chapter-5...of the ink. tlc separates the dyes as well as the colourless organic components in the...

CHAPTER-5

Application of High Performance Thin Layer

Chromatography in Examination of Magenta Coloured

Printed Matter

Application of HPTLC in Examination of Magenta Coloured Printed Matter Page 83

5.1. Introduction

Inks are complex mixtures of colourants, vehicles, and other additives. Different components are

added for the composition of inks to produce the desired printing /writing characteristics. Due to

light absorption and emission properties, colourants are at the prior focus in ink analysis.

Vehicles or carriers are the solvents used in inks that evaporate gradually from the document and

should be analyzed in date-of-origin investigations. The additives in inks can be specific to a

manufacturer. Additives include flow (viscosity) modifiers, surface activators, corrosion

controllers, solubility enhancers and preservatives.

Various forms of chromatography have gained prominence from past several decades to separate

the components of inks. The process involves carrying the components of ink by a mobile phase

through a stationary phase. Based on the types of stationary and mobile phases, chromatography

is divided into various categories of column, paper, thin layer, gas and liquid chromatography.

The stationary phase can be a solid or liquid and the mobile phase is either a gas or a liquid.

Thin layer chromatography (TLC) involves a stationary phase through which a solvent system

migrates across the plate by capillary action, separating the ink components by virtue of

adsorption or partition on stationary phase or between the stationary and mobile phases

respectively. The separation occurs due to different migration rates of non-volatile components

of the ink. TLC separates the dyes as well as the colourless organic components in the ink. TLC

allows a direct comparison of the several samples of inks being examined on the same TLC

plate. Simultaneously TLC densitometry is used in absorption or reflection mode in

visible/UV254/UV366 mode to determine the relative concentrations of the dyes present and

other components. In HPTLC the efficiency and resolution of separation is increased by using

uniform and finer particle size (3-5µm) of stationary phase; usually silica gel.

For ink analysis by HPTLC, commercial (like Merck®) pre-coated silica gel, high performance

TLC plates are used. The silica gel plates have silanol (Si-OH) groups as active sites at which the

adsorption and desorption of analytes occurs. The HPTLC plates should be activated for 15

minutes at 100° C prior to use to remove any moisture from the plate, as moisture covers up(or


blocks) many of the Si-OH sites. Excessive activation of TLC plates can also cause a reduction

of site activity due to formation of inactive Si-0-Si linkages.

The HPTLC method is fast, reliable, and economical for direct comparison and identification of

ink. The technique involves use of very small sample and is sensitive because of the intense

colour of dye components in the visible region, absorption in UV region and fluorescence.

Kelly and Cantu (1975), suggested two methods for the identification of inks; one method

utilizes Spectrophotometric scanning of the HPTLC plate whereas the other method utilizes

solution spectrophotometry. Both these methods incorporate physical and chemical procedures.

The differences are primarily in chemical methods involving spot tests and thin layer

chromatographic (TLC) techniques.

Verma et al., (1979), reported the possibility of differentiation of ink using thin layer

chromatography. Twelve inks made by three firms for fibre-tip pens were undertaken for the

study.

Zimmerman et al., (1986), successfully differentiated 35 raw photocopy toners and copies

processed from machines using the respective toners from five manufactures. They classified the

sample toners in seven different groups and distinguished them from each other. The similar

spectra were obtained for the raw toner (the toner taken from cartridge i.e. before printing) and

the respective processed toner (the toner extracted from the printed document). Toners were

categorized into eighteen different groups, of which seven groups included more than one toner.

Application are foreseen in an IR spectrophotometer library search for peak match or functional

groups or both to identify the toner of a questioned document, or matching or eliminating the

toner from a questioned document with standards from suspect machines with pyrolysis gas

chromatography.

Lennard et al., (1991), developed the combined technique of DRIFTS/PyGC for the extraction

& analysis of adhesives and toners from questioned documents. The combined technique

requires small quantity of sample and minimal damage to questioned document to obtain IR

spectra & pyrograms with excellent reproducibility.


Valery, N.A. (1993), stated two procedures for dating ballpoint inks using gas chromatography

and densitometric TLC. Using densitometric TLC, separation of ink components and evaluation

of the resulting chromatograms using a specially developed mass-independent technique is also a

very effective tool for the comparative TLC examination of coloured inks of similar hue, paints,

fibers and other materials of forensic interest. The said procedures have been used in many real

case situations and the results of the examinations were reported to have been accepted as

conclusive evidence by the courts of law.

Aginsky (1993), employed the technique of TLC in ascending mode using a multiple

development procedure for separating coloured components of computer printing inks, artist's

paints, copier toners, and colour pencils. The procedure used was able to separate phthalocyanine

pigments and slightly soluble organic pigments. He analyzed 120 synthetic pigments and dyes

used for commercial production of modern artist’s paints, toners for copying machines, printing

and writing inks by TLC. The sample was taken by scratching the writing material using razor

and extracted by dimethylformamide. He concluded that three step TLC procedures gives

valuable information about inks, coloured organic components including the sparingly soluble

ones.

Varshney et al., (1995), analyzed the inks of type scripts of seven electronic typewriters by

HPTLC. The method though destructive one, is extremely sensitive. They concluded that using

the HPTLC technique, six typewriter ribbon inks out of seven sample analyzed show same

chemical composition in the formative period of electronic typewriters .The seventh sample was

found, completely different from the other six.

Tandon et al., (1995), used the technique of thin layer chromatography for the analysis of 16

photocopy toners, consisting of different brands, as well as different batches of the same brand.

Dye components as well as resin components were analyzed and the results are interpreted. A

modified technique to lift the toner from the photocopy has also been described.

Aginsky (1996), used GC-MS to analyze the volatile components of writing, stamp pad ink and

inkjet printer ink. The technique was used to determine the age of handwritten entries in a

document.


Jasuja and Sharma (1997), successfully analyzed 20 different green, blue, and red offset

printing inks with TLC. A 5 sq mm sample of these inks was taken from the documents and

extracted the ink from paper with few drops of mixture of pyridine and glacial acetic acid (3: 1).

They reported that the inks could be differentiated by TLC based on the number of spots, colour

and Rf values. They also reported different solvent systems for different colours of ink.

Doherty (1998), compared and studied ink samples from current and discontinued inkjet printer

models for the classification and dating the formulations of ink. The black samples printed with

18 types of cartridges and unprocessed samples from 8 black ink cartridges were analyzed for

their physical & chemical properties. The authors reported methanol and water (1: 1) as best

solvent to dissolve ink from the printed document. They concluded that (a) processed and raw

inks from the same model cartridges produced consistent chemical and different spectral results

(b) many of the inks could be differentiated and classified and (c) the limited sampling of inks

available for dating could be correlated to their respective introduction or reformulation date.

Sidhu et al., (2000), used TLC to analyze 22 black and 17 colour ink writing samples of various

models of inkjet printers. According to the conducted research it was concluded that the samples

from black and coloured inks could be separated and differentiated from each other. For the

separation of black ink, solvent system used was butanol: propanol: water (80:15:5) and butanol:

ethanol: water (50:15:5) and for the coloured inks the solvent systems found suitable by the

authors are butanol: propanol: glacial acetic acid (60:15:05) and chloroform: methanol: n-

Hexane:Glacial Acetic Acid (70:20:5:0.5).

Pagano et al., (2000), separated the components of cyan, magenta, yellow and black inks after

extracting with the solvent ethanol/water (1:1). They suggested that ethyl

acetate:ethanol:water(70:35:30) and water: acetic acid:butanol:butyl acetate(32:17:41:10) were

the best solvent systems for separation of ink components. They felt the need of having library

with database of various original and refilled inks chromatograms so that the questioned inks

could be matched with the standard inks. Besides, the authors also described the inkjet printing

technology along with the composition of inkjet ink analyzed. Lyter (2003) successfully

employed High-performance Liquid Chromatography methods to separate different dye

compounds.


Wilson et al.,(2004), stated that gel ink pens have become a common writing instrument in the

United States. Questioned document examiners often attempt to optically differentiate gel inks

from each other and from other non-ballpoint ink writings (e.g., those from roller-ball pens).

Since early formulations were primarily pigment-based, they did not elute when analyzed by

thin-layer chromatography. However, recent gel ink formulations (i.e., within the past five years)

include dye-based inks which can be easily separated.

Egan et al., (2005), suggested an alternative separation and identification tool for forensic ink

examination. Two different buffer systems were designed to analyze dye compounds by capillary

electrophoresis in various black ballpoint pen ink formulations. Results were compared to thin-

layer chromatography experiments to evaluate the sensitivity and performance of capillary

electrophoresis.

Brazeau and Gaudreau (2007), studied the solid-phase micro extraction (SPME) technique,

together with gas chromatography–mass spectrometry (GC-MS), have been used to quantify

solvents in writing inks and were able to opine on the brand of ink. In conventional approaches,

the analysis of ink on documents requires some degree of destructive sampling. The method

commonly used to remove ink samples from paper is that of using a scalpel or a micro paper

punch. To avoid document destruction, a sampling cell was designed that allows solvents to be

adsorbed directly onto the SPME fiber after mild application of heat from the headspace above

the document surface. Volatile ink analyte components are then desorbed from the SPME fiber

on a gas chromatograph equipped with a mass selective detector (GC-MSD).

Kaur et al., (2006), reported the non destructive examination of inks from carbon paper. They

further employed TLC technique for the chemical analysis of 14 blue, 6 black and 2 red carbon

papers from different manufacturers. They reported that the methods employed are useful for the

examination and comparison of carbon paper writing.

Khera et al., (2006), Studied and analyzed several varieties of blue ballpoint pen inks by high

performance liquid chromatography (HPLC) and infrared spectroscopy (IR). The

chromatographic data extracted at four wavelengths (254, 279, 370 and 400 nm) was analyzed

individually and at a combination of these wavelengths by the soft independent modeling of class

http://www.sciencedirect.com/science/article/pii/S0924203105001438#aff1


analogies (SIMCA) technique using principal components analysis (PCA) to estimate the

separation between the pen samples.

Wang et al., (2008), under the optimized conditions, the 18 fountain pen inks were differentiated

individually by comparing the number of detectable major or minor dye components, and the

relative peak intensities of each component. The ink entries were artificially and naturally aged,

and the analysis results showed that the ink dye components were significantly degraded when

exposed to UV or fluorescent light compared to those of inks stored under natural conditions.

Djozan et al., (2008), provided a new and fast method for differentiation of inks on a questioned

document. The data acquisition was carried out by designing specific image analysis software for

evaluating thin layer chromatograms (TLC-IA). The ink spot was extracted from the document

using methanol and separated by TLC using plastic sheet silica gel 60 plates, and a mixture of

ethyl acetate, ethanol, and water (70:35:30, v/v/v) as mobile phase .This new method allowed

discrimination among different pen inks with a high reliability and the discriminating power of

92.8%. Blue ballpoint pen inks of 41 different samples available in the local market were

successfully analyzed and discriminated.

Boileau et al., (2012), used various techniques like thin layer chromatography (TLC), high

performance liquid chromatography (HPLC), pyrolysis gas chromatography coupled with mass

spectrometry (PyGC/MS) and attenuated total reflection Fourier Transform Infrared

Spectrophotometry (ATR-FTIR) for the analysis of black inkjet printed inks. The results

produced can assist the forensic scientist in the examination, identification and discrimination of

the different inkjet computer generated documents.

5.2 Experimental

5.2.1 HPTLC Instrumentation

A HPTLC instrument from Camag, Switzerland with computer system and installed Cats

Software Version 1.4.2 was used. TLC Scanner II was employed for scanning of developed TLC

plate and ATS 4 as an application device. Precoated HPTLC plates with silica Gel 60 (20 cm ×

10 cm) from Merck were used. The TLC plates were developed in twin trough Chamber (TTC)

to accommodate standard 20cm X 10 cm plates.

Application of HPTLC in Examination of Magenta Coloured Printed Matter 9

5.2.2 Scheme for Sample Collection

The sample documents were collected in the form of printed documents from 32 inkjet printers.

The magenta colour was prepared by keeping the constant value of Red, Blue & Green in the

colour palette of MS-Office (Nicholas 2003). The RGB scheme used was as follows:-

Table-5.1 Values of RGB (Red, Green, Blue) in colour palette of MS-Word application of

Windows used for printing of documents on the same substrate of paper ‘Bilt copier’

Paper used to print samples

White paper of A4 size from ‘Bilt Copier’ company manufactured in 2008 by ‘Ballarpur

Industries Limited’ GSM 75 was used throughout the study to take print sample.

5.2.3 Sample Preparation

All the solvents used were of analytical grade unless otherwise stated. Ten (10) ml capacity glass

vials with airtight cap for sample collection were purchased from the local Market. Coloured

sample documents printed from 32 inkjet printers were collected from 4 different leading

companies as given in Table-5.2, collected from different markets of Hyderabad, New Delhi,

Agra and Allahabad.

A Magenta coloured squared block of 3x3 cm was taken from the sample document and cut into

pieces. The pieces of paper were then transferred to 15 mL measuring cylinder and triturated

with 10 ml of methanol. The sample was then allowed to extraction process at room temperature

with intermittent trituration and shaking. The methanol extract was then transferred to sample

vials after filtering through a Whatman No.1 filter paper.

Inkjet Ink R G B

Magenta 255 0 255

Application of HPTLC in Examination of Magenta Coloured Printed Matter 0

Table- 5. 2 List of printers used to print the sample documents along with Brands &

Models of Inkjet Printer.

S.No. Sample No. Model

Brand- HP

1. 1 HP DeskJet 1050 J410 (M-1)

2. 2 HP DeskJet 1050 J410 (M-2)

3. 3 HP DeskJet 1050 J410 (M-3)

4. 4 HP DeskJet F4185

5. 5 HP PSC 1608

6. 6 HP DeskJet D1550

7. 7 HP DeskJet 5550

8. 31 HP Photosmart D7168


10. 10 HP Photosmart C4688

11. 26 HP DeskJet D1668 (M-1)

12. 27 HP DeskJet D1668 (M-2)

13. 28 HP Officejet 4355


15. 8 HP Business Inkjet 1000 (M-1)



Brand- Canon

18. 12 Canon Pixma MP-258

19. 13 Canon Pixma IP 2770

20. 20 Canon Pixma MX308

21. 21 Canon Pixma ip 1300

Brand- Epson

22. 14 Epson Stylus TX121

23. 15 Epson R-220

24. 17 Epson Stylus Photo R230X

25. 22 Epson Stylus T13 (M-1)

26. 25 Epson Stylus T13 (M-2)

Brand-Brother

27. 16 Brother MFC-295 CN

28. 18 Brother MFC-J415 W

29. 19 Brother DCP J125 (M-1)



32. 29 Brother DCP 6690 CW


5.2.4 Sample Pool

32 coloured printouts were taken from different Inkjet printers. The Magenta colour was the

target ink. The all coloured ink samples were then marked as the sample identification no.1-M,

2-M, 3-M, 4-M ……32-M for Magenta colour Ink. Total sample 32 samples were analysed.

5.2.5 Analysis

Sixteen (16) tracks of sample solutions were applied on each 20 cm × 10 cm HPTLC

plate.15microlitre solution of sample was sprayed as bands of 6mm from ATS 4 (Automatic

TLC Sampler). A distance from lower edge 2.5cm, distance from the left side 2.5cm, distance

between bands 2.5 cm was maintained. Before the application of sample solution the HPTLC

plates were activated in oven at 1000

C for 15 minutes. The plates were allowed to develop using

different mobile phases (Table 5.3) for separation of ink components. Solvent System No. I, N-

butanol: Acetone: Distilled water: Ammonia was found best for the separation of magenta Inkjet

Inks.

The chamber was saturated to equilibrate the solvent system for 20 minutes. The mobile phase

was allowed to migrate till 6 cm from the origin point (spotting point) of plate. Besides all the

visible coloured spots, the ink components may have colourless components. These components

often exhibit ultraviolet fluorescence providing additional identifying features. Long wavelength

UV (366nm) excites UV fluorescence in certain ink components while short wavelength UV

(254nm) reveals UV absorbing components.

After development the spots were visualized at short wavelength and long wavelength UV. The

chromatograms are reproduced in Figure-5.1. After separation of the ink components the plates

were then scanned under TLC Scanner 3 from 200-700 nm wavelengths (Aginsky, 1994). The

images of chromatogram were documented by using DigiStore2 documentation system

(CAMAG) under UV 254 and 366 nm.

Among all the ten solvent systems studied the solvent system I found to be best for the

separation of magenta inkjet ink.


Table 5.3: The different solvent system used for TLC separation of ink samples (Stahl

1969).

S.No. Solvent System Ratio

I N-butanol: Acetone: Distilled water: Ammonia

(25:25:5:17.5)

II Ethyl Acetate: Ethanol: Distilled water

(70:35:30)

III Butanol : Propanol: Acetic Acid

(60:15:05)

IV Propanol: Acetone: Distilled water: Ammonia

(15:5:5:1)

V Chloroform: Methanol

(80:20)

VI Butanol: Ethanol: Acetic Acid: Distilled water

(70:35:0.5:5)

VII Ethyl Acetate: Ethanol: Acetic Acid: Distilled water

(50:25:20:0.5)

VIII Isoamyl Alcohol: Acetone: Distilled Water: Ammonia (15:15:10:1)

IX Butanol: Ethanol: Distilled water (50:15:5)

X Butanol: Propanol: Distilled H2O (80:15:5)

5.2.6 Evaluation

After separation of the ink components the plates were then scanned under TLC Scanner 3 from

200-700 nm wavelengths.

5.2.7 Documentation

The images of chromatogram were documented by using DigiStore2 documentation system

(CAMAG) under UV 254 and 366 nm.

5.2.8 Consistency

The reproducibility of results was checked 3 times on 3 different days at an interval of 5 days.

5. 3 Results and Discussion

Many a times the forensic document examiners are required to identify a printer from which a

counterfeit currency, a threatening letter or questioned document etc. was printed. In an effort to


develop a suitable methodology a protocol was developed to examine and opine on this issue

with respect to colour prints by using High Performance Thin Layer Chromatography. During

the preliminary study it was found that Yellow and Cyan colours were having only one

component and discrimination between various makes would be difficult. On the other hand

Magenta colour was found to have 1-6 components on the basis of which this colour was

selected for the detailed study. In a trail the TLC of Black ink was carried out and it was found

that the Black ink as is a mixture of several colours, however was not amenable to good

separation in various solvent systems studied. In the case of Black ink no single solvent system

was capable of separating all the colours. For the initial studies, therefore Magenta colour was

chosen. Different solvent systems are required to differentiate different colour of ink (Sharma et

al., 1997) so the same solvent system was not applied to differentiate Cyan, Magenta and Yellow

colour ink. Based on the methodology developed, subsequently studies for Black inks would be

continued separately. The present study is devoted to the study of the Magenta colour only.

Printed 32 Magenta colour material samples from four different companies were selected and

drawn for study as listed in Table no.5.2. Samples were extracted with methanol as per the

procedure given and subjected to HPTLC by spotting 15 ul solution of each sample. The

separation of samples were carried out in the optimized solvent system n-butanol: acetone:

water: ammonia (25:25:5:17.5) (Stahl, 1969).After separation the plates were viewed in day

light, short wave (254 nm) and long wave (366 nm), (Osborn, 1927), (Harrison, 1958), (Hilton,

1982) and the observation about the colour / fluorescence of the spots was recorded as shown in

Figure 5.1.

Just to check its adaptability to real case the examination was carried out on 10 microplugs of the

printed documents (Lyter, 2003). This study gave similar results. Based on the above study the

following observations can be made. Different brands of Magenta coloured computer printer inks

are showing discriminating differences by using visible, short wave UV and long wave UV

observation whereas within the same brand discrimination is poor. Presently as limited numbers

of components are being used by all the manufacture there are some limitations of comparison.

As the technology gets more advanced more components may be added to coloured computer

printing inks to improve the flow properties, fastness, brightness and reactivity with the paper

etc., which would improve the discrimination power of the proposed method. As of now since


most of the manufacturers are using same chemical components in varying quantities, we are

getting appropriate repeatability of these components in different samples with the same Rf

values. Major components being same we may have to largely dependent on the minor

components.

Figure 5.1: Chromatograms obtained for different samples of Magenta ink in visible light,

under short wave UV (254nm) and long wave UV (366nm) light.

Lighting

Conditions

Sample No.from 1 to 16 Sample No.from 17 to 32

Visible

Light

Short Wave

UV

254 nm

Long Wave

UV

366 nm


Usually along with the questioned document the suspected printer is submitted for examination

to determine whether the particular printer was used to produce a particular printed document.

The examination then can be carried out by taking a printout from the suspected printer and

comparing the printer ink with questioned document ink by conducting physical and chemical

analysis. As the investigation is carried out usually after a long time and it might be possible that

the cartridges has been changed or worn out or refilled during that course of time. In such cases

another printed document which was printed during or approximately same time is taken as an

admitted specimen. That printout can be considered as a printed exemplar for comparison with

the suspected printed documents. If a data bank is built for the current Magenta coloured

computer printing inks drawn from different manufacturers there is a fair chance of identifying

the manufacturer of a questioned sample after taking into consideration various variable factors

like storage condition, exposure to light, wear and tear etc. If an admitted sample from a

questioned printer is given, the same can be compared with the suspect printed document by

using this method to give a reliable opinion. In the real sample study in place of the 3 x 3 cm

pieces, with the permission of the court we may be required to take micro punch samples as

indicated by the experiments carried out in this study. As shown in the Table 5.4 the data of Rf

values of spots and their colour can be fairly discriminated for various source samples with

reference to the control samples of printed material obtained from different manufactures.

4- 6- 7- 28- 31- 32-

Figure 5.2: A typical superimposition of spectra’s of Magenta colour samples.


Figure 5.2 shows the superimposition of magenta colour sample no. 4,6,7,28,31,32 at the same

Rf value i.e. 0.44.

Figure 5.3: Graphical representation of number of spots obtained for different ink samples

of HP printer.

Figure 5.3 represents the number of spots obtained for specific printing ink from HP. As a

representative we have given graphical representation of HP printer Inkjet inks for the

discrimination of ink from same manufacturer. The opinion of source of questioned document

encountered for examination can also be formed on the basis of number of spots obtained.

Although this alone could not form the base of an opinion. The origin of printed document can

be examined on the basis of all discriminating factors obtained after analysis of a sample from

high performance thin layer chromatographic technique such as retention factor, number of spots

obtained, colour of spots under visible light, fluorescence of spots under short wave and long

wave UV etc. In case the samples are more then discrimination can be made on the basis of

number of spots obtained for respective sample. It is proposed to carry out further studies on

Black inks and other colours using the proposed technique.


.

Table 5.4: Showing the Rf of spots obtained in the chromatograms respective to their colour under different lighting conditions.

Sampl

e

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Under

Visible

Light

No. of Spots 1 2 2 2 3 2 2 3 4 2 3 4 3 2 2 2

Colour

Of

Spots

&

hRf

Pink

(0.53)

Pink

(0.53)

Brown

(0.44)

Pink

Light

(0.53)

Brown

(0.44)

Pink

(0.53)

Brown

(.44)

Pink Light (0.53)

Brown(0.46)

Brown (.44)

Pink(.53)

Brown (.44)

Pink (.53)

Brown (.44)

Pink (.53)

Blue(.46)

Brown

(.44)

Pink (.53)

Light Pink(.46)

Light Pink(.45)

Light Pink(.44)

Dark wide

brown (.53)

Brown(.44)

Pink(.53)

Light Blue(.50)

Light Brown

(.48)

All

Light

Pink

(.53,.44

.43,.42)

All

Light

Pink

(.44,

.43,

.12)

Light

Blue

(.46)

Light

Pink

(.44)

Light Pink

(.53)

Light Blue

(.46)

Pink (.53)

Brown

(.44)

Under

Short

UV

Light

(254 nm)

No.Of Spots 1 2 1 2 3 2 2 2 3 2 2 1 4 1 ------- 2

Colour

of

Spots

&

hRf

Orange

(.53)

Orange

(.53)

Black

(.44)

Orange

(.53)

Orange(.53)

Black(.44)

Orange

(.53)

Light

Black(.48)

Black(.44)

Orange(.53)

Black(.44)

Orange(.53)

Black(.44)

Orange(.53)

Black(.44)

Orange(.53)

Light Black(.48)

Light Black(.44)

Dark wide

Black

Band(.53)

Black(.44)

Light Orange

(.53)

Light Black

(.48)

Light

Black

(.48)

Blue (.53)

Black (.42)

Black (.41)

Black(.12)

Light

Black

(.41)

-------

Black

(.53)

Black

(.44)

Under

Long

UV

Light

(366 nm)

No.Of Spots 3 3 3 2 2 2 2 2 2 3 2 2 3 1 1

Colour

of

Spots

&

hRf

Blue

(.55)

Orange

(.53)

Blue

(.52)

Blue

(.55)

Orange

(.53)

Blue

(.52)

Blue

(.55)

Orange

(.53)

Blue

(.52)

Orange(.53)

Blue(.44)

Orange(.53)

Blue(.44)

Orange(.53)

Blue(.44)

Orange(.53)

Blue(.44)

Orange(.53)

Blue(.44)

Orange(.53)

Blue(.44)

Dark wide

yellowish red

band(.53)

Red (.45)

Blue(.44)

Orange

(.53)

Light Blue(.44)

Orange

(.53)

Blue(.44)

Blue (.56)

Blue (.53)

Light

Orange

(.12)

Light

Blue

(.44)

Light Orange

(.53)

Light Blue

(.44)

Light

Blue

(.44)

Sampl

e

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

Under

Visible

Light

No. of

Spots

2 2 2 2 2 2 2 2 2 2 4 2 3 1 2 2

Colour

of

Spots

&

hRf

Light

pink

(.53)

Light

brown

(.44)

Pink

(.53)

Brown

(.44)

Light

pink

(.53)

Brown

(.44)

Light pink

(.44)

Pink(.26)

Light pink(.44)

Pink(.26)

Pink (.53)

Light

Brown (.44)

Pink (.53)

Brown (.44)

Pink (.53)

Brown(.44)

Blue(.53)

Pink(.44)

Pink (.53)

Brown(.44)

Red (.55)

Pink (.53)

Brown(.45)

Brown(.44)

Pink (.53)

Brown

(.44)

Brown (.46)

Clubbed

band of

brown(.45)

Brown (.44)

Pink

(.45)

Pink (.53)

Brown (.24)

Pink (.53)

Brown

(.44)

Under

Short

UV

Light

(254 nm)

No. of

Spots

2 2 1 2 2 4 4 4 2 3 3 2 4 1 2 2

Colour

of

Spots

&

hRf

Light

Black

(.53)

Light

Black

(.44)

Black

(.53)

Black

(.44)

Black

(.53)

Light

Black(.44)

Black(.26)

Light black (.44)

Black (.26)

Light Blue

(.59)

Light Blue

(.55)

Black (.53)

Light Black

(.44)

Light Blue

(.59)

Light Blue

(.55)

Black (.53)

Black (.44)

Light Blue

(.59)

Light Blue

(.55)

Black(.53)

Black(.44

Light Black (.53)

Light Black (.44)

Light Blue

(.62)

Light Orange

(.53)

Light Black

(.44)

Black (.58)

Orange (.53)

Light Black

(.44)

Orange

(.53)

Light

Black

(.44)

Blue (.62)

Blue (.53)

Wide black

band (.40)

Light Black

(.44)

Light

Black

(.40)

Orange (.53)

Black (.24)

Orange

(.53)

Black (.40)

Under

Long

UV

Light

(366 nm)

No. of

Spots

3 3 3 4 4 3 4 4 1 5 6 2 6 ----- 2 2

Colour

of

Spots

&

hRf

Light

Orange

(.53)

Light

Blue

(.44)

Light

Blue

(.44)

Light

Blue

(.44)

Blue (.56)

Blue (.53)

Light Blue

(.44)

Orange(.26)

Blue (.56)

Blue(.53)

Light Pinkish

Blue (.44)

Orange (.26)

Light Blue

(.58)

Blue(.56)

Blue(.53)

Light Blue

(.62)

Light Blue

(.58)

Blue(.56)

Blue(.53)

Light Blue

(.62)

Light Blue

(.58)

Blue (.56)

Blue (.53)

Light Blue (.44)

Light Blue

(.62)

Light Blue

(.58)

Blue (.55)

Orange (.53)

Blue (.52)

Light Blue

(.58)

Blue (.55)

Orange (.54)

Orange(.53)

Blue(.52)

Orange(.44)

Orange

(.53)

Blue (.44)

Light Blue

(.62)

Light Blue

(.58)

Blue(.56)

Light Blue

(.54)

Light Blue

(.54)

Blue(.53)

-----

Orange(.53)

Blue (.44)

Orange

(.53)

Blue (.44)


5.3.1 Statistical Analysis

The experimental data obtained by HPTLC was statistically analyzed using analysis of variance

two-way classification with one observation per cell (Ray and Sharma 2004, p-788) for soil and

paint analysis. The significance of various factors was judged by calculating ‘F’ value at 5%

level of significance (Skeleton of ANOVA Appendix Table-12). The analysis for all of the

coloured ink shows non significant difference due to no. of spots obtained in all brands of

printing ink as well as due to sample for HP and Brother brand whereas remains non significant

due to the sample for Canon and Epson brands of printer. (Appendix, Table 8-11).

5.4 Conclusion

The proposed methodology can be successfully utilized for the examination of questioned colour

prints and questioned printers successfully where magenta colour is involved. In the absence of

the questioned printer some idea of the possible manufacturer can also be given. With the

advancement and diversification of printer technology by introducing newer vehicles,

surfactants, dyes, pigments, stabilizers, pH controllers, biocides, anti corrosives, solubility

enhancers, preservatives and other additives, the variability of different manufacturers will be

increased giving good room for discrimination. Further a better scanning technology of the

HPTLC can also improve the discrimination power of this technique in reflectance / absorbance /

fluorescence modes.

chapter-5...of the ink. tlc separates the dyes as well as the colourless organic components in the...

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