Breaking New Ground with IC-MS

Then: a bright but chilly day in 2007...

About nine years ago, we were having problems with the analysis of glyphosate and glufosinate. We’d been using derivatization prior to GC-MS/MS, but too many repeats of samples told us we needed a new solution. We got in touch with Dionex to assess whether ion chromatography (IC)-MS could help reduce the amount of time spent in the laboratory and produce more reliable results. That first conversation kicked off a collaboration with Dionex, who supplied an ICS-3000; we provided a mid-range mass spectrometer with a few upgrades. Sensitivity was always going to be an issue, so we sought inventive ways to get the most out of the system. We came up with the idea of using inline concentrators for sample cleanup. But if you inject as much as 4700 µL of extract onto a system, you add an awful lot of background matrix, so we needed to flush the concentrator with water to remove the non-ionic components of the matrix before bringing it inline with the rest of the system.

For years, we worked with this solution. But it wasn’t without its own challenges. We had to use two sets of control software (and therefore two PCs), so errors occasionally but inevitably crept into the sequences, meaning that the IC and MS systems were not always synchronized. We fudged around those problems by running the two control systems on the same PC, but we were still a little uneasy.

We spent the first couple of years  – the “honeymoon period” – understanding what preventative maintenance was necessary to keep the IC-MS system running as smoothly as was possible. In fact, all of our systems go through weekly preventative maintenance – something that we’ve found to be a real time-saver in the long run. For our IC-MS system,  the most important task was re-conditioning the columns each week.

There was always a certain “home-built” feel to the system – after all, we were one of the first labs working at this particular frontier. Nevertheless, the benefits were also clear; the number of repeated runs dropped dramatically. Essentially, we’d moved on from analysis that was very difficult using any other technique to much improved analysis on an albeit slightly cranky system. It also allowed us to expand our analytical services; the scope of IC-MS was not limited to glyphosate and glufosinate. A third compound – ethephon – appeared; I remember running the first batch of grapes for the Pesticide Residue Committee Survey and finding an MRL exceeding sample. We’d not done such analysis before, so we weren’t sure what to expect – but from that point on, we regularly found ethephon in grapes...

Now: June 8, 2016

Where we are today is very different. Sample injection volumes have dropped from 4700 µL of extract to 100 µL of 10-fold-diluted extract (so 10µl in reality) – less is more! A stark and pertinent difference between “then and now” is how much the technology has advanced. Our Thermo Scientific™ Dionex™ ICS-5000™ is paired with a TSQ Quantiva™ MS system, both of which are controlled with a single software platform, TraceFinder™. Not only is the system easier to use but it is also much more reliable. In other words, we’ve progressed from the initial excitement of getting our first system to (mostly) work to the excitement of using a system that works the way we want it to out of the box. Columns have also become much more efficient in the intervening years, which allows us to get better peak shapes. And the TSQ Quantiva has got a special low-mass tuning solution – perfectly suited to our compounds of interest in IC-MS.

The scope of IC-MS analysis has also increased with chlorate, perchlorate, and phosphonic acid, all of which have become very topical. Rather than using an LC-MS system with uncertainty about the retention mechanism, we’ve got a tool that’s designed specifically for anionic compounds. It’s another robust tool in our toolbox that allows us to step away from the constraints of other techniques when we need to.

Nine years ago, we were certainly an early adopter of IC-MS for pesticide residue analysis. Today, I get the sense that IC-MS is being embraced by an increasing number of organizations in our field and beyond. And now that we’ve got a reliable system – and experienced staff – we certainly sell the technique internally.

When I started at Fera, there were a lot of single-residue methods. Over the years, such methods are diminishing as compounds are getting slotted into multi-residue methods. IC-MS fits into that evolution with its ability to target a suite of 40-50 analytes. We have developed and validated methods for anionic pesticides and going forward we hope to work with Thermo Fisher Scientific to evaluate cationic pesticides.

It’s clear that we all want to test for more compounds with less effort – and in 5–10 years’ time, I suspect we’ll be working on unknown screening, which will complement our targeted analyte approach. We are also evaluating the Q Exactive™ Focus Hybrid Quadrupole-Orbitrap™ Mass Spectrometer for other analyses, and hopefully IC-Orbitrap MS, especially given that, as Amadeo Fernandez-Alba noted last month, high-resolution accurate-mass MS systems are likely to become more dominant in the future. As analytical chemists, we don’t want to be tied to a list, waiting for a problem – we want to be able to identify upcoming problems and trends. And for that, we need the right tools for the job.