Mass Spectrometry

As we approach the holiday season, in what has a been the most challenging of years both inside and outside of the laboratory, I wanted to produce a more light-hearted yet inspiring review of 2020 within the Arch Sciences Group laboratories.

Per- and poly-fluoroalkyl substances (PFAS) are a family of potentially thousands of synthetic compounds that have long been used in the manufacture of a variety of common products with stain-repellent and nonstick properties. Their signature strong fluorine and carbon bonds make them difficult to break down and, as a result, they are among the most persistent of today’s environmental pollutants. Alarmingly, PFAS can be found in drinking water and have been shown to accumulate in the body with the potential to cause multiple health problems, such as hormone disruption and cancer. Advances in mass spectrometry have facilitated the detection of known PFAS contaminants as well as the identification of poorly studied and novel compounds in watersheds. This article explores the detection of known and novel PFAS contaminants in aqueous film-forming foams and raw drinking water sources in North Carolina, using new advances in mass spectrometry and data acquisition to improve identification and quantitation.

Long chain fatty acids (LCFAs) function as a source of metabolic energy, substrates for membrane biogenesis, and storage of metabolic energy. Oxylipins, oxygenated derivatives of LCFAs, regulate the activity of many cellular processes. Existing methods for the analysis of LCFAs and oxylipins have limited compound coverage and sensitivity that, therefore, prevent their application in biological studies. In this work, we developed a high-throughput LC–MS method for analysis of 51 LCFAs and oxylipins. LCFAs and oxylipins were first extracted from biological samples via solid-phase extraction. The extracted molecules were analyzed by targeted comparative metabolomics. Saturated and monounsaturated LCFAs were analyzed in single ion reaction mode, while polyunsaturated LCFAs and oxylipins were analyzed in multiple reaction monitoring mode. Using this method, we successfully quantified 31 LCFAs and oxylipins from mouse livers.

Over the last decade, matrix-assisted laser desorption–ionization (MALDI) imaging has become an indispensable tool for a broad range of applications, from studying plant metabolomics to discovering biomarkers of disease to developing new therapies. As such, MALDI imaging is revolutionizing preclinical drug discovery pipelines by providing direct distribution monitoring of therapeutic compounds and their metabolites along with untargeted pharmacodynamic information. A key application of MALDI imaging is tissue analysis for oncology, and recent developments in MALDI technology promise greater benefits to cancer research. The combination of MALDI with laser-induced post-ionization (PI) enhances the detection and imaging of pharmaceutical compounds and other classes of compounds, allowing for significant advances in the use of MALDI imaging for studying drug metabolism and pharmacodynamics in tumor tissues. This article describes the value of MALDI Imaging for oncology applications and examines the potential for laser-induced PI, including the ability to achieve up to three orders of magnitude higher sensitivity and to image metabolite classes previously undetectable with traditional MALDI.

Consumer marketing approaches are creeping into the marketing of scientific instruments. With a careful approach, you can cut through the hype.

Gas chromatography–mass spectrometry (GC–MS) with cold electron ionization (EI) is based on interfacing the GC and MS instruments with supersonic molecular beams (SMB) along with electron ionization of vibrationally cold sample compounds in SMB in a fly-through ion source (hence the name cold EI). GC–MS with cold EI improves all the central performance aspects of GC–MS. These aspects include enhanced molecular ions, improved sample identification, an extended range of compounds amenable for analysis, uniform response to all analytes, faster analysis, greater selectivity, and lower detection limits. In GC–MS with cold EI, the GC elution temperatures can be significantly lowered by reducing the column length and increasing the carrier gas flow rate. Furthermore, the injector temperature can be reduced using a high column flow rate, and sample degradation at the cold EI fly-through ion source is eliminated. Thus, a greater range of thermally labile and low volatility compounds can be analyzed. The extension of the range of compounds and applications amenable for analysis is the most important benefit of cold EI that bridges the gap with LC–MS. Several examples of GC–MS with cold EI applications are discussed including cannabinoids analysis, synthetic organic compounds analysis, and lipids in blood analysis for medical diagnostics.

When explosives are encountered on the battlefield, the use of portable GC–MS is valuable for the detection and confirmatory identification of pre- and post-detonation threats. In addition, this technique provides information about the source of explosives based on the detection and identification of trace-level chemicals in the sample. The data presented here confirm this capability.

Liquid chromatography coupled with high-resolution mass spectrometry (LC–HRMS) is used in combination with a comprehensive data analysis workflow to screen water samples for potentially hazardous transformation products from organic micropollutants to determine the efficacy of different water treatment methods.

Size-exclusion chromatography (SEC), with the use of ammonium acetate buffer, can be coupled on-line to electrospray ionization MS for the characterization of size variants of therapeutic monoclonal antibodies (mAbs). A quadrupole time-of-flight (QTOF) MS system was employed, and the MS method was optimized to achieve favorable sensitivity for high-mass detection, while maintaining the structural integrity of the aggregates (or high molecular weight species) and fragments (or low molecular weight species).

LC–MS techniques, particularly those using high-resolution MS and nontargeted analysis, are advancing many areas of water research. Here, Imma Ferrer of the University of Colorado shares some of her recent work in this field.

In this study, atmospheric pressure photoionization (APPI) is compared to the default ionization method, electrospray ionization (ESI), for solution-phase samples. These mass spectrometry methods are compared and optimized relative to artificial wastewater for the detection and quantitation of pharmaceuticals frequently found as environmental contaminants.

Per- and polyfluoroalkyl substances (PFAS) are found in firefighting foams and consumer products. They are ubiquitous in the environment and are an emerging human health concern. This work compares the 2009 and 2018 revised US Environmental Protection Agency (EPA) LC–MS/MS methods of analysis for PFAS in drinking water.

In late-stage pharmaceutical development a new generation of high-resolution mass spectrometers and ion mobility mass spectrometers operate as orthogonal separation techniques and have greatly increased the ability to resolve impurities and increase the level of analytical information gained from a single analysis.

In the human food supply, public confidence is affected by contaminants and misreporting of nutritional information. This article highlights three events that required development of new mass spectrometry methods, including the detection of pesticides (such as fipronil and glyphosate), and the detection and quantification of fat-soluble vitamins.

HS-SPME-GC–MS is a valuable technique for identifying volatile organic compounds, additives, and degradation products in industrial rubber, car labeling reflection foil, and bone cement materials.

To address the challenges of analyzing new illicit drugs, emerging techniques such as UHPSFC with MS and UV detection, and GC with VUV detection, may be needed, particularly for distinguishing positional isomers and diastereomers.

LCGC, the leading resource for separation scientists, is proud to announce that Ronald E. Majors and Zachary S. Breitbach are the winners of the 11th annual LCGC Lifetime Achievement and Emerging Leader in Chromatography Awards, respectively. Majors and Breitbach will be honored in a symposium as part of the technical program at the Pittcon 2018 conference in Orlando, Florida, on February 26, 2018.

Tips for effective use of chromatography and mass spectrometry for the analysis of antibody–drug conjugates, glycoengineered proteins, and biosimilars.

Under a suitable thermal oxidation regime, vegetable oils yield a mixture of volatile and semivolatile organics that exhibit very high antimicrobial activities against a variety of microbial species. Volatile and semivolatile products were characterized with GC–MS using electron ionization and chemical ionization. The thermal oxidation of vegetable oils resulted in the formation of an array of short and medium-chain acids, aldehydes, and ketones that act synergistically to yield a potent antimicrobial disinfectant.

Since glycans are responsible for bioactivity, solubility, immunogenicity, and clearance rate from circulation, it is vital to have a detailed map of glycans in therapeutic glycoproteins. Detailed glycoprotein structural analysis must be able to identify the peptide sequence where the glycans are attached as well as the structure of the glycan portion, including oligosaccharide sequence and glycosyl linkages. This article details methods for mass spectrometry experiments on both released glycans (“glycomics”), as well as on intact glycopeptides (“glycoproteomics”) using electron transfer dissociation, high-energy collision dissociation, and collision-induced dissociation fragmentation pathways, which are needed to fully elucidate the structure of glycoproteins.

Wastewater analysis has become an established approach for retrieving additional epidemiological information about the use of illicit drugs, alcohol, and tobacco at the population level. Here, we present an overview of the recent analytical frameworks and workflows for target and suspect analyses using low- and high-resolution mass spectrometry and discuss the latest advances in wastewater-based epidemiology (WBE).

The disinfectants commonly used to treat public drinking water can react with naturally occurring organic and inorganic matter in the source water to form disinfection byproducts such as haloacetic acids. Here, we describe the use of two-dimensional matrix-elimination ion chromatography (MEIC) for haloacetic acid analysis. This method minimizes the impact of matrix ions.

Leading separation scientists share their perspectives on current challenges in separation science and where the field is heading.

In this study, general extract screening of food storage materials was done with nontargeted analytical methods to understand what analytes could potentially leach into food or beverages. GC and mass spectral deconvolution effectively separated analytes within the complex mixture and TOF-MS provided full mass range spectral data for identification. This workflow can be used for confident characterization of components present as extractables from food packaging materials.

There is growing interest in the determination of endogenous proteins in biological samples for diagnostic purposes, because a concentration increase or decrease of such proteins can allows us to monitor the state of a pathological condition such as cancer. Immunocapture LC–MS/MS analysis combines the workflow of conventional immunological assays with LC–MS analysis. This article describes typical challenges, such as cross reactivity and the mass spectrometer’s dynamic range, as well as the advantages of isoform differentiation and multiplexing.

Interest in connecting ion mobility spectrometry (IMS) to GC and especially to LC is now growing. One favorable property of IMS is that it can work with ambient pressure and can be easily connected to a gas or liquid chromatograph. Analytical applications of GC–MS and LC–MS are very different and encompass investigations into food, medical science, environment, drugs of abuse, chemical warfare agents, and explosives.

In drug development, quantitative determination of a candidate drug and its metabolites in biofluids is an important step. The standard technique for quantitative metabolite profiling is radiolabeling followed by HPLC with radiodetection, but there are disadvantages to this approach, including cost and time, as well as safety and ethical concerns related to administering radiolabeled compounds to humans. Frank Vanhaecke and his research group at Ghent University have been developing an alternative technique, and he recently spoke to us about this work.

We present a brief review of this year’s ASMS conference, which took place June 4–8 in Indianapolis, Indiana.

A model set of analytes and selected applications are used to demonstrate the effects that buffers can have on the selectivity of a separation and the sensitivity of a reversed-phase analysis when using MS detection.

Buffers are commonly used in reversed-phase liquid chromatography (LC) to control the ionization state of analytes. However, the addition of buffers is much more complex than simple pH control. Complex equilibria exist between these mobile-phase additives, the analytes, the silica surface, and even the stationary phase in certain circumstances. The addition of mass spectrometry (MS) as a primary detection technique makes decisions about mobile-phase additives even more crucial. In this column instalment, we use a model set of analytes and selected applications to demonstrate the effects that buffers can have not only on the selectivity of a separation, but also on the sensitivity of a reversed-phase analysis when using MS detection.