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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.
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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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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.
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Are You Sure You Understand USP <621>?In this column, we look at the current version and the update of USP <621> on high-performance liquid chromatography (HPLC) that becomes effective 1st May 2025.
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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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Optimizing Column Lifetime of TSK-GEL Size Exclusion ColumnsColumn lifetime is a more and more important issue when developing an analytical method for HPLC. Besides sample treatment, column cleaning and storage, operational parameters of the analytical method will have an influence on column lifetime. This question may not always be addressed early enough in the methods development process.
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Determination of PAHs in Combustion-Related Samples via Multidimensional Chromatographic MethodsGas 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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My 50+ Years in ChromatographyThe former "Milestones in Chromatography" editor returns to give readers the story of his time in the field.
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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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Factors and Parameters that Directly Affect Recovery of Collected Fractions in Preparative HPLCPurification of synthetic, natural and biological compounds in any quantity usually requires the use of preparative HPLC.
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Analysis of Fructose, Glycine and Triglycine using UV/vis Detection and Evaporative Light-Scattering DetectionThe development of a method for the simultaneous determination of glycine, triglycine and fructose using UV/vis and evaporative light-scattering is presented. The study formed part of a research project dealing with the recovery of functional peptides from aqueous streams on an industrial scale using absorption or related technologies.
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Influence of Na+- and K+- Concentration in Solvents on Mass Spectra of Peptides in LC/ESI–MSIn this article, the authors examine the concentration-dependent influence of Na+- and K+ ions on mass spectra of peptides, with human gastrin as a model peptide using LC/ESI–MS as the selected ionization technique.
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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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Analysis of Fructose, Glycine and Triglycine using UV/vis Detection and Evaporative Light-Scattering DetectionThe development of a method for the simultaneous determination of glycine, triglycine and fructose using UV/vis and evaporative light-scattering is presented. The study formed part of a research project dealing with the recovery of functional peptides from aqueous streams on an industrial scale using absorption or related technologies.
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Directions in Automated Sample Preparation of ProteinsThe guest authors discuss current procedures for protein sample preparation, protein analysis, and automation.
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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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Simultaneous Determination of Chelating Agents by Ion-Suppression and Ion-Pair Chromatography in WastewaterChelating agents such as NTA, CDTA and DTPA are considered by ANDRA (the French national agency for radioactive waste management) as compounds to be investigated because they may enhance the release of radioactive isotopes in the environment.
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Estimation of Triterpenes in Wines, Spirits, and Oak Heartwoods by LC–MSThe authors report the use of LC–MS for monitoring triterpenes in oak heartwoods, wines, and spirits.
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Tandem GC–MS Analysis of Pesticides in Food Oils by Large Volume Injection with a Back-flush OptionAs the global sourcing of foodstuffs becomes more common, the number of pesticide analyses performed continues to increase to test these sources for compliance with various regulations. The sheer number of analyses dictates that utilized methods must be reliable, robust and inexpensive.
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Benchmarking for Analytical Methods: The Horwitz CurveAnalytical chemists are concerned with the quality of their methods and results. An important question in this context is whether the precision of a newly developed and validated method is up to standard. In other words: is the precision of the newly developed method comparable to what could be expected? This article looks at how the Horwitz equation can answer this. It also describes the results of an extensive study involving 10000 laboratories which indicates that the relative reproducibility approximately doubles for every 100-fold decrease in concentration and that, surprisingly, it does not depend on the type of material or method.
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On-line Supercritical Fluid Extraction-Capillary Gas Chromatography for the Analysis of DieselDirect coupling of SFE with GC has advantages over the off-line alternative.
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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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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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System Suitability and Validation for Chiral Purity Assays of Drug SubstancesMeasurement of chiral purity is a necessary means of quality control for drug substances that exhibit chiral centers. This article describes a simple and practical approach to setting up system suitability and validation for chiral purity assays.
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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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Analysis of Biodiesels Using LC–MSPreliminary studies of biodiesel samples by a high speed LC–MS system using electrospray ionization and a patented cone-wash feature demonstrate that LC–MS reduces the analysis time to 20 minutes and reveals information about higher molecular weight compounds in biodiesel while still detecting many low molecular weight chemicals, including FAMEs, at high sensitivity.
