Orthogonal analytical screening for liquid chromatography–mass spectrometry method development and preparative scale-up

A simulation-guided approach to the selection of RPLC columns for platform small molecule separations

Simulations were conducted to evaluate the potential of several hundred reversed-phase columns to separate small molecules. By calculating the retention factor of compounds in randomly generated virtual mixtures via the HSM (hydrophobic subtraction model) and applying basic chromatography theory, the simulation can estimate the retention time and peak width of every virtual compound and calculate the resolution between every adjacent pair of compounds. A preferred column set based on the number of successful separations of randomly generated virtual mixtures was developed. The tandem-column liquid chromatography (TC-LC) approach can separate 53.2 % of the 16-compound samples using 20 tandem-column pairs, while a single-column approach can only separate 42.6 % of the 16-compound samples with 20 single columns. The preferred set of columns obtained from the simulation was almost the same as the empirical set of columns previously obtained. In screening applications, TC-LC can achieve a comparably successful separation factor (selectivity) with a smaller column inventory (nine 50-mm columns) compared to the larger inventory needed by single-column LC (twenty-one 100-mm columns).

Automated open-access liquid chromatography high resolution mass spectrometry to support drug discovery projects

The need of a continuous productivity increases in medicinal chemistry laboratories of the pharmaceutical industry motivated the development, over the years, of new software solutions to enable Open-Access in many analytical techniques such as NMR or LC, among others, to characterize and assess the purity of new molecules. These approaches have been widely spread in LC with low resolution MS systems, but similar automated platforms have been rather less explored with high resolution MS. In this work, an improved Automated Open-Access methodology on an UHPLC with DAD coupled to ESI and quadrupole time-of-flight MS system is described. Detailed reports from standard UHPLC-MS runs containing chromatograms and different spectra (MS with different fragmentation) are automatically sent to the chemists. High resolution MS data is typically achieved within ± 1 mDa mass accuracy regardless of sample concentration. Upon training, chemists log-in samples into the system by selecting appropriate methods, being able to interpret the results by themselves in 95% of the cases. The instrument is working unattended, except for a limited number of samples (5%) which require more complex experiments. To the best of our knowledge, this is the first time a completely automated Open-Access LC-HRMS approach has been implemented for medicinal chemists of a pharmaceutical industry.

Two-dimensional LC-MS fractioning and cross-matching of mass spectrometric data for rational identification of bioactive compounds in crude extracts

Bioprospecting aims at the identification of biological compounds with novel properties. Identification of such compounds in crude complex biological extracts is a comprehensive challenge. As a large number of extracts must be screened for successful identification of one potential promising lead, rational screening strategies must be developed. Here we report on a novel two stage rational LC-MS strategy of extracts already pre-screened and proven to contain bioactive compound(s). All extracts are initially fractionated using one and the same LC condition with parallel mass spectrometric detection. Fractions containing bioactive compound(s) are then subjected to a second fractional stage using two different chromatographic conditions. Mass detection is also included at this stage, and a cross-matching algorithm for comparison of processed mass chromatograms from the two dimensions was developed. The algorithm reports only masses present in bioactive fractions in both dimensions and enable therefore an efficient identification of potential masses that causes the bioactivity. This mass list can be used to search in natural compound database(s) for a rapid evaluation if the mass belongs to an already identified compound or if it is a potentially new one. This strategy enables thorough screening of several hundred crude extracts in one week on one single instrument.