Plate-height model of ion mobility-mass spectrometry: Part 2-Peak-to-peak resolution and peak capacity.

In a previous work, we explored zone broadening and the achievable plate numbers in linear drift tube ion mobility-mass spectrometry through developing a plate-height model [1]. On the basis of these findings, the present theoretical study extends the model by exploring peak-to-peak resolution and peak capacity in ion mobility separations. The first part provides a critical overview of chromatography-influenced resolution equations, including refinement of existing formulae.

Uncertainty Estimations for Collision Cross Section Determination via Uniform Field Drift Tube-Ion Mobility-Mass Spectrometry.

Uniform field drift tube ion mobility-mass spectrometry (DTIM-MS) has emerged as a valuable tool for a range of analytical applications. In focus here are standardized collisional cross section values from DTIM-MS (CCS) as a candidate identification point for various analytical workflows. Of critical importance in establishing this parameter as a valid identification point is a rugged estimation of uncertainties according to the procedures used for their derivation.

Plate-height model of ion mobility-mass spectrometry.

In the past decade, ion mobility spectrometry (IMS) in combination with mass spectrometry (IM-MS) became a widely employed technique for the separation and structural characterization of ionic species in the gas phase. Similarly to chromatography, where studies on the mechanism of band broadening and adequate plate-height equations have been aiding method development and promoting advancements in column technology, a suitable resolving power theory of drift tube ion mobility-mass spectrometry (DTIM-MS) is essential to stimulate further progress in this emerging field of separation science. In the present study, therefore, we explore dispersion processes in detail and present a plate-height model of ion mobility-mass spectrometry.

Drift-Tube Ion Mobility-Mass Spectrometry for Nontargeted 'Omics.

This chapter describes the developments in drift-tube ion mobility-mass spectrometry (DTIM-MS) that have driven application development in 'omics analyses. Harnessing the additional, orthogonal separation that DTIM provides increased confidence in compound identifications as the mass spectral complexity can be reduced and mobility-derived parameters (most prominently the collision cross section, CCS) used to support identity confirmation goals for a variety of 'omics application areas. Presented within this contribution is a methodology for improving the transmission and maintaining accurate determination of drift time-derived CCS (CCS) for low molecular weight compounds for a typical nontargeted 'omics (metabolomics) workflow using liquid chromatography in combination with DTIM-MS.

Fundamental study of ion trapping and multiplexing using drift tube-ion mobility time-of-flight mass spectrometry for non-targeted metabolomics.

This study of ion accumulation/release behavior relevant to ion mobility-mass spectrometry (IM-MS) as employed for non-targeted metabolomics involves insight from theoretical studies, and controlled reference experiments involving measurement of low and high molecular mass metabolites in varying concentrations within a complex matrix (yeast extracts). Instrumental settings influencing ion trapping (accumulation time) and release conditions in standard and multiplexed operation have been examined, and translation of these insights to liquid chromatography (LC) in combination with drift tube IM-MS measurements has been made. The focus of the application is non-targeted metabolomics using carefully selected samples to allow quantitative interpretations to be made.

Rapid screening methods for yeast sub-metabolome analysis with a high-resolution ion mobility quadrupole time-of-flight mass spectrometer.

Rationale: 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.

Methods: Prior to low-field drift tube ion mobility (IM) separation and quadrupole time-of-flight mass spectrometry (QTOFMS) detection, rapid ultrahigh-performance liquid chromatography separation was used for analysis of different concentration levels of dansylated metabolites present in a yeast cell extract.

Fingerprinting of traditionally produced red wines using liquid chromatography combined with drift tube ion mobility-mass spectrometry.

The characterization of wine via MS-based metabolic fingerprinting techniques remains a challenging undertaking due to the large number of phenolic compounds that cannot be confidently annotated and identified within analytical workflows. The combination of high performance liquid chromatography with low-field drift tube ion mobility time-of-flight mass spectrometry (HPLC × IMS-TOFMS) offers potential for the confident characterization and fingerprinting of wine using a metabolomics-type workflow. In particular, the use of collision cross section values from low-field drift tube IMS using nitrogen as drift gas (CCS) in addition to retention time and a high resolution mass spectrum for putative compounds allows rugged statistical assessment and identity confirmation using CCS libraries (<0.

The potential of ion mobility-mass spectrometry for non-targeted metabolomics.

Non-targeted analysis of metabolites in hypothesis-generating workflows has proven its potential to answer essential questions that arise when dealing with complex biological systems. Nevertheless, tracking changes in perturbed systems via accurate quantification and the identification process itself represent the most critical challenges in these workflows. Recent advances in ion mobility-mass spectrometry have enabled this technique to increase the confidence of metabolite annotation by introducing a complementary conditional molecular descriptor, that is collision cross section.

An Interlaboratory Evaluation of Drift Tube Ion Mobility-Mass Spectrometry Collision Cross Section Measurements.

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 (CCS) for over 120 unique ion species with the lowest measurement uncertainty to date.

Comparison of fully wettable RPLC stationary phases for LC-MS-based cellular metabolomics.

Reversed-phase LC combined with high-resolution mass spectrometry (HRMS) is one of the most popular methods for cellular metabolomics studies. Due to the difficulties in analyzing a wide range of polarities encountered in the metabolome, 100%-wettable reversed-phase materials are frequently used to maximize metabolome coverage within a single analysis. Packed with silica-based sub-3 μm diameter particles, these columns allow high separation efficiency and offer a reasonable compromise for metabolome coverage within a single analysis.

Integrating ion mobility spectrometry into mass spectrometry-based exposome measurements: what can it add and how far can it go?

Measuring the exposome remains a challenge due to the range and number of anthropogenic molecules that are encountered in our daily lives, as well as the complex systemic responses to these exposures. One option for improving the coverage, dynamic range and throughput of measurements is to incorporate ion mobility spectrometry (IMS) into current MS-based analytical methods. The implementation of IMS in exposomics studies will lead to more frequent observations of previously undetected chemicals and metabolites.

Review of sample preparation strategies for MS-based metabolomic studies in industrial biotechnology.

Fermentation and cell culture biotechnology in the form of so-called "cell factories" now play an increasingly significant role in production of both large (e.g. proteins, biopharmaceuticals) and small organic molecules for a wide variety of applications.

Theoretical evaluation of peak capacity improvements by use of liquid chromatography combined with drift tube ion mobility-mass spectrometry.

In the domain of liquid phase separations, the quality of separation obtainable is most readily gauged by consideration of classical chromatographic peak capacity theory. Column-based multidimensional strategies for liquid chromatography remain the most attractive and practical route for increasing the number of spatially resolved components in order to reduce stress on necessary mass spectrometric detection. However, the stress placed on a chromatographic separation step as a second dimension in a comprehensive online methodology (i.

Using sheath-liquid reagents for capillary electrophoresis-mass spectrometry: application to the analysis of phenolic plant extracts.

The combination of CE and MS is now a widely used tool that can provide a combination of high resolution separations with detailed structural information. Recently, we highlighted the benefits of an approach to add further functionality to this well-established hyphenated technique, namely the possibility to perform chemical reactions within the sheath-liquid of the CE-MS interface . Apart from using hydrogen/deuterium exchange for online determination of numbers of exchangeable protons, the addition of DPPH• (2,2-diphenyl-1-picrylhydrazyl) to the sheath-liquid can be used as a fast screening tool for studying antioxidant characteristics of individual components.

Critical differences in chromatographic properties of silica- and polymer-based monoliths.

Chromatographic analytical columns containing porous monolithic beds based on cross-linked polymers and derivatized silica have now been commercially available for several years and, despite some apparent conceptual similarities, are marketed and utilized for quite different chromatographic applications. While this distinction is well-accepted by users, the fundamental differences in chromatographic behavior of these materials that lead to this clear distinction in their primary application areas have not yet been systematically studied. To this end, the present experimental study investigates differences in the apparent chromatographic characteristics when using small molecules with commercially available monolithic reversed-phase analytical columns based on poly(styrene-co-divinyl benzene) and C18-derivatized silica.

Addition of reagents to the sheath liquid: a novel concept in capillary electrophoresis-mass spectrometry.

Conventional coupling of capillary electrophoresis with electrospray ionisation mass spectrometry typically relies on the use of a triaxial sheath-flow liquid interface to facilitate electrical contact and provide a stable electrospray. In this type of analysis, the use of additives in the sheath liquid itself can also be used to improve ionisation of analytes and even facilitate reactions between separation and detection steps (which we broadly term "sheath-flow chemistry"). In the present work, this concept is demonstrated using two types of sheath-flow reactions for CE coupled with quadrupole time-of-flight (Q-TOF) MS detection.

Assessing the nanoscale structure and mechanical properties of polymer monoliths used for chromatography.

Concerning polymeric monolithic materials utilized in separation science, the structural and mechanical characteristics from the nanoscopic to the macroscopic scale remain of great interest. Suitable analytical tools are urgently required to understand the polymer monolith's constituent structure, particularly in the case of nanoscale polymer properties that tend to develop gel porosity in contact with a mobile phase ultimately affecting the chromatographic performance. Herein described are our first findings from a characterization of commercially available analytical polymer monoliths based on styrene/divinylbenzene and methacrylate chemistries utilizing confocal Raman spectroscopy imaging and atomic force microscopy (AFM).

Identification of polyimide materials using quantitative CE with UV and QTOF-MS detection.

Polyimides (PIs) are a group of widely used synthetic materials that service a variety of different purposes including microelectronics, insulating films and aerospace applications. Depending on the requirements (defined by the particular final product), the actual composition of PIs may show substantial chemical variation. To study this variation in chemical structure, CE-MS can be employed for the determination of PI composition following chemical degradation of the polymer sample.

Impact of mobile phase composition on the performance of porous polymeric monoliths in the elution of small molecules.

The influence of mobile phase solvent composition and consequently retention factor on the chromatographic performance for a set of small molecules was studied using a commercially available poly(styrene-co-divinyl benzene) analytical scale porous polymeric monolithic column as an example. Chromatographic elution performance was studied across retention factors from close to 0 up to 100 realized for a set of structurally similar small molecules in a binary reversed-phase solvent environment of acetonitrile and water. By altering the mobile phase composition from volume fractions of acetonitrile of just 10% (v/v) to only acetonitrile it was systematically shown that gel porosity of the monolithic column plays a dominant role in modulating mass transport and the associated chromatographic efficiency in a consistent manner.

Recent developments and future possibilities for polymer monoliths in separation science.

Within recent years there has been an increase in research focused on the design and application of organic polymer monoliths in all areas of separation science. This is largely driven by the theoretical and practical benefits that these materials should be able to provide, particularly in terms of improved biocompatibility and high permeability. This review summarises recent new developments in this field with a focus on new approaches to the design and synthesis of polymeric monolithic materials for analytical separation science.

Review of recent advances in the preparation of organic polymer monoliths for liquid chromatography of large molecules.

In recent years the use of monolithic polymers in separation science has greatly increased due to the advantages these materials present over particle-based stationary phases, such as their relative ease of preparation and good permeability. For these reasons, these materials present high potential as stationary phases for the separation and purification of large molecules such as proteins, peptides, nucleic acids and cells. An example of this is the wide range of commercial available polymer-based monolithic columns now present in the market.

Temperature pulsing for controlling chromatographic resolution in capillary liquid chromatography.

In this study we introduce the implementation of rapid temperature pulses for selectivity tuning in capillary liquid chromatography. Short temperature pulses improved resolution in discrete sections of chromatograms, demonstrated for ion-exchange chromatography (IC) and hydrophilic interaction chromatography (HILIC) modes. Using a resistively heated column module capable of accurate and rapid temperature changes, this concept is first illustrated with separations of small anions by IC using a packed capillary column as well as a series of nucleobases and nucleosides by HILIC using a silica monolithic column with zwitterionic functionality (ZIC-HILIC).

Kinetic optimisation of open-tubular liquid-chromatography capillaries coated with thick porous layers for increased loadability.

The kinetic optimisation of open-tubular liquid chromatography (OTLC) columns has been revisited by taking the thick-film effects for porous coatings on retention, column resistance, band broadening and mass loadability into account. Considering the most advantageous case (i.e.

Kinetic performance optimisation for liquid chromatography: principles and practice.

This HPLC tutorial focuses on the preparation and use of kinetic plots to characterise the performance in isocratic and gradient LC. This graphical approach allows the selection of columns (i.e.

Probing the kinetic performance limits for ion chromatography. I. Isocratic conditions for small ions.

The first use of the kinetic plot method to characterise the performance of ion-exchange columns for separations of small inorganic anions is reported. The influence of analyte type (mono- and divalent), particle size (5 and 9microm), temperature (30 and 60 degrees C) and maximum pressure drop upon theoretical extrapolations was investigated using data collected from anion-exchange polymeric particulate columns. The quality of extrapolations was found to depend upon the choice of analyte, but could be verified by coupling a series of columns to demonstrate some practical solutions for ion chromatography separations requiring relatively high efficiency.