The coupling of the DESI (desorption electrospray ionisation) and ESI (electrospray ionisation) atmospheric ionisation methods with the Mini-10 MS brings the research group from Purdue University a step closer to realising its dreams of enabling the instruments to become Star Trek-like 'Tricorders'.
The latest research published in the journal Analytical Chemistry details the coupling of the Mini-10 with the atmospheric ionisation sources and its use to identify peptides and drugs in aqueous solution as well as illicit drugs such as cocaine deposited on bank notes.
"This new work represents the first time we've been able to use ambient ionisation methods with the Mini-10 and that means you can simply electrospray from solution or directly look at solid materials outside the MS," Prof. Cooks told LabTechnologist.com
"We are very, very pleased with where this work is going and in particular with this ability to study solid and solution phase samples and even study proteins on these mass spectrometers."
The handheld Mini-10, so called because it only weighs 10kg, is a miniature tandem MS (MS/MS) that has been developed by researchers led by Professor Graham Cooks and Dr Zheng Ouyang.
One of the major challenges encountered by the group was in coupling the atmospheric pressure ionisation sources to the miniature MS due to its reduced pumping capacity.
The ESI source requires that the samples first be dissolved in a solvent (such as 1:1 Mixture of water and methanol), before they are ionised are sucked into the MS for analysis.
The DESI source that sprays a sample with a stream of high-velocity gas that causes surface particles to be break off from the sample's surface where they are ionised by reactive chemicals in the gas stream and sucked into the MS by a vacuum pump.
Previous work from the group has shown that the DESI source can be used to fingerprint bacteria.
According to Prof. Cooks, the addition of either of the atmospheric sources does add some weight to the MS as a supply of solvent and gas is needed.
"In order to make a completely general purpose MS you need to add a little bit of weight to enable these more complex and useful ionisation methods," he said.
"However, we have just developed the Mini-11, which gives similar performance to the Mini-10 but weighs only half as much!"
According to Prof. Cooks the major application areas are in routine quality control applications where this instrument would enable the use of MS much closer to the manufacturing process.
"There are various other applications such as in environmental testing, public safety with regards to explosive, forensics for looking for drugs of abuse and various biomedical uses as well," said Prof. Cooks.
"We aim to develop a MS that can be used at the primary point of care in physicians offices because we think that with a small mass spectrometer that is capable of looking at the distribution of lipids in biological fluids or even tissue samples taken from a needle biopsy to get an indication of a disease state almost instantaneously."
The rights to technology used in this latest instrument have been licensed to two different companies, with the DESI technology having been licensed to Prosolia and the Mini-10 technology to Griffin Analytical.
While Prof. Cooks was understandably guarded about ongoing projects, he did say that there was "a lot more coming".
"On thing that should be possible with miniature instruments, but has yet to be demonstrated, is the imaging experiment looking at samples in a spatially resolved fashion. These experiments are being done with larger instruments and from what we know should be possible with these miniature mass spectrometers," he continued.
"This can include imaging latent fingerprints where you get a chemical analysis along with the image, allowing you to associate the fingerprint with a mass spectrum of what the person has been handling."
