Dr. Bertrand Rochat is convinced of quantitative Orbitrap HRAM mass spectrometer for clinical research and targeted and non-targeted metabolomics. He has been on the front line of the absolute quantification using Thermo ScientificTM OrbitrapTM high-resolution mass spectrometers (HRAM). His last review, published in Trends in Analytical Chemistry, advocates that HRAM can be used from absolute and targeted quantification to untargeted metabolomics. Let’s ask him about this opinion.
What type of work are you involved in and what is your expertise?
For the last 15 years, I have been involved in MS analysis in pharma or universities. First with GC-MS and LC-triple-quadrupole MS (QQQ-MS), then with ion traps. And during the last four years, essentially with LC-high-resolution (HR) Orbitrap MS. I have focused mainly on quantitative assays of small molecules. Over the past few years, I have worked in metabolomics. I have performed analyses with various sample types such as tissues, cell media and human blood.
How are you confident that Orbitrap technology can be as quantitative as triple-quadrupole MS?
For the last four years, I have questioned myself to know whether HRAM, and especially the (Q) Exactive Orbitrap instruments, could perform as well as QQQ-MS for absolute quantifications (the main work in clinical research labs). Like other colleagues in various fields (food safety, forensic, toxicology, water analysis), I have been amazed to see the results obtained with these Orbitrap MS instruments whereas performing HR-full scan acquisitions. I have tested many compounds in many matrices, and consulted various HRAM users. Continuously, I have tried to find the Achilles’ heel in Orbitrap HRAM analyses, but the ones I found were insignificant or related to the ion-source (independent of MS technology). My own experience as well as accumulating published data shows that Orbitrap HRAM is comparable to QQQ-MS for detection sensitivity, selectivity and robust quantifications. Overall, Orbitrap HRAM is not better for quantification but offers many additional key advantages related to the HRAM capability. As mentioned by some authors, it makes less and less sense to proceed further into the development of QQQ-MS. I truly believe that once you work with HRAM, like the Thermo ScientificTM Q ExactiveTM mass spectrometer, it is really hard to come back to low resolution MS.
Why do you think that it is better to have two or three Orbitrap MS instruments rather than a mix of Orbitrap MS and triple-quadrupole MS?
When you have different technologies you can benefit from their individual advantages. This is true with Orbitrap HRAM and QQQ-MS, but also true with CE-MS, SFC-MS or GC-MS. In a perfect world, you would have all of them! But the question is rather if you can afford various technologies in terms of costs, production efficiency, etc. If yes, buy various analytical platforms and form various specialists in your lab. If your budget is limited, you have to find the best compromise. In this frequent constraint, I think that, usually the best solution is to have a few Orbitrap HRAM because you simplify your quantitative and qualitative workflow(s), save time and eventually facilitate projects to be realized. You can also consider dedicating one Orbitrap HRAM for low LC flow-rate (nano or capillary columns) or for MALDI, whereas the other Orbitrap HRAM will work with a more standard LC set-up. When looking at quantitative or qualitative Q Exactive MS performance, I am convinced that a QQQ-MS is usually not needed except for analyses which require the ultimate limits of detections. In such cases, a test sample could be sent to a demo lab which will help to make the right decision.
Eventually, if you have the budget for three or more instruments, I would possibly consider buying a CE-MS, GC-MS or SFC-MS on the top of the Orbitrap HRAM rather than only LC-MS instruments.
How can Orbitrap HRAM technology change the lab organization?
The use of one technology allows more efficient workflows. When the LC-HRAM acquisition records virtually all ions in your samples, there are no strict barriers between quantitative and qualitative workflows. Your cursor moves from one to the other according to your needs. With HRAM like the Thermo ScientificTM Q ExactiveTM Focus I have worked on, you can perform from targeted quantifications to untargeted metabolomics. This is what has been performed in my lab with the exact same platform: absolute quantification of hepcidin, 25-hydroxyvitamin D3, anticancer agents, etc., quantitative/qualitative analysis with drug quantification, drug metabolite identification and profiling, global screening (HR-full scan) of pollutants and drugs in toxicological samples as well as discovery of cancer biomarkers (untargeted metabolomics).
Like what you are learning?
Does it mean that one technology fits all?
It sounds almost impossible… But I believe so. In the past few years, I have tried to convince people to change their minds, even in labs where quantification is the main duty. My hope would be that I could convince a lab head to purchase an Orbitrap HRAM rather than a QQQ-MS and that his PhD candidate or lab tech working on this new Orbitrap HRAM would discover new things that would have been so much more difficult or even impossible to find with a QQQ-MS.
How do you see the future of LC-MS analysis in clinical labs?
When you look at the data obtained with an Orbitrap high resolution full scan acquisition, you rapidly understand that you have a global picture of what is in your sample. I asked myself: Why can’t we get some information from these thousands of detected molecules? I think that we have to identify and use them! We should build biological passports like the WADA (World Anti-Doping Agency) is already doing for world athletes. Of course, targeted and absolute determinations will always be key analyses in clinical labs. However, I think that metabolite phenotyping should soon become a screening analysis allowing a more global person’s evaluation: simultaneous determinations of pollutants, drugs, specific metabolite ratios, etc. It could help medical doctors in their anamnesis before complementary and absolute quantifications would be requested. Taking global pictures of metabolites is the work for Orbitrap HRAM instruments. In addition, this is what we need to study the gene-environment relationship; our true biological identity.
How would you convince young scientists to consider mass spectrometry for their career?
For the last 10 years, I have seen so much evolution in the MS field that it is a bit scary! But in the meantime, it means that the field is very diverse and growing amazingly. There are many different job opportunities to find his or her way. There are also many new territories to explore in biomedical sciences where LC-MS expertise is crucial. This will also be true in the future.
Bertrand, thank you for sharing your Orbitrap mass analyzer experience with me and we look forward learning more about your work at upcoming conferences and publications.
- Rochat B. From targeted quantification to untargeted metabolomics: Why LC-high resolution-MS will become a key instrument in clinical labs. Trends Analyt Chem. Epub ahead of print.
- Grund B, Marvin L, Rochat B. Quantitative performance of a quadrupole-orbitrap-MS in targeted LC-MS determinations of small molecules. J Pharm Biomed Anal. 2016; 124:48-56.
- Rochat B. Is there a future for metabotyping in clinical laboratories? 2015;7:5-8.
- Dahmane E, Boccard J, Csajka C, Rudaz S, Décosterd L, Genin E, Duretz B, Bromirski M, , Leyvraz S, Zaman K, Testa B and Rochat B. Quantitative monitoring of tamoxifen in human plasma extended to 40 metabolites using liquid-chromatography high-resolution mass spectrometry: new investigation capabilities for clinical pharmacology. Anal Bioanal Chem. 2014;406:2627-40.
- Rochat B, Kottelat E and Justin McMullen J. The future key role of LC-high-resolution-MS analyses in clinical laboratories: a focus on quantification. Bioanalysis. 2012; 4:2939-58.
Henry H, Sobhi HR, Scheibner O, Bromirski M, Nimkar SB, Rochat B. Comparison between a high-resolution single-stage Orbitrap and a triple quadrupole mass spectrometer for quantitative analyses of drugs. Rapid Commun Mass Spectrom. 2012;26:499-509.