Tomislav Bolanča, Šime Ukić, Mirjana Novak Stankov, Marko Rogošić
A priori knowledge of the retention time of a given analyte simplifies the determination of separation conditions therefore quantitative structure retention relationship (QSRR) modelling might be considered a reasonable selection. The first problem in QSRR modelling is to select the most informative descriptors from among a large number of mutually correlated descriptors, while the second one is to build the core model of isocratic and/or gradient elution retention. A lot of conventional methods have been elaborated that are mainly based on different types of regression and simple variable selection methodology (i.e. principal component analysis), showing rather questionable prediction ability. This work reveals recent results on development of artificial intelligence (AI) hybrid methodology implementing all three AI paradigms: artificial neural networks, genetic algorithms and fuzzy logic. The developed models were fully optimized and validated with external set of compounds showing significant improvement of generalization ability. Furthermore, recent demands for increasing the productivity using the gradients, in combination with ever growing complexity of analyzed samples, are introducing an additional request on the analytical system – beside being fairly separated, the peaks are required be as “smoothly” shaped as possible to ensure their precise quantification. In other words, the analysts are becoming interested in peak shapes and peak shape modelling as well. This work also discusses recent developments is peak shape modelling based on QSRR modelling. The developed models are based on generalized logistic distribution and hybrid AI systems. The external validation results show promising predictive ability, but still indicate that there is much to be done before QSRR based optimization strategy could be efficiently built into a useful commercial software.
1 Thermo Fisher Scientific GmbH, Im Steingrund 4-6, D-63303 Dreieich
HPLC applications based on capillary columns have seen an impressive progress in the last decade. As an analytical tool capillary HPLC offers the following advantages:
Easier hyphenation with mass spectrometers
Significant reduction of eluent consumption
Higher mass sensitivity in comparison to conventional HPLC
Ideal for applications with limited sample volume
Introduced in 2010, capillary ion chromatography with electrolytic eluent generation offers similar advantages, although the advantages listed above have a different significance for ion chromatography applications. The most significant advantage of ion chromatography in the capillary format is the marked reduction of eluent consumption, which allows continuous operation over a long period of time. In conventional water analysis, sample volume is usually not the issue, but users investigating corrosion phenomena or metabolic pathways are benefitting from much smaller sample volumes (<< 1 µL) used in capillary IC. The higher mass sensitivity in capillary IC in comparison to conventional IC has a huge impact on trace analysis, because the same concentration sensitivity can be achieved with much smaller sample volumes. Last but not least, capillary IC operating with very small flow rates improves the compatibility with modern mass spectrometers.
The expanded pressure tolerance of electrolytic eluent generation in capillary IC systems up to 34.5 MPa (5000 psi) allows the use of higher linear velocities of the mobile phase and thus much faster analysis times. On the other hand, it also facilitates high-resolution separations of complex samples through the use of packing materials with smaller particle sizes. In this presentation, examples of high-throughput and high-resolution separations of inorganic and organic ions from different application areas will be shown, utilizing resin-based as well as monolithic stationary phases.
Bogusław Buszewski, Viorica Railean-Plugaru, Paweł Pomastowski
Rapid detection and identification of microorganisms is a challenging and important aspect in many areas of our life, beginning with medicine, ending with industry. Unfortunately, classical methods of microorganisms’ identification are based on time-consuming and labor-intensive approaches. Screening techniques require rapid and cheap grouping of bacterial isolates, however modern bioanalytics demands comprehensive bacterial studies on molecular level. The new approach to the rapid identification of bacteria is to use the electromigration techniques, especially capillary zone electrophoresis (CZE). CZE is an important technique used in the analysis of microorganisms. However, the analysis of microbial complexes using this technology still encounters several problems – uncontrolled aggregation and/or adhesion to the capillary surface. One way to resolve this issue is the CZE analysis of microbial cell with surface charge modification by bivalent metal ions (e.g. Ca2+aq, Zn2+aq). Under the above conditions, bacterial cells create compact aggregates, and fewer high-intensity signals are observed in electropherograms. The capillary electrophoresis of microbial aggregates approach with UV and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) detection has been presented.
The aim of this study was to characterize the charge and surface of the bacteria in order to determine their role in adhesion and aggregation phenomena during the electrophoretic separation. The use of experimental techniques, including electrochemical and electrophoretic allowed the description of the relationship between the acid-base properties of pathogens and their behavior. In this studies was performed the identification of bacterial via spectrometric techniques.
This work was supported by the National Science Centre (NCN, Warsaw, Poland) projects No. 2013/08/W/NZ8/701 – Symfonia-1, Maestro-6 (2015-2017) and by European Social Found, Polish National Budget, Kuyavian-Pomeranian Voivodeship Budget (within Sectoral Operational Programme Human Resources) “Krok w przyszłość 2014-2015”
In this lecture the advantages of comprehensive two-dimensional liquid chromatography (LC×LC) will be discussed. LC×LC may provide high peak capacities in a much shorter time than conventional 1D-LC. Moreover, LC×LC provides unique selectivity. It is an attractive option for separating the very complex mixtures that are encountered in many fields (life science, food science, material science, etc.).
LC×LC is instrumentally straightforward, but the development and optimization of methods may be an obstacle. If method development in LC is a time-consuming task, then method development in LC×LC threatens to be a (time)2 consuming task. Some guidelines will be discussed to help understand LC×LC and to develop methods more efficiently. If we are able to “modulate” collected fractions from the first-dimension separation we may minimize the effects of the first-dimension eluent on the second-dimension separation and we may essentially optimize the two separations independently. This is demonstrated for the separation of peptides by a combination of ion-exchange chromatography and reversed-phase LC. After the first-dimension separation the analytes are focussed on a trapping column. This allows the second-dimension column to me much narrower than the first-dimension column and it provides an increase in sensitivity by several orders of magnitude. In addition, salt is removed from the eluent, which promotes the MS compatibility of the system.
Finally, directions for further development of multi-dimensional LC methods will be discussed.