Mass Spectroscopy Articles

The chemical detection of ignitable fuel traces in fire debris is a challenge requiring highly sensitive, hyphenated analytical systems. One coupled system suitable for the task is thermal desorption cold trap injection–gas chromatography–mass spectrometry (TCT–GC–MS). In this study, thermal desorption and cryogenic trapping were optimized to eliminate matrix interferences and to enrich target compounds in fire debris.

Introduction On-line SPE–LC–MS is becoming increasingly popular for automation of bioanalytical assays, especially in the pharmaceutical industry (1). Total automation, high precision and high sensitivity are among the most favoured features. For highspeed bioanalysis based on SPE–LC–MS, the challenge for on-line SPE is to keep pace with the very short LC–MS cycle times. Ideally, on-line SPE should be faster than, and run in parallel with, LC–MS analysis to avoid any limitation of assay cycle time. Another major challenge in drug analysis that should be faced is the reduction of assay development time. A generic method for SPE and LC is urgently needed to eliminate method development for preclinical assays or as a universal starting point for the development of high-quality, high-throughput clinical assays.
 
In this technical article, we present new instrumentation for on-line SPE that has been designed to achieve SPE cycle times of less than one minute.

BR> Introduction Sensitivity is one of the most crucial issues in proteome analysis: while typical amounts of proteins loaded on a 2-D gel are in the range of a few hundred femtomol or less, sample losses during the in-gel-digest procedure and subsequent extraction often leave only a few femtomol of the peptides for mass spectrometric identification and characterization.
 
Ion trap mass spectrometry answers this challenge with unsurpassed sensitivity down to the sub-femtomol range. Moreover, its multiple fragmentation stages provide data with excellent information content. These features allow for highly reliable protein identification even from mixtures or poorly separated proteins and thus make ion trap MS one of the leading mass spectrometric techniques in proteomics.
 
Here, we want to report on an ion trap system customized for routine protein identification in the low- to sub-femtomol range: the esquire3000 plus.

Introduction The efficiency of inductively coupled plasma (ICP) in producing singly charged positive ions for most elements makes it an effective ionization source for mass spectrometry (MS). ICP-MS is considered the method of choice for trace metal analysis because it combines parts per trillion detection limits, a linear range over 6 to 7 orders of magnitude, multi-elemental and multiisotopic measurement capabilities, and limited spectral interferences with a high sample throughput, and almost complete elemental coverage (1–4).

BR> Introduction When searching for a suitable technique for the analysis of mixtures, often containing unknowns and/or analytes in low concentration, the combination of liquid chromatography (LC, separation) with mass spectrometry (MS, sensitivity and structural information) appears to be an obvious choice. However, LC–MS is an “odd couple” (1). First, there is the nature of the analytes. LC is preferred over gas chromatography (GC) because of the higher polarity and lower volatility of the samples. One of the prerequisites for mass spectrometric analysis is the formation of volatilized ions. Second, and a harder problem to solve, is the necessary elimination of the mobile phase. A flowrate of 1 mL/min water is converted in 1244 mL/min vapour at atmospheric pressure, which is far too much to be handled by the standard MS vacuum systems.

Introduction:

Mass spectrometry (MS) is slowly but surely becoming the detection system of choice for liquid chromatography (LC) analysis in many areas.

Translating methods from conventional LC–ultraviolet (UV) detection to LC–MS is often required because optimized LC–UV mobile phases usually contain buffers and additives that have a negative effect on MS ionization, MS performance and maintenance of the mass spectrometer. Moreover, depending on the LC–MS configuration, all or part of the effluent is directed towards the MS optics. In addition, because of the high selectivity of MS, column dimensions have changed drastically over recent years leading to high-throughput screening in, for example, combinatorial chemistry, clinical/ pharmaceutical studies, bioanalysis etc. In this section, an overview is presented of column and mobile phase selection for LC–MS. In the framework of this guide it is impossible to strive for completeness.

Coupling of liquid chromatography (LC) techniques with matrix-assisted laser desorption ionization (MALDI) or electrospray ionization (ESI) time-of-flight (TOF) mass spectrometry (MS) provides both MS-based structural information and LC-based quantitative data in polymer analysis. In one experimental set-up three different LC modes can be interfaced with MS: size-exclusion chromatography (SEC)–MS, gradient polymer elution chromatography (GPEC)–MS and liquid chromatography at the critical point of adsorption (LCCC)–MS. In SEC–MS both absolute mass calibration of the SEC column based on the polymer itself as well as determination of monomers and end-groups from the mass spectra are achieved. GPEC–MS shows detailed chemical heterogeneity of the polymer and the chemical composition distribution within oligomer groups.

Capillary Electrophoresis– Mass Spectrometry: Practical Implementation and Applications

Introduction Mass spectrometry (MS) is becoming increasingly popular as a detection method for capillary electrophoresis (CE) (1–5). The combination of CE’s high efficiency and high speed with the high sensitivity and high selectivity offered by MS detection is very attractive. CE is very tolerant of complex sample matrices, and therefore its combination with MS provides for highly selective detection of compounds in variously complex mixtures. MS detection also helps to improve the general sensitivity of CE analyses in appropriate instances. The power of combining MS detection with any separation technique is that it provides a second dimension of separation.

Throughout 2005 in this column, we will investigate various aspects of mass spectrometry (MS), viewed from the perspective of some leading practitioners. I wish to acknowledge at the outset their gracious cooperation in this project. Their willingness to share knowledge gained from years of highly successful efforts so that I might distill it into a few thousand words to benefit the rest of us speaks well of their dedication. In this month's installment, I specifically want to thank Kathleen Cox and Timothy Baker for their time and effort in discussing metabolism identification and structural characterization. A number of mechanisms exist to eliminate drugs and other foreign substances from the body. Enzymatic alterations provide the most common ways of producing a more polar compound and therefore improving clearance of a drug. But alteration has some important physiological effects, including prolonging or (more commonly) halting a desired effect.