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Microemulsion-based HPLC (MELC) is a recent development offering reduced sample preparation times for complex samples and generic separation conditions applicable to a wide range of solutes. This article introduces the concepts of MELC and discusses the possible benefits and future applications.

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The use of mobile phase pH to control analyte ionization states (pH-LCâ„¢) in reversed phase HPLC separations is a highly effective way to change selectivity. The ionized species of an analyte is shown to have higher polarity (less hydrophobicity) than the neutral species, which results in a loss of expected retention for that analyte. This can be attributed to less interaction with the hydrophobic stationary phase and greater affinity with the aqueous portion of the mobile phase. Ionized species also participate in ionic interactions with exposed and activated silanols, which impact peak shape and reproducibility.

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Synthetic fused silica capillary tubing is commonly used as the preferred substrate for chromatographic separation columns. In limited instances the absorption and diffusion of molecules into and through the fused silica deserves consideration.

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Thermo Fisher Scientific Application Note

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The combination of reversed-phase high performance liquid chromatography (RP-HPLC), atmospheric pressure ionization (API), mass spectrometry (MS) and tandem mass spectrometry (MS/MS) is ideal for determining and characterizing analytes in complex biological matrices. This review looks at the importance of parameters such as hydrophobicity, ionization properties, molecular mass and, partially, the molecular structure resulting from applied LC–MS–MS systems in analytical laboratories. The use of these parameters to investigate biomolecules and their unambiguous identification is also described.

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Monoliths are separation media in the format that can be compared to a single large "particle" that does not contain interparticular voids. As a result, all the mobile phase must flow through the stationary phase. This convective flow greatly accelerates the rate of mass transfer. In contrast to diffusion, which is the typical driving force for mass transfer within the pores of particulate stationary phases during chromatographic processes, convective flow through the pores enables a substantial increase in the speed of the separation of large molecules such as proteins. A thorough theoretical treatment of the mass transfer within monolithic materials has been developed by Liapis (1) and Tallarek (2).

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Gel Permeation Chromatography (GPC) is widely used for sample clean up in mycotoxin analysis. The most commonly described methods use GPC columns packed with SX-3 BioBeads suitable for cleaning Zearalenone, Aflatoxins, and Trichothesenes from edible oils and fatty matrices. Separation of Fumonisins from the oil fraction are inadequate with this column.

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An introduction from guest editor, Gert Desmet from Vrije Universiteit Brussel, Belgium

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The screening of pesticides, mycotoxins, and veterinary drugs is of great importance in regulated environments such as food or feed analysis. Due to some of the limitations of traditional triple quadrupole approaches (for example, targeted analyte detection, limited number of compounds, and unidentified unknown compounds), there is currently a trend towards use of full-scan MS data for the analysis of residue samples. Current screening approaches mainly rely on the use of ToF instruments coupled to U-HPLC delivering mass accuracy (~5 ppm) at a maximum resolution of <15,000. This can produce inaccurate mass measurements due the presence of unresolved background matrix interferences. In this work we show a full-scan MS screening approach with the Thermo Scientific Exactive mass spectrometer, a novel single-stage Orbitrapâ„¢ MS capable of providing precise mass accuracies at resolutions of up to 100,000 without the need for internal mass calibration.

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The authors discuss the use of GC-MS in drug doping testing.

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This article addresses the contribution of thermal stability and column activity to BDE-209 breakdown and also describes an optimized method that resolves BDE-209 and other important congeners.

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Since September 2008, 294,000 infants and young children suffered urinary problems due to the contamination of melamine in infant milk powder and were hospitalized. This hospitalization was required to treat the symptoms caused by the ingestion of melamine contaminated infant formula and related dairy products. Previously in 2007, pet food, animal feed, wheat gluten, and other protein-based foods were found to contain residues of melamine and its degradation product cyanuric acid (2).

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This month, guest columnists Kind and Fiehn discuss small-molecule structure elucidation (excluding peptides) using hyphenated chromatographic techniques, mass spectrometers, and other spectroscopic detectors.

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Gel Permeation Chromatography (GPC) is widely used for sample clean up in mycotoxin analysis. The most commonly described methods use GPC columns packed with SX-3 BioBeads suitable for cleaning Zearalenone, Aflatoxins, and Trichothesenes from edible oils and fatty matrices. Separation of Fumonisins from the oil fraction are inadequate with this column.

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Sample preparation is an essential technique to remove unwanted matrix components prior to LC–MS-MS analysis of drugs in biological fluids. Plasma matrix components whether endogenous (salts, proteins, and phospholipids) or exogenous (dosing vehicles, e.g. PEG 400), can interfere with compounds of interest leading to regions of ion suppression or enhancement. This can lead to inaccurate quantitation and have adverse effects on sensitivity. Mixed-mode SPE provides cleaner extracts as a result of rigorous interference wash steps, afforded by the dual retention mechanism of the sorbents.

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A review of advances in mRNA analysis using LC and LC–MS.

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The analysis of chemical residues in food requires techniques sensitive enough to detect and quantify contaminants at or below the maximum residue limit (MRL) of the compound in a given sample matrix. Because of increased food safety regulations and the growing numbers of samples to be analyzed, it is critical that the analytical techniques provide high sample throughput.

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Today's ion traps use advanced scanning techniques such as automatic gain control, axial modulation, and triple resonance scanning, resulting in efficient control of both ionization and optimal storage of ions in the trap during analysis. These instruments provide excellent sensitivity and quantitative data, even in "dirty" samples.

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Various modes of capillary electrochromatography (CEC) for the separation of enantiomers on immobilized cyclodextrin derivatives are described. The following techniques have been used: (i) open-tubular electrochromatography (o-CEC), (ii) packed electrochromatography (p-CEC) and (iii) monolithic electrochromatography (rod-CEC). Three different strategies to prepare enantioselective cyclodextrin-coated chiral monoliths are described. The advantages and disadvantages of the various methods are outlined.

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Gas chromatography–mass spectrometry (GC–MS), reversed-phase LC with stop-flow fluorescence (FL), and constant energy synchronous fluorescence spectroscopy (CESFS) are explored to determine PAH isomers in three combustion-related standard reference materials.

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A detection method based upon aerosol charging was examined for its applicability and performance with high performance liquid chromatography.

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Mass spectrometry (MS) has advanced to analyze ever-larger biomolecules with the invention of soft ionization techniques like electrospray ionization (ESI). Although ESI has provided a method of generating ions of high mass, mass spectrometers generally suffer both lower sensitivity and lower resolution as the mass-to-charge ratio of an ion increases. To extend the mass range of ionized macromolecules beyond the limits of MS, macroion mobility spectrometry utilizes ion mobility sizing to characterize charge-reduced ESI-generated macroions from >5 kDa to beyond megadalton masses. One prominent application of macroion mobility spectrometry, highlighted here, is the high sensitivity analysis of intact proteins, antibodies, and conjugates in which molecular masses range from antibody light-chain fragments to high mass immunoglobulin multimers.

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Out of the several options available for retaining polar compounds like nucleotides, this application note focuses on the use of polar-modified C18 bonded phases for their analysis.

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Electrophoretic techniques, such as sodium dodecyl sulphate polyacrylamide (SDS-PAGE) and isoelectric focusing (IEF) gels, have traditionally been part of release testing in the biopharmaceutical industry. However, these slab gel methods are inconvenient and irreproducible because of the staining/destaining steps used in analyte detection, the use of toxic reagents and high intra- and inter-gel effective mobility variability.

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Out of the several options available for retaining polar compounds like nucleotides, this application note focuses on the use of polar-modified C18 bonded phases for their analysis.

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Fossil fuels are a limited resource, and the petroleum industry is always on the lookout for ways to extract more useful materials from crude oil. This session focuses on the use of mass spectrometry in the analysis of petroleum.

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Semiquantitative elemental analysis by ICP-MS is a powerful tool for quick screening of unknown samples for a wide range of elements.