Mass Spectroscopy Articles

Introduction :

Hyphenation of efficient separation methods such as high performance liquid chromatography (HPLC) or capillary electrophoresis (CE) with detection methods that provide structural or functional information is a powerful tool for the analysis of biological macromolecules. In particular, characterization of complex molecules such as proteins, peptides and carbohydrates necessitates the use of combined analytical methods to assign molecular structures to the peaks occurring during chromatography or electrophoresis. The combination of HPLC and mass spectrometry (LC–MS) is particularly powerful and a mainstay method in most laboratories dealing with the analysis of biomacromolecules. Recent years have seen a shift from hypothesis-driven biological research towards the global analysis of the cell components, tissues or living organisms.

Introduction :

The term “forensic science” covers those professions that are involved in the application of the social and physical sciences to the criminal justice system. Forensic experts are obliged to explain the smallest details of the methods used, to substantiate the choice of the applied technique and to give their unbiased conclusions. The final result of the work of the forensic scientist, the expert evidence, exerts a direct influence on the fate of a given individual. This burden is a most important stimulus and one that determines the way of thinking and acting in forensic sciences. Consequently, the methods applied in forensic laboratories should assure a very high level of reliability and must be subjected to extensive quality assurance and rigid quality control programmes.1 Legal systems are based on the belief that the legal process results in justice — a belief that has come under some question in recent years.

One of the most important research areas concerning food proteins and peptides is to establish a relationship between the structure and functionality of these compounds.

Introduction :

Food products are very complex mixtures that contain many nutrients of organic (lipids, carbohydrates, proteins, vitamins) and inorganic (water, minerals, oxygen) nature. In addition to natural constituents, food products may contain xenobiotic substances that can come from technological processes, agrochemical treatments or packaging materials (residues of pesticides, drugs, toxins, mutagenic compounds, migrants from packaging, metals and inorganic compounds of toxicological concern).

Introduction :

LC–MS is becoming an essential tool for environmental analysis. Environmental laboratories dealing with the analysis of large numbers of samples are increasingly realizing that, notwithstanding the relatively high price of LC–MS instrumentation, the technique has a lot to offer in terms of productivity, ruggedness, ease-of-use, accuracy and precision. As an example, the analysis of N-methyl carbamates is nowadays commonly performed by LC–fluorescence detection after postcolumn reaction and derivatization. In many routine laboratories, the technical staff are not highly specialized in separation sciences and to operate the postcolumn device properly, the help of a service engineer is often required. Stateof- the-art LC–MS instrumentation is very user-friendly and the productivity for carbamate analysis is much higher.

Microcystins represent an emerging class of algal toxins of concern to the drinking-water industry. Consequently, the World Health Organization, Australia and Brazil have established guidelines for the amount of microcystins permissible in drinking water, and the US has begun to evaluate the occurrence, health effects and susceptibility of water treatments from these algal toxins. This article will focus on the initial development of a liquid chromatography–mass spectrometry method to screen for many of these toxins at low ppb levels.

Introduction :

Most of the world’s population relies on surface freshwaters as their primary source for drinking water. The drinking-water industry is constantly challenged with surface water contaminants that must be removed to protect public health. Contaminants associated with cyanobacteria (blue-green algae) are called cyanotoxins.

The publication of several genome sequences has dramatically changed the scope of biochemical sciences. The availability of the libraries of genes that an organism can use to develop and to adapt to external stress has shifted biochemical research to the analysis of the final gene products; that is, proteins, their posttranslational modifications and their interactions with other biomolecules. The first step in this ‘proteomics’1 approach is the identification of proteins involved in a particular biological process. This work is generally based on so-called differential expression analysis, which generates information about genes that are switched on or off in the presence of a particular external signal.

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Introduction :

The environmental effects of organotin compounds have been well documented1 and have led to extensive research into analytical methodologies for their determination. As a consequence of their widespread use organotin compounds have been detected in most marine and fresh-water sediments, as well as in open-ocean waters.2 In recent years, the focus of research in organotin analysis has shifted to include matrices with human health implications, such as seafood,3 artificial matrices (PVC pipes used for drinking water distribution4) and human blood samples.5

Organotin analysis has traditionally been performed by chromatographic separation, gas chromatography (GC) or high performance liquid chromatography (HPLC), coupled to a variety of detectors.

LCGC Europe, Sep 2, 2002.
Evaporative light scattering detectors, such as the PL-ELS 1000, can be used as stand-alone detectors or as one of two or more detectors operated in combination. It can be used in series, as the last detector, or the flow can be split in part to the PL-ELS 1000 and in part to an alternative detection system. By using multidetector HPLC systems, the amount of information, which can be obtained from a single chromatographic run, is maximized. The principle of operation of the PL-ELS 1000 detector involves the evaporation of the volatile eluent to leave particles of nonvolatile solute, which scatter light. This means that it has the same eluent requirements as mass spectrometry, (i.e., that the eluent must be volatile). It is, therefore, an ideal detection procedure for developing LC–MS methods offline or as a concentration detector in an LC–MS system.

Introduction :

Pharmaceutical drug discovery and development is mainly based on data obtained from the quantitative determination of drugs (and related compounds) from biological samples.1 Fast evaluation of possible drug candidates can be provided by assays that measure more than one analyte simultaneously. Automated SPE–LC–MS2 has contributed to fast, sensitive and selective assays that provide quantitative data for many compounds much faster than ever possible in the past. Yet there are still some difficulties with reproducibility and accuracy when low concentrations of drugs have to be analysed in complex biological samples. Interferences apparent in LC with UV detection are not directly observed in LC–MS and affect the response in a different way. Especially in ESIMS, interferences can reduce the extent of analyte ionization, which is often observed as a loss in signal.

Introduction :

Standard reversed-phase LC–MS and LC–MS–MS techniques have limited effectiveness in the analysis of complex biomolecule mixtures because of co-eluting species compromising MS–MS data collection. Components present in relatively small concentrations, such as small peptide fragments, can be neglected by the detection method or interpreted as background noise. Two-dimensional (2D) LC–MS methods increase the efficiency of protein identification as co-eluting components are separated into different fractions, in effect removing interferences from more abundant co-eluting species.