the world, just as it would be impossible to obtain every fingerprint or all paints. For this reason, is is not possible to identify every questioned ink submitted for analysis. Further, absolute identification of ink is difficult because all of the components which we-re o~iginally put into the ink by the manufacturer caf!not be determined. In some unusual cases a positive identification can be (Turn Page Please)
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made when it can be established that a unique dye or combination of components was used. For example, in one particular case, it was possible to establish that a document dated 1958 was back dated because a dye identified in the questioned ink was not synthesized unti11959. This type of identification can be considered absolute. In another case, four specific ingredients of the ink were identified and it was established that only one ink manufacturer in the U. S. and Europe produced an ink with the same combination of ingredients. The methods described for the analysis of inks are not by any means the only ones that can be used, nor are they represented to be the best possible methods. However, these methods are bel·ieved to be the most practical when considering the sample size. Since each ink is unique, no specific method will apply in aII cases. For this reason, the analyst must use the best analytical techniques available and determine as many points of identification as possible. The success of the described approach to ink identification depends largely on the cooperation of the various ink manufacturers who supply the ·ink standards. Without their help, sufficient standard samples would not be available to compare with questioned inks for this approach to be practica I. The Alcohol, Tobacco and Firearms Laboratory has been very fortunate because ink companies have recognized the value of th-is type of program to the law abiding citizens and as a result have been extremely cooperative, not only by providing ink samples, but by presenting testimony at court whenever necessary.
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REFERENCES
1. Somerford, A. W., J. Crim. Law, 43, 124-27 0952). 2. Brown, C., and Kirk, P. L., J. Crim. Law, 45, 334-33 (1954).
3. Brown, C., and Kirk, P. L., J. Crim. Law, 45, 473-48 (1954). 4. Brackett, J. W., and Bradford, L. W., J. Crim. Law, 43 (No.4), 530-539 (1952). 5. Coldwell, B. B., Analyst, 80, 68-72 (1955}. 6. Raju, P. S., Banerjee, R. C., Iyengar, N. K., J. Am •. Acad. For. Sci., 8, 268-285 (1963). 7. Feinberg, J. G., and Smith, 1., Chromatography and: Electrophoresis on Paper, Pergamon Press (1962).' 8. Thompson, J. W., J. For. Sci., Soc., 7 (4), 194-203,! (1967). 9. Tholl, J, Police, November 7-15 (1960)
10. MacDonell, H. L., J. Crim. Law, 53, 507-521 (1962}. 11. Crown, D. A., Conway, J. U., and Kirk, P. L., J. Crim. Law, 52, 338-343 (1961). 12. Nakamura, G. R., and Shimada, S.C., J. Crim. Law, 56, 113-118 (1965). 13. Hofman, W., Zurich Cantonal Police (unpublished work-1969). 14. Hammon, B. L., J. For. Sci., 13, 544-556 (1968).
IV FUTURE INK COMPARISONS The identification of writing inks by the described procedure can help ·investigators by pro\/liding investigative leads and the results obtained and conclus}ons formulated very often are excellent corroborative evidence in criminal cases. Since the identification is statistical, this laboratory is working on a marking program that can be used by all ink manufacturers. Markers added by each producer and changed every year, can provide a positive identification of the manufacturer of the ink and permit the deterniination of the year the ink was produced.
58th Annual Conference, I.A.I. Jackson, Wyoming July 29 -August 2, 1973 Conference headquarters will be in the Wort Hotel, · and all meetings will be in the Pink Garter Plaza and.' Theater, directly across the street. The Pink G3rter is a conference center, fully quipped with lighting, audio-