Technology Transition Workshop
DART Mass Spectrometry of
Writing Inks
Roger Jones
Midwest Forensics Resource Center and
Ames Laboratory—USDOE,
Iowa State University
Midwest Forensics Resource Center
Technology Transition Workshop
DART MS of Writing Inks
• Comparison to Conventional Ink Analysis
• Spectrum Acquisition
– Presentation of Sample
– Instrumental Conditions and Data Acquisition
– NIST Mass Spectral Search Program
• Interference from Paper
• Effects of Writing Age
– Identification of Ink Components
• Ink Identification Using NIST Software
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Comparison to Conventional
Methods
• Optical Inspection
– Side-by-side comparison under various
illuminations through various filters
– Strengths: Quick, cheap, non-destructive, often
sufficient
– Weaknesses: Requires physical reference,
provides minimal information, no library
possible, cannot identify ink
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Comparison to Conventional
Methods
• Thin Layer Chromatography
– Side-by-side comparison, separates and
detects dyes and fluorescent components
– Strengths: Cheap, usually sufficient, more
information than optical inspection, can build
library, may identify ink
– Weaknesses: Slow, destructive, requires
physical reference, sensitive to environment,
less information than DART, requires physical
sample library
Technology Transition Workshop
Comparison to Conventional
Methods
• DART MS
– Elemental formula determination of all volatile
and semi-volatile components
– Strengths: Quick, non-destructive, no physical
reference, provides lots of information,
database library, can identify ink,
complementary to dye-sensitive methods
– Weaknesses: Expensive equipment, sensitive
to vehicle, paper occasionally interferes
Technology Transition Workshop
MS of Extracts vs. DART MS in Situ
DART MS of Ink on Paper
139
100
Bic Wide Body
183
50
351
269
0
100
100
0
100
Bic Velocity
50
0
100
Bic Round Stic
50
0
100
Bic Cristal Grip
50
0
100
Bic Wide Body
372
50
374
Relative Intensity (m/z 372 = 100)
Relative Intensity (m/z 139 = 100)
367
ESI-MS of Extracts
5 Black Bic
Ballpoints
Bic Velocity
50
0
100
Bic Round Stic
50
0
100
Bic Cristal Grip
50
0
100
Bic Atlantis
358
Bic Atlantis
50
50
0
0
100
200
300
m/z
400
500
100
200
300
m/z
400
500
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Presentation of Sample
Modified Wikipedia image, with acknowledgement to JEOL USA, Inc., and author R. B. Cody
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Full Page in Open Sample Holder
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Full Page in Open Sample Holder
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Sample Held by Cover-Plate Hook
1/8-inch hole in cover plate gives access to sample.
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Page in Closed Sample Holder
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Sample in Position for Analysis
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Instrumental Conditions
Mount wired to
spectrometer
inlet
–3500 V
+150 V
3.25
L/min
He
255 °C
+650 V
+20 V, 80 °C
Modified Wikipedia image, with acknowledgement to JEOL USA, Inc., and author R. B. Cody
Technology Transition Workshop
Raw Spectra from Chromatogram
Zebra Rubber 80 Ballpoint on Hammermill Fore DP Paper
Intensity (counts)
50000
40000
30000
20000
279
10000
0
269
40000
315
30000
279
20000
359
10000
0
100
200
300
400
500
600
100
200
300
m/z
3.0e+7
Total Ion Count
Intensity (counts)
50000
400
500
m/z
PEG 600
2.5e+7
30 second averages
2.0e+7
1.5e+7
Ink on Paper
1.0e+7
Blank Paper
5.0e+6
0.0
0
1
2
3
Time (min)
4
5
600
Technology Transition Workshop
Final Spectrum from Raw Spectra
Zebra Rubber 80 Ballpoint on Hammermill Fore DP Paper
Intensity (counts)
50000
40000
30000
20000
279
10000
269
40000
315
30000
279
20000
359
10000
0
0
100
200
300
400
500
600
100
200
m/z
50000
Intensity (counts)
Intensity (counts)
50000
300
m/z
269
40000
315
30000
359
20000
279
10000
0
100
200
300
m/z
400
500
600
400
500
600
Technology Transition Workshop
DART MS of 3 Main Ink Types
100
75
50
Relative Intensity
25
269
Zebra Rubber 80
Ballpoint
255
315 359 403
100 139
0
100
150
Bic Cristal Gel Roller
75
50
25
106
168
239
0
100
239
75
50
121
195
Mont Blanc
Le Grand Rollerball
283
25
403
0
100
200
300
m/z
400
Technology Transition Workshop
NIST Spectral Search Software
• NIST Mass Spectral Search Program
– Demo Version 2.0d is a free download.
– Fully functional software with a small library
• Search Types
– Spectral match; reverse/forward, with m/z limits,
identity/similarity, match ring number
– Search formula, name, CAS number, NIST
registry number, peaks
– Constraints; molecular weight, elemental
abundance, peak presence
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NIST Spectrum Search Results
Distribution of matches
Comparing unknown and highlighted match
Unknown
Spectrum of unknown
List of matches
Spectrum of highlighted match
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Calculating Match Quality
Match Quality, Q, combines two factors, F1 and F2,
that range from 0 to 1.
F1 is a mass-weighted dot product of the two
spectra:
1/ 2
M
(
A
A
)

L U
F1 
1/ 2
 MAL  MAU 
Sums are over M; M = m/z
AL = relative intensity of library peak
AU = relative intensity of unknown peak
From Stein, J. Am. Soc. Mass Spec., 1994, 5, 316.
Technology Transition Workshop
Calculating Match Quality
F2 compares ratios of successive peaks:
 1 
 
F2  
 NU & L  i  2
NU & L
 AL ,i 


A 
 L ,i 1 
n
 AU ,i 


A

 U ,i 1 
n
NU&L = number of peaks common to both unknown
and library spectra. Sum is over those peaks.
n = 1 if AL ratio < AU ratio, n = -1 if AU ratio < AL ratio.
999
NU F1  NU & L F2 
Q
NU  NU & L
Q is 999 for a perfect match.
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Test of Paper Effects
• Lines written freehand on 16 different types of
paper with three pens—1 ballpoint, 1 gel, 1
fluid ink.
• Stored in closed file in drawer for 8–9 months.
• Three spectra acquired for each ink on each
paper. Samples handled with gloves.
• All spectra for one ink placed in a NIST library.
• All spectra searched against the library and
match qualities determined for each spectrum.
Reverse matching with no m/z limit.
Technology Transition Workshop
Papers Used in Test
White Office Paper
Envelopes
Champion Benefit Writing
Brown Manila
Crane’s Resume
White Ames Lab Letterhead
Great White Multipurpose 20
Hammermill Color Copy
Miscellaneous Types
Hammermill Color Laser
Gloss
Ampad Evidence (ruled legal
pad)
Hammermill Fore DP
Colored paper, goldenrod
Hammermill Great White Copy Post-It Note, yellow
HP Color Inkjet
Whatman #1 filter paper
Staples Copy
Notepaper with printing under
writing
Technology Transition Workshop
Ballpoint Spectrum Match Qualities
Percent of Ballpoint Samples
Distribution of Match Qualities of One Spectrum with
45 Spectra of the Same Ink on Different Paper:
Black Zebra Rubber 80 Ballpoint Ink on Hammermill Fore
Median Match Quality = 880
30%
20%
10%
0%
1000
Hammermill Color Laser Gloss
900
800
700
Match Quality Index
600
500
Technology Transition Workshop
100
Unknown Being Matched
Hammermill Fore DP #1
80
Spectral Matching for a sample of
Zebra Rubber 80 Black Ballpoint on
Hammermill Fore DP Paper
40
20
0
100
Best Match on Different Paper
Manila Envelope #1
Match Quality = 925
80
60
Relative Intensity
Spectra Matching
a Ballpoint
Spectrum
60
40
20
0
100
Worst Match Other Than
Hammermill Laser Gloss
Post-It Note #2
Match Quality = 816
80
60
40
20
0
100
Worst Match
Hammermill Laser Gloss #1
Match Quality = 548
80
60
40
20
0
100
200
300
m/z
400
500
600
Technology Transition Workshop
Median Match Qualities for Ballpoint
Percent of Ballpoint Samples
Distribution of Median Match Qualities with 45 Spectra
of the Same Ink on Different Paper:
Black Zebra Rubber 80 Ballpoint Ink
30%
20%
10%
0%
1000
Hammermill Color Laser Gloss
900
800
700
Median Match Quality Index
600
500
Technology Transition Workshop
Gel Ink Spectrum Match Qualities
Percent of Gel-Ink Samples
Distribution of Match Qualities of One Spectrum with
45 Spectra of the Same Ink on Different Paper:
Black Bic Cristal Gel Roller Ink on Hammermill Fore DP
Median Match Quality = 854
30%
20%
10%
0%
1000
900
800
700
Match Quality Index
600
500
Technology Transition Workshop
Median Match Qualities for Gel Ink
Percent of Gel-Ink Samples
Distribution of Median Match Qualities with 45 Spectra
of the Same Ink on Different Paper:
Black Bic Cristal Gel Roller Ink
30%
20%
10%
0%
1000
900
800
700
Median Match Quality Index
600
500
Technology Transition Workshop
Fluid Ink Spectrum Match Qualities
Percent of Fluid-Ink Samples
Distribution of Match Qualities of One Spectrum with
45 Spectra of the Same Ink on Different Paper:
Blue Mont Blanc Le Grand Roller Ink on Hammermill Fore
Median Match Quality = 777
30%
20%
10%
0%
1000
900
800
700
Match Quality Index
600
500
Technology Transition Workshop
Median Match Qualities for Fluid Ink
Percent of Fluid-Ink Samples
Distribution of Median Match Qualities with 45 Spectra
of the Same Ink on Different Paper:
Blue Mont Blanc Le Grand Rollerball Ink
30%
20%
H. Color Laser Gloss
Crane's Resume
10%
0%
1000
900
800
700
Median Match Quality Index
600
500
Technology Transition Workshop
Effects of Writing Age
• Lines written freehand periodically on white
copy paper (Hammermill Fore DP).
• Stored in closed folder in desk drawer with
blank pages surrounding each written page.
• Samples handled with gloves during analysis.
• Three spectra at each age averaged for time
plots.
Technology Transition Workshop
200
332 Days Old
Black Bic
Round Stic
Ballpoint at
Two Ages
Relative Intensity (m/z 367 = 100)
150
183
367
100
139
351
50
165
100
200
0
200
374
269
199
4 Days Old
139
100
150
367
183
100
351
269
50
374
165
0
100
200
300
m/z
400
Technology Transition Workshop
Components of Bic Ballpoint
Observed
m/z
100.076
139.076
165.094
183.102
Chemical
Formula
Actual
m/z
Most Probable
Identity
100.076 N-methyl-2-pyrrolidone
139.076 Phenoxyethanol
165.092 Various fragrant liquids
[C5H9NO+H]+
[C8H10O2+H]+
[C10H12O2+H]+
[C10H14O3+H]+ 183.102
Diethylene glycol monophenyl ether
199.142 [C11H18O3+H]+ 199.133 Various fragrant liquids
269.166 [C17H20N2O+H]+ 269.166 Michler’s ketone
351.215
uncertain
---- ---367.210 [C20H30O6+H]+ 367.212 Dibutylglycol phthalate
374.264 [C25H30N3+2H]+ 374.260 Crystal violet
Technology Transition Workshop
Crystal Violet Cationic Dye
Technology Transition Workshop
Relavtive Intensity (m/z 372 = 100)
Crystal Violet DART Spectrum
120
[Crystal Violet] +
372.242
100
[Crystal Violet + 2H] +
374.259
80
60
[Methyl Violet] +
358.232
40
[Crystal Violet + H2O] +
390.260
[Crystal Violet + O2] +
404.237
345.205
20
0
300
320
340
360
380
m/z
400
420
440
Technology Transition Workshop
300
Aging of
Black Bic
Round Stic
Ballpoint
Relative Intensity (m/z 367 = 100)
250
m/z 100
m/z 139
m/z 199
200
150
100
50
0
m/z 165
m/z 183
m/z 269
m/z 351
150
100
50
0
0
100
200
Age (days)
300
Technology Transition Workshop
150
100
336 Days Old
Black Bic
Cristal Gel
Roller Ink at
Two Ages
Relative Intensity (m/z 150 = 100)
80
60
40
151
148
20
168
106
0
100
195
239
150
9 Days Old
80
151
60
301
40
195
20
148
239
168
106
0
100
150
200
250
m/z
300
350
400
Technology Transition Workshop
Components of Bic Gel Ink
Observed
m/z
Chemical
Formula
106.088 [C4H11NO2+H]+
148.100
C7H16O3+
150.114 [C6H15NO3+H]+
151.102 [C6H14O4+H]+
Actual
m/z
Most Probable
Identity
106.087 Diethanolamine
148.110 Dipropylene glycol monomethyl ether
150.113 Triethanolamine
151.097 Triethylene glycol
168.127
C10H16O2+ 168.115 Dipentene diepoxide
195.124 [C8H18O5+H]+ 195.123 Tetraethylene glycol
239.151 [C10H22O6+H]+ 239.149 Pentaethylene glycol
301.186
[C18H24N2O2+H]+
or [C19H24O3+H]+
301.192 ---301.180
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m/z 148
m/z 151
m/z 239
m/z 301
70
Aging of
Black Bic
Cristal Gel
Roller Ink
Relative Intensity (m/z 150 = 100)
60
50
40
30
20
10
30
0
m/z 106
m/z 168
m/z 195
20
10
0
0
100
200
Age (days)
300
Technology Transition Workshop
100
340 Days Old
239
Blue
Mont Blanc
Le Grand
Rollerball
Fluid Ink at
Two Ages
Relative Intensity (m/z 239 = 100)
80
60
40
195
121
283
256
20
403
300
299
212
151
0
100
327
239
4 Days Old
283
80
195
60
40
121
343
327
299
256 300
255
20
150 151
0
100
200
344
387
388
431 432 476
475
371
415
212
211
300
m/z
400
500
Technology Transition Workshop
100
340 Days Old
239
Blue
Mont Blanc
Le Grand
Rollerball
Fluid Ink at
Two Ages
Relative Intensity (m/z 239 = 100)
80
60
40
195
121
283
256
20
403
300
299
212
151
0
100
327
239
4 Days Old
283
80
195
60
40
121
343
327
299
256 300
255
20
150 151
0
100
200
344
387
388
431 432 476
475
371
415
212
211
300
m/z
400
500
Technology Transition Workshop
Components of Mont Blanc Ink
Observed m/z
Chemical Formula
121.075
[C8H8O+H]+
403.193
Not determined
151.101, 195.126, 239.152,
283.178, 327.207, 371.233,
415,254
Probable Identity
Acetophenone
Not in ink
[HO(C2H4O)nH+H]+ Polyethylene
glycols
n = 3 to 9
211.132, 255.159, 299.185, [C8H10O(C2H4O)n+H] Polyethylene
+ n = 3 to 9
343.214, 387.243, 431.267,
glycol ethyl phenyl
475.292
diethers
212.154, 256.179, 300.206, C16H20(C2H4O)n+ or Polyethylene
344.231, 388.257, 432.288, C7H12N2(C2H4O)m+ glycol derivatives
476.313
n = 0 to 6, m = 2 to 8
Technology Transition Workshop
100
m/z 121
m/z 255
m/z 256
m/z 283
m/z 299
Aging of Blue
Mont Blanc
Le Grand
Rollerball Fluid
Ink
Relative Intensity (m/z 239 = 100)
80
60
40
20
0
m/z 195
m/z 300
m/z 327
m/z 343
m/z 344
m/z 403
80
60
40
20
0
0
100
200
Age (days)
300
Technology Transition Workshop
Ink Identification
• Library of 166 inks: 76 ballpoints, 50 fluid inks
and 40 gel inks.
• Written 10 to 35 months before testing.
• 2 spectra of each ink placed in NIST library for
the correct ink type. Handled with gloves.
• Every spectrum tested as an unknown.
– Perfect match with self is ignored, so Hit #1 is
next best match
• Ink correctly identified if Hit #1 is the other
spectrum for the same ink.
Technology Transition Workshop
Ink Identification Test Results
Ink
Type
Black Inks
Blue Inks
No. of Inks
Correct
No. of Inks
Correct
in Library Identifications in Library Identifications
Ballpoint
48
99%
28
100%
Fluid
26
81%
24
77%
Gel
21
93%
19
97%
All (black
& blue)
166
92%
--
--
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Unknowns that Matched Incorrectly
• Black Ballpoints – 1 error
– PaperMate Flexgrip Elite matched Papermate
Flexgrip Ultra
• Blue Ballpoints – 0 errors
• Black Gels – 3 errors
– 2 Pentel Sunburst Gels matched a Parker Gel
Refill and an Integra Roller Gel
– Zebra Jell 3 matched Parker Gel Refill
• Blue Gels – 1 error
– Pentel Hybrid H2 matched Pentel Sunburst Gel
Technology Transition Workshop
Unknowns that Matched Incorrectly
• Black Fluids – 10 errors
2 PaperMate Liquid Expresso
Staedtler Silver Ball 404
Pilot Precise Rolling Ball
Uni-ball Deluxe Roller
Sheaffer Slim Rollerball Refill
Uni-ball Vision Roller
Staedtler Lumocolor
2 Waterman RollerBall Refill
• Blue Fluids – 11 errors
Bic Z4
Parker Roller Ball Refill
2 Cross Porous Tip Refill
2 Sheaffer Slim Rollerball Refill
2 PaperMate Flair
2 Zebra Zeb-Roller 2000
PaperMate Liquid Expresso
Technology Transition Workshop
Correct Match
30%
20%
Percentage of Matches
Match Quality
of Correct
and Closest
Incorrect
Matches for
Black
Ballpoints
10%
0%
Closest Incorrect Match
12%
9%
6%
3%
0%
1000
900
800
700
600
Forward-Matching Match Qualities
500
Technology Transition Workshop
Correct Match
20%
15%
Percentage of Matches
Match Quality
of Correct
and Closest
Incorrect
Matches for
Blue
Ballpoints
10%
5%
0%
12%
Closest Incorrect Match
9%
6%
3%
0%
1000
900
800
700
600
500
Forward-Matching Match Qualities
under
400
400
Technology Transition Workshop
20%
15%
Percentage of Matches
Match Quality
of Correct
and Closest
Incorrect
Matches for
Black Gel
Inks
Correct Match
10%
Pentel Sunburst
5%
0%
12%
Closest Incorrect Match
9%
6%
3%
0%
1000
800
600
400
Forward-Matching Match Qualities
under
300
Technology Transition Workshop
30%
20%
Percentage of Matches
Match Quality
of Correct
and Closest
Incorrect
Matches for
Black Fluid
Inks
Correct Match
10%
0%
Closest Incorrect Match
12%
9%
6%
3%
0%
1000
900
800
700
600
500
Forward-Matching Match Qualities
under
400
400
Technology Transition Workshop
Match Qualities in Ink Identification
Ink Type
Correct Match
Closest Incorrect
Match
Difference Between
Correct & Incorrect
Average Median Average Median Average Median
Black
Ballpoint
Blue
Ballpoint
Black
Fluid
882.3
888.5
749.7
750.0
138.4
119.0
878.0
884.0
626.0
620.5
252.0
249.0
773.2
792.5
647.7
695.0
125.5
83.0
Blue Fluid
702.3
743.5
563.7
592.0
138.6
130.0
Black Gel
793.9
832.0
609.0
602.5
188.3
155.5
Blue Gel
752.2
719.0
590.3
560.5
152.7
125.0
Technology Transition Workshop
Acknowledgements
• National Institute of Justice
– This project was supported by Award No. 2006-DNBX-K017 awarded by the National Institute of
Justice, Office of Justice Programs, US Department
of Justice. The opinions, findings, and conclusions
or recommendations expressed in this exhibition
are those of the author and do not necessarily
reflect the views of the Department of Justice.
• John McClelland, principal investigator
• Susan Lorge, worked out optimum conditions
and acquired library data