Author


R. Wijntje

Latest:

Analysis of Fructose, Glycine and Triglycine using UV/vis Detection and Evaporative Light-Scattering Detection

The 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.


Sylvie Héron

Latest:

Factors Affecting Sensitivity of Evaporative Light Scattering Detection

An evaporative light scattering (ELS) detector is a powerful detection tool if the solutes are less volatile than the eluent. Three main processes occur successively: nebulization, evaporation of the liquid chromatographic (LC) effluent and measurement of the light scattering by the residual particles. This leads to a non-linear calibration curve such as, A= a.m b where A is the peak area,m the sample mass and b the response coefficient measured as the slope of Log A = b>Log m + Log a.


Sophie Tijou

Latest:

Estimation of Triterpenes in Wines, Spirits, and Oak Heartwoods by LC–MS

The authors report the use of LC–MS for monitoring triterpenes in oak heartwoods, wines, and spirits.


Y. Vander Heyden

Latest:

Screening Designs (Part 2) Data Analysis

Screening for important factors during method optimization or in robustness testing involves two-level screening designs, such as fractional factorial and Plackett–Burman designs, as described in Part 1. This second part on screening designs discusses the experimental protocol for executing these designs and the data analysis of their results.


Ana María Santos-Montes

Latest:

Method Development and Validation for Phenol and Nitrophenols in Tap Water by HPLC using a Monolithic Column

An 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.


Gary Scharrer

Latest:

Factors and Parameters that Directly Affect Recovery of Collected Fractions in Preparative HPLC

Purification of synthetic, natural and biological compounds in any quantity usually requires the use of preparative HPLC.



Alain Tchapla

Latest:

Factors Affecting Sensitivity of Evaporative Light Scattering Detection

An evaporative light scattering (ELS) detector is a powerful detection tool if the solutes are less volatile than the eluent. Three main processes occur successively: nebulization, evaporation of the liquid chromatographic (LC) effluent and measurement of the light scattering by the residual particles. This leads to a non-linear calibration curve such as, A= a.m b where A is the peak area,m the sample mass and b the response coefficient measured as the slope of Log A = b>Log m + Log a.


M. Jackowski

Latest:

Practical Electromigration Techniques to Separate Microorganisms in Medical Analysis

This 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.


Kelly François

Latest:

Enhanced Sample Throughput for Environmental Analysis

As environmental legislation becomes more stringent, the need to deliver quantitative results in shorter times and greater volumes is necessary for routine environmental analysis. Most of the high-throughput screening methods used to analyze pharmaceutical compounds are, however, useless for environmental monitoring. This is because these methods primarily aim to retrieve as much information from a single sample using the broadest range of techniques. The chromatographic separation process is considered to be the bottleneck in the process. This is not the situation for environmental procedures, in which the bottleneck is the sample preparation step and is usually very tedious and time-consuming.


Yves Glories

Latest:

Estimation of Triterpenes in Wines, Spirits, and Oak Heartwoods by LC–MS

The authors report the use of LC–MS for monitoring triterpenes in oak heartwoods, wines, and spirits.



Cameron George

Latest:

Determination of Phthalate Esters by Positive Chemical Ionization MS with Retention-Time Locked GC

The authors describe a new instrumental method for determining phthalate esters using positive chemical ionization and retention-time locking GC.


Paul Rammage

Latest:

Asymmetric Flow Field-Flow Fractionation (AF4) with Multi-Angle Light Scattering (MALS) for High-Throughput Protein Refolding

One 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.


Elke Anklam

Latest:

The Benefits of Including Certified Reference Materials in a Collaborative Trial

This 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.


Jens Donath

Latest:

Cost Beneficial Validation of a Site-wide Chromatography Data System

The 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.



David S. Bell

Latest:

Recent Developments in HPLC & UHPLC

In the world of liquid chromatography, innovative strides in column technology continue to take place. We are also reminded that there is always more to learn about “well-known” methodologies, and our craft is continuously influenced by important social concerns.


T. Górecki

Latest:

Non-Discriminating Analytical Pyrolysis — A Novel Tool for Studying Environmental Samples

Conventional pyrolysis can cause defunctionalization of polar structural moieties carrying functional groups, which leads to biased results.


Andrew H. Grange

Latest:

Identifying Compounds Despite Chromatography Limitations: Organophosphates in Treated Sewage

The authors descrive the use of GC–MS to isolate and identify potentially toxic compounds in concentrated extracts of sewage treatment plant effluents.


Caitlin McEathron

Latest:

A NanoLC–MS Primer for Expression Proteomics: Part II

This 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.


Kit-Sum Wong

Latest:

The Application of Multiplexed Microemulsion Electrokinetic Chromatography for the Rapid Determination of log POW Values for Neutral and Basic Compounds

This 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.


Steven Collier

Latest:

A Four-Column Approach to Developing Stability-Indicating HPLC Methods

This 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.


Jonathan J. Gilroy

Latest:

Gradient Performance Problems — A Case Study

The 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.


Irena Choma

Latest:

The Use of Thin-Layer Chromatography with Direct Bioautography for Antimicrobial Analysis

This 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.


Marie-Geneviève Maloumbi

Latest:

Experimental Proofs of a Correlation Between the Coefficients for the Slope of the Response Line and the Response Factor of an ELSD

The 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.


Eberhardt R. Kuhn

Latest:

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.


Paul Budworth

Latest:

Analysis of Combinatorial Natural Products by HPLC and CE

In 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.


Z. Parsi

Latest:

Non-Discriminating Analytical Pyrolysis — A Novel Tool for Studying Environmental Samples

Conventional pyrolysis can cause defunctionalization of polar structural moieties carrying functional groups, which leads to biased results.


Thomas Wenzl

Latest:

The Benefits of Including Certified Reference Materials in a Collaborative Trial

This 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.