Peter W. Carr: The Career of a Lifetime Achievement Award Winner

LCGC recently spoke with the 2013 LCGC Lifetime Achievement Award winner, Peter W. Carr of the University of Minnesota, about his early start with science, his career choices, and his vast accomplishments.

Were you always interested in a scientific career? Why did you choose to get your B.S. and PhD in chemistry?Carr: Well, I think things started for me back in high school when I started to define what I wanted to be when I grew up. I am definitely a child of the Sputnik era. I started high school in September, 1957 and of course Sputnik was launched in October, 1957 and that really had a tremendous impact on education in the United States. Not just education, but the whole political climate in the United States changed radically and science certainly became both a lot more glamorous and a more viable way to earn a living. So those were certainly factors, if not the chief factor, involved. I am not sure if I was a particularly curious kid or not, but somehow there was a lot that attracted the attention of lots of kids of my age at that point in time. So I would say that’s how I got interested in science more than anything else. There was a great movie made few years back called “October Sky,” which I think captured lots of the feelings of that time. It’s a very nice movie.

Now, how did I get interested in chemistry? Probably my high school chemistry teacher was more interesting than any of the other science teachers I had and chemistry was a hands-on kind of science. You could go in the lab and do something with it. The other part of your question had to do with “why did I go for a PhD in chemistry?” Well the answer to that is a lot more straightforward. I had a wonderful experience in undergraduate school at Brooklyn Polytechnic. They actually required a chemistry major to write a Bachelor’s thesis and defend it. I chose as my research advisor, or rather he allowed me to work with him, Professor Louis Meites. He was a wonderful guy to work with, a really inspiring person. He planted the research bug deeply in me and there was no question that I was going to go on to graduate school and try to get a PhD after that research experience. So that’s what got me to graduate school.

How did you get started working with liquid chromatography (LC)?Carr: That’s a more complicated question. I had no training or education at all in chromatography. Back when I was an undergraduate student, electrochemistry was clearly the dominant form of analytical chemistry, but when I was on the faculty at the University of Georgia, each of us in the faculty chose one area of analytical chemistry for a graduate course. No one had much experience with chromatography, but we all recognized how important it was, so I took the graduate course in chromatography as my area. So it was more through my teaching work that I became interested in chromatography than in anything else. I got into LC because at that point in time, I was really doing a lot of bioanalytical stuff and I was very interested in affinity chromatography, which is much more connected to LC than it is to gas chromatography. Basically it was my teaching responsibilities that got me involved in chromatography. Probably one of the best things that ever happened to me was to get involved in chromatography.

Of your 18 patents, which do you think have had the greatest impact on the field?Carr: Of the 18 patents, probably 15 or so were related to zirconia. So lumping them together, my interest in the development of zirconia-based phases is probably going to have the biggest influence in the long run. That certainly is my current view.

Your work on detailed thermodynamic measurements and solvatochromic modeling of retention and selectivity led to a clearer understanding of the role of the mobile and stationary phases as well as the relative contributions of polarizability and dipolarity, hydrogen-bond donor, and hydrogen-bond acceptor interactions. What started you on this research path?Carr: Well, this actually goes back to my teaching again. Lloyd Snyder’s papers, particularly his solvent triangle paper and a paper that he wrote with Barry Karger and, I believe, Georges Guiochon, on using Hildebrand solubility parameters really got me thinking about how we could better define the chemical role of the solvent in doing separations. At that time, I was really reading the chemical literature pretty broadly and I happened upon some papers by Mort Kamlet and Bob Taft, two extremely well known physical organic chemists. They were taking an approach defining the solvent selectivity that was really completely different than anything the chromatographers were doing. That was, they were using spectroscopic measurements to help elucidate whether it was simply a general bipolar effect, a hydrogen-bond accepting effect, or a hydrogen-bond donating effect that was governing the role of a solvent. So I attempted to bring together these two really mutually supporting fields that were being practiced by two very different groups of people. That proved to be a tremendously fruitful combination and led to many collaborations with Lloyd Snyder and also Mort Kamlet and Bob Taft over the years. I haven’t added up all those papers but that’s probably on the order of 30 papers and those collaborations led to the development of the linear solvation energy relationships and their applications in phase equilibria.

Later on, again reading the literature, I found some papers by Chuck Eckert, who was then in the chemical engineering department at Illinois in Urbana-Champaign, but is now with Georgia Tech; chemical engineers have done an enormous amount of work in understanding the thermodynamics of phase transfer equilibria. I wrote him and said that I thought one of his papers was really great, but there was what I considered to be an error in it, because he was not aware of this work by Kamlet and Taft. That first contact initiated a long series of collaborations — Chuck and I have collaborated now for well over 20 years. There are even some papers with Eckert, Kamlet, Taft, and Mike Abraham and lots of people that came out of this whole business. So this was not a small project but turned out to be a multi-year, multi-decade project for me. It certainly is the most interesting area intellectually that I have been involved in and perhaps, in the long run, will be the most significant.

Were you hoping to find the results that you ended up with, that led to that greater understanding?Carr: At the outset, I don’t think we had a clear objective of “we are going to do this and do that and do that.” Rather we saw that there were relationships that we could apply more broadly and we started to apply them and get feedback that things looked like they were fitting, that they were working. So it’s not that there were any “aha” moments other than at the beginning when we said, “hey the solvatochromic stuff can be applied to phase equilibria.” It had been applied to chemical reactions, it had been applied to the rates of chemical reactions, it had been applied to the understanding of spectroscopic shifts, but it had not been applied to understanding chromatography and what governs the transfer between the two phases. So it had sort opened up a whole new business for us.

What was the most challenging research project you undertook? Which one was the most rewarding?Carr: Well, challenging to me means the most frustrating and difficult. One project that we put a tremendous amount of effort into was the development of an automated, high-precision, headspace GC system for measuring the thermodynamics of liquid-to-gas transfer. Several postdocs and several graduate students worked on this before we had any reproducible results at all, but it was a really valuable project. I recall a talk with Dan Martire at Georgetown where he said I had chained a bunch of grad students to a desk to do these really hard measurements. Actually once we got the special headspace apparatus up and running it was so automated that it was easy work but getting it working was a killer. 

We were able to then do studies that would have been impossible to do by other mechanisms and that supported our work in the solvatochromic area. So we were combining accurate thermodynamic measurements with spectroscopic measurements. In that project, it really took a long time to get the instrumentation working.

I would say that the challenging project was different than the most rewarding, which was certainly the development of the high stability stationary phases, which took place several years after the headspace GC studies. I would say that the work with high stability phases is the most rewarding because it really has branched out so much from where it began. It got me into trying to make new kinds of selective stationary phases, it got me into doing high-speed LC, and it got me into doing two-dimensional LC. So without that initial work on the zirconia phases, the last 10 years of my lab work probably would not have existed. It was amazing, the way everything got connected to everything else through the development of those stable phases. It is really interesting to look back on it and see how unpredictable where we are now was from where we began. It is a good reason for doing so-called fundamental work; you never know what is going to come out of it.  I fear there is a lot of nonsense about applied vs. fundamental work that various agencies are pushing. My work with solute-solvent interactions helped design new stationary phases. The high stability phases led to very fast, high temperature one-dimensional chromatography, which in turn led to fast 2D-LC.  I could never have predicted this.

Can you tell us a little about your research on chemically and thermally stable zirconia stationary phases?Carr: That actually is an interesting story. A lot of the research I do comes from reading the literature but this had nothing to do with reading the literature. For quite a few years, I was a general analytical consultant for 3M, and usually what happened was I would go out there periodically, on the order of once a month to meet with my good friend Don Hagen, one of the founders of the Minnesota Chromatography Forum and he would put me into a little room. People who had analytical problems would come by to talk with me for a while, and see what I could come up with. One day this fellow came in and he had this material made out of zirconia. I forget specifically what was interesting about this material at that time, but I asked him if there was some way he could make a spherical particle that was porous out of zirconia, and he assured me that it would basically be trivial to do that. I asked if he thought he could get me some particles that were about 5 or 10 µm in diameter and he said yeah, that shouldn’t be too difficult. I said that if he could get me some of those particles, I could probably coat them with a   stationary phase and we could see what we could do with those in terms of LC. I pointed out that one of the really significant limitations of silica phases back then was they weren’t very stable. They certainly dissolved in base and they weren’t really stable in acid either, so maybe there would be some way that we could coat the zirconia, and because of its inherent chemical stability, we could come up with a more stable stationary phase.

It turned out not to be very difficult to make the porous particles, but to get the bonding chemistry to be as stable as the particles were was a lot more challenging, but we worked that out over a couple of years with a bunch of really great graduate students at the University of Minnesota and a lot of collaboration with the ceramics technology group at 3M. You may know that 3M is very good at ceramic materials. They make, among other things, the tiles on the space shuttle that keep it from burning up on re-entry. They have a big dental products division, which uses a lot of their ceramics. They had a lot of ceramic technology, and they certainly were able to make zirconia spheres that were nicely porous. So, that’s how we got started in the zirconia area — it came out of consulting work with 3M. All of our patents on zirconia are joint with 3M except for perhaps one or two that were developed after ZirChrom got started. So that’s the story on the zirconia.

Your most recent work is in ultrafast and two-dimensional LC. How important do you think speed has become in separations recently?Carr: Actually, it was the zirconia that led to that work. One other thing that became evident after a while is that the zirconia could be used at low pH, it could be used at high pH, and it could also be used at relatively high temperatures and the particles didn’t dissolve in the mobile phase and the stationary phase didn’t get stripped off of the surface. So it occurred to me, based on some work that Csaba Horvath had done about 22– or 23 years ago, that one could do much faster chromatography by going to higher temperatures because that lowers the viscosity of the eluent and gives you the option of going faster. Also, increasing the temperature increases the diffusion coefficient. So you didn’t need to go to super high pressures with very small particles to go fast and the concomitant increase in the diffusion coefficient meant that you didn’t pay as much of a price in terms of decreased efficiency plate count by going to the higher velocity, because you simultaneously speeded up diffusion. That is what led to our early work in high-speed one-dimensional LC.

Then several years after, we learned a lot about how to do high-speed chromatography. We said, “Well, what about doing 2D- LC?” The second dimension really needs to be done superfast if you are going to control the timescale of the overall separation and that led us into doing two-dimensional LC. There is no question that over the past 8–10 years, there has been an enormous interest in speeding up LC. This has given rise to the high-pressure systems, with an increase in the pressure from 400 bar to 1000 or 1200 bar, to the decrease in particle size from 3.5 µm, which was the predominant particle size 6–7 years ago, to 1.8 µm, which is now a very common particle size. We also did development of the micropellicular or micro-core–shell type particles, which a number of companies are now producing to speed up LC.

Of course the reason for the speed is to reduce the cost of handling samples. You don’t want to tie an instrument up for half an hour if you can do the separation in 5 min, and there are lot more samples to be run predominately in the research phase of developing pharmaceuticals. Time is basically money, so the faster you can do things, the better. So speed has become enormously important in LC. I think it will remain as a very important subject. I’d say that over the past 5 years, certainly the improvement in speed has been the major thing that’s happened in LC. I shouldn’t say that bluntly — of course the combination of the liquid chromatograph and the mass spectrometer have had an enormous impact on analytical chemistry in general. So speed and the mass spectrometer combined have been the dominant facts of life in both GC and LC over the past decade.

Why did you choose an academic career path?Carr: I think it was my interest in research more than anything else. You get a taste for the freedom of following up on your own ideas in graduate school and that’s what pushed me in the direction of an academic career versus an industrial career. Of course my wife went along with that back in 1968 when I got my PhD. It was clear that academic salaries would be lower than industrial salaries, but it seemed like a life that we both wanted. So that had a lot to do with going down that path. It has been very rewarding in lot of different ways. Given my age, I have been asked a number of times if I would do the same thing again, and I have said many, many times that I can’t imagine having done anything different in terms of a career path. I have enjoyed it enormously. It has been a good life for us and our family. It has been very rewarding. I had a lot of fun and I‘ve learned a lot. I have met a lot of interesting people. I have made a lot of friends and I just don’t imagine I would have been happy in an industrial career path.

What kind of impact have your students had on your career?Carr: I think it is the biggest factor in any academic career. I read once some years back that an assistant professor wouldn’t be any better than his or her best postdoc or student. To a certain extent, that’s true. I have been blessed with a tremendous number of really excellent students. Quite a few of them have gone very far in their careers and have had a major role in analytical chemistry in the United States, both in industry and in their own academic careers. They have had a huge impact on the research that had been done frequently determining its direction and depth. I know in the long run, I have learned more from them than they have from me. So it is a huge factor in the success of anyone in academia: how good their students are and how dedicated their students are. It is the most important factor in my opinion in choosing the school that you go to. As a faculty member, it should have more of an impact on where you go than any other consideration. I just want to tell you a story. Quite some years ago now we were interviewing a young person for an assistant professorship and he and I were standing outside Kolthoff Hall. He asked me more or less “What did Kolthoff do any way?” The fact is that Kolthoff published almost 1000 papers before his death, and had written or edited nearly 50 books. He was known as the “Father of Analytical Chemistry” in the United States. He had numerous awards including a knighthood from the Netherlands.  This somewhat impertinent, but honest question convinced me that the only lasting contribution of an academician is his or her  students. Kolthoff’s geneology indicates well over 1000  PhDs .

Why did you start the Minnesota Chromatography Forum in 1978 and how has that forum affected your research?Carr: Well, back when I got here in 1977, I had come from the University of Georgia in Athens, which was a fairly isolated community. It was a great place to go to school, and as an analytical chemist, it was really an excellent place to be from. There was lot of local interest in analytical chemistry because of the presence of a major Environmental Protection Agency (EPA) laboratory. But mainly it was the tremendously talented and interactive group of faculty who were there along with their students that made it such a productive time for me.

When I got to the Twin Cities, it was really a major urban area with lots of industry, and I was aware of things like the Delaware Valley Chromatography Forum and the impact that had had on the East Coast, in the Pennsylvania and Delaware areas, and I wanted to see if we could get something of that nature going here. So I met with some of the leaders in chromatography in the area, both at the university and the local industry. Some of the key players early in the chromatography forum were a cadre of really excellent sales representatives from the major chromatography companies: like John Freeburg from Hewlett-Packard, now Agilent; Waters; and a local distributor, specifically Larry Bell. These sales reps knew all the players and helped me right away get in touch with them.

One of my former students, Larry Bowers, actually preceded me at the University of Minnesota. He had been an assistant professor in laboratory medicine and got here a year or two before I got here. Larry had already made some associations with the chromatography community, so it was fairly easy to get things going and we were pretty successful. It took a lot of effort in the first 5 years or so, but since then it has taken almost no effort on my part. There is a great group of people here who do chromatography for a living, like Peter Johnson at 3M, and they have put an enormous amount of effort in over the last 30+ years. We have a really strong chromatography community in the Twin Cities. A number of people have told me that it’s one of the strongest chromatography groups in the country.  There are typically 300 people at our Spring Symposium and it is not unusual to get 75 people to a quarterly meeting in January, which really says something about interest.

You asked how it has influenced my research. Well, it has in a number of ways. I have a huge network of experts I can call on. I know a lot of people and I know what they know about, and when I get into trouble, when I need some specific information, I can just pick up a phone and get an answer to a problem. Those problems run from things that come up in my lab where there is some expertise that I don’t have or I haven’t read the right paper or I have never worked with the material before, on up to higher level things like reviewing proposals for the National Science Foundation (NSF). A number of times I have been able to call on people who had experience directly in fields of proposals and have persuaded me that my ideas were wrong and that the proposal was a good idea, and vice versa when I was impressed with the proposal, they persuaded me why my idea was again wrong but in the other direction. So, it has had a big effect on my research over the years. It has been one of the most rewarding things I have ever been involved in. Again, it led to forming a lot of friendships, both locally and through people we have been able to invite to the chromatography forum meetings.

I have made good friends all over the country, including people like Steve Weber at Pittsburgh,  and Fred Cantwell at the University of Alberta who have all been speakers at the Minnesota Chromatography Forum. The late Les Ettre of Perkin-Elmer  was a very early guest at the chromatography forum and suggested that we start the Leroy Sheldon Palmer Award. Palmer was a professor of biochemistry and plant science and was the first American to do  chromatography after Tswett announced its development early in the last century. Lloyd Snyder, Barry Karger, and Csaba Horvath have all been here. John Dolan comes to see us virtually every spring because he teaches a terrific short course at the spring Chromatography Forum Symposium. One year I joked that he was one of the harbingers of spring. If Dolan has been in town, then we know that spring is going to happen some time soon in Minnesota. So it had a big effect on my career and my research. It was one of the best ideas I ever had.

What advice would you offer a scientist just starting out?Carr: These are the kind of questions you get asked when you are old. It’s too bad you aren’t asked them earlier because maybe they would ignite some fires in your brain. This makes me think about something I read about two years ago. There is a very famous computer scientist named Richard Hamming. He worked for many years at Bell Labs. He is very famous in computer science and he gave a speech summing up his career that struck me really hard. He had many pieces of advice, but the overall global advice he had for people starting out in science is “work on the big problems.” Find out what is the biggest problem in your field or the bigger problems in your field, and when the methods exist to solve those problems, work on those problems. That’s my big advice. I would add to that there is no substitute for being very familiar with the literature and it is essential to read broadly across chemistry and related fields. For an analytical chemist it is very important to stay up on electronics and instrumentation. Despite the great new tools for doing this, there just are not enough hours in the day

Number two, you’ve got to really love what you are doing. If you don’t, find something else that you love and do that instead. Science is, or can be, an extremely frustrating profession. A friend of mine who was an industrial psychologist said that chemists are like lab rats. What she meant by that is that they respond best to a “variable reward schedule”. What that means is if you give the rat some food every time it does the right thing, it won’t do the right thing that much. If you give the reward to the rat randomly, the rat will kill itself trying to do the right thing. Research is a lot like that. It’s very, very frustrating, but every now and then, the payoff is fantastic. You have to be able to deal with those frustrations. So, you had better be working on something that’s worthwhile and you had better enjoy working on it, because there are going to be a lot of rough moments when you are scratching you head wondering what you are doing.

That’s my advice: you had better like it, think about the big problems, and read the literature. And, let me add, have a lot of great students and a very supportive family.