Tag: Bob Pirok

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Funding

VENI Grant for Bob Pirok

UPSTAIRS

CAST member Bob Pirok of the Van ‘t Hoff Institute for Molecular Sciences at the University of Amsterdam was awarded VENI grant in the TTW domain of the Dutch Research Council (NWO). With his grant, Pirok aims to improve the applicability of modern separation technology to enhance its relevance to society.

The Veni grants are part of the Talent Scheme of NWO and are aimed at excellent researchers who have recently obtained their doctorate. The grants of up to € 280,000 confirm the quality and innovative nature of their research and help to further establish themselves in their field over a three-year period.

The UPSTAIRS project aims to develop technology to reduce the resources required to use powerful separation systems.

The UPSTAIRS project aims to resolve this problem by developing algorithms that allow the automated development of methods using state-of-the-art instrumentation for the complex samples of this era. In UPSTAIRS, innovative peak-tracking algorithms will be developed that yield the capability of automated workflows to interpret the data. By utilizing these data for the construction of fundamental retention models for each analyte in the mixture, the algorithm can simulate numerous potential methods, regardless of the sample complexity. Novel equations will be designed for combinations of chemical method parameters. Candidate methods will be selected using novel chromatographic response functions based on Bayesian statistics and submitted for (automatic) validation by the instrument.

By Unleashing the Potential of Separation Technology for Achieving Innovation in Research and Society, UPSTAIRS will solve pressing problems and allow us to better understand materials, art, pharmaceuticals, environment, and other matrices.

Bob Pirok

Ultimately, the algorithms will enable a control computer to directly interact with the analytical instrumentation and interpret the resulting methods to then propose and evaluate a better method. According to Pirok, ‘a computer can do all this much more effectively than a human being, so that it takes far less time to develop an optimal method. This will bring the full potential of modern separation technology to society.’

Knowledge utilization is a strong focus of this project and will be achieved through a diverse and strong user committee and a demonstration of this workflow on a highly complex sample in the final work package. Moreover, a protocol will be published along with the developed open-access toolbox to allow analysts to use this work.

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Publications

Parallel gradients as alternative to shifted gradients in 2D-LC

In pursuit of full usage of the two-dimensional separation space as prescribed by Giddings [1], the LC×LC chromatographic community is continuously scouting for new methods that yield fully orthogonal separations. With the rich and diverse LC toolkit of available retention mechanisms, chromatographers mainly focus on improving the compatibility of orthogonal – yet incompatible – separation methods. This has spurred the development of active-modulation techniques such as stationary-phase-assisted modulation [2] and active-solvent modulation (ASM) [3]. Ultimately, this angle of innovation is mainly driven by the selection of stationary -and mobile phases, as well as their underlying retention mechanisms.

Rather than fine-tuning selectivity, another branch focuses on tweaking retention factors. For LC×LC separations, this has led to the introduction of shifted gradients. Here, the second-dimension gradient is altered and adapted as a function of the first-dimension gradient program [4]. While extremely effective, the optimization of shifted-gradient assemblies introduces additional complexity to the already more-complex method development process for comprehensive 2D-LC.

The situation of LC×LC contrasts heavily with that of GC×GC. For GC×GC, orthogonal separations are extremely difficult if not impossible due to analyte volatility. As a consequence, wrap-around effects are frequently generated, yet this is rather seen as advantage than disadvantage.

Prof. Tadeusz Gorecki (University of Waterloo, Canada) thus set to investigate what would happen if the same approach would be applied in LC×LC [5]. The project was an international collaboration with Alshymaa Aly (Minia University, Egypt, and University of Waterloo, Canada), Prof. Andre de Villiers and Magriet Muller from Stellenbosch University in South Africa, and Bob Pirok from the CAST team at the University of Amsterdam in the Netherlands.

RPLC×RPLC separations were simulated based on experimental data using the MOREPEAKS framework (formerly PIOTR [6]). Predicted separations using shifted gradients and parallel gradients were compared. The results suggested that parallel gradients indeed may advantageous. To verify this assessment, optimized experimental methods were executed and the resulting separations compared.

Supported by both experimental data and theoretical simulations, the authors concluded that non-orthogonal separation mechanisms could still yield good separation methods in LC×LC.

References

[1] Two-dimensional separations: concept and promise. J.C. Giddings, Anal. Chem. 1984, 56(12), 1258A–1270A, DOI: 10.1021/ac00276a003

[2] Recent Developments in Two-Dimensional Liquid Chromatography: Fundamental Improvements for Practical Applications. B.W.J. Pirok, D.R. Stoll and P.J. Schoenmakers, Anal. Chem., 2019, 91(1), 240-263, DOI: 10.1021/acs.analchem.8b04841

[3] Active Solvent Modulation: A Valve-Based Approach To Improve Separation Compatibility in Two-Dimensional Liquid Chromatography. D.R. Stoll, K. Shoykhet, P. Petersson, and S. Buckenmaier, Anal. Chem. 2017, 89(17), 9260–9267, DOI: 10.1021/acs.analchem.7b02046

[4] Optimizing separations in online comprehensive two-dimensional liquid chromatography
B.W.J. Pirok, A.F.G. Gargano and P.J. Schoenmakers, J. Sep. Sci., 2018, 41(1), 68–98, DOI: 10.1002/jssc.201700863

[5] Parallel gradients in comprehensive multidimensional liquid chromatography enhance utilization of the separation space and the degree of orthogonality when the separation mechanisms are correlated. A.A. Aly, M. Muller, A. de Villiers, B.W.J. Pirok, T. Górecki, J. Chromatogr. A, 1628, 2020, 461452, DOI: 10.1016/j.chroma.2020.461452

[6] Program for the interpretive optimization of two-dimensional resolution. B.W.J. Pirok, S. Pous-Torres, C. Ortiz-Bolsico, G. Vivó-Truyols and P.J. Schoenmakers, J. Chromatogr. A, 2016, 1450, 29–37, DOI: 10.1016/j.chroma.2016.04.061

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Publications

Challenges in Obtaining Information from 1D- and 2D-LC

Earlier this June, CAST-member Bob Pirok (Van ‘t Hoff Institute for Molecular Sciences) and Johan Westerhuis (Swammerdam Institute for Life Sciences) published their vision on current challenges in data analysis in one-dimensional (1D) and two-dimensional (2D) chromatography [1].

In their article, the authors discuss the caveats of common data-analysis strategies that are typically employed in processing data obtained from 1D and 2D chromatography. The authors discuss the importance of data pre-processing and the associated challenges. Highlighting one of the conclusions of an earlier review [2], the authors again emphasized that no current studies provide an objective numerical comparison of background correction metrics.

image_2020-11-05_085441

Figure 1. Comparison of commonly applied methods to assess the area of a peak. Reprinted from [1] with permission.

Pirok and Westerhuis furthermore explained the difficulties with common curve resolution methods such as matched filtering (a.k.a. curve-fitting) and derivated-based approaches. While multi-dimensional separations increase the likelihood of resolution, the authors noted that this by no means eases the job of obtaining information of these datasets. The authors also discussed some key opportunities currently in the works by scientists around the globe. You can read the article freely here.

Figure 2. The availability of an additional dimension of data through the detector (in these case DAD) certainly helps to distinguish the peaks, but does not aid in easing extracting the information of the data.

References

[1] Challenges in Obtaining Relevant Information from One- and Two-Dimensional LC Experiments
B.W.J. Pirok & J.A. Westerhuis, LC-GC North America, 6(38), 2020, 8-14 [LINK]

[2] Recent applications of chemometrics in one- and two-dimensional chromatography
T.S. Bos, W.C. Knol, S.R.A. Molenaar, L.E. Niezen, P.J. Schoenmakers, G.W. Somsen, B.W.J. Pirok, J. Sep. Sci. 43(9-10), 2020, 1678-1727, DOI: 10.1002/jssc.202000011