THIN LAYER CHROMATOGRAPHY OF COMPUTER PRINTER RIBBON ... Twenty-five computer printer ribbons, al1 black in colour, were analysed by thin layer ...
Forensic S&ence International, 53 (1992) 51- 60 Elsevier Scientific Publishers Ireland Ltd.
THIN LAYER CHROMATOGRAPHY INKS
51
OF COMPUTER
PRINTER
RIBBON
NAVNEET KAURa, OM PRAKASH JASUJAa and ATUL K. SINGLAb aDepartmat of Forensti Science, Punjabi Unive-rsity,bForensicScience Consultant,Patiala-147 002 (India) (Received August Z’th, 1991) (Revision received November lOth, 1991) (Accepted December 30th, 1991)
Summary Twenty-five computer printer ribbons, al1 black in colour, were analysed by thin layer chromatography. With the use of proper solvent solutions al1 different brands were differentiated on the basis of colour spots and their RF values. Key words: Computer crimes; Questioned documents; Thin layer chromatography
Introduction Computer printed documents (computer printouts) make a distinctive group of documents. Occasional problems may arise about the source and authenticity of these printouts. The print quality, print style, alignment and other unique identifying characteristics may be helpful in the examination of these documents using methods for conventional typescript examinations. In addition thin layer chromatography of the inks from these printouts may provide an additional alternative for comparing two printouts or to establish the identity of the printer in cases where the printer ribbon may not have been yet changed. Thin layer chromatography is probably the most widely used technique to differentiate between similar coloured inks and almost every type of ink available has been analysed with the help of this method [l - 91. While reviewing the literature, the authors could not find any reference to thin layer chromatography of computer printer ribbon inks, and it would seem no work has been reported so far on this problem. In the present study, various computer printer ribbon inks have been differentiated with the help of thin layer chromatography.
Correspondence India.
to: O.P. Jasuja, Lecturer
in Forensic Science, Punjabi University,
0379-0738/92/$05.00
0 1992 Elsevier Scientific Publishers Printed and Published in Ireland
Ireland Ltd.
Patiala 147-002,
52
Materials and Methods Twenty-five computer printer ribbon inks of different brands were collected from various computer centers. Al1 the ribbons appeared black in colour. A smal1 sample of about 0.5 cm2 was cut from each ribbon and extracted in 1 ml pyridine for 30 min. The colour of each extract was noted and stains of these extracts were prepared on a white sheet of paper. Also a few lines were drawn by writing some strokes with the ribbon pressed against the paper. Round plugs (8 - 10) were punched from these strokes with a modified hypodermic needle and then extracted with pyridine. The number of plugs used depended on the intensity of the stroke. The ribbons, extracted stains and writing strokes were examined under ultraviolet radiation for any flourescence. The colour of these extracts, stains and writing strokes were noted. Al1 the samples were divided
TABLE 1 COLOR OF STAINS OF SAMPLES (IN DAYLIGHT) Specimenno.
Brand
2 4 6 8 9 11 19
Cokw of stain
code no.
T.L. System’ Gold Line’ Ink Link’ Full Mark Uni Products Diablo ’ Uni Products
Blue-black Blue-black Blue-black Light blue-black Blue-black Blue-black Blue-black
A B C D E F G
1 12 16 17 23 24
Klear Point Trent Epson LX 80 Full Mark L and T Universal
Black Black Black Black Black Black
3 5 7 10 15 13 14
Data Products Peng Gone Kores Universal Kores Gold Line Kores
Violet-black Violet-black Violet-black Violet-black Violet-black Violet-black Violet-black
18 20 21 22 25
Data Products TVSE Ink Line Matrix Honeywell
Violet-black Violet-black Violet-black Violet-black Violet-black
of ribben
‘Plastic ribbons: al1 other are cloth ribbons.
U V W X Y
53 TABLE 2 BLUE-BLACK
COLORED INKS
Solvent front run: 9.8 cm; temperature: Sample na.
A
C
D
E
room temperature
(32°C).
spots
RF Values
No. of spots
color of spots
8
Blue Torquoise blue Purple Blue Violet Purple
0.041 0.071 0.194 0.316 0.449 0.755
Violet Torquoise Torquoise Torquoise Pink Pink Blue Violet Purple Violet Torquoise
0.918 0.973 0.041 0.071 0.194 0.214 0.326 0.439 0.765 0.928 0.973
11
Blue Torquoise Pink Purple Pink Blue Violet Pink Purple Violet Torquoise Pink Purple Torquoise Torquoise Black Torquoise Skyblue
blue blue blue
blue
blue
blue
blue blue blue
Pink Purple Torquoise blue Black Torquoise blue Skyblue
0.041 0.071 0.184 0.204 0.234 0.326 0.449 0.653 0.765 0.918 0.975 0.347 0.367 0.428 0.459 0.541 0.561 0.938 0.357 0.367 0.459 0.531 0.561 0.959
54 TABLE 2 (continwd) Sample no.
F
RF Valws
spots
of spots
No. of spots
colm
14
Purple Blue Pink Purple Blue Pink Torquoise blue Skyblue Blue Skyblue Pink Purple Violet Torquoise blue
0.031 0.061 0.092 0.204 0.306 0.367 0.398 0.428 0.459 0.50 0.643 0.785 0.918 0.969
11
Pink Purple Violet Blue Purple Black Purple Torquoise blue Pink Purple Pink
0.367 0.388 0.479 0.49 0.50 0.52 0.531 0.551 0.888 0.939 1.0
into three groups based on the colour of the extracts and stains (Table 1). Thin layer chromatography of each sample was performed on precoated Silica Gel-60 glass plates of 0.25 mm layer thickness showing no flourescence (Merck, Darnstadt, Germany). Three standard size spots from each sample (i.e. one each from ribbon extract, stain and written stroke) were applied with disposable capillaries. In the cases of dilute extracts, extracts were applied repeatedly to the same spot. After drying the spots, the plates were kept in a saturated developing chamber containing a solvent system for 35 min at room temperature (31 f 2°C). After development, the plate was taken out of the chamber and the solvent front was marked. The developed plates were allowed to dry in the open. They were then examined in daylight as wel1 as under ultraviolet radiation for any additional spot or fluorescente of the spots. Results and Discussion Al1 twenty-five
ribbon samples, which appeared black in daylight could not be
55
TABLE 3 BLACK COLORED SAMPLES Solvent front run: 10 cm; temperature: Sample no.
H
room temperature
(31°C).
spots
RF values
No. of spots
color
4
Black Pink
of spots
Sky Pink
0.04 0.13 0.79 0.99
Pink Pink Pink Sky Blue Pink Brown
0.26 0.33 0.51 0.79 0.98 0.99 1.00
J
Skyblue Blue Pink
0.8 0.98 0.99
K
Black Violet Pink Blue Torquoise blue Black Skyblue Green Pink
0.14 0.21 0.24 0.26 0.30 0.32 0.79 0.98 0.99
1
7
L
7
Purple Pink Torquoise blue Skyblue Blue Pink Brown
0.24 0.26 0.33 0.81 0.97 0.99 1.0
M
5
Pink Pink Skyblue Skyblue Pink
0.18 0.24 0.81 0.98 0.99
56 TABLE 4 VIOLET-BLACK
COLORED INKS
Solvent front run: 7.5 cm; temperature: Sample
120.
(32°C).
RF Values
spots No.
N
room temperature
6
of spots
cobr
ofspots
Violet Purple Light purple Pink Deep blue Black
0.466 0.615 0.626 0.720 0.92 0.973
Violet Blue Purple Light purple Pink Blue Black
0.360 0.493 0.533 0.613 0.693 0.933 0.986
Violet Blue Purple Light purple Pink Brown Green Brown
0.333 0.507 0.889 0.613 0.693 0.88 0.933 0.986
Violet Violet Purple Light purple Pink Green Brown Violet Violet Purple Light purple Pink Blue Brown
0.40 0.466 0.533 0.626 0.693 0.933 0.986 0.44 0.48 0.533 0.613 0.933 0.986 1.0
Violet Purple Light purple Pink Brown Green Brown
0.36 0.52 0.613 0.693 0.907 0.933 0.987
57 Table 4 (Cmtinud) Sample no.
T
U
RF Values
spots No. of spots
cokn” ofspots
7
Violet Purple Light purple Pink Brown
0.36 0.507 0.613 0.693 0.893
Green Brown
0.933 0.973
Violet
0.36
Purple Light purple Pink Pink
0.533 0.627 0.720 0.733
Deep blue Black
0.933 1.0
Violet Purple Purple Light purple
0.306 0.360 0.40 0.533 0.613
Pink Blue Brown Purple
0.707 0.96 0.986 0.52
Grey Black Deep blue Black
0.613 0.786 0.946 1.0
Violet Violet Purple Light purple
0.32 0.386 0.533 0.626
Pink Blue Brown
0.72 0.933 0.986
Violet Purple Pink Blue
0.386 0.52 0.626 0.92
7
8
Violet
W
5
7
Y
4
differentiated under ultraviolet radiation as none of the samples showed any fluorescente. It was interesting to note that while al1 the ribbons and their strokes were black, this was not the case of their extracts and stains. Of the twenty-five
58
samples, extracts of ‘7 were blue-black, 6 were black and 12 were violet-black. In this way the twenty-five samples could be subdivided into three groups (Table 1). Within the three sets no differente in RF values or number of spots were developed. There were differences in the intensity of the shades of the spots. The spots developed from written strokes were less intense, while they were darker in the case of stains and ribbon extracts. Tables 2-4 record the developed spots and their RF values for the ink samples. Figures 1 - 3 are diagrammatic representations. It is evident from the Tables that the inks of the three subgroups display different colours and different RF values. For the separation of the various inks a number of solvent systems reported in the literature were tried. It was found that the violet-black group could be separated and differentiated effectively with the solvent suggested by Brunelle et al. [8] for TLC of conventional typewriter inks (butanol:ethanol:distilled water 50:10:5). This solvent was not effective for the black and blue-black subgroups.
AP
B
C
D
E
F
G
Fig. 1. Diagramatic representation of thin layer chromatograms of blue-blackinks. Spot colours identified as: 1, blue; 2, black; 5, torquoise blue; 9, pink; 10, purple; 11, sky blue; 12, violet. See Table 2 for RF values. See Discussion for solvent.
59
09
?? s
02
&
i : .i2
09 010
?? 2
eg
09 eg
2 0
0
?? H
I
0
0
I
L
K
J
I* I
idRlGl#
0
.
M
03
0 N
.
I
.
.
.
.
P
0
s
R
.
.
T
LI
.
.
V
w
. X
?? wr
Fig. 2. Diagramatic representation of thin layer chromatograms of black inks. Spot colour identified as; 1, blue; 2, black; 3, brown; 5, torquoise blue; 9, pink, 10, purple; 11, sky blue; 12, violet. See Table 3 for RF values. See Discussion for solvent. Fig. 3. Diagramatic representation of thin layer chromatograms of violet -black inks. Spot colours identified as; 1, blue, 2, black, 3, brown, 4, deep blue; 6, green; 7, grey; 8, light purple; 9, pink; 10, purple; 12, violet. See Table 4 for RF values. See Discussion for solvent.
60
For these latter inks a series of tests was made with solvents based on polarity [lol. These experiments led to a solvent formula (butanol:ethyl acetate:chloroform 1:1:2) for black inks. A solvent formula (ethyl acetate:ethanol:chlorobenzene:methanol:ammonia 2:3:10:3:0.5) was the most suitable for blue-black inks. Conclusion The computer printer ribbons, which were al1 black in colour, could be divided into three subgroups on the basis of the colour of their extract in pyridine. The inks of each sub-group and using a different solvent could be further successfully differentiated from each other by thin layer chromatography, except in the case of samples no. 14 and 15, both of which are the same brand (Kores). Acknowledgment The authors thank Mr. J. S. Juneja, Incharge, Computer Center, Punjabi University, Patiala, for providing the samples of computer printer ribbons. References 1
S.N. Tiwari and N. Bhat, Thin-layer chromatography
of fountain pen inks. Int. Grim. Police
Rev., 260 (1972) 201- 203.
G.R. Nakamura and S.C. Shimoda, Examination of microquantities of bal1 point pen inks from documents by thin layer chromatography. J. Grim. Luw, Crim&oZ. PoZti Sci., 56 (1965) 280. 3 R.S. Verma, K.N. Prasad and G.J. Mishra, Thin layer chromatographic analysis of fibre tip pen inks. For& Sci. Int., 13 (1979) 65-70. 4 O.P. Jasuja and A.K. SingIa, Thin layer chromatographic analysis of fibre tip and hi tec point pen inks. Zndtin J. Forensic EX., 4(4) (1990) 167 - 170. 5 R.S. Verma, K.N. Prasad and G.J. Mishra, TLC examination of dyes used in some Indian red coloured pencils. J. India Acad. Forensic Sci., 17 (1978) 69- 70. 6 R. Jindal, O.P. Jasuja and R.M. Sharma, Thin layer chromatographic analysis of some coloured pencils. Zn&an J. Fwensic Sh., 4 (4) (1990) 191-202. 7 O.P. Jasuja, A.K. SingIa and Seema B.L., Thin layer chromatographic analysis of Indian stamp pad inks. Forensic Sci. Int., 42 (1989) 255-262. 8 R.L. Brunelle, J.F. Negri, A.A. Cantu and A.H. Lyter 111,Comparison of typewriter ribbon inks by thin layer chromatography. J. Fortic Sc%., 22 (1977) 807. 9 E.A. Davis, and A.H. Lyter 111,Comparison of typewritten carbon paper impressions. J. Forensic Sci., 27 [2] (1982) 424-427. 10 J.M. Bobbit, Thin Luyer Chromatogruphy, Reinhold, New York, 1963. 2
