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The Application of Multiplexed Microemulsion Electrokinetic Chromatography for the Rapid Determination of log POW Values for Neutral and Basic CompoundsThis article illustrates the use of multiplexed microemulsion electrokinetic chromatography with UV detection to develop a rapid approach for obtaining log POW values of neutral and basic compounds.
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LC–MS Characterization of Mesquite Flour ConstituentsUsing a liquid chromatography–mass spectrometry (LC–MS) method in conjunction with two complementary types of chromatographic retention modes-reversed phase and aqueous normal phase-various compounds present in mesquite flour extracts were identified. Because of the diverse types of chemical constituents found in such natural product extracts, a single chromatographic mode may not be sufficient for a comprehensive characterization. However, the combination of reversed-phase and aqueous normal phase LC can encompass a wide range of analyte polarity. This characterization of the composition of mesquite flour could be used in future studies to elucidate the beneficial health effects of its consumption.
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Pressure-driven Chromatography in Perfectly Ordered Pillar Array Columnshis article reveals the first liquid chromatography (LC) separations performed on a microfabricated pillar array column under pressure-driven conditions. The pillars were non-porous and produced using a Bosch-type deep reactive ion etch (DRIE) to pattern the surface of a silicon wafer and had a diameter of approximately 5 μm. Two different packing densities were compared: one similar to the packing density of a packed bed (external porosity of approximately 49%) and one similar to the packing density of monolithic columns (external porosity of approximately 70%).
Latest:
The Application of Multiplexed Microemulsion Electrokinetic Chromatography for the Rapid Determination of log POW Values for Neutral and Basic CompoundsThis article illustrates the use of multiplexed microemulsion electrokinetic chromatography with UV detection to develop a rapid approach for obtaining log POW values of neutral and basic compounds.
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A Laser Diode Double-Pumped Solid-State Laser-Induced Fluorescence Detector for Capillary Electrophoresis and Liquid ChromatographyThe authors describe a new laser-induced flourescence detector for application to both capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC).
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GC Analysis of Trihalomethanes in Drinking Water — A Rapid and Direct Quantitative MethodThe authors describe a GC assay of trihalomethanes in drinking water.
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MS and Emerging Environmental ContaminantsThe environment and possible contaminants will take center stage in a Wednesday afternoon session at the 57th annual ASMS Conference in Philadelphia, Pennsylvania.
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Advances in Sample Preparation: Removing Phospholipids from Biological SamplesAdvances in Sample Preparation: Removing Phospholipids from Biological Samples
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Strategies for The Purification of Synthetic Products in The Pharmaceutical IndustryBy taking advantage of the benefits provided by normal-phase mode, highly productive and cost-effective strategies for high-throughput purification of drug discovery products have been developed in the analytical laboratories at Lilly-Spain. The straightforward scaling-up of generic protocols from an analytical to a preparative scale has yielded successful results not only when working in HPLC but also when transferring conditions to other standard low and medium pressure chromatographic systems that are routinely used by synthetic chemists.
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Improving the Confidence of Unknown Compound Identification by First Responder Mobile GC–MS Laboratories...A novel method that significantly improves the accuracy and reliability of "unknown" compound identification for volatile organic compounds by GC-MS is described.
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Column Pore Size—An Underutilized Variable for OptimizingIn advance of Pittcon 2018, leading scientists-Ronald Majors, Richard Henry, John W. Dolan, Zachary S. Breitbach, and Daniel W. Armstrong-who will be speaking at the LCGC awards symposium give us a preview of their talks.
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Analysis of Ethylene Oxide and 2-Chloroethanol in Food Products: Challenges and SolutionsThe importance of accurate analysis methods for EtO and 2-CE in food is essential and the demand for robust methods that are able to deliver high sample throughput with minimal instrumental downtime is high.
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A GC–MS Purge-and-Trap Method Comparison Study for MTBE Analysis in GroundwaterThis article describes a study that assesses the ability of commercially available GC–MS methods to meet project criteria for MTBE in groundwater matrices.
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Multi-Residue Pesticide Screening Method Using GC–MSPesticides are widely used by farmers to control pests, weeds and molds that would otherwise decrease crop production. While this has significantly increased worldwide food productions, these same pesticides pose health risks to humans. The restrictions for specific pesticides differ from one country to the next and as world trade increases, the potential threat to other countries' populations increases. For this reason, pesticides and other food related allergens are currently the subjects of increasing scrutiny and regulation.
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Is Cyclohexane a Suitable HPLC Solvent? It Can Become Solid Under PressureIf cyclohexane is mixed with even low amounts of other solvents, the melting pressure increases remarkably.
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Determination of Soft Drink IngredientsSoft drink formulas often include preservatives, artificial sweeteners, flavours or caffeine in their list of ingredients. Using the Acclaim OA column, as many as eight common additives may be determined in a single run. Many of these additives are hydrophilic organic acids for which this column was designed. Notably, benzoate and sorbate, which do not resolve on C18 columns at low pH, are fully separated.
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Practical Electromigration Techniques to Separate Microorganisms in Medical AnalysisThis article looks at the use of electromigration techniques to determine microorganisms, such as viruses, bacteria and other biologically important macromolecules (erythrocytes), in medical analyses. It was found that electromigration techniques could be used for the identification of several viruses, including the identification of a specific marker for the Hepatitis C virus infection and another for a urinary tract infection. The determination of cell viability and the quality control of probiotics and consumer products that contain active bacteria is also possible using electromigration. Special attention is paid to the modification of capillary wall surfaces using different monomers and the application of monolithic columns to determine active bacteria in pharmaceutical products using capillary electrochromatography (CEC) conditions. This approach represents a new frontier for separation science and the possibility to apply it in medical diagnosis.
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Liquid Chromatography–Time-of-Flight Mass Spectrometry for Cannabinoid Profiling and Quantitation in Hemp Oil ExtractsA primary impediment to cannabinoid research is the fact that materials possessing psychoactive Δ-9-tetrathydrocannabinol are considered Schedule I drugs as defined in the U.S. Controlled Substances Act. An alternative source of cannabinoids may be found in hemp oil extracts. Hemp contains a low percentage of Δ-9-tetrathydrocannabinol (THC) by weight but relatively high amounts of non-psychoactive cannabinoids. The liquid chromatography-time of flight mass spectrometry (LC-TOF) method presented herein allows for the accurate, precise and robust speciation, profiling and quantification of cannabinoids in hemp oil extracts and commercial cannabinoid products for research and development laboratories. The method was determined to chromatographically separate 11 cannabinoids including differentiation of Δ-8-tetrahdrocannabinol and THC with excellent linear dynamic range, specificity and sensitivity.
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The Application of Multiplexed Microemulsion Electrokinetic Chromatography for the Rapid Determination of log POW Values for Neutral and Basic CompoundsThis article illustrates the use of multiplexed microemulsion electrokinetic chromatography with UV detection to develop a rapid approach for obtaining log POW values of neutral and basic compounds.
Latest:
A Global Approach to HPLC Column Selection Using Reversed Phase and HILIC Modes: What to Try When C18 Doesn't WorkExperimental data are presented to help understand HPLC column retention in a way that should make column selection and method development proceed faster when initial results with C18 columns are disappointing.
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SQL — The Database Language for Getting ResultsAn introduction to SQL, the language that creates, maintains, manipulates, and queries relational databases.
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Stationary Phases for Planar Separations — Plates for Modern TLCThe authors provide the latest information on new stationary phases for modern TLC and high performance TLC (HPTLC), along with helpful hints on how to get the most out of this flexible form of chromatography.
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A Chromatographic Screening Method to Identify Agents that Reverse Intrinsic Drug Resistance in Colon Cancer CellsConjugation catalysed by the UDP-glucuronosyltransferase (UGT) superfamily of drug-metabolizing enzymes is an important mechanism of anticancer drug resistance in colon cancer cells. The mechanism manifests itself by a reduction in the intracellular concentrations of the parent drug through increased export of the glucuronide metabolites to the extracellular compartment. Modulation by an inhibitor of UGT inhibits the formation of metabolites and restores intracellular concentrations of the drug. This article describes a screening method using HT29 human colon cancer cells and based on HPLC methodology that allows the identification of effective modulators of the glucuronidation mechanism of drug resistance. A rapid solid-phase sample preparation technique using C2-bonded 40 ?m silica particles was developed for the extraction of cell lysates and culture media without degradation of unstable parent compounds and their glucuronides or artefactual in situ formation of metabolites.
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Quantitative Analysis of the Composition of Tea Tree OilThe analysis of tea tree oil requires a severe quality control due to its potential to induce and elicit skin allergies. Tea tree oil is an essential oil and consists of a large number of constituents. Heart-cut Multidimensional GC–MS is very well suited to analysis of samples of such high complexity.
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Practical Electromigration Techniques to Separate Microorganisms in Medical AnalysisThis article looks at the use of electromigration techniques to determine microorganisms, such as viruses, bacteria and other biologically important macromolecules (erythrocytes), in medical analyses. It was found that electromigration techniques could be used for the identification of several viruses, including the identification of a specific marker for the Hepatitis C virus infection and another for a urinary tract infection. The determination of cell viability and the quality control of probiotics and consumer products that contain active bacteria is also possible using electromigration. Special attention is paid to the modification of capillary wall surfaces using different monomers and the application of monolithic columns to determine active bacteria in pharmaceutical products using capillary electrochromatography (CEC) conditions. This approach represents a new frontier for separation science and the possibility to apply it in medical diagnosis.
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Method Development and Validation for Phenol and Nitrophenols in Tap Water by HPLC using a Monolithic ColumnAn isocratic HPLC method for the determination of phenol and nitrophenols (4-nitrophenol, 2-nitrophenol, 4,6-dinitro-o-cresol and 2,4-dinitrophenol) has been developed and validated using 2-chlorophenol as internal standard (IS) and a monolithic column in tap water samples. Prior to HPLC, the method requires solid-phase extraction (SPE) using polymeric Lichrolut EN cartridges. The method development involved the study of methanol and acetonitrile as organic modifiers, pH and flow-rate using a Chromolith RP-18e (150 mm × 4.6 mm I.D.) column. After comparing the performance of the separations obtained with both organic modifiers, the optimum separation of these compounds was achieved using 50 mM acetate buffer (pH 5.0)-acetonitrile (80:20, v/v) as mobile phase, 3 mL min-¹ flow-rate and UV detection at maximum absorbance wavelength. Under these conditions, all analytes were separated (Rs > 2.0) in an analysis time of less than 3.5 min and the most important validation parameters were evaluated. The recoveries obtained in the accuracy test for all phenols studied were in the 90–112% range using a preconcentration factor of 40, and the intraday and interday precisions [expressed as coefficient of variation (CV)] were smaller than 15%. Finally, the proposed method was applied to wastewater samples from several industries.
Latest:
Strategies for The Purification of Synthetic Products in The Pharmaceutical IndustryBy taking advantage of the benefits provided by normal-phase mode, highly productive and cost-effective strategies for high-throughput purification of drug discovery products have been developed in the analytical laboratories at Lilly-Spain. The straightforward scaling-up of generic protocols from an analytical to a preparative scale has yielded successful results not only when working in HPLC but also when transferring conditions to other standard low and medium pressure chromatographic systems that are routinely used by synthetic chemists.
Latest:
Analysis of Combinatorial Natural Products by HPLC and CEIn this article the authors report on a combinatorial natural product discovery methodology that uses a viral vector system to transfer secondary metabolite-related enzymes from C. roseus to tobacco cell cultures. Using high-resolution separation techniques, including HPLC, CE and MS, they describe the analysis of secondary metabolite patterns.
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An Introduction to OPLC Operation and ApplicationsThis article describes the basis of OPLC and its instrumentation, and provides brief details of recent applications for which this technique is suited.
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Validation of an Aqueous Normal Phase Chromatography Method for the Analysis of Ergothioneine in Commercial MushroomsThe authors developed a new analytical HPLC method using a silica hydride-based column to analyze mushrooms.
