The wide chemical diversity and complex matrices inherent to metabolomics still pose a challenge to current analytical approaches for metabolite screening. Although dedicated front-end separation techniques combined with high-resolution mass spectrometry set the benchmark from an analytical point of view, the increasing number of samples and sample complexity demand for a compromise in terms of selectivity, sensitivity and high-throughput analyses.
Collision cross section (CCS) measurements resulting from ion mobility–mass spectrometry (IM-MS) experiments provide a promising orthogonal dimension of structural information in MS-based analytical separations. As with any molecular identifier, interlaboratory standardization must precede broad range integration into analytical workflows. In this study, we present a reference drift tube ion mobility mass spectrometer (DTIM-MS) where improvements on the measurement accuracy of experimental parameters influencing IM separations provide standardized drift tube, nitrogen CCS values (DTCCSN2) for over 120 unique ion species with the lowest measurement uncertainty to date. The reproducibility of these DTCCSN2 values are evaluated across three additional laboratories on a commercially available DTIM-MS instrument. The traditional stepped field CCS method performs with a relative standard deviation (RSD) of 0.29% for all ion species across the three additional laboratories. The calibrated single field CCS method, which is compatible with a wide range of chromatographic inlet systems, performs with an average, absolute bias of 0.54% to the standardized stepped field DTCCSN2 values on the reference system. The low RSD and biases observed in this interlaboratory study illustrate the potential of DTIM-MS for providing a molecular identifier for a broad range of discovery based analyses.
Itaconic acid is a biobased organic acid with clear potential to become a relevant renewable building-block chemical. However, to compete with petrochemical processes, the production cost of biobased processes, particularly the downstream processing contribution, needs to be reduced. In this work, composite membranes comprising ultrathin films of crosslinked poly[(o-cresyl glycidyl ether)-co-formaldehyde] and branched polyethyleneimine on mixed cellulose ester supports were developed for application in the primary recovery of itaconic acid from fermentation broths. In contrast to commercial and literature-reported counterparts, these membranes exhibit low itaconic acid rejections over a wide range of pH, ionic strength, organic acid concentration and operating pressure. Moreover, these membranes can efficiently recover itaconic acid from clarified fermentation broth as well as unclarified fermentation broth of Pichia pastoris cultivations, with average rejections below 15% recorded over 8 hours of operation. Lastly, a comparison between these membranes and literature-reported strategies for primary recovery of biobased organic acids highlighted that, with a recovery of 99%, the membranes developed in this work are among the best performing recovery strategies reported to date. The efficient recovery of itaconic acid from unclarified fermentation broth opens the possibility to perform clarification and primary recovery simultaneously, thus simplifying the downstream processing of biobased itaconic acid considerably
Rugged analytical methods for the screening and identity confirmation of anthocyanins require a dedicated sample preparation, chromatographic setup, and the reliable generation of multiple identification points to confirm identity against the wide range of phenolic compounds typically present in food, beverage, and plant material samples. To this end, combinations of spectroscopic and mass spectrometric detection are frequently employed for this application to provide higher confidence in the absence of authentic standards. In the present work, low-field drift tube ion mobility (DTIM) separation is evaluated for this task using a LC-DAD-DTIM-QTOFMS method. DTIM-MS allows accurate determination of collision cross sections (DT CCS) for all analysed compounds as well as a precise alignment tool for reconciling fragment and precursor ions in data independent acquisition mode. The presented approach thereby allows for an anthocyanin screening method taking true advantage of all dimensions of the analytical platform: relative retention (RPLC), UV/VIS absorption spectrum, accurate mass, DT CCSN2 , and confirmed high-resolution fragment ions. From the analysis of authentic standards and several berry samples primarily from the Vaccinium genus, Level 1 confirmation data for six anthocyanins from the cyanidin family, and Level 2 confirmation for a further 29 anthocyanins confirmed in berry samples is provided. The method and accompanying dataset provided as part of this work provides a means to develop anthocyanin screening methods using the ion mobility dimension as an additional alignment and filtering parameter in data independent analysis acquisition across any LC-IM-MS platform.
The major benefits of integrating ion mobility (IM) into LC-MS methods for small molecules are the additional separation dimension and especially the use of IM-derived collision cross sections (CCS) as an additional ion-specific identification parameter. Several large CCS databases are now available, but outliers in experimental interplatform IM-MS comparisons are identified as a critical issue for routine use of CCS databases for identity confirmation. We postulate that different routine external calibration strategies applied for traveling wave (TWIM-MS) in comparison to drift tube (DTIM-MS) and trapped ion mobility (TIM-MS) instruments is a critical factor affecting interplatform comparability. In this study, different external calibration approaches for IM-MS were experimentally evaluated for 87 steroids, for which TWCCSN2, DTCCSN2 and TIMCCSN2 are available. New reference CCSN2 values for commercially available and class-specific calibrant sets were established using DTIM-MS and the benefit of using consolidated reference values on comparability of CCSN2 values assessed. Furthermore, use of a new internal correction strategy based on stable isotope labelled (SIL) internal standards was shown to have potential for reducing systematic error in routine methods. After reducing bias for CCSN2 between different platforms using new reference values (95% of TWCCSN2 values fell within 1.29% of DTCCSN2 and 1.12% of TIMCCSN2 values, respectively), remaining outliers could be confidently classified and further studied using DFT calculations and CCSN2 predictions. Despite large uncertainties for in silico CCSN2 predictions, discrepancies in observed CCSN2 values across different IM-MS platforms as well as non-uniform arrival time distributions could be partly rationalized.
Steroids play key roles in various biological processes and are characterized by many isomeric variants which makes their unambiguous identification challenging. Ion mobility-mass spectrometry (IM-MS) has been proposed as a suitable platform for this application, particularly using collision cross section (CCS) databases obtained from differ-ent commercial IM-MS instruments. CCS is foreseen as an ideal additional identification parameter for steroids as long-term repeatability and interlaboratory reproducibility of this measurand are excellent and matrix effects are negligible. While excellent results were demonstrated for individual IM-MS technologies, a systematic comparison of CCS derived from all major commercial IM-MS technologies has not been performed. To address this gap, a comprehensive interlabor-atory comparison of 142 CCS values derived from drift tube (DTIM-MS), traveling wave (TWIM-MS) and trapped ion mo-bility (TIM-MS) platforms using a set of 87 steroids was undertaken. Besides delivering three instrument-specific CCS databases, systematic comparisons revealed excellent interlaboratory performance for 95% of the ions with CCS biases within ±1% for TIM-MS and within ±2% for TWIM-MS with respect to DTIM-MS values. However, a small fraction of ions (<1.5 %) showed larger biases of up to 7% indicating that differences in the ion conformation sampled on different in-strument types need to be further investigated. Systematic differences between CCS derived from different IM-MS analyz-ers and implications on the applicability for non-targeted analysis are critically discussed. To the best of our knowledge this is the most comprehensive interlaboratory study comparing CCS from three different IM-MS technologies for analysis of steroids and small molecules in general.
A combination of ion mobility-mass spectrometry (IM-MS) measurements and computational methods were used to study structural and physicochemical properties of a range of quinoline-based drugs: amodiaquine (AQ), cinchonine (CIN), chloroquine (CQ), mefloquine (MQ), pamaquine (PQ), primaquine (PR), quinacrine (QR), quinine (QN), and sitamaquine (SQ). In experimental studies, ionization of these compounds using atmospheric pressure chemical ionization (APCI) yields monoprotonated species in the gas phase while electrospray ionization (ESI) also produces diprotonated forms of AQ, CQ, and QR and also for PQ, SQ, and QN in the presence of formic acid as an additive. Comparison of the trajectory-method-calculated and experimental IM-derived collisional cross sections (CCS
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