Mass Spectrometry

With the advances in LC-MS in recent years, is there another practical option on the horizon for those who need the specificity of MS and can justify the narrow definition of a purpose-built system?

This month's installment addresses some elementary aspects of the mass spectrum, the tools employed by the experienced practitioner, and advances being made into identifying unknowns.

Michael Balogh uses examples such as the recent acetonitrile shortage to examine the topic of "the unknowable" as it pertains to separation science.

Mass spectrometry-based electronic nose technology (MS-nose technology) is a fast hyphenated technique for digital odour characterization of food and beverage products.

Part 2 of this three-part series focuses on comparing operation and performance of the most well known mass spectrometers.

Researchers at the University of Utah's (Salt Lake City) Sports Medicine Research and Testing Laboratory developed a test for testosterone and epitestosterone in urine that uses liquid chromatography with tandem mass spectrometry detection (LC-MS-MS).

Ramipril impurities D and E are well-known degradation products of ramipril in the finished dosage form. A significant amount of an additional impurity was detected in ramipril tablets by an isocratic reversed-phase high performance liquid chromatography (HPLC) method on a short column. The structure of this impurity was proposed based on liquid chromatography–mass spectrometry (LC–MS) data using an electron spray ionization source. Structural elucidation using nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy was facilitated by a newly developed preparative isolation method. This impurity was characterized as (2R,3aR,6aR)-1-[(R)-2-[[(R)-1-(ethoxycarbonyl)-3-phenylpropyl]amino]propanoyl]octahydrocyclopenta[b]pyrrole-2-carboxylic acid (impurity L). Its identification, synthesis and characterization are discussed.

Over the last 10 years, several solvent-free microextraction techniques for gas chromatography (GC) and mass spectrometry (MS) have been developed. Two of these techniques, solid-phase microextraction (SPME) and stir-bar sorptive extraction (SBSE), are available commercially for the analysis of volatile compounds, such as flavors in foods and beverages, and toxic organic compounds in environmental applications. Other techniques, such as open tubular trapping, inside needle capillary adsorption trap (1), in-tube SPME, capillary microextraction, needle trap, and headspace solid-phase dynamic extraction (2), were also developed for different applications. The basic principle for all of these techniques is essentially the same. Volatile and semivolatile compounds are adsorbed on a sorbent coating, often packed on the interior surface of a capillary column or stainless steel needle. After the sample is concentrated on the coating, the compounds are desorbed thermally in the heated injection port of a gas..

Automated solid-phase extraction (SPE) has been used extensively with liquid chromatography–tandem mass spectrometry (LC–MS-MS) to facilitate high-throughput analysis in the pharmaceutical, diagnostic, and forensic toxicology areas. In this work, we demonstrate the use of a systemized approach to SPE method development and LC–MS-MS analysis. This approach provides dramatic savings in analysis time and takes advantage of new innovations in high performance liquid chromatography (HPLC) columns to provide the cleanest extracts for LC–MS injection.

Illegal drug use worldwide is at an all-time high. There is a crucial need for fast and accurate analysis to positively identify suspected drugs in criminal investigations. Gas chromatography combined with time-of-flight mass spectrometry (GC–TOFMS) can be a valuable tool for drug testing in forensic crime laboratories. Method development and GC–TOFMS experimentation was conducted in cooperation with a local crime laboratory. The laboratory testing presented will illustrate highly efficient methods and data developed for crime labs that assist in the battle against illegal drugs. Many drug classes have chemical properties that present particular analytical challenges, such as poor detector response, chemical lability, or poor chromatographic peak shape. This article presents GC–TOFMS methods developed for several major drug classes and chemical functionalities. The major drugs included in the initial method development are methamphetamine, ecstasy, and heroin. Robust and accurate..

A summary of the five-day mass spectrometry conference held this month in Denver, Colorado.

This article describes the ability to increase the sensitivity for a target compound in the presence of high-level background impurities by removing the dosing vehicle using a high-field asymmetric waveform ion mobility spectrometry gas-phase separation before mass spectrometry analysis.

Liquid chromatography with tandem mass spectrometry (LC–MS-MS) led to a revolution in environmental testing. The coupling of liquid chromatography with tandem mass spectrometry created a powerful analytical tool for the analysis of emerging environmental contaminants. Pharmaceuticals and personal care products, perfluorinated compounds, brominated flame retardants, and disinfection byproducts were chosen as examples to illustrate the use of this new technique in environmental analysis.

Successful characterization of protein posttranslational modifications (PTMs) is critical to our understanding of many biological processes. Unfortunately, attempts to describe PTMs often prove experimentally difficult and result in ambiguous conclusions. As technologies in the field of mass spectrometry (MS) continue to improve, people are turning increasingly to mass spectral techniques for PTM characterization. Recently, novel modes of peptide fragmentation have emerged that are giving scientists greater ability to elucidate protein posttranslational modification. One example is electron-capture dissociation (ECD), an alternative fragmentation mechanism for use in peptide analysis via tandem mass spectrometry. ECD selectively cleaves N-Cα bonds of the peptide backbone, yielding c- and z-ions without the loss of labile PTMs. ECD therefore holds advantages over conventional fragmentation techniques such as collisionally induced dissociation (CID), which often cleave PTMs from the peptide backbone,..

The matter of perfluorinated compounds (PFCs) came to focus at the United States Environmental Protection Agency (EPA) some eight years ago.

Recent work suggests that the practical value of hyphenated techniques is limited by difficulties inherent in achieving definitive compositional answers in general MS. This article argues that it is not impossible in certain cases.

Nearly a dozen incipient technologies have appeared in recent years. Which will survive? Which will find extensive, robust usage as did electrospray ionization? Which are fated to become footnotes in mass spectrometry practice?

"As research advances, about half of what we will teach you . . . will turn out to be wrong. The problem is, we presently don't know which half." Powerful Medicines, Jerry Avorn, 2004

Understanding how imaging can advance life science research and what issues need to be addressed to unlock the true potential of mass spectrometry-based imaging raises awareness of new possibilities for researchers. This article explores mass spectrometry imaging, aiming to educate about scientific opportunities to consider and the pitfalls to avoid.

This month's installment of "MS - The Practical Art" provides a slightly different view of how practitioners employ the skills of interpretation that have been the focus in recent columns.

This month's column brings much of the previous discussion on how to interpret mass spectra to a practical examination of detecting substitutions in counterfeit pharmaceuticals.

In this month's "MS-The Practical Art," Michael Balogh takes a closer look at insight provided by Chuck McEwen regarding obstacles while using solvents.

Serum protein profiling using mass spectrometry (MS) is one of the most promising approaches for biomarker identification.

In Part I of this two-part look at spectral interpretation, Michael Balogh examined the ability to see and appreciate the product of our analytical devices. In Part II, he takes a closer look at the tools of the trade.

Despite their different levels of technological maturity, CE and LC coupled with electrospray ionization MS techniques can be operated at the same level of automation. However, they differ in their configuration, selectivity, sensitivity, and method development.

Current sample preparation procedures for LC–MS as applied to samples from biological matrices.