Special Issues-03-01-2016

Simultaneous quantification of metabolites in biological fluids, where they are present at different concentration levels, is usually a challenging analytical task. One of the steps that should be undertaken to increase analytical method efficiency is optimization of the electrospray ionization source (ESI), which can be especially helpful in increasing method sensitivity of agents with poor ionization characteristics. We present here a step-by-step ESI optimization strategy with the use of the design of experiments (DoE. This multivariate statistical approach allows effective evaluation of the effects of multiple factors and interactions among factors on a given response in a minimum number of experimental runs.

Naltrexone (Depade, Re Via, Trexan) is a potent narcotic antagonist structurally similar to oxymorphone and naloxone. It blocks the subjective effects of heroin and other opiates and is primarily used in the management of opioid dependence and alcohol dependence. While conjugated 6β-naltrexol is the major urinary metabolite in man, conjugated naltrexone and free 6β-naltrexol are also major urinary species. To assist with monitoring substance abuse patients who are prescribed naltrexone, a rapid, selective, and sensitive LC–MS-MS method was developed to analyze for both naltrexone and 6β-naltrexol post-enzymatic hydrolysis. The validation of this method and some representative patient data are discussed in this report.

The enhanced resolution of comprehensive two-dimensional gas chromatography (GCxGC) was combined with the increased resolving power, speed, and mass accuracy of the Pegasus® HRT's mass analyzer to confidently characterize molecules in light cycle oil (LCO) and vacuum gas oil (VGO). Optimized chromatographic and mass spectrometry parameters were implemented to improve data acquisition, processing, and heteroatomic speciation of these light to midlevel petroleum fractions. Software tools were utilized to process the data and facilitate robust compound identifications. GCxGC-HRT data was processed using comprehensive Peak Find and resulted in comprehensive characterization of molecules in LCO and VGO samples. Compound classes consisted of, but were not limited to alkanes, cycloalkanes, aromatics, benzothiophenes, and carbazoles. Selective processing of alkylbenzothiophenes and dibenzothiophenes was conducted by retrospectively processing data using rapid two-dimensional, accurate mass Target Analyte Finding (TAF).

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.

Special Issues

The sensitive, selective, and real-time analysis characteristic of the SIFT-MS technique provides simple, robust, and continuous analysis of extremely diverse odor compounds at trace levels in air. This application note illustrates instantaneous, broad spectrum odor analysis with monitoring data from a chicken meat production facility.

Click the title above to open the March 2016 issue of Current Trends in Mass Spectrometry, Volume 14, Number 1, in an interactive PDF format.