Can. Soc. l'orens. Sci. J. Vol. 24, No I (1991)
A PRELIMINARY REPORT ON THE NONDESTRUCTIVE EXAMINATION OF BALLPOINT PEN INK ON QUESTIONED DOCUMENTS BY FT-IR SPECTROSCOPY 1 JOEL HARRIS 2
ABSTRACT The applicability of FT-IR microsampling techniques to the nondestructive analysis of ballpoint pen inks on questioned documents is discussed. Preliminary spectral results using conventional transmission FT-IR, micro-transmission/reflectance FT-IR, and diffuse reflectance infrared fourier transform (DRIFT) spectroscopy are presented. DRIFT spectroscopy may offer a viable, nondestructive method for the analysis of ballpoint pen inks on questioned documents.
RESUME Le present article traite des techniques d'analyse de micro-echantillons d'encre de stylo
a bille a I' aide de Ia spectroscopie a I' infra rouge avec transformation de Fourier (FT-IR}. On y expose les resultats preliminaires de tests effectues a !'aide de Ia spectroscopie FT-IR par transmission, Ia spectroscopie FT-IR par micro-transmission/reflectance, et Ia spectroscopie FT-IR par reflectance diffuse (DRIFT). La spectroscopie DRIFT est une methode non destructive et pourrait etre appliquee a !'analyse des encres de stylo a bille sur les documents contestes.
INTRODUCTION Ink examinations on questioned documents are requested in order to determine whether or not two or more inks are similar or different (1, 2, 3), to determine the relative date (4, 5, 6, 7) of one or more questioned ink entries among a group of entries such as those found in a diary, and to backdate (8) questioned ink entries in order to confirm or refute the date at which a document was purportedly executed. The ink or inks in question are first examined by physical techniques (different light sources) which are nondestructive (9, I 0, II) in nature. These examinations may then be followed by chemical analyses to further characterize the questioned inks. The chemical exan1inations generally involve the removal of a portion of the document bearing a sample of the ink in question. The ink is chemically extracted from the paper sample and the dye components are separated by thin layer chromatography (8, !2, 13, 14). Other analytical chemical techniques such as pyrolysis gas chromatography (15), high performance liquid chromatography ( 16). and X-ray microanalysis (17), have also been used in an attempt to characterize writing inks following physical examination.
l. 2.
Presented at the 35th Annual Meeting of the C.S.F.S .. 路路FT-IR Microsampling Techniques and Questioned Document Examinations路路. Toronto. Ontario, Canada. October 18-21, 1988. Questioned Document Examiner. Central Forensic Laboratory, Royal Canadian Mounted Police, Ottawa, Ontario. Canada.
5
The sampling procedures and the subsequent analysis of writing inks as described above raise several concerns in respect of the document under examination. First, the document is altered, albeit not seriously, but altered none the less when an ink bearing paper sample is removed. ln certain cases the coutt may restrict the types of analyses perfom1ed to those examinations which do not involve destruction or alteration of a questioned document's original condition. Secondly, although the different components of the ink may be collected following analysis by certain chemical techniques, the ink itself cannot be recovered in its original form and returned to its original condition as found on the document Thirdly, these chemical examinations reduce the quantity of ink on the document available for subsequent analyses by opposing experts, thereby jeopardizing the rights of the accused. Because of the semi-destructive nature of these chemical analyses and the concerns they raise, serious consideration was given to determining alternative chemical methods which could nondestructively characterize writing inks directly on paper. FT-IR spectroscopy was the only analytical technique considered as a possible method to chemically analyze inks nondestructively on documents. FT-IR spectroscopy has been wide! y used in forensic science to analyze a variety of evidence ( 18, 19, 20). This technique offers the high sensitivity required for the small samples encountered in criminal investigation and generates spectral results which act as fingerprints to characterize a particular material allowing for quick comparison and/or identification against a data base. More specifically, infrared microscopy (21, 22, 23, 24, 25), DRIFT spectroscopy (26, 27, 28, 29, 30, 31, 32, 33, 34), and FT-IR Photothermal Beam Deflection Spectroscopy (35) have been used to nondestructively analyze a variety of materials on different substrates including ballpoint pen ink on paper. In the article by Varlashkin (35) the nondestructive analysis of ballpoint pen ink on strips of paper is described. Although their apparatus could not examine documents larger than a dollar bill, they do indicate that a larger instrument could be built in order to handle the standard size documents typically encountered. Another publication (Notes No. 73, April 1990), entitled "FT-IR Microcarnpling Techniques" from K. Krishnan and S. L. Hill of Digilab Bio-Rad Division (22), contains a description of nondestructive chemical analysis of writing ink on paper. The transmission spectrum of ink on normal writing paper, recorded in situ, is shown. The following will discuss the application of infrared microscopy and DRIFT spectroscopy to the nondestructive chemical analysis of ballpoint pen inks on questioned documents and compare spectra of raw samples of inks generated by diamond anvil cell transmission spectroscopy. Two samples each of correction fluids, photocopy toners, writing inks, printing inks, and adhesives, in their raw form and on different substrates, were submitted to BioRad's Digilab Division, Barrick Scientific Corporation and the R.C.M.P. Central Forensic Laboratory for analysis. Only those results for the writing inks are presented at this time.
EXPERIMENTAL I.
Ink Samples Samples of Bic and Eagle medium blue ballpoint pen inks were obtained from cartridges of their respective pens. Sample inks were chosen without prior knowledge of their chemical formulation.
2. Sample Size The volume and/or size of ink satnple examined varied between the different FT-IR microsampling techniques, however, these ink samples were similar in size to those generally encountered in forensic investigations and were well within the sensitivity range of the FT-JR Spectrometers with which they were examined.
6
3. Sampte Preparation
4.
i)
Samples of raw ink and fibres of paper bearing ink were placed on watch glasses and air dried a minimum of 24 hours under ambient conditions. The raw ink residues and the dried paper fibres bearing ink were then separately positioned between the diamond cell windows for diamond cell transmission.
ii)
Samples of raw ink were prepared on KBr salt plates, positioned on the microscope stage, and analyzed by micro-transmission. Ink on paper and on aluminum foil were positioned on the microscope stage and run by micro-reflectance.
iii)
Samples of ink-on-paper were placed directly on the stage of the diffuse reflection attachment.
FT-RT Microsamplers i)
Diamond Anvil Cell The diamond anvil cell was purchased from High Pressure Diamond Optics, Tuscan, Arizona. The FT-IR spectra were collected at 4 em -I resolution over a spectral range of 4000 to 250 wavenumbers (em - 1) using a Digilab FTS40 spectrometer (Digilab Division of Bio-Rad, Cambridge, MA). This spectrometer was fitted with Harrick 6X beam condensers, cesium iodide (Csl) optics and a deuterated triglycine sulphate (DTGS) detector. The single-beam spectrum of the sample in the diamond cell is ratioed against the reference single-beam spectrum of the empty diamond cell to produce a transmission spectrum essentially free of any diamond cell absorption (37).
ii)
Digilab UMA-300A IR Microscope Sample inks were analyzed on a Digilab UMA-300A IR microscope (Digilab Division of Bio-Rad, Cambridge, MA) equipped with a narrow band mercury cadmium telluride {MCT) detector. All spectroscopic data were collected at 8 em- 1 resolution over a spectral range of 4400 to 700 wavenumbers using a Digilab FTS40 spectrometer equipped with a KBr bcamsplitter. Single beam spectra (non-background corrected) were prepared together with ratioecl spectra.
iii)
Praying Mantis Nanoscope Diffuse Reflection Attachment The Praying Mantis Nanoscope Diffuse Reflection Attachment (Harrick Scientific Corporation, Ossining, New York) is equipped with an xyzO translation stage and a detachable sample viewing 60X microscope. The sample area to be analyzed is focused on the xyzO stage by first placing a sheet of fluorescent paper on the stage and then locating the infrared signal visually. The crosshairs of the clet<-tehable microscope are then focused over theIR signal. The tluorescent paper is removed and the sample area of interest is inserted under the crosshairs. This procedure ensures that the area of interest receives the maximum IR signal. The praying mantis accessory was fitted on a Mattson Sirius 100 FT-IR spectrometer equipped with a cleuterated triglycine sulphate (DTGS) pyroelectric crystal detector. At the time the samples were analyzed a purge was not available on the spectrometer. Therefore, to prevent the water vapour rotational fine structure from dominating the spectrum, samples were run at 8 em -I resolution. All DRIFT spectra data were recorded over 4000 to 630 wavenumbers using Csi optics and plotted in Kubelka-Munk units (38 and 39).
7
I"C::'"'tl ••
''~-'
::~
.......
!ll::ll'r!GUV-~1-,.
-
oc 11111
. . . ~l
OIG!LAB
~~ --~-~~;;---,.. -,-.f.~~-~~;:,~~---~---;;-.JI:Oa (liCIIQ.tlii..,l!<t£;~
~lil'illf1l..C.',, ~.t
Figure I.
?•
'"''~'",.
l"t¥.!
'l'('""t'j~;oolf
CS••·•
>OIDOQ•~ID.!DO , .
I'. niUOtll
Diamond anvil cell transmission spectra (left) and IR microscope micro-transmission (right) of Bic medium blue ballpoint ink {bottom) and Eagle medium blue ballpoint ink (top).
RESUl.TS Figure I shows spectral results for the raw samples of Bic and Eag!e inks measured by diamond cell transmission (left) and micro-transmission (right). The micro-transmission spectra for both inks nearly replicate the diamond cell transmission spectra, however, there are discernible differences in peak intensities and the fine structure observed between the two spectra. These minor differences are mainly due to the ditlerent spectral resolution parameters used on each of the spectrometers. The differences in resolution and intensity will be discussed in detail in the next section. The spectra for the two inks are different, each exhibiting varying band structures below 2000 em -l, even though they display a common intense band at approximately 1590 em -l, similar absorption in the C-H stretching region around 2800 em -l and a broad 0-H band at 3500 em -I. The intense band at 1590 em -I may be due to a C = N or N=N functionality common to azo dyes. A search of lhe Sadt!er standard spectra! library (40) failed to identify any of the dyes, organics or polymers present in either of the inks (Figure 2). This is to be expected as typical ballpoint pen inks consist of a mixture of components comprised of approximately
8
Figure 2.
Diamond cell transmission spectra for Bic and Eagle ink.~ were unsuccessfully searched against the Sad tier Standard spectra library. In the above, the spectra of the Bic ink was searched against spectral libraries of dyes (a), organics (b), and polymers (c).
25% dyes, 25% resins (natural and synthetic polymers added to impart viscosity) and 50% solvent or vehicle (41 and 42). The Sadder library lists spectral data for mostly pure substances and as such, searching for a mixture (i.e. ink) would fail. While FT -IR spectroscopy may differentiate between two or more inks of similar colour, identifying the constituents within these inks may be difficult or impossible. Therefore some sample pretreatment may be necessary (i.e. thin layer chromatography) in order to chemically separate and purify the various ink components. These purified components would be more suitably searched and identified against the Sadtler library. Ultimately the most useful library would be a 9
PAPEft BKGll B IC
~
.
~ '
__....... ... .. -···--,__
....-·
--
., ...
a
INK ON PAI'ER -----
.......
_____ lllr; ...
bo-.
•r cr •• ••••- -
b
·-1
···-·
.......
-r ~r-=.~.:.:.u._ L.: --'--L
---
c Figure 3.
Diamond cell transmission spectra presented for the paper substrate (a), Bick ink-on-paper (b), and Eagle ink-on-paper (c).
lO
e-.:~1
0 !G !lAB
. - -·T-w..e
---
- '
-·•
us:i..11
'8.e
IICI•IIJIII
1""'1'01.
(~I
ll'l .. rtJQ-fl:nJXTJI:U ISIJ X Sll ~t£121U'i!J) n.. _.,l:.llltlltftU .... I -
a
iI I
I
I ···j
'
I
~:~-~ ~
SM ll!lo Ill
... 11 ••
Ill~~~ ~
(10' I">Y'Uii i T - IIi 1-•ID~Dft) .... IDIII>D•o:D-1-
b
'·'1
DIGILAB
I .. J
~::i . -----------r-----------~-------·-·-----...-----. -..-
--·
--11
·--·
,.,_ ..
- - Bl ll~f....Z. CIPTIW"al IS. II 511ttUIJIIHH I\E.I4-If_l .. 915ool-
c
Figure 4.
Micro-reflectance transmission spectra presented for the paper substrate (a). Bic ink-on-paper (b), and Eagle ink-on-paper (c).
ll
collect-ion of spectral data on various known inks. Spectral data on an unknown ink could then be searched from this library to determine the possible manufacturer or source. The intended purpose of this paper was not to identify the various components within an ink but rather to determine if the aforementioned FT -IR microsamplers could produce characteristic spectra of ink on a document, in situ. The spectra generated by diamond cell and micro-transmission for the two blue inks are complex, both characterizing and differentiating the inks. Figures 3 and 4 show spectral results for the paper and ink-on-paper samples measured by diamond cell transmission and micro-reflectance, respectively. The spectra in each figure closely resemble one another and are consistent with the pattern of peaks recorded for the paper substrate (Figures 3a and 4a, respectively). While it is difficult to directly compare the spectra in Figures 3 (absorbance vs wavenumber) and 4 (response vs wavenumber, non corrected background) with the spectra in Figure I (% transmittance vs wavenumber), it should be noted that the fine band structure observed below 2000 em - 1 for the raw inks in Figure I allow these inks to be clearly differentiated from their respective spectra. The spectra for the two inks displayed in Figures 3 and 4 cannot be clearly differentiated from one another. The strong band observed between Ll 00 and I 000 em- 1 in the diamond cell spectra (Figure 3) together with the band between 3000 em -I and 1000 em- 1 and the sharp band at 1050 em -I recorded under micro-reflectance (Figure 4) may be caused by extraneous absorbances attributed to the paper substrate which would appear to dominate the respective spectra. The general appearance of the spectra in Figures 3 and 4 may also be due to the fact that these are single beam (non corrected) background spectra and dependent upon the detector response feature. These results would suggest that diamond cell transmission and micro-reflectance spectroscopy are not suited for the analysis of ink on paper. An attempt to generate paper-subtracted diamond cell spectra of the inks (Figure 5) was not successful since the paper contribution could not be removed. Subtraction of the paper substrate from the micro-reflectance spectra of ink-on-paper samples (Figure 6) was difficult to achieve because the detected signal (response) is nonlinear with respect to path length. 3 The spectra in Figure 6 do, however, show a more characteristic pattern of peaks than that seen for the paper-substracted diamond cell spectra of the inks. Still the paper contribution could not be totally removed from the microreflectance spectra. The variation in reflectance properties between the sample and paper surface only add to the subtraction difficultues. A number of sharp bands are noted for each ink (Figure 6), however, these spectra do not compare with the micro-transmission spectra of the raw ink samples (Figure L). The differences between these two groups of spectra (Figure 6) may or may not be due to artifacts arising during paper subtraction. Although the reproducibility of the paper subtracted mciro-reflectance spectra was not addressed, repeated sample analysis may in fact determine whether or not any of the spectral results observed are due to artifacts. Until the presence or absence of spectral artifacts is con tirmed, the differences between the spectra of the two inks (Figure 6) can only suggest that it may be possible to use micro-reflectance to compare similarly coloured inks on documents in situ.
3.
Pcr,onal Communication. David J. Johnson. Digilab.
12
Figure 5.
.-a.•l
The paper-subtracted spectra (a) for Bic (left) and Eagle (right) inks (b) versus paper background (c) measured by diamond cell transmission .
D!G.ILAB
-~
i
·-·----~·
~-- ·-~.-:;-····· IIIDI•Ii.ll Sll~lm"""rtu<
......
---~~-
fi.OU!,.,..,._
-·-----·-----~-----
'UBI-~
-~rw.-c~:~
TU::.a:••e>D•a••-
' 1'1111-11
~
!U!.foUG-ID•GII•U•IIe
"'·' DIGILAB
OIGILAB
0~±~~---------=~----------~~----------~~
m~~ .• ----------~~--------~~~---~
--.::In
Figure 6.
_,.,.,EN;a. ..
·--0:
... ···-------- r-·--··
......
Hltlll-~talll . .
Jll- lt!D'DOI
Paper-subt.racted spectra for Bic (top left) and Eagle (bottom left) inks measured by micro-rellectance and compared with micro-transmission spectra of the raw sample of Bic (top right) and Eagle (bottom right) inks from Figure l.
l3
Figure 7.
Paper-subtracted spectra for Bic (left) and Eagle (right) inks measured directly on paper by DRIFT spectroscopy.
Figure 7 shows two different spectra for the inks measured on paper and recorded by DRIFT spectroscopy. At the time these spectra were produced a purge system was not available on the spectrometer, therefore these spectra include some C02 and H20 noise contributions. The results in Figure 7 contrast those of the micro-reflectance spectra in Figure 4, which are similar to one another due to the dominating paper background reference which could not be properly subtracted. The paper background was automatically subtracted for the DRJFT spectra in Figure 7. The fact that the DRIFT spectra for the two inks in Figure 7 are significantly different from one another confirms the removal of the paper contribution, indicating that these spectra are due to the ink residue and not paper artifacts. The results were reproducible, however, it was found that slight variations in alignment of the accessory produce differences in the minor spectral features of these samples. To overcome this problem a fixed alignment diffuse reflection attachment is suggested, or the use of a fixed sampling stage of some sort be adapted to the Praying Mantis. 4 In Figure 8 the diamond cell transmission spectra of the raw samples of ink have been converted to Kubelka-Munk units and compared with the inks measured on paper by DRIFT also recorded in Kubelka-Munk units. The band structure of the DRIFT spectra Figure 8 is different from the bands produced by diamond cell transmission for the same inks. However, the DRIFT spectra can be used to differentiate between the two different inks and were produced nondestructively, in situ.
4.
Personal Communication. Ms. S. Barets, Harrick Scientific Corp.
14
a.o
&.:s
r.a
111
'l\\1
11-'----'---'-1~ 1
,--.
~ 1\
f\;1 I ,.~i
1.1_,
I:i:
II
I'
:1 .
j\f\J~V "V~~WI .. ..
L...,.--,~,-.--~,----~.--~-.---.---,-.-~-,~rj ,..,
.......
:;.o
,
Figure 8.
1..0
Ul
1a
Comparison of diamond cell transmission spectra (i.)r raw samples of Bic (top Ieli) and Eagle (bottom left) inks with DRIFT spectra of the Bic (top right) and Eagle (bottom right) inks measured directly on the paper.
DISCUSSION The raw inks were analyzed and the data collected on the diamond anvil cell in order to generate reference spectra for comparison purposes. The microsampler itself has proven its suitability to the analysis of forensic size samples and the generation of characteristic spectra for a host of materials. The diamond cell is comprised of windows which are transparent in the infrared region from 1800 to 200 em- 1 with a wide absorption band between 2700 to 1800 em -I, but can be used in the region between 4000 to 2700 em -I (43). The low signal-to-noise ratio in this region is due to low energy throughout caused by absorption of the diamond cell windows. These cells are therefore suited for analyzing both the group frequency and fingerprint regions of organics, inorganics, and their mixtures. While the diamond cell can be used to analyze some media removed from the surface of paper substrates,
15
.. ~~~ .. 1
·~-~
\
v :L I i
O!G!LAB
\
J
t
......
-
Figure 9.
0~~~~------~------~-------=~ ~a:ao
.....
... D'fo. C.O.M..UooiJl.loof()ll. &l lt~1~ , ••• • • tgog.d)
Micro·re!lectance spectra of raw sample of Bic ink (left) collected on an aluminum foil substrate, compared with micro-transmission spectra of raw ink collected on a KBr salt plate.
such as correction fluids (44), this microsampler is not suited for the analysis of ink on paper fibres- even when destructive analyses are permitted. The predominant paper contribution to the resulting spectra may mask bands attributed to the ink. The micro-reflectance spectra of ink-on-paper did generate a limited pattern of peaks (Figure 6) for the inks examined, however, it would appear that this mocrosampler is more suited to collecting spectra from samples which rest on reflective surfaces such as aluminum foil, are prepared on KBr salt plates, or are themselves translucent. Figure 9 compares the micro-transmission spectra of raw ink on a KBr salt plate with the micro-reflectance spectra of ink on aluminum foil. Although there are some differences in peak intensities between the two spe.ctra, there is close agreement in band frequencies. The micro-reflectance spectra of the ink on aluminum foil contains the attributes of bot.h the front surface reflection and double pass transmission (air-surface-substrate-surface-air) spectra (22). Comparison of the micro-reflectance spectra of the ink on foil (Figure 9) to the ink on paper (Figure 6) show differences in peak intensity, shape, and band frequency, highlighting the overiding contributions of the non-reflecting paper substrate. Characterizing ink on reflecting metal surfaces by microreflectance would appear useful except that documents are not generally executed on metal surfaces. The DRIFT spectra in Figure 7 suggest that a characteristic pattern of peaks can be generated when using the Praying Mantis Nanoscope microsampler (Figure 10) for nondestructive in-situ analyses of ballpoint pen inks on paper substrates. The Praying Mantis attachment has the capability to expand the available sampling area by rotating the ellipsoids and rotating the sampling points above the optical plane (21 and 45). Large substrate surfaces bearing a wide variety of materials can be studied nondestructively in the absence of any sample preparation. Because this sampler will accommodate a wide range of substrates, it might be interesting to look at DRIFT spectra of ink dye components on a TLC plate (26). Figure 11 shows DRIFT spectra of two different paper products. Because of the uniform sample size and area of interest, the paper products were analyzed directly on the diffuse reflection attachment sample stage without the required focusing of the infrared beam.
16
The Praying Mantis Nonoscope
Figure 10.
The Praying Mantis Nanoscope Diffuse Rctlcction Attachment (after Harrick, Optical spe<:troscopy:Sampling Techniques Manual) .
.!.1-路! u--1 I
...
..:a--~-~-
-Jm-~-~---~ -~,-;.,-~
8111
----;-..----~~
路""~路
Figure I I.
Diffuse reflection spectrum of drarling paper (left) ami white duplicator paper (right), afier Harrick (22).
Inks analyzed on paper, however, require some focusing of the IR signal over the sample area of interest. For this reason the Praying Mantis attachment is equipped with a detachable sample viewing microscope. The differences in spectral results observed for the samples measured on the three microsamplers may be attributed to such factors as instrument sensitivity, sample size,
17
complexity of sample, and strong substrate contributions. Spectra collected at a resolution of 4 em_, will resolve some bands which are not resolved on spectra generated at a resolution of 8 em -I. The narrow band MCT detector used in conjunction with the IR microscope is approximately 40 times more sensitive than the DTGS detector used with the di.amond cell, however, the MCT detector only covers a spectral range of 4400 to 700 wavenumbers. This is not a significant drawback, since for most inks very little spectral information resides in the region below 700 em -I. The analysis of ink on paper by the different IR microsamplers may be influenced by the varying concentration of ink at any given sample location. This is due in part to the differential vertical absorbance of ink into the paper fibres and the nonuniform deposition of ink onto the document by the writing instrument. Varlashkin (35) suggests that paper fibre and ink composition may screen each other causing the absorption band intensities of the components to vary and to depend not only on the relative quantities of the components but also on the complexity of these components. The micro-reflectance spectra generated for the ink-on-paper samples were collected from only those pen strokes displaying a heavy build up of ink, i.e. gooping. The DRIFT spectra for the ink-on-paper samples were generated from arbitrarily selected sample sites. The above results show that two similarly coloured inks residing on paper can be nondestructively differentiated by DRIFT. The fact that only two inks were analyzed precludes commenting on the application of DRIFT spectroscopy to the comparison and characterization of writing inks on paper. Wider groups of similarly coloured inks must be analyzed in both their raw form and on paper and factors such as: different paper substrates, varying concentration of ink at different sampling sites along the same written stroke, differential aging of ink on paper, and the reproducibility within different batches of the same ink or different inks of the same formulation, must be addressed before DRIFT can be considered a useful method to characterize writing inks directly on paper. These preliminary results warrant additional study of the nondestructive application of DRIFT spectroscopy to the analysis of writing inks on paper.
CONCLUSIONS The IR microscope and Praying Mantis diffuse retlection attachment are both nondestructive FT-IR microsampling accessories, however, it would appear that DRIFT spectroscopy is more suited to the analysis of ink-on-paper type samples. The substrate paper contribution to the generated spectra are more easily subtracted in DRIFT spectroscopy and have less effect on the final results than those same samples run on the IR microscope. While a spectral library of inks based on DRIFT spectroscopy is an attractive possibility, additional test studies must first be conducted to determine the reproducibility of results and how factors such as varying ink concentrations and aging of a document affect the spectral peak intensities and band frequencies observed. The results of these tests would determine whether or not DRIFT spectroscopy represents a viable, highly sensitive, and rapid nondestructive alternative to the current analytical techniques used in the identification, comparison, and dating of writing inks on questioned documents. The analytical techniques of thin layer chromatography (TLC), pyrolysis gas chromatography (PGC), and high perf(mnance liquid chromatography (HPLC) allow for components within inks to be separated, characterized, and the sample fractions collected at the completion of the analysis. These techniques. however, are semi-destructive in nature, altering the original
condition of the document. It may be possible to combine the nondestructive analysis offered by DRIFT for the examination of inks on paper with the qualitative analysis offered by techniques such as TLC, PGC, and HPLC in developing a comprehensive and rapidly accessible standard reference library of writing inks. ACKNOWLEDGEMENTS
I would like to thank Mr. D. MacDougall, FT-IR Project Manager, Central Forensic Laboratory, Royal Canadian Mounted Police for first suggesting the use of DRIFT spectroscopy to analyze inks on paper. Appreciation is also extended to Harrick Scientific Corporation and Digilab Division of Bio-Rad for performing sample analyses on their respective FT-IR microsampling accessories. REFERENCES I.
Crown, D.A., Conway, J.V.P., and Kirk, P.L Differenriation Of Blue Ballpoint Pen Ink. J. Crim. Law, Crim., Pol. Sci. 1961; 52: 338-343.
2.
Chowdhry, R., Gupta, S.K .• and Bami. H.L Ink Differentiation With Infrared Techniques. J. For. Sci. 1973; 18: 418-433.
3.
Totty. R.N., Ordidge, M.R., and Onion, LJ. A Comparison OfThe Use Of Visible Microspectrometry And High Performance Thin Layer Chromatography For The Discrimination Of Aqueous Inks Used In Porous Tip And Roller Ball Pens. For. Sci. Int. I985; 28: 137-144.
4.
Stewart. L.F. Ballpoint Ink Age Determination By Volatile Component Comparison- A Preliminary Study. J. For. Sci. 1985; 30: 405-411.
5.
Bmnelle, R.L.. Antonio, M.S .. and Camu, A. A Critical Evaluation Of Current Ink Dating Techniques. J. For. Sci. 1987; 32: 1522.-1536.
6.
Brunelle, R.L., Breedlove, C.H .• and Midkiff. C.R. Determining The Relative Age Of Ballpoint Inks Using A Single-Solvent Extraction Technique. 1. For. Sci. 1987; 32: 1511-1521.
7.
Camu, A.A. Comments On The Accelerated Aging Of Ink. J. For. Sci. 1988; 33: 744-750.
8.
Crown. D.A., Brunelle, R.L.. and Cantu. A.A. The Parameters Of Ballpen Ink Examinations. J. For. Sci. 1986: 21: 917-922.
9.
Hamman, B.L. Nondestructive Spectrophotometric Identification Of Inks And Dyes On Paper.
J. For. Sci. 1968; 13: 544-556. 10.
Tappolet, J.A. Comparative Examination Of Ink Strokes On Paper With Infrared And Visible Luminescence. 1. For. Sci. Soc. 1986: 26: 293-299.
II.
Zimmerman. J. and Mooney. D. Laser Examination As An Additional Nondestructive Method Of Ink Differentiation. 1. For. Sci. 1988; 33: 310-318.
12.
Nakamura. G.R. and Shimada, S.C. Examination Of Micro-Quantity Of Ball Poim Inks From Documems By Thin-Layer Chromatography. 1. Crim. Law. Crim .. Pol. Sci. 1965: 56: 113-118.
13.
Tholl, J. Applied Thin-Layer Chromatography In Document Examination. Police 1970: 14: 6-16.
14.
Brunelle. R.L. and Pro, M.J. A Systematic Approach To Ink Identification. 1. Ass. Off. Ana. Chern. 1972; 55: 823-826.
15.
Wampler, T.P. and Levy. E.J. Pyrolysis GC In The Analysis Of Inks And Papers. LC-GC Mag. 1986: 4: 1112-1116.
16.
White. P.C. and Wheals. B. B. Use Of A Rotating Disc Multiwavelength Detec!Or Operating In The Visible Region Of The Spectrum For Monitoring Ball Pen Inks Separated By High Pert<:mnance Liquid Chromatography. J. of Chrom. 1984: 303: 211-216.
17.
Harada. H. A Rapid Identification Of Black Colour Materials With Specific Reference To Ballpoint Ink And Indian Ink. I. For. Sci. Soc. 1988: 28: 167-177.
19
18.
Shearer, J .C., Peters, D.C., and Kubic, T.A. Forensic Microanalysis By Fourier Transfom1 Infrared Spectroscopy. Trends In Anal. Chem. 1985; 4: 246-251.
19.
Burke, P., Curry; C.J., Davies, L.M., and Cousins, D.R.A. Comparison of Pyrolysis Mass Spectrometry. Pyrolysis Gas Chromatography And Infra-Red Spectroscopy For The Analysis Of Paint Resins. For. Sci. Int. 1985; 28: 201-219.
20.
Pandey. G.C. Fourier Transform Infrared Microscopy For The Determination Of The Composition Of Copolymer Fibres: Acrylic Fibres. Analyst 1989; 1!4: 231-232.
2l.
Harrick, N .1. Optical Spcctroscopy:Sampling Techniques Manual, Harrick Scientific Corporation, 88 Broadway, Box 1288, Ossining, New York, 10562, 1987; 133 p.
22.
Krishnan, K. and Hill, S.L. Exotic Sampling Methods Using The Infrared Microscope. In: Ferraro, J.R. and Krishnan, K .. Editors. Practical Fourier Transform Infrared Spectroscopy: Industrial and Laboratory Chemical Analysis. San Diego, Ca: Academic Press, 1990; 104-167.
23.
Reffner, J.A., Coates, J.P., and Messerschmidt, R.G. Chemical Microscopy With FT-IR Microspectrometry. Amer. Lab. 1987; 4: 86-97.
24.
Kellner, R., Fischbikk, G., and Minich, Ch. FTIR-Microscopy Versus FTIR-ATR-Spectroscopy For The Analysis Of Multilayer Polymer Films. Mikrochim. Acta 1986; 1: 271-279.
25.
Harthcock, M.A .. Lentz, L.A., Davis, B.L., and Krishnan, K. Applications Of Transmittance And Reflectance Micro/FT-lR to Polymeric Materials. Appl. Spect. 1986; 40: 210-214.
26.
Zuber, G.E., Warren, R.J., Begosh, P.P., and O'Donnell, E.L. Direct Analysis Of Thin-Layer Chromatography Spots By Diffuse Retlectance Fourier Transform Infrared Spectrometry. Anal. Chem. 1984; 56: 2935-2939.
27.
Suwki, E.M. and Gresham, W .R. Forensic Science Applications Of Diffuse Retlectance Infrared Fourier Transform Spectroscopy (DRIFTS): l. Principles, Sampling Methods, And Advantages. J. For. Sci. 1986; 31: 931-952.
28.
Lee, J.Y., Moska1a, E.J., Painter, P.C., and Coleman, M.M. The Application Of DRIFT Spectroscopy To Polymer Complexes. Appl. Sect. 1986: 40: 991-994.
29.
Yang, P.W., Mant.sch, H.H .â&#x20AC;˘ and Baudai:;, F.A. Critical Evaluation Of Three Types Of Diffuse ReOectance Infrared Acces!>ories. Appl. Spect. 1986; 40: 974-978.
30.
Chalmers, J.M., Mackenzie, M.W.. and Sharp, J.L. Characterization Of Thin-Layer Chromatographically Separated Fractions By Fourier Transform Infrared Diffuse Reflectance Spectrometry. Anal. Chem. 1987; 59: 415-418.
31.
Poslusny. M. and Dangherty, K.E. Nondestructive Adhesive Analysis On Stamps By Fourier Transf01m Infrared Spectroscopy. Appl. Spect. 1988: 42: 1466-1469.
32.
Taboudoucht, A. and Ishida, H. Diffuse Transmittance Spectroscopy Of Polymeric Fibers. Appl. Spect. 1989; 43: 1016-1021.
33.
Suzuki, E.M. Forensic Science Applicati<ms Of Diffuse Retlect<mce Infrared Fourier Transform Spectroscopy (DRIFTS): IV. Direct Analysis Of Metallic Paints- Sampling Considerations. J. For. Sci. 1989; 34: 164-179.
34.
Suzuki, E. M. and Brown, J.A. Forensic Science Applications Of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS): V. Direct Analysis Of Metallic Paints - Screening Of Panels . .1. For. Sci. 1989: 34: 180-196.
35.
Varlashkin, P.G. and Low, M.J.D. FT-IR Photothermal Beam Defection Spectroscopy Of Black Inks On Paper. Appl. Spec. 1986; 40: 507-513.
37.
Digilab. Digilab FTS Manual. Digilab, A Division Of Bio-Rad. Boston, Mass. 1980.
38.
Kubelka. P. and Munk, F. Title Unknown. Z. Tech, Phys. 1931: 12: 593.
38.
Kubelka. P. and Munk, F. New Contributions To The Optics Of Intensely Light-Scattering Materials. J. Opt. Soc. Amer. 1948: 38: 448.
40.
Sadtler. The Sadtler Standard Spectra. Pub. By Sadtler Research Laboratories, A Division Of BioRad Laboratories. 3316 Spring Garden St., Phil. PA .. 19104, 1988.
20
41.
Breedlove, C.H. The Analysis Of Ball-Point Inks For Forensic Purposes. J. Chern. Ed. 1989; 66: 170-!71.
42.
Patterson, D. The Chemistry Oflnks For Writing, Printing And Copying. For. Sci. Soc. Jour. !964; 4: 20Q--208.
43.
Tweed, F.T., Cameron, R., Deak, J.S., and Rodgers, P.O. The Forensic Microanalysis of Paints, Plastics and Other Materials by an Infrared Diamond Cell Technique. For. Sci. Int. 1974; 4: 211-218.
44.
Harris, J.S. and MacDougall, D. Characteriz.ation And Dating Of Correction Fluids On Questioned Documents Using FTIR. Can. Soc. Forensic Sci. J. 1989; 22: 349-376.
45.
Harrick, N.J. Developments In IR-VIS-UV Accessories From Harrick Scientific. An informational supplement to our catalogue HSC-831; Harrick Scientific Corporation, Ossining. New York, U.S. A. 1989; 10.