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Thin-layer chromatographic analysis of fibre-tip pen inks
65
Forensic Science International, 13 (1979) 65 - 70 @ Elsevier Sequoia S.A., Lausanne - Printed in the Netherlands
THIN-LAYER INKS
RANJIT Central
SINGH Forensic
(Received
CHROMATOGRAPHIC
VERMA, Science
September
KEDAR Laboratory,
29, 1978;
NATH
ANALYSIS
PRASAD
Chandigarh
accepted
OF FIBRE-TIP
and GOPAL
PEN
JI MISRA
(India)
December
7, 1978)
Summary Twelve inks made by three firms for fibre-tip chromatography. It has been possible to differentiate
pens have been studied by thin-layer among most of these inks.
Introduction Fibre-tip pens, commercially known as sign pens, are a recent addition to writing instruments. They combine the qualities of conventional nib pens, pencil, and brush in one. The availability of pen writing in different colours and effortless writing has caused their increasing popularity. Consequently, their abuse is also simultaneously increasing in the writing of disputed signatures and for preparing multicoloured unlawful posters: questioned documents which a forensic scientist may be called upon to study. Optical [l] , electrophoretic [ 21, chromatographic [3 - 61, and spectrographic [7] techniques are frequently used for comparing coloured dyes in pencils, and pen and ball-pen inks, but no attempts have so far been made to differentiate the inks used in fibre-tip pens. The colour constituents used in preparing various shades of fibre-tip pen inks have been studied in this paper, perhaps for the first time. Thin-layer chromatography (TLC) has been used to separate and differentiate the dyes used by different Indian manufacturers in various sign-pen inks.
Materials Twelve sign-pen inks of three pearl, available in the local market consisted of glass plates (200 mm and ultraviolet lamp. Butan-l-01, Merck. Glacial acetic acid was from
brands, Luxor-camlin, Ecko, and Fleethave been studied. The TLC equipment X 200 mm), activation oven, desiccator, 1,4-dioxane, and silica gel were from BDH (AR grade).
66
Method Silica gel G TLC plates (0.25 mm thick) were prepared, activated at 110 “C for an hour, and then cooled in a desiccator. Spotting was done at 25 mm above the baseline of the plate employing two techniques: (1) spotting from ink solutions prepared in alcohol; (2) by embedding a small piece of paper (1 mm X 1 mm) bearing ink cut from writing strokes of a given ink as reported earlier [ 81, and leeching the ink with solvent mixture. The developing chamber was saturated for half an hour with the solvent mixture. Butan-l-ol-acetic acid-water (6:1:2) was used for inks 1 - 10 in Table 1, and butan-l-olacetic acid-water-1,4dioxane (6:2:2:1) for inks 11 and 12. The spotted plates were developed by ascending chromatography at a temperature of 32 t 0.5 “C. When the solvent front had ascended about 130 mm from the spotting line, the plates were removed and dried, and examined immediately in visible light and ultraviolet rays since some coloured spots fade after a few hours even at room temperature.
Observations The Rf values are reported in Table 1. These are the mean values obtained from three sets of experiments with each ink using both spotting techniques. The deviations in Rf values are also indicated.
Discussion It is evident from the Rf values listed in Table 1 that a clear-cut separation and differentiation of colour constituents present in various fibre-tip pen inks is possible by TLC. It has been possible to differentiate the three brands, each of twelve shades of sign-pen inks, using only two solvent mixtures. It is interesting to note that constituents of the blue inks of Ecko and Fleet-pearl are similar, as are those of the violet inks of Luxor-camlin and Fleet-pearl brands. Here no differentiation could be made. Possibly the manufacturers used the same dyes for these inks. Some highly fluorescent and additional spots were observed under ultraviolet rays in the case of the orange, dark pink, red, and crimson inks, giving additional differentiation data for the brands under study. The results obtained by both spotting techniques are similar with all inks. However, in the case of ink 2 for Luxor-camlin and Ecko brands, and ink 3 for Luxor-camlin, when the ink solutions were directly spotted, dark spots remained at the base point even after chromatography. This did not happen when spotting was done by embedding the piece of paper. Evidently the solvent system does not dissolve all the colour constituents of these three inks.
No.
Ink
TABLE
a
a
Royal
Violet
a
Black
a
a
Brown
Blue
a
Yellow
blue
Solvent*
Shade
1
Violet streak Violet
Red Blue
Violet Violet Violet Royal blue Light violet
Blue
Royal blue Royal blue Yellow Red Royal blue
Black Yellow Red
Yellow Light red
Spot colour
Luxor-camlin
0.77 0.11 2.30 3.60 4.54
0.30 0.50 0.50 0.50 1.90 2.85
f 2.40 r 1.19
* 2 * r +
+ * f + * t
f 0.50 + 3.10
f 0.39 + 2.54
0.00 to 41.93 f 5.00 74.81 + 1.79
21.55 35.81
26.92 48.46 51.54 59.23 72.31
0.00 3.59 4.87 11.88 12.00 to 19.41 82.50
4.36 50.17
0.00
4.24 34.85
Rf x 100
blue
+ 0.60 * 2.70
41.92 Violet
+ 2.50 + 1.50
42.56 56.15 12.05
-f 2.16
* 1.20 * 3.10 + 4.54
49.62 57.31 65.39
87.81
i 2.50 + 4.10
f 0.39
0.00 59.04 65.14
4.24
Rf x 100
Red
Light blue Blue
Royal
Violet Blue Orange
Black Blue Orange
Yellow
Spot colour
Ecko
blue
Violet streak Violet
Light blue Blue
Royal
Blue Violet Violet Violet
Violet Violet Orange
2.10 2.31 2.54 2.80
+ 2.50 f 1.50
+_ 2.90
* + 2 f
overlea f)
0.00 to 23.08 + 4.00 15.38 * 2.00
42.56 56.15
80.39
67.70 76.16 80.17 85.39
+ 1.80 ? 2.85 2 4.00
20.51 47.62 65.14
2.36 2.20 2.40 2.70
i + * +
100
38.51 70.88 91.69 95.44
Rfx
(continued
Yellow Light yellow Pink Light pink
Spot colour
Fleet-pearl
4
0)
a
a
Red
Red**
79.23 79.23
Pink Golden yellow with high fluorescence
a a
9
8
Dark pink Dark pink**
6.54 10.40 13.75
Dull red Bluish Dull red
a
Orange**
6.54 + 0.40 13.75 * 1.75 33.85 F 2.80
Yellow Red Light red
a
Orange
7
i 1.50 ? 1.50
i 0.40 f 0.40 + 1.75
+ 1.10 i 1.10 +_ 2.00
78.97 82.57 85.63
Violet Violet Violet
100
a
RfX
Spot colour
Luxor-camlin
Solvent*
Shade
1 (continued)
No.
Ink
TABLE
41.28 70.00 88.22 92.56 70.00 88.22 92.56
Light red Orange Light pink Pink Dull red Lemon yellow Lemon yellow
69.49
69.49
40.77 34.23
Orange
Dull red
Pink Lemon
+ 1.54 2 2.15 + 3.08 i 4.10 i 3.90 t 3.08 i 3.10 i 4.10 i 3.90
40.77 46.53 40.77 89.49 93.08 40.77 76.15 89.49 93.08
Light red Red Orange Crimson with high fluorescence Greenish Red surrounded by yellow Orange
i 1.54 i 1.90
Crimson with high fluorescence Red
yellow
+ 2.50
t 2.50
Dull red
Red with a long tail
71.88
71.88
Pink 84.10 Golden yellow 84.10 with high fluorescence and a long tail Brown 87.66
78.46 82.01 84.10
Violet Violet Violet
48.46 63.28 68.46
Violet Violet Violet
t 2.80 t 2.60 t 2.20
Rfx
Spot colour
Spot colour
Fleet-pearl Rf x 100
Ecko
1.30 1.50 2.61 4.10 1.50 2.61 4.10
i 2.65
i- 2.65
+ 3.80
i 3.60 * 3.60
+ f * i t f t
* 2.80 ? 2.10 + 2.80
100
co
ul
b
Green
12
acid-water (6:1:2);
54.74 * 1.50 81.91 f 3.90
8.46 + 0.77 55.95 + 1.90
Green Light blue
Yellow Green
(6:2:2:1).
Green Yellow Light yellow
2.31 * 0.20 10.56 t 1.30 19.62 * 1.90
Pale yellow Dull red Bluish
acid-water-1,4-dioxane
Green Yellow Light blue
10.56 * 1.30
Crimson
(b) Butan-1-olacetic
54.41 f 1.70 61.95 + 1.95
Green Yellow
t 0.40 * 1.13 * 0.20 * 1.30 ?; 1.90
5.38 10.56 2.31 10.56 19.62
Crimson Crimson Pale yellow Dull red Bluish
*Solvent mixtures: (a) Butan-1-olacetic **Rf values measured in UV rays.
b
a
Emerald
Crimson* *
Crimson
11
10
57.10 f 2.90 72.70 A 2.50 82.31 + 3.85
55.37 f 2.30 64.67 + 2.50 80.00 + 2.77
70
Acknowledgement The authors express their thanks to Dr. B. R. Sharma, Director, Central Forensic Science Laboratory, Chandigarh, for his keen interest in this study.
References 1 0. Hilton, Identification and differentiation between coloured pencils, Forensic Sci., 6 (1975) 221 - 228. 2 J. W. Thomson, The identification of inks by electrophoresis, J. Forensic Sci. Sot., 7 (1967) 199 - 202. 3 S. N. Tiwari and N. Bhat, Thin-layer chromatography of fountain pen inks, Int. Crim. Police Rev., 260 (1972) 201 - 203. 4 C. Brown and P. L. Kirk, Horizontal paper chromatography in the identification of ball-point pen inks, J. Crim. Law, Criminol. Police Sci., 45 (1954) 334 - 339. 5 R. L. Brunelle and M. J. Pro, Systematic approach to ink identification, J. Ass. Offic. Anal. Chem., 55 (1972) 823 - 826. 6 J. D. Kelly and A. A. Cantu, Proposed standard methods for ink identification, J. Ass. Offic. Anal. Chem., 58 (1975) 122 - 125. 7 V. K. Mehrotra and S. K. Sidhana, Non-destructive identification of metallic ions of inks used on documents, Forensic Sci., 9 (1977) 1 - 3. 8 R. S. Verma, K. N. Parsad and G. J. Misra, TLC examination of dyes used in some Indian red coloured pencils, J. Ind. Acad. Forensic Sci., 17 (1978) 69 - 70.
Forensic Science International, 13 (1979) 65 - 70 @ Elsevier Sequoia S.A., Lausanne - Printed in the Netherlands
THIN-LAYER INKS
RANJIT Central
SINGH Forensic
(Received
CHROMATOGRAPHIC
VERMA, Science
September
KEDAR Laboratory,
29, 1978;
NATH
ANALYSIS
PRASAD
Chandigarh
accepted
OF FIBRE-TIP
and GOPAL
PEN
JI MISRA
(India)
December
7, 1978)
Summary Twelve inks made by three firms for fibre-tip chromatography. It has been possible to differentiate
pens have been studied by thin-layer among most of these inks.
Introduction Fibre-tip pens, commercially known as sign pens, are a recent addition to writing instruments. They combine the qualities of conventional nib pens, pencil, and brush in one. The availability of pen writing in different colours and effortless writing has caused their increasing popularity. Consequently, their abuse is also simultaneously increasing in the writing of disputed signatures and for preparing multicoloured unlawful posters: questioned documents which a forensic scientist may be called upon to study. Optical [l] , electrophoretic [ 21, chromatographic [3 - 61, and spectrographic [7] techniques are frequently used for comparing coloured dyes in pencils, and pen and ball-pen inks, but no attempts have so far been made to differentiate the inks used in fibre-tip pens. The colour constituents used in preparing various shades of fibre-tip pen inks have been studied in this paper, perhaps for the first time. Thin-layer chromatography (TLC) has been used to separate and differentiate the dyes used by different Indian manufacturers in various sign-pen inks.
Materials Twelve sign-pen inks of three pearl, available in the local market consisted of glass plates (200 mm and ultraviolet lamp. Butan-l-01, Merck. Glacial acetic acid was from
brands, Luxor-camlin, Ecko, and Fleethave been studied. The TLC equipment X 200 mm), activation oven, desiccator, 1,4-dioxane, and silica gel were from BDH (AR grade).
66
Method Silica gel G TLC plates (0.25 mm thick) were prepared, activated at 110 “C for an hour, and then cooled in a desiccator. Spotting was done at 25 mm above the baseline of the plate employing two techniques: (1) spotting from ink solutions prepared in alcohol; (2) by embedding a small piece of paper (1 mm X 1 mm) bearing ink cut from writing strokes of a given ink as reported earlier [ 81, and leeching the ink with solvent mixture. The developing chamber was saturated for half an hour with the solvent mixture. Butan-l-ol-acetic acid-water (6:1:2) was used for inks 1 - 10 in Table 1, and butan-l-olacetic acid-water-1,4dioxane (6:2:2:1) for inks 11 and 12. The spotted plates were developed by ascending chromatography at a temperature of 32 t 0.5 “C. When the solvent front had ascended about 130 mm from the spotting line, the plates were removed and dried, and examined immediately in visible light and ultraviolet rays since some coloured spots fade after a few hours even at room temperature.
Observations The Rf values are reported in Table 1. These are the mean values obtained from three sets of experiments with each ink using both spotting techniques. The deviations in Rf values are also indicated.
Discussion It is evident from the Rf values listed in Table 1 that a clear-cut separation and differentiation of colour constituents present in various fibre-tip pen inks is possible by TLC. It has been possible to differentiate the three brands, each of twelve shades of sign-pen inks, using only two solvent mixtures. It is interesting to note that constituents of the blue inks of Ecko and Fleet-pearl are similar, as are those of the violet inks of Luxor-camlin and Fleet-pearl brands. Here no differentiation could be made. Possibly the manufacturers used the same dyes for these inks. Some highly fluorescent and additional spots were observed under ultraviolet rays in the case of the orange, dark pink, red, and crimson inks, giving additional differentiation data for the brands under study. The results obtained by both spotting techniques are similar with all inks. However, in the case of ink 2 for Luxor-camlin and Ecko brands, and ink 3 for Luxor-camlin, when the ink solutions were directly spotted, dark spots remained at the base point even after chromatography. This did not happen when spotting was done by embedding the piece of paper. Evidently the solvent system does not dissolve all the colour constituents of these three inks.
No.
Ink
TABLE
a
a
Royal
Violet
a
Black
a
a
Brown
Blue
a
Yellow
blue
Solvent*
Shade
1
Violet streak Violet
Red Blue
Violet Violet Violet Royal blue Light violet
Blue
Royal blue Royal blue Yellow Red Royal blue
Black Yellow Red
Yellow Light red
Spot colour
Luxor-camlin
0.77 0.11 2.30 3.60 4.54
0.30 0.50 0.50 0.50 1.90 2.85
f 2.40 r 1.19
* 2 * r +
+ * f + * t
f 0.50 + 3.10
f 0.39 + 2.54
0.00 to 41.93 f 5.00 74.81 + 1.79
21.55 35.81
26.92 48.46 51.54 59.23 72.31
0.00 3.59 4.87 11.88 12.00 to 19.41 82.50
4.36 50.17
0.00
4.24 34.85
Rf x 100
blue
+ 0.60 * 2.70
41.92 Violet
+ 2.50 + 1.50
42.56 56.15 12.05
-f 2.16
* 1.20 * 3.10 + 4.54
49.62 57.31 65.39
87.81
i 2.50 + 4.10
f 0.39
0.00 59.04 65.14
4.24
Rf x 100
Red
Light blue Blue
Royal
Violet Blue Orange
Black Blue Orange
Yellow
Spot colour
Ecko
blue
Violet streak Violet
Light blue Blue
Royal
Blue Violet Violet Violet
Violet Violet Orange
2.10 2.31 2.54 2.80
+ 2.50 f 1.50
+_ 2.90
* + 2 f
overlea f)
0.00 to 23.08 + 4.00 15.38 * 2.00
42.56 56.15
80.39
67.70 76.16 80.17 85.39
+ 1.80 ? 2.85 2 4.00
20.51 47.62 65.14
2.36 2.20 2.40 2.70
i + * +
100
38.51 70.88 91.69 95.44
Rfx
(continued
Yellow Light yellow Pink Light pink
Spot colour
Fleet-pearl
4
0)
a
a
Red
Red**
79.23 79.23
Pink Golden yellow with high fluorescence
a a
9
8
Dark pink Dark pink**
6.54 10.40 13.75
Dull red Bluish Dull red
a
Orange**
6.54 + 0.40 13.75 * 1.75 33.85 F 2.80
Yellow Red Light red
a
Orange
7
i 1.50 ? 1.50
i 0.40 f 0.40 + 1.75
+ 1.10 i 1.10 +_ 2.00
78.97 82.57 85.63
Violet Violet Violet
100
a
RfX
Spot colour
Luxor-camlin
Solvent*
Shade
1 (continued)
No.
Ink
TABLE
41.28 70.00 88.22 92.56 70.00 88.22 92.56
Light red Orange Light pink Pink Dull red Lemon yellow Lemon yellow
69.49
69.49
40.77 34.23
Orange
Dull red
Pink Lemon
+ 1.54 2 2.15 + 3.08 i 4.10 i 3.90 t 3.08 i 3.10 i 4.10 i 3.90
40.77 46.53 40.77 89.49 93.08 40.77 76.15 89.49 93.08
Light red Red Orange Crimson with high fluorescence Greenish Red surrounded by yellow Orange
i 1.54 i 1.90
Crimson with high fluorescence Red
yellow
+ 2.50
t 2.50
Dull red
Red with a long tail
71.88
71.88
Pink 84.10 Golden yellow 84.10 with high fluorescence and a long tail Brown 87.66
78.46 82.01 84.10
Violet Violet Violet
48.46 63.28 68.46
Violet Violet Violet
t 2.80 t 2.60 t 2.20
Rfx
Spot colour
Spot colour
Fleet-pearl Rf x 100
Ecko
1.30 1.50 2.61 4.10 1.50 2.61 4.10
i 2.65
i- 2.65
+ 3.80
i 3.60 * 3.60
+ f * i t f t
* 2.80 ? 2.10 + 2.80
100
co
ul
b
Green
12
acid-water (6:1:2);
54.74 * 1.50 81.91 f 3.90
8.46 + 0.77 55.95 + 1.90
Green Light blue
Yellow Green
(6:2:2:1).
Green Yellow Light yellow
2.31 * 0.20 10.56 t 1.30 19.62 * 1.90
Pale yellow Dull red Bluish
acid-water-1,4-dioxane
Green Yellow Light blue
10.56 * 1.30
Crimson
(b) Butan-1-olacetic
54.41 f 1.70 61.95 + 1.95
Green Yellow
t 0.40 * 1.13 * 0.20 * 1.30 ?; 1.90
5.38 10.56 2.31 10.56 19.62
Crimson Crimson Pale yellow Dull red Bluish
*Solvent mixtures: (a) Butan-1-olacetic **Rf values measured in UV rays.
b
a
Emerald
Crimson* *
Crimson
11
10
57.10 f 2.90 72.70 A 2.50 82.31 + 3.85
55.37 f 2.30 64.67 + 2.50 80.00 + 2.77
70
Acknowledgement The authors express their thanks to Dr. B. R. Sharma, Director, Central Forensic Science Laboratory, Chandigarh, for his keen interest in this study.
References 1 0. Hilton, Identification and differentiation between coloured pencils, Forensic Sci., 6 (1975) 221 - 228. 2 J. W. Thomson, The identification of inks by electrophoresis, J. Forensic Sci. Sot., 7 (1967) 199 - 202. 3 S. N. Tiwari and N. Bhat, Thin-layer chromatography of fountain pen inks, Int. Crim. Police Rev., 260 (1972) 201 - 203. 4 C. Brown and P. L. Kirk, Horizontal paper chromatography in the identification of ball-point pen inks, J. Crim. Law, Criminol. Police Sci., 45 (1954) 334 - 339. 5 R. L. Brunelle and M. J. Pro, Systematic approach to ink identification, J. Ass. Offic. Anal. Chem., 55 (1972) 823 - 826. 6 J. D. Kelly and A. A. Cantu, Proposed standard methods for ink identification, J. Ass. Offic. Anal. Chem., 58 (1975) 122 - 125. 7 V. K. Mehrotra and S. K. Sidhana, Non-destructive identification of metallic ions of inks used on documents, Forensic Sci., 9 (1977) 1 - 3. 8 R. S. Verma, K. N. Parsad and G. J. Misra, TLC examination of dyes used in some Indian red coloured pencils, J. Ind. Acad. Forensic Sci., 17 (1978) 69 - 70.