L8: Chemical analysis of Trace Evidence
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whats the wavelength range?
200nm – 800nm wavelength range
colour absorbance or transmittance by the fibre can be measured at?
400 - 800 nm
is Microspectrophotometry destructive?
nope
what does thin layer chromatography do?
separates the colour components to give a “fingerprint”
is TLC destructive?
yes
what does uv-vis spectrophotometry do?
Measures colour, often due to dyes or pigments, in a quantitative object manner. works on fibres, paints and inks
is uv-vis spectrophotometry destructive?
no its normaly non destructive but when dyes extracted the analysis is carried out on the solution and this is destructive
what does FTIR measure?
absorbance or radiation above ~800nm wavelength
is FTIR destructive?
no
FTIR looks at the characteristics of?
the vibration of chemical bonds in the material
what does Raman Spectroscopy measure?
the gain or loss in energy of laser light scattered inelastically by molecules
what does the spectrum in Raman Spectroscopy show?
difference in energy is characteristic of vibrations of the chemical bonds in the material
Raman Spectroscopy is _______
non destructive
what does FTIR identify?
functional groups from the pigment
forensic vibrational spectroscopies characterise _______
the bulk chemical composition of a material
start at
elemental analysis