May 17th 2024
Here are the top five articles that the editors of LCGC International published this week.
Liquid Chromatography Coupled with Tandem Mass Spectrometry for Clinical Applications
November 1st 2008The use of mass spectrometry (MS) in clinical diagnosis goes back to the early 1970s with the application of gas chromatography (GC)–MS to the determination of a variety of biologically significant molecules. Because GC requires a certain level of analyte volatility, and since most biologically active molecules are polar, thermolabile, and involatile, elaborate extraction and derivatization protocols needed to be devised to make GC–MS useful for the analysis of clinically relevant samples. To make sample analysis less difficult by MS there had been a significant amount of R&D invested over several decades aimed at coupling high performance liquid chromatography (HPLC) with MS since HPLC is a much better separation technology than GC for polar thermolabile biologically relevant molecules. This coupling was not without significant challenges; most of the LC–MS coupling techniques that evolved during the 1970s and 1980s were not very successful, and many of those that enjoyed some widespread..
Micellar Liquid Chromatography: How to Start
September 1st 2008Micellar liquid chromatography (MLC) is a reversed-phase liquid chromatographic mode with a solution of surfactant forming micelles as the mobile phase. The interaction of solutes with the stationary phase coated with surfactant monomers, combined with the increased solubilization capability of micelles, have profound implications with regard to retention, selectivity and efficiency. Practical steps that a chromatographer involved in MLC should consider when developing an analytical procedure are described, including mobile phase preparation, column conditioning and cleaning.
Extracting Information from Chromatographic Herbal Fingerprints
September 1st 2008Herbs and their extracts are currently being used for preventive and therapeutic goals. Consequently, the identification and quality control of these natural products is becoming increasingly important. Fingerprint chromatography is accepted as an appropriate identification and quality evaluation technique for medicinal herbs. This article reviews the development procedure of a fingerprint and different ways to handle the fingerprint data.
The Application of Capillary Electrophoresis for Vaccine Release and Characterization
September 1st 2008Capillary electrophoresis (CE) is increasingly being used in vaccine analysis. Applications include vaccine quantification, purity assessment, process monitoring, characterization and nucleic acid analysis. CE has been used because it offers advantages over other techniques. Vaccine manufacturers such as Sanofi-Aventis, Merck and Wyeth are actively investigating the use of CE for vaccine analysis. While CE can be considered a mature technique, its application to vaccine release and characterization has been limited. It is difficult to ascertain if its use is expanding because there are still a small amount of publications, but given the inherent advantages of CE and the need for better analytical techniques in vaccine analysis, the application must be growing. This article illustrates some of the uses of CE in vaccine analysis.
Linear Thinking in a Nonlinear World
August 1st 2008A very useful construct in engineering and analytical chemistry is the concept of a time-invariant linear system. The properties of the system (as for a mathematical function) are defined by a relationship between the response and the excitation, and ...
A Hydrophilic Interaction Chromatography Method for the Purity Analysis of Cytosine
July 1st 2008The authors meet the need for a method for the determination of cytosine purity by developing a hydrophilic interaction chromatography (HILIC) method with demonstrated advantages in comparison to other separation techniques.
LCxLC: Comprehensive Two-Dimensional Liquid Chromatography
July 1st 2008Guest Editor Peter Schoenmakers provides an introduction to LCxLC, and then goes on to talk about peak capacity, sample dimensionality, phase orthogonality, and some of the successes of the technique and the obstacles yet to be overcome.
Quantitative Analysis of 25-OH-D2 and 25-OH-D3 in Serum by LC-MS-MS
March 30th 2008Vitamin D is a group of fat-soluble prohormones that helps the body absorb calcium and maintain proper levels of calcium and phosphorus in the blood. A vitamin D deficiency results in impaired bone mineralization and leads to bone-softening diseases, such as rickets in children and osteomalacia and osteoporosis in adults, as well as autoimmune and nervous system diseases. A vitamin D overdose can raise blood levels of calcium and cause gastrointestinal symptoms and kidney disease. High blood levels of calcium also can cause heart rhythm abnormalities and calcinosis, the deposition of calcium and phosphate in the body's soft tissues.
Successful Extraction of Basic Drugs from Plasma Using Mixed-Mode Solid-Phase Extraction
February 29th 2008This article aims to demonstrate the unique capability of resin-based mixed-mode solid-phase extraction (SPE) to achieve efficient extraction of basic drugs from plasma. Optimized pore size of the method minimizes retention of high molecular weight matrix components present in the biological fluid samples. The interferences are removed, ensuring extremely clean extracts for subsequent liquid chromatography?mass spectrometry-mass spectrometry (LC-MS-MS) analysis.
Immunosorbents for Selective Sample Preparation of Complex Mixtures
January 1st 2008Selective sample preparation techniques are particularly attractive for the analysis of trace amounts of small molecules in complex matrices. In this month's instalment, columnist Ron Majors covers the field of immunoextraction, a technique that employs immobilized antibodies to selectively capture specific analytes using molecular recognition via antibody–antigen interactions. Recently, the introduction of commercial products for specific high-volume environmental and food safety applications should spur further applications of this technique.