ANALYSIS of ink and paint

Question 1

both inks and paints dissolved in solvent when delivered to a substrate based on __

Answer 1

polymerization

Question 2

open system:
closed system:

Answer 2

when you write with pen (solvent evaporates and aging occurs)
ink is in the pen

Question 3

what instrumental machinery would work with analysis

Answer 3

• Light Microscopy
• TLC** for paints
• Raman
• IR
• UV-Vis
  etc…

Question 4

T/F Raman has sharper peaks than IR

Answer 4

T - they are also inverted of IR, where IR has broad peaks

Question 5

what is optical microscopy

Answer 5

reveals the presence of metallic particulates and other solids that are part of the formulation (based on optical properties- crystalline or not)

Question 6

what is alternative illumination

Answer 6

UV/IR
non destructive method for analysis of questioned documents (fluoresce)

Question 7

what is TLC/ HPTLC

Answer 7

thin layer chromatography
- if a colorant is soluble it can be evaluated using TLC
- uses a silica gel stationary phase and ethanol/water mobile phase to separate

Question 8

what is IR spectroscopy used for ?

Answer 8

characterizing colorants binders and coatings

Question 9

what is Raman used for ?

Answer 9

inks and paints

Question 10

why does FTIR use form binders found in paint

Answer 10

because paints are mixtures and the entire spectrum is of interest and not just the fingerprint section

Question 11

what is the difference between ink and paint structures by IR

Answer 11

ink produces mixtures NOT layered structures like paints

Question 12

Mass spec can be used for

Answer 12

ink and paints

Question 13

Why is LCMS better than HPLC

Answer 13

HPLC lacks specificity

Question 14

what instruments are good for elemental analysis?

Answer 14

XRF (x ray fluorescence for elemental id.)
XRD (x ray diffraction for structure)
SEM (scanning electron microscopy)

Question 15

within elemental analysis XRF is good for

Answer 15

metallic constituents of pigments using SEM imaging

Question 16

within elemental analysis XRD is good for

Answer 16

crystal structures + small amounts of inorganic colorants

Question 17

T/F ink in a pen is distinct from ink applied to paint on a car

Answer 17

T : in a pen (closed system) and on a car ( open system)

Question 18

which system is more important in forensics (open or closed)?

Answer 18

closed , but the comparison of both helps with determining age

Question 19

what is the aging process ?

Answer 19

• solvent evaporation
  -film formation (oxidation/polymerization/ cross linking)
• degradation (exposure to light/moisture, temp, environmental…)

Question 20

absolute vs relative age in ink

Answer 20

absolute: date when ink was placed on the substrate (compare to fresh ink)
relative: uses an aging curve, whether applied at the same time or not (evaporation rate is steady early on then hardening occurs)

Question 21

describe aging

Answer 21

chemical analysis for time frames of days to years has been useful using HPLC, MS, UV-VIS, and IR

Question 22

which is better solvent evaporation vs film formation

Answer 22

film formation is more reliable

Question 23

heat accelerated aging shows that the spectral peaks of the ___ decreases over time

Answer 23

phenyl ring

Question 24

how can you observe degradation of smaller peaks

Answer 24

UV radiation