For decades, selenium has been considered an essential element to human nutrition. It plays an important role in many biological processes, generally exerting its biological affect through selenoproteins. Selenium is incorporated specifically into proteins by a UGA codon that encodes for selenocysteine. There are over 30 known selenoproteins in mammalian systems, including a number of glutathionine peroxidases (GPx), iodothyronine 50-deiodinases (IDI), sperm capsule selenoprotein, and thioredoxin reductase (1, 2). Selenium also is required for the production of triiodothyronine, a thyroid hormone necessary for healthy brain and bone development, normal growth, and thermoregulation (3). Proper immune function also is selenium-dependent, which recently has prompted investigations into its ability to inhibit HIV and AIDS progression (4).

In the pharmaceutical industry, liquid chromatography–tandem mass spectrometry (LC–MS-MS) is already an established method for quality control and quantification of drugs in different matrices. Additionally, this hyphenated analytical tool is becoming more and more important in clinical chemical analysis (that is, in therapeutic drug monitoring).

LC–MS-MS is a very powerful analytical technique because it combines the separation power of LC with the sensitivity and selectivity of MS. However, LC–MS-MS possesses two major drawbacks when analyzing drugs in biological fluids. The first, associated with the mass spectrometer, is that the electrospray source is very susceptible to matrix-related ion-suppression effects. The second drawback concerns the LC. Because of irreversible adsorption and precipitation effects caused by high molecular weight sample components (for example, proteins) complex biofluids cannot be injected and analyzed directly.

GUIDE TO LC–MS.
Summary Mass spectrometry provides a faster of fractions. The procedure described involves initial protein purification on ÄKTA™ purifier 10, automated and rapid desalting of fractions on Ettan microLC, and MS analysis by electrospray ionization time-of-flight mass spectrometry (ESI-ToF MS) using Ettan ESI-ToF. Ettan LC–MS provides high-quality mass spectra of a wide range of high molecular weight proteins including bovine serum albumin, cytochrome C, transferrin, ovalbumin, myoglobin, a monoclonal antibody and two -lactoglobulin variants.
 

Mass spectrometry systems have specific vacuum requirements. New developments in oil-free, or dry, primary vacuum pumps have been introduced recently and are discussed in this article with respect to capacity, throughput, and specific pumping requirements for process gases.

 There are many drivers for vacuum configuration in mass spectrometry (MS) and other scientific instrumentation applications. These include: vacuum performance of the primary pump itself (speed, compression, power, and so forth); environmental impact, power, construction, service interval, and the requirements (if any) for oil; regulatory compliance; cleanliness of the vacuum produced; and compatibility with process and target gases–vapors. MS systems have very specific vacuum (physics and engineering) requirements. The systems primarily considered here are liquid chromatography–MS (LC–MS), gas chromatography– MS (GC–MS) and inductively coupled plasma MS (ICP-MS).

In the last five years, the acceptance and implementation of packed-column supercritical fluid chromatography–mass spectrometry (pSFC–MS) to drug discovery applications has gained momentum. This article describes the pros and cons of pSFC–MS and attempts to demonstrate its broad applicability to such fields as high-throughput analysis, purity assessment, structure characterization and purification. Finally, an outlook for the future of this technique is presented.

A system for automated off-line comprehensive packed column supercritical fluid chromatography (pSFCpSFC) was developed for the characterization of triglycerides (TGs) in vegetable oils. In the first dimension, TGs are separated according to their hydrophobicity using octadecyl silicagel as stationary phase. In the second dimension, separation occurs according to degree of unsaturation using a silver-loaded stationary phase. Fraction collection, concentration and re-injection are fully automated. The two orthogonal separation mechanisms give a better insight into the TG composition of vegetable oils. UV detection at 210 nm is normally applied for both columns. For unequivocal TG elucidation, a mass spectrometer (MS) operated in the atmospheric pressure chemical ionization mode may be coupled after the second UV detector. The potential of pSFCpSFC–MS is illustrated.

Introduction :

A positive chemical ionization GC–MS method for the analysis of acrylamide monomer in foods will be described and future areas for development offered. The method had a limit of detection of 5 ppb and was found to show good linearity to 1000 ppb. PCI SIM using ammonia as a reagent gas provided the best blend of sensitivity and selectivity.

Introduction :

Introduction :
High-throughput mass spectrometry–based protein identification requires a complete solution which includes a complete hardware setup starting from a 2D gel, and an integrated software package. The Bruker PROTEINEER™ line meets these requirements. The flow of information through the whole line enables data handling in a highly integrated level. The backbone of the PROTEINEER™ suite is the embedded Workflow Administration by Result-driven Processing (WARP™, Figure 1). The workflow for each sample is controlled across all PROTEINEER™ hardware components (robotics and mass spectrometers), and depends on the intermediate results from the mass spectrometric stages. For this task, all robots and mass spectrometers track sample IDs by electronic transponders and exchange the related processing parameters and results with the central control unit: ProteinScape™.

>Introduction :

In the April edition of this magazine1 Ron Majors, in his annual report on new columns and accessories from the Pittsburgh conference, reported how at the 2002 conference the largest number of product introductions were for biomolecule separations and for liquid chromatography–mass spectrometry (LC–MS). He went on to state that speciality HPLC columns for chiral compounds, biomolecules, combinational chemistry, carbohydrate analysis and LC–MS represented the largest category of entries. Supporting these products was an increase in capillary and nano-LC columns for LC–MS. But more important the support accessories (e.g., mixers, valves and connecting tubes) were also shown for the new capillary columns.

Introduction :

The implementation of new tools within the discovery process, including combinatorial chemistry, proteomics and ADME/tox profiling, demand the creation of new strategies for pharmaceutical analysis. Sample generation has increased very rapidly and, as a consequence, traditional analytical approaches are unable to fulfil the requirements set by lead generation. Therefore, a great challenge has developed to create new, rapid, high-throughput analytical methods to speed-up the whole discovery process.

CE–MS

Capillary electrophoresis (CE) is a relatively new tool for chiral analysis. Chiralty is very important in biochemistry because different enantiomers can produce diverse pharmacological and toxicological actions. Fujiware and Honda described the use of CE in the pharmaceutical industry.1 Once a screening method has been developed, CE can be used as an additional technique for the detection of impurities.

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.

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.