Author
Latest:
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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Determination of Phthalate Esters by Positive Chemical Ionization MS with Retention-Time Locked GCThe authors describe a new instrumental method for determining phthalate esters using positive chemical ionization and retention-time locking GC.
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Asymmetric Flow Field-Flow Fractionation (AF4) with Multi-Angle Light Scattering (MALS) for High-Throughput Protein RefoldingOne of the biggest problems facing researchers involved in pharmacogenomics is analysing the recombinant proteins of interest to monitor if they are in a folded state. This article describes a rapid and economical method using asymmetric flow field-flow fractionation combined with multi-angle light scattering (AF4–MALS) to characterize refolded proteins, which overcomes some of the disadvantages associated with other techniques.
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The Benefits of Including Certified Reference Materials in a Collaborative TrialThis article assesses the advantages of including certified reference materials in collaborative method validation studies in food analysis. A recently conducted collaborative trial on the determination of acrylamide in bakery and potato products is described to illustrate this.
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Cost Beneficial Validation of a Site-wide Chromatography Data SystemThe implementation and validation of a new site-wide chromatography data system for a major active pharmaceutical ingredient custom manufacturer provided the opportunity to map and optimize the GMP and ISO business processes to use electronic signatures effectively. This article describes the process optimization and how it integrates with the validation activities of the system. This overall approach provides substantial business benefits from the use of electronic signatures as evidenced by the savings resulting from process improvement and by the fact that the non-GMP laboratories implemented a similar process to analyse and approve results electronically.
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The Role of HPLC Columns in Shaping a Greener Analytical FutureThis article delves into advancements in green chromatography, focusing on how innovative HPLC column design can drive eco-conscious practices.
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Non-Discriminating Analytical Pyrolysis — A Novel Tool for Studying Environmental SamplesConventional pyrolysis can cause defunctionalization of polar structural moieties carrying functional groups, which leads to biased results.
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Identifying Compounds Despite Chromatography Limitations: Organophosphates in Treated SewageThe authors descrive the use of GC–MS to isolate and identify potentially toxic compounds in concentrated extracts of sewage treatment plant effluents.
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A NanoLC–MS Primer for Expression Proteomics: Part IIThis is the second installment of a two-part series on the practical aspects of configuring and operating a nano liquid chromatography-mass spectrometry (LC-MS) system.
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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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A Four-Column Approach to Developing Stability-Indicating HPLC MethodsThis article describes a method development approach that uses different packing materials and mobile-phase pH levels to optimize the chromatographic separation of degradation products from active ingredients.
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Gradient Performance Problems — A Case StudyThe gradient linearity and step tests are two of the most useful performance tests that can be made for a liquid chromatography (LC) system. These check the linearity of gradient generation and the accuracy of mobile phase proportioning. These tests, and examples of problems detected as a result of these tests, have been the subject of at least seven "LC Troubleshooting" columns over the last 18 years.1–7 We strongly recommend that every LC system undergo these tests at least on an annual basis, and preferably semiannually. When a new and different example of a problem detected by these tests is discovered, it is hard to bypass the opportunity to share it with our readers. So this month, you get yet another example of how an LC system can fail.
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The Use of Thin-Layer Chromatography with Direct Bioautography for Antimicrobial AnalysisThis article gives an overview of screening methods for the detection of antimicrobials, including dilution and diffusion methods and bioautography, mainly direct bioautography. The thin-layer chromatography method with direct bioautography was worked out to analyse enrofloxacin and ciprofloxacin residues in milk.
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Experimental Proofs of a Correlation Between the Coefficients for the Slope of the Response Line and the Response Factor of an ELSDThe authors describe a study that was conducted to evaluate the correlation between the slope of the response line and the response factor of an ELSD that are ordinarily regarded as independent numerical coefficients.
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Water Injections in GC — How Wet Can You Get?The author reports results from a systematic study of the effect of water injections on column performance with a number of common GC stationary phases.
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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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Non-Discriminating Analytical Pyrolysis — A Novel Tool for Studying Environmental SamplesConventional pyrolysis can cause defunctionalization of polar structural moieties carrying functional groups, which leads to biased results.
Latest:
The Benefits of Including Certified Reference Materials in a Collaborative TrialThis article assesses the advantages of including certified reference materials in collaborative method validation studies in food analysis. A recently conducted collaborative trial on the determination of acrylamide in bakery and potato products is described to illustrate this.
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A Geometric Approach to Robustness Testing in Analytical HPLCThe authors describe a new approach for verifying robustness testing in HPLC.
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Non-Discriminating Analytical Pyrolysis — A Novel Tool for Studying Environmental SamplesConventional pyrolysis can cause defunctionalization of polar structural moieties carrying functional groups, which leads to biased results.
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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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De Novo Formula Generation with "Sub-ppm" Confidence using Compass OpenAccess and the micrOTOFAccurate mass measurements are a key element of chemical characterization. However, the accepted mass accuracy tolerance of 3–5 ppm can still leave significant ambiguity in the proposed chemical formula. Consequently a further input from other analytical techniques such as NMR or MS/MS, along with some judgment based on the synthetic history is often required to arrive at a confident formula assignment.
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Forensic Drug Screening by LC–MS Using Accurate Mass MeasurementBecause of progress in liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS) instrumentation, data processing and reporting, the measurement of compounds' accurate masses is becoming routine practice in screening analysis based on target databases. As such databases of monoisotopic masses can be easily updated with recent data from the literature; rapid characterization of new compounds and metabolites is possible without the need for primary reference standards. This approach has already been established in comprehensive toxicological urine screening and in analysis of drugs-of-abuse in seized street drug samples. Currently, a mass accuracy within 5 ppm can be routinely achieved, and confirmation via a numerical isotopic pattern match (SigmaFit) is provided by a new generation LC/TOF-MS instrument.
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Classifying Chromatographic Systems by ClusteringIt would help to have a restricted set of chromatographic systems (CS) that together serve as potential starting points in method development.
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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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Preparative Chromatography with Improved LoadabilityThe authors show that the loadability and throughput of ionizable compounds can be enhanced by using hybrid packings.
