LCGC Europe January 2017

January 2017 | Volume 30, Issue 1
Cover Story
Parallel artificial liquid membrane extraction (PALME) is a miniaturized version of liquid–liquid extraction (LLE) and is based on two 96-well plates in a sandwich-like configuration. With a very simple workflow, 96 samples can be processed simultaneously in PALME, providing analyte enrichment, highly efficient sample cleanup, and direct compatibility with liquid chromatography–mass spectrometry (LC–MS). The consumption of hazardous organic solvents is also almost eliminated using PALME as the sample preparation technique. This article summarizes current experiences with PALME, based on work both in a university laboratory and in an analytical services contract laboratory.
Features
A glimpse of what’s on offer for chromatographers at Pittcon 2017, which will be held from 5–9 March 2017 at McCormick Place in Chicago, Illinois, USA.
Using 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.
The free spreadsheet-based program HPLC Teaching Assistant was developed for effective and innovative learning and teaching of liquid chromatography. This software allows teachers to illustrate the basic principles of high performance liquid chromatography (HPLC) using virtual chromatograms (simulated chromatograms) obtained under various analytical conditions. In the first instalment of this series, we demonstrate the possibilities offered by this spreadsheet to illustrate the concept of chromatographic resolution, including the impact of retention, selectivity, and efficiency; understand the plate height (van Deemter) equation and kinetic performance in HPLC; recognize the importance of analyte lipophilicity (log P) on retention and selectivity in reversed-phase HPLC mode; and manipulate or adapt reversed-phase HPLC retention, taking into account the acido-basic properties (pKa) of compounds and the mobile-phase pH.
LC Troubleshooting
The mobile-phase pH can be a powerful tool to control retention and selectivity, but it can also get you in trouble if it is not controlled properly.
GC Connections
Separation scientists may seek an optimum spot between chromatographic performance required to obtain sufficient results quality, and the time and resources needed to do so. This instalment of “GC Connections” examines the factors that control peak resolution — one of the main drivers of separation quality — and how chromatographers can use this information to find an optimum between time, cost, and performance.
Sample Preparation Perspectives
This instalment describes several commonly used microextraction sample preparation techniques and their applications to forensic toxicology analysis. Solid-phase microextraction (SPME), microextraction by packed sorbent (MEPS), and different types of liquid-based microextraction (LPME), including single‑drop microextraction (SDME), hollow-fibre supported LPME, three-phase LPME, and dispersive liquid–liquid microextraction (DLLME), are discussed. Examples of application of these techniques to determine illicit drugs and drugs of abuse from various biological specimens are provided as well.
The Essentials
By LCGC Editors
An excerpt from LCGC’s e-learning tutorial on common solid-phase extraction (SPE) problems at CHROMacademy.com
Events
By LCGC Editors
The 45th International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC 2017) will be held from 18 to 22 June 2017 at the Prague Congress Centre, Prague, Czech Republic.
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