Ion Legend

Sitting Down With... Chris Pohl, Vice President, Chromatography Chemistry, Thermo Fisher Scientific, San Francisco Bay Area, USA.

What first attracted you to science?

My dad was an engineer, so I was always interested in technology. But what really inspired me was a seventh grade science teacher. I did receive a chemistry set for Christmas one year (back in the day when you were allowed useful chemicals), but it was the short introduction at school that made me realize I wanted to be a chemist. I actually remember a specific triggering experiment; our teacher was explaining acids and bases with sodium hydroxide and hydrochloric acid, and did the classic titration with a pH indicator (phenolphthalein). She told us that at the end of the titration it was basically salt and asked for a volunteer to taste it. I was the volunteer... The fact that you could take two really poisonous chemicals and mix them together to form something as innocuous as salt really piqued my interest. Science almost seemed like magic. My father helped me build a small laboratory in the basement (complete with its own natural gas supply) and I had an electrolysis set up – but my main interest was explosives. I found that gunpowder is not that explosive – but I had a lot of fun with silver acetylide...

You’re clearly an inventive and experimental chemist – does that explain your drive to publish patents?

I guess so! My original goal was to publish 50 patents by the time I retired. I’m now at 77 and don’t feel like retiring yet; I’ve upped it to 100... for now. I remember the very first patent was based on work that I did at Clorox. As an analytical chemist, one of my roles was competitive product analysis – it was like being a detective. Many of the washing powders back then used sodium sulfate as diluent, and I had to use barium sulfate precipitation in a convoluted and, to my dismay, not very accurate analytical method. I became interested in analyzing inorganic ions with chromatography, and Hamish Small had published a paper on ion chromatography in Analytical Chemistry. When I showed the paper to my boss, trying to convince him to invest, he told me I should make one. We bought the components and, sure enough, we made a functioning ion chromatograph. But one critical aspect was a column that could function at high pH. I only had access to silica-based materials, which wouldn’t last too long. One evening, when I was driving home from work an idea popped into my head (based on my experience with ion-pair chromatography): if I used a suppressor, I could use C18 silica rather than ion exchange material. I realized that probably wasn’t even covered by the ion chromatography patent.

Clorox decided it was “unpatentable,” but I ended up meeting with both the CEO and the head of R&D at Dionex, who later bought the rights to my invention (from Clorox) for the price of a single instrument. A few months later, they offered me a job. Dionex filed the patent, which was granted with ‘no office actions’. The whole process fascinated me, and I wondered if I could do it again – or was I a ‘one hit wonder’?

What about the fish that got away?

When you get a rejection letter from the patent office, in a weird way they are testing your determination – you have to be persistent. We gave up too early on one important potential patent, which was based on my invention of high pH anion exchange chromatography for the separation of carbohydrates. There was some prior art and the patent office argued that it was “obvious.” But the previous work was done in the 1950s, and other papers noted that reducing sugars could not be separated at high pH because they would degrade – so it was clearly not so obvious. Nevertheless, we didn’t know enough to push at the time. Funnily enough, we wrote “patent pending” in that paper (my second highest cited), and no one was brave enough to challenge it for nearly 10 years...

Which patent are you most proud of?

The first patent is always special but, to be honest, it wasn’t all that successful. Two patents top my list. The first is a technique for accelerated (or pressurized) solvent extraction. I think it’s the only patent where I did nothing other than come up with the idea. Nevertheless, it essentially kick-started an analytical industry by itself. The second is more recent and was based on hyperbranched chemistry that I originally dreamt up in 2003; it has proven to be very versatile in the manufacture of anion exchange columns. It’s kind of like the chemistry equivalent of LEGO, and rather uniquely uses a HPLC pump to alternatively react a linear polymer with two reagents (diepoxide and a primary amine) to coat a resin in a column. In addition to being commercially successful, it’s also a completely new synthesis method for anion exchange materials and a pure chemistry patent, which makes it special for me.

Your ideas often seem to stem from thought experiments...

In a way. A lot of my ideas come from keeping my eyes open to what’s really happening in the chemistry, and not taking as gospel what people think about a particular system. People can sometimes make the mistake of turning speculation into fact... But it’s also about testing the limits and curiosity. The work on my first patent stemmed from wanting to see how far I could push ion pairs – at what point are they no longer ion pairs? It also made me wonder whether there was some other interaction going on – something that was postulated much later on, but which is insinuated in the patent.

Sometimes it’s simply about patience. Hamish Small talks of a “mental attic” where he stores ideas until the day he figures out a way to use them. I guess I’m similar in that way.