My name is Rosie and I’m studying chemistry at the university. My 10 week EPSRC project is based on mass spectrometry, a technique for analysing the mass to charge ratio of ions, and I have been focussing on matrix-assisted laser desorption/ionisation (MALDI), which is a widely used ionisation technique for biological mass spectrometry.

To run an analysis, an analyte sample is spotted on a target plate with a matrix, which is typically a weak organic acid dissolved in a solvent. The droplet is dried to allow solvent evaporation and this will result in a solid matrix/analyte crystalline sample. The target plate is then inserted into the mass spectrometer and a laser is fired at the sample. The purpose of the matrix is to absorb UV light form the laser and this leads to ionisation of the analyte. The result from this analysis is a spectrum showing peaks at different mass to charge ratios and their relative intensities.

There are disadvantages to using a solid sample for analysis, for example, the analyte may not be evenly distributed throughout the crystals, so there is research into using liquid matrices as an alternative. For liquid MALDI, there are differences in sample preparation and the addition of glycerol means that the sample is still a liquid droplet after solvent evaporation.

My project is to investigate the effect of various surfaces and surface structures to see how ionisation of the analyte is affected and to see differences in the quality and quantity of the ion signal. I have been provided with a variety of target plates of different materials and properties to experiment with and see how these compare to the ion signal I get when I use a conventional stainless steel target plate. I have also been provided with a range of films to stick on to target plates and to put my sample on top of, as this may also have an effect on the intensity of ions.

Sample preparation is a crucial step for successful MALDI analysis so I have spent a significant amount of my project mastering the preparation of first solid matrices and then liquid matrices, experimenting with different solvents and seeing what matrices gave me the best results.

I was really nervous about starting this project as I only had a basic knowledge in mass spectrometry, but this summer I have learnt so much more about analytical chemistry and it has also been really useful in helping me decide what I’d like to do after university. It has given me more confidence in my lab skills and I’m less nervous about doing my final year project now that I’ve had research experience.

Rosie Nicholson