Mass Spectrometry

In clinical and forensic/toxicology laboratories, urine is a preferred matrix from which to quantify drug concentrations because it yields accurate results and allows for noninvasive collection methods. Prior to excretion, drug metabolites in the body undergo a glucuronidation reaction, resulting in a glucuronide bond that must be cleaved before mass spectrometry (MS) analysis by a β-glucuronidase enzyme hydrolysis. Many laboratories employ a “dilute-and-shoot” method after hydrolysis to decrease residual protein or enzyme concentration, but this method negatively affects column lifetime and reduces the sensitivity of analyte detection. By using a β-glucuronidase removal approach, analysts are able to see an increase in sensitivity and a reduction in MS instrument maintenance.

While immunoassay (EIA) is a prevalent screening technique it is also prone to issues such as high false positive rates because of lack of analyte specificity. Mass spectrometry was therefore investigated as an alternative screening technique for the ability to improve analyte specificity on a comparable time scale. In this study, a rapid online sample preparation and injection method was developed using a commercially available guard cartridge on a conventional LC–MS-MS system. Using a two-point calibration curve to provide semi-quantitation, a robust method was developed and validated that improved upon the high false positive rate observed in immunoassay screening.

This study of a selected group of PPCP contaminants in eastern North Carolina demonstrates the advantages and disadvantages of LC–MS and GC–MS as well as SPE and liquid–liquid extraction.

An LC–MS method for simultaneous quantification of buprenorphine and three metabolites: norbuprenorphine, buprenorphine glucuronide, and norbuprenorphine glucuronide.

A look at the use of field-portable GC–MS with solid-phase microextraction, purge-and-trap, thermal desorption, and heated headspace sampling techniques to provide a fast response for in-field analysis of SVOCs in a wide variety of environmental-type samples including potable waters, tea, plants, and road gravel.

Validation of this rapid bioanalytical method for the determination of moxidectin in cattle hair demonstrated that the method is accurate, reliable, and reproducible.

We present a brief review of this year's ASMS conference, which took place June 5–9 in San Antonio, Texas.

A newly discovered method, matrix-assisted ionization (MAI), is described for generating gas-phase ions from volatile and nonvolatile compounds. The method is both simple and sensitive.

High-resolution mass spectrometry (MS) is not readily compatible with chromatographic techniques using high-salt mobile phases. This study presents the development and use of 2D-LC–MS via an on-line desalting step for the analysis of monoclonal antibodies and antibody–drug conjugates.

Measuring trypsin inhibitors in legumes is important to feed processors, who are concerned with providing high-quality products for animal feed. In this study, a rapid, accurate, and precise method for the quantification of trypsin inhibitor activity is evaluated.

The development of various analytical MS methods to investigate the chemical composition of liquids used in electronic cigarettes and characterize their quality is presented in this study.

A review of the central role LC–MS plays in characterizing mAbs and biosimilars, including highlights of top-down and middle-up approaches to measure the intact masses of mAbs and their subunits, the current state of peptide mapping techniques, and glycoprofiling methods.

The past decade has brought exponential growth in the number of mass spectrometry (MS) ionization techniques based on desorption and ionization (DI) processes. Here, the three key applications for DI are discussed: rapid, in situ screening; direct analysis of extracted samples or of planar chromatography spots; and scanning samples along x and y axes.

This study describes the need to recover compounds above the boiling point of naphthalene by optimizing the thermal desorption chemistry for the determination of VOCs from C3 to C26 in soil gas samples using Method TO-17. Figures of merit, such as breakthrough, precision, linearity and detection capability will be presented, in addition to evaluating its real-world capability at sites with moderate diesel and semi-volatile polynuclear aromatic hydrocarbon (up to pyrene) contamination, in the presence of high humidity.

An LC–MS-MS method is presented that can assist with monitoring substance abuse patients who are prescribed naltrexone, a narcotic antagonist.

This article presents a step-by-step DoE optimization strategy for an electrospray ionization source with the aim to quantitatively analyze 18 compounds in a metabolomic study of human urine.

Enhanced chromatographic resolution (GC×GC), increased resolving power with high-resolution TOF-MS, and software designed to leverage these attributes are combined to provide data that are easy to process and interpret.

This article provides useful tips for smooth validation of multi-analyte LC–MS-MS methods and summarizes important validation outcomes for 295 analytes, including more than 200 mycotoxins.

Non-targeted metabolite profiling by ultrahigh-performance liquid chromatography coupled with mass spectrometry (UHPLC–MS) is a powerful technique to investigate the influence of genetic and environmental influence on metabolic phenotype in plants. The approach offers an unbiased and in-depth analysis that can reveal molecular markers of desirable phenotypic traits which can be complementary to genetic markers in plant breeding efforts. Here, the power of non-targeted metabolite profiling is illustrated in a study focused on the determination of molecular markers in malting barley that are predictive of desirable malting quality for brewing applications.

Is your swimming pool clean and safe? Recreational water illness, most commonly in the form of digestive tract illness or skin, ear, or respiratory infections, is often caused by water contamination. The authors present a robust method, using solid-phase extraction and high-resolution mass spectrometry, for monitoring swimming pool water.

Higher Order Mass Spectrometry Techniques Applied to Biopharmaceuticals

Recent progress in high-resolution mass spectrometry (HRMS) and liquid chromatography–mass spectrometry (LC–MS) methods for the structural characterization of brentuximab vedotin and trastuzumab emtansine are presented.

When evaluating the performance of mass spectrometers, one needs to consider the best (or most meaningful) figure of merit to use; options include instrument detection limit (IDL) and signal-to-noise ratio (S/N). In the last 15 years, vendor specifications for S/N have increased from 10:1 to greater than 100,000:1. Does that accurately reflect improvements in mass spectrometers? Although there have been many significant changes, the change in S/N specifications has been far greater than the corresponding change in method detection limits (MDL). Under appropriate conditions, S/N is a meaningful standard, but the value of any S/N must be evaluated in context of the chromatography and sample. Factors influencing the validity of vendor S/N specifications are reviewed, and the statistical alternative of IDL is presented as a replacement that is more consistent with regulatory guidelines and a more relevant indicator of instrument performance.

An analytical methodology for the characterization of the primary structure of biotherapeutic proteins using sheathless CE–ESI-MS-MS instrumentation is presented. For the first time, complete sequence coverage can be achieved using a bottom-up proteomic approach from a single analysis of a tryptic digest. In a biosimilarity assessment, a single amino acid substitution was detected.

GC–MS Analysis of Aroma Compounds in Edible Oils by Direct Thermal Desorption

To translate the enormous potential of MS into meaningful, actionable, and safe test results in the specific setting of a clinical laboratory is a very substantial challenge. It is essential to realize that reliability is not inherent to this technology but must be addressed carefully and questioned systematically.

We have developed a miniaturized, multifunctional device, called the "Single-Probe," that is capable of probing small targets and of sampling and ionizing molecular species.

A new method was developed and validated using automated on-line solid-phase extraction (SPE) with tandem mass spectrometry (MS). Urine samples were enzyme-hydrolyzed and diluted before detection. The validated method was applied to positive authentic urine samples to evaluate concordance with high performance liquid chromatography (HPLC)–MS-MS results.

An important attribute of a novel ionization process for use in mass spectrometry (MS) is its simplicity and flexibility to be hyphenated to conventional liquid-based separation methods.

The main objective of this study was to evaluate the capabilities of gas chromatography (GC) with time-of-flight mass spectrometry (MS) for screening pesticides in fruits and vegetables using a purpose-built accurate-mass database.