Korf, A., Fouquet, T., Schmid, R., Hayen, H., Hagenhoff, S., 2020. Expanding the Kendrick mass plot toolbox in MZmine 2 to enable rapid polymer characterization in liquid chromatography-mass spectrometry data sets. Analytical Chemistry 92, 628-633.

https://doi.org/10.1021/acs.analchem.9b03863 Technological advances in mass spectrometry (MS) toward more accurate and faster data acquisition result in highly informative but also more complex data sets. Especially the hyphenation of liquid chromatography (LC) and MS yields large data files containing a high amount of compound specific information. Using electrospray- ionization for compounds such as polymers enables highly sensitive detection, yet results in very complex spectra, containing multiply charged ions and adducts. Recent years have seen the development of novel or updated data mining strategies to reduce the MS spectra complexity and to ultimately simplify the data analysis workflow. Among other techniques, the Kendrick mass defect analysis, which graphically highlights compounds containing a given repeating unit, has been revitalized with applications in multiple fields of study, such as lipids and polymers. Especially for the latter, various data mining concepts have been developed, which extend regular Kendrick mass defect analysis to multiply charged ion series. The aim of this work is to collect and subsequently implement these concepts in one of the most popular open-source MS data mining software, i.e., MZmine 2, to make them rapidly available for different MS based measurement techniques and various vendor formats, with a special focus on hyphenated techniques such as LC - MS. In combination with already existing data mining modules, an example data set was processed and simplified, enabling an ever faster evaluation and polymer characterization.

Koshel, B., Birdsall, R., Chen, W., 2020. Two-dimensional liquid chromatography coupled to mass spectrometry for impurity analysis of dye-conjugated oligonucleotides. Journal of Chromatography B 1137, 121906.

http://www.sciencedirect.com/science/article/pii/S1570023219313789 Two-dimensional liquid chromatography coupled to mass spectrometry (2D-LC/MS) has been successfully implemented for several biopharmaceutical applications, but applications for oligonucleotide analysis have been relatively unexplored. When analyzing oligonucleotides in one-dimension, selecting an ion-pairing agent often requires a balance between acceptable chromatographic and mass spectrometric performance. When oligonucleotides are modified or conjugated to include extremely hydrophobic groups, such as fluorophores, the separation mechanism is further complicated by the impact the fluorophore has on retention. Triethylamine (TEA) buffered in hexafluoroisopropanol (HFIP) is the most commonly used ion-pairing agent for analyses requiring mass spectrometry, but the elution order of dye-conjugated failed sequences relative to the main peak is not length-based compared to what would be predicted for unconjugated oligonucleotides having the same sequence. Hexylammonium acetate (HAA) offers more efficient ion-pairing for a length-based separation, but MS response is compromised due to ion suppression. In this study, 2D-LC/MS is used to show that dye- conjugated oligonucleotide failed sequences can be resolved from the parent oligonucleotide using a strong ion- pairing agent in the first-dimension and further identified using a weaker but MS compatible ion-pairing agent in the second-dimension, results that are not achievable in a one-dimensional analysis. More specifically, a heart-cut configuration using ion-pair reversed-phase chromatography in both the first and second dimension (IP-RP - IP-RP) is used to transfer the n-1 impurity from a length-based separation in the first-dimension to a second-dimension analysis for identity confirmation using a single quadrupole detector. Identical C column 18 chemistry is used in both the first and second dimension to exploit changes in selectivity that are due to mobile phase selection. The n-1 impurity from the two-dimensional analysis can be detected at low nanogram levels, comparable to results achieved in a one-dimensional dilution series, which approaches the limit of detection of the instrumentation. This work has future applicability to more complex impurity profiling using high- resolution instrumentation, where a more extensive set of impurities could not be evaluated using one- dimensional techniques.

Kou, Y., Zhang, L., Fan, D., Cheng, S., Li, D., Hodel, R.G.J., Zhang, Z., 2019. Evolutionary history of a relict Pseudotaxus chienii conifer, (Taxaceae), in south-east China during the late Neogene: old lineage, young populations. Annals of Botany 125, 105-117.