JEOL expands capabilities of AccuTOF-DART with ionization module

The FilterSpray module makes it possible to spot a sample on a disposable paper triangle for analysis by ambient ionization.

It is an alternative to Electrospray Ionization and eliminates the need for a special pump or plumbing, spray needle, desolvating gas or precise alignment.

The FilterSpray module is put onto the linear rail of the AccuTOF-DART, to permit FilterSpray analysis on the sample platform. Samples and solvent are deposited onto a paper triangles cut from a porous substrate such as filter or chromatography paper.

Typical applications for FilterSpray analysis include polar and highly charged compounds, cationic and anionic compounds, thermally labile compounds, polymers, inorganic compounds and metals, peptides, digests and small proteins.

F&B application potential​

Chip Cody, product manager for mass spectrometry at Jeol USA, said with the evolution into a third generation instrument it is more of a universal analytical toolbox.

“It has broad food and beverage application potential. We started off looking at everything we could find. For example, we went into a grocery store and compared the flavourless basil leaves we bought there and the delicious ones in the Vietnamese restaurant and we were able to tell the difference,” ​he told FoodQualityNews. ​

“The Vietnamese basil leaves have which is the p-allylanisole or methyl chavicol in them which is the liquourice flavour that makes them taste so good and the grocery store ones just had a little bit eugenol in it. It is also used for characterising pesticides in fruit.”​

The AccuTOF-DART ambient ionization mass spectrometer system was introduced in 2005. The atmospheric pressure ionization interface (API) for the AccuTOF system became the platform for developing the Direct Analysis in Real Time (DART) ion source.

Cody explained how DART works.

“You have essentially a tube and you blow a gas, typically helium, nitrogen or argon, through the tube and you set up a glow discharge between a needle at about 3000 volts and a grounded electron and as the gas blows out of the chamber where the glow discharge is, what survives is primarily excited state atoms,” ​he said.

“So you have tripled state helium for example and electronically excited helium has a lot of energy in it so when it comes in contact with a sample or the air you can produce ions, then the ions will bond into the gas stream in the mass spectrometer. ​

“You can heat the gas to desorb things that require more temperature to see, you can do a number of tricks, but in short what happens is you wind up with a protonated molecule a M+ H+ in positive ion mode or a M- H- in negative ion mode, of course it is never quite that simple but that’s the first order of mechanism.”​

Software aid and identifying compounds​

The software has grown with the instrument, said Cody.

“In terms of interpreting it, you can do a number of things, you can use the exact mass as an isotopic information to get elemental compositions and that would you give candidate compounds and you can then match the fragmentation against the database,” ​he said. ​

“For example, morphine and piperine for black pepper are isomeric so they have exactly the same composition, you need the fragmentation to tell whether you have pepper or drugs. But it you have a set of flavour compounds you can gave the software an excel spreadsheet with a list of compounds and their formulas and it can identify what’s present in the spectrum and label them.”   ​

Cody said time to result depends on the level of problem you are trying to solve.

“It only takes seconds to measure the sample. If it is a complete unknown you may need to spend a bit of time looking at the data and trying to assign the peaks but it can pretty quickly give compositions if you have targeted compounds and that can be done in minutes or automatically,”​ he said. ​

“If you have unknowns sometimes you have to look at the data and try and decide what makes sense. If you are just looking at exact masses and isotope ratios then you will be given a list of compositions, well probably one composition is clearly the right one but even then there are a number of isomers so interpreting unknowns takes a bit longer.”​

Expertise needed depends on the level of information you want to get.

“If you’d just like to get a mass spectrum, exact mass or elemental composition it’s trivial and there’s an advantage to the rapidness of the instrument,” ​said Cody. ​

“You could make an open access system but if you are relying on chromatography someone, somewhere will always put peanut butter in the auto sampler vial. Because it is an open source we don’t have that problem if the orifice gets dirty we can just wipe it off, if it gets clouded up I just poke a wire in there and I don’t have to turn anything off. ​

“We’ve put chocolate, peanut butter and melted plastic in front of it over the years and it has not caused us any problems but if you really want to use all the capabilities of the instrument that does require some training.”​