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Precision of Internal Standard and External Standard Methods in High Performance Liquid ChromatographyInternal standard methods are used to improve the precision and accuracy of results where volume errors are difficult to predict and control. A systematic approach has been used to compare internal and external standard methods in high performance liquid chromatography (HPLC). The precision was determined at several different injection volumes for HPLC and ultrahigh‑pressure liquid chromatography (UHPLC), with two analyte and internal standard combinations. Precision using three methods of adding the internal standard to the analyte before final dilution was examined. The internal standard method outperformed external standard methods in all instances.
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Enantiomer and Topoisomer Separation of Acidic Compounds on Anion-Exchanger Chiral Stationary Phases by HPLC and SFCQuinine- and quinidine-derived anion-exchanger chiral stationary phases have proven to be versatile in enantiomer separation of acidic compounds in HPLC. In this article, the authors demonstrate their performance in specific HPLC applications involving enantiomer resolution and topoisomer separation.
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Fast Cap IC Determinations of Inorganic Anions and Cations in Drinking WaterThermo Scientific Application Note
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Challenges in Small-Molecule Quantitation by Mass SpectrometryDrug discovery scientists are continually striving to improve productivity and efficiency in their workflows. From early discovery to clinical development, existing workflow bottlenecks represent an opportunity to develop solutions to speed the process and improve productivity. The key requirements for quantitative analysis are precision, accuracy, and linear dynamic range. With any quantitative instrument, the hope is that it will be applicable to a vast range of coumpounds, ruggest, and fast. New mass spectrometry (MS) technologies are being developed that meet these criteria and permit high throughput while enabling its application to areas in which speed limitations previously curtailed its practicality. In particular, in the area of ADME profiling, new MS platforms are becoming available that increase the throughput by at least 25-fold, by combining the speed of matrix-assisted laser desorption ionization (MALDI) with the specificity of triple-quadrupole MS. This is bound to greatly accelerate the ADME..
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Sulfated β-Cyclodextrin as Chiral Mobile Phase Additive for Ultrahigh-Pressure Liquid ChromatographyA fast enantiomeric separation of a chiral aromatic amine was achieved, using ultra high pressure liquid chromatography and highly sulfated β-cyclodextrin (S-β-CD) as a chiral additive in the mobile phase. The stationary phase consisted of a core shell support with a particle size of 2.7 µm. Under these conditions the baseline separation was obtained within 2.5 min. The influence of the concentration of the additive, along with the thermodynamics of the separation, were studied. Molecular mechanics calculations were consistent with the experimental data for the order of elution, providing further evidence of these interactions. The enantiomeric separation at high temperature (90 °C) using only water as mobile phase also was achieved for the first time.
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Removal of Endogenous Matrix Components Using EVOLUTE® CX Mixed-Mode Cation Exchange Solid Phase ExtractionSample 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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Evaluation of Extraction Methods and Bias Correction by EPA Method 6800 Protocol for Mercury Species in Tuna Fish Tissue Using an Ion Chromatograph Coupled to an ICP–MSMercury pollution mainly originates from industrial activities such as chlorine production, garbage incineration and above all coal-fueled power generation. The US Environmental Protection Agency (US EPA) considers mercury as highly toxic with a pronounced accumulative and persistent character.
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Facilitating Discovery of Prion Disease Biomarkers by Quantitative GlycoproteomicsThe authors examine MS-based methods to search for protein biomarkers of prion diseases from plasma samples.
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Liquid Chromatography Coupled with Tandem Mass Spectrometry for Clinical ApplicationsThe use of mass spectrometry (MS) in clinical diagnosis goes back to the early 1970s with the application of gas chromatography (GC)–MS to the determination of a variety of biologically significant molecules. Because GC requires a certain level of analyte volatility, and since most biologically active molecules are polar, thermolabile, and involatile, elaborate extraction and derivatization protocols needed to be devised to make GC–MS useful for the analysis of clinically relevant samples. To make sample analysis less difficult by MS there had been a significant amount of R&D invested over several decades aimed at coupling high performance liquid chromatography (HPLC) with MS since HPLC is a much better separation technology than GC for polar thermolabile biologically relevant molecules. This coupling was not without significant challenges; most of the LC–MS coupling techniques that evolved during the 1970s and 1980s were not very successful, and many of those that enjoyed some widespread..
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A Feasibility Study of Using Supercritical Fluid Chromatography (SFC)-UV-ELSD for Food and Beverage AnalysesSupercritical fluid chromatography (SFC) is a normal phase separation technique. In SFC, supercritical CO2 in combination with one or more polar organic solvents, most commonly alcohols, is used as the mobile phase. Owing to the lack of intermolecular interactions, supercritical fluid typically possesses lower viscosity and higher diffusivity than those solvents used in traditional high performance liquid chromatography (HPLC). This allows for higher flow rates, faster analyses, and the use of longer columns for higher chromatographic efficiencies. Initially deemed a niche chromatographic technique for chiral separation, the horizon of SFC applications has rapidly expanded to include achiral analyses of natural products, biodiesel, oligomer, pesticides/herbicides, and peptides. This is due, in part, to the improvements in detection choices and performances for SFC. Evaporative light scattering detectors (ELSDs) coupled with SFC have found wide use in many pharmaceutical and chemical laboratories (1).
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Automated Extraction Technique for Improved Recovery of PhenolsDionex has developed a new standard for flow-through solvent extraction which allows accelerated solvent extraction (ASE®) of matrices that have undergone acid or alkaline pretreatment or digestion. The new ASE 150 and ASE 350 systems use extraction cells and post-cell solvent pathways constructed of Dionium™ material. This pH-hardened substance resists corrosion under acidic or alkaline conditions used in standard pretreatments, widening the scope of ASE applications and significantly expanding its capabilities.
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Linear Thinking in a Nonlinear WorldA very useful construct in engineering and analytical chemistry is the concept of a time-invariant linear system. The properties of the system (as for a mathematical function) are defined by a relationship between the response and the excitation, and ...
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A Quality-by-Design Methodology for Rapid LC Method Development, Part IIIThe guest columnists continue their examination of how statistically rigorous QbD principles can be put into practice.
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Dosing Vehicle Removal in Discovery Phase Pharmacokinetic Studies Using High-Field Asymmetric Waveform Ion Mobility SpectrometryThis article describes the ability to increase the sensitivity for a target compound in the presence of high-level background impurities by removing the dosing vehicle using a high-field asymmetric waveform ion mobility spectrometry gas-phase separation before mass spectrometry analysis.
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Study of Free Radical Fragment Ions Generated from ESI-CID-MS-MS Using LTQ and LTQ Orbitrap Mass SpectrometersStudies of odd-electron CID behaviors reveal that free radical fragmentation is structure-dependent and is directly correlated with the functional groups that stabilize the newly-formed free radicals.
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The Improved Chiral Resolution of MecopropThis application note demonstrates how the use of DCM in particular had a dramatic effect on the separation and afforded conditions that could be further adapted to a preparative scale application.
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Application of Silica Monoliths for BioanalysisIn this article, the application of silica monoliths with bimodal pore structure (macro and mesopores) is described for the chromatographic analysis of biomolecules including peptides, proteins, and antibodies.
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Detection of Doping Agents by LC–MS and LC–MS-MSIn the last decade, research on the detection of all groups of doping agents has been investigated by LC-MS, and routine LC-MS screening applications are now available for almost all classes of doping agents.
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Sulfated β-Cyclodextrin as Chiral Mobile Phase Additive for Ultrahigh-Pressure Liquid ChromatographyA fast enantiomeric separation of a chiral aromatic amine was achieved, using ultra high pressure liquid chromatography and highly sulfated β-cyclodextrin (S-β-CD) as a chiral additive in the mobile phase. The stationary phase consisted of a core shell support with a particle size of 2.7 µm. Under these conditions the baseline separation was obtained within 2.5 min. The influence of the concentration of the additive, along with the thermodynamics of the separation, were studied. Molecular mechanics calculations were consistent with the experimental data for the order of elution, providing further evidence of these interactions. The enantiomeric separation at high temperature (90 °C) using only water as mobile phase also was achieved for the first time.
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Recent Advances in Ultrahigh-Pressure Liquid ChromatographyUltrahigh-pressure liquid chromatography (UHPLC) is a technique that is experiencing continued growth due to the benefits in separation power and speed of analysis over traditional HPLC. We attempt here to give an overview of some of the advances that have occurred in UHPLC since 2003, from the standpoint of both fundamental research and the introduction of commercially-available technology.
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Facilitating Discovery of Prion Disease Biomarkers by Quantitative GlycoproteomicsThe authors examine MS-based methods to search for protein biomarkers of prion diseases from plasma samples.
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Using the iDQuant Standards Kit for Pesticide Analysis to Analyse Residues in Fruits and Vegetable SamplesAB Sciex Application Note
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The Benefits of Multi‐angle Light Scattering for Size‐Exclusion ChromatographyAnalytical size-exclusion chromatography (SEC) often suffers from several limitations. This article shows how some of these limitations can be partly (or even completely) resolved by a multi-angle light scattering (MALS) detector for the determination of molar mass distributions of synthetic and natural polymers.
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Analysis of Allergens in Fragrances using Multiple Heart-cut Multidimensional Gas Chromatography–Mass SpectrometryA total of fourteen cuts were defined because the retention time difference between several skin sensitizors was only slight.
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Investigation of Transferrin Structure via Novel Electron Capture Dissociation Techniques Using a Hybrid Linear Ion Trap Time-of-Flight Mass SpectrometerProtein and peptide analysis via tandem mass spectrometry (MS-MS) has resulted in a wealth of information regarding protein identification, structure, and abundance levels over the past 10 years. Techniques such as neutral loss scanning and collision-induced dissociation (CID) have been especially helpful in facilitating the identification of a multitude of previously unknown sites of protein phosphorylation. However, many of the techniques used to obtain this information are labor intensive and work inconsistently. To address this problem, much effort has been put forth to find alternative methods of fragmenting peptides and proteins that are less difficult and applicable to a wide gamut of peptide classes. Examples of recently developed dissociation techniques include infrared multiphoton dissociation (IRMPD) and electron transfer dissociation (ETD). The implementation of these new techniques has widened the spectrum of peptides amenable to tandem mass spectral analysis.
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Evaluation of Extraction Methods and Bias Correction by EPA Method 6800 Protocol for Mercury Species in Tuna Fish Tissue Using an Ion Chromatograph Coupled to an ICP–MSMercury pollution mainly originates from industrial activities such as chlorine production, garbage incineration and above all coal-fueled power generation. The US Environmental Protection Agency (US EPA) considers mercury as highly toxic with a pronounced accumulative and persistent character.
Latest:
Facilitating Discovery of Prion Disease Biomarkers by Quantitative GlycoproteomicsThe authors examine MS-based methods to search for protein biomarkers of prion diseases from plasma samples.
