What does DESI do?

Desorption Electrospray Ionisation (DESI) is a powerful new mass spectrometry technique [Cooks et al, Science, 306, 471 (2004)] that can identify pharmaceuticals, explosives, proteins and a range of biological materials. DESI is capable of molecular image analysis for a range of samples including tissues, with optimum spatial resolution of the order of 150 µm. DESI can achieve femtomole sensitivity and provides high throughput analysis and real time analysis for reaction monitoring. In addition, DESI can be combined with mini-MS for a handheld ambient molecular analysis device.

How does DESI work?

It uses an electrospray source of highly charged aqueous spray droplets to gently desorb and ionise molecules from a sample surface. These molecules are transferred into a standard electrospray mass spectrometer through an ion transfer tube. Since the process is very soft, there is very little fragmentation, which is reflected in the mass spectra. The advantage of the technique is that it can be coupled to any mass spectrometry allowing for quantification, identification and MS/MS capability. The technique directly analyses a surface under ambient conditions.

What is DESI used for?

• Forensics, trace analysis of drugs and explosives directly from complex matrices, chemical mapping, detection from fingerprints, ink analysis.
• Personal care products direct from textiles, skin or hair.
• Biological analysis of amino acids, peptides and proteins.
• Small molecules detection directly from plant, cell or tissue substrates.
• Volatiles or molecules weakly bound to the substrate.

See our DESI measurement services page to find out how DESI can help with your specific application.

What are the measurement challenges?

Robustness and reliability needs to be improved. Typically, repeatability is 50% and, for industrial use, this needs to be regularly <10 %, and results need to be comparable between instruments. NPL is making significant progress in improving the reliability of DESI, investigating the effects of parameters and furthering our understanding of the DESI process by exploring the DESI/surface interaction and efficiency of the process. NPL aims to take the technique forward and fulfil its potential for ambient imaging, in field, in vitro or in vivo, by developing the underpinning metrological research

See our DESI research page to find out more.