Chemical imaging

A picture says more than a thousand words… or at least that is what they say. So what is better, in terms of showing the chemical composition of a fingerprint? Exactly, a chemical image.

It is understandable that the average fingerprint expert hasn’t got a clue about chemistry. I can’t blame them. But that doesn’t mean that technology is advancing and that at this moment in time we are able to produce chemical images with a very high (spatial) resolution.

This week we have had a DESI installed. In the image below the DESI part of the whole setup is shown.

The abbreviation DESI stands for Desorption Electro Spray Ionisation. And that is exactly what it does:

Desorption of the materials of interest is achieved by running a solvent/gas flow over a surface

Electrocharging is necessary for the desorption to be effective and helps with further ionisation in the mass spectrometer.

Spray is the solvent/gas flow running over the surface to achieve the desorption

Ionisation is needed for a mixture of a solvent and nitrogen gas to get the materials of interest of a surface into the mass spectrometer.

So an engineer from the US came over to our institute to install and explain the setup and the operation of the equipment. The DESI is attached to a mass spectrometer and communicates with that part through a computer interface. The mass spectrometer we are using is a QToF and here is the first image that we got!

WhatsApp Image 2018-03-06 at 16.03.19

What you see here is the letter W, written with a marker on a piece of glass, and the image is build on the basis of a molecule in the ink of the marker. Blue means there is a little amount of that particular molecule, yellow means that is a higher amount.

Next step of the implementation of this equipment in the lab is using it for fingerprint analysis. When this method is optimised we will be able to detect particular molecules in the fingerprint. We have published various studies on this matter – for further information see the publication tab on this site.