HPLC

An overview of contemporary techniques in environmental analysis.

A rapid and simple high performance liquid chromatography (HPLC) method with basic extraction assays was developed to investigate free diazepam levels in the plasma and urine samples of patients medicated with this drug for the management of alcohol withdrawal syndrome. The HPLC analysis was optimized and evaluated for linearity, imprecision, recovery, detection and quantification limits. The method showed linearity between 50–500 ng/mL (r2 ≥ 0.990). Coefficients of variations (%CV) were calculated to be in the range of 1.77–9.60. According to ICH guidelines, theoretical limits of detection (LOD) and quantification (LOQ) for plasma and urine were calculated as 8.3 ng/mL, 27.5 ng/mL and 8.2 ng/mL, 26 ng/mL respectively. Diazepam monitoring in plasma and urine displayed remarkable variations. The importance of adjusting doses according to individual requirements and the routine monitoring of plasma or urine for patients under medication is highlighted.

The primary goal of early phase development is to gain a fundamental knowledge of the chemistry of drug substances and drug products to facilitate optimization of synthetic schemes and drug product formulations. At the same time, methods are required for release and stability studies to support clinical trials. Ultimately, the knowledge gained during early development translates into designing control methods for commercial supplies. Our approach to meeting this challenge is based upon the use of a primary method along with orthogonal methods. This paper will discuss the overall strategy, with an emphasis on the chromatographic conditions selected to provide systematic othogonality for a broad range of drugs. Case studies will be presented to demonstrate the utility of orthogonal methods to resolve issues that could not have been addressed using a single release and stability method.

This month's "LC Troubleshooting" looks at some different calibration models, how to decide if a calibration curve goes through zero, and some problems that can occur if the wrong choices are made.

Ron Majors brings readers his yearly review of all that was new and innovative at the annual Pittsburgh Conference.

This month's "LC Troubleshooting" discussion will center on the recommendations of the CDER document, especially in terms of what it means from a practical method performance standpoint.

Guest columnist Dick Henry traces the history of HPLC back more than 40 years, starting with his days at DuPont.

The authors investigate applications for ICP-MS detection with reversed-phase HPLC.

Using a fixed length-variant of the kinetic plot method, it is illustrated how an analysis that is performed near the optimal flow-rate of a given commercial column can, in many cases, be performed between 50–200% faster by switching to a longer column and operating it at a higher pressure - at least, if the available instrument pressure admits so. The present article aims to show that short columns are not always the best choice to get the fastest separation.

At the beginning of the year, it is good to look back in time- are there things that we can learn from the past? After a series of troubleshooting and method development seminars in Istanbul, Turkey, and Amman, Jordan, John Dolan looks back.

This second part of the series describes the data loss inherent in most early method development experiments due to coelution, peak exchange, and the general difficulty of accurately identifying peaks across the experiment trial chromatograms.

Guest authors show how mixed modes can be used successfully in the optimization of protein purification, and discuss how various experimental parameters can be used to regulate the binding of proteins to mixed-mode sorbents.

Cytosine (chemical name 4-amino-2-hydroxypyrimidine) is a pyrimidine derivative with a hetereocyclic aromatic ring and two substituents (amine and keto groups) attached and is a polar compound of significant biological and pharmaceutical interest. In response to the intended use of bulk cytosine as a raw material in pharmaceutical manufacturing, a method for the determination of the purity of cytosine was developed.

This month's "LC Troubleshooting" installment will take a look at the design of these durable pumps and also examine some of the potential weaknesses and how to overcome them.

An alphabetical listing of all 2008 LCGC articles by author and subject.

This installation of "Validation Viewpoint" describes how statistically rigorous quality-by-design (QbD) principles can be put into practice to accelerate each phase of liquid chromatography (LC) instrument method development.

All the buzz lately about LC columns packed with particles smaller than 3 mm often comes with warnings about extracolumn effects. This month's installment will take a look at what these effects are and more.

The combination of reversed-phase high performance liquid chromatography (RP-HPLC), atmospheric pressure ionization (API), mass spectrometry (MS) and tandem mass spectrometry (MS/MS) is ideal for determining and characterizing analytes in complex biological matrices. This review looks at the importance of parameters such as hydrophobicity, ionization properties, molecular mass and, partially, the molecular structure resulting from applied LC–MS–MS systems in analytical laboratories. The use of these parameters to investigate biomolecules and their unambiguous identification is also described.

HPLC with ELSD continues to grow in popularity as a "quasi- universal" detector. Improvements in ELSD instrument design, including low temperature evaporation, have recently been commercialized...

This "LC Troubleshooting" installment marks the beginning of the 26th year that John Dolan has written this column.

A variety of chromatographic sorbents are commercially available for reversed-phase liquid chromatography (RPLC) and while many of these columns are nominally similar, in practice the columns may provide significantly different separations.

Applied Biosystems Inc., (Norwalk, CT) announced that the U.S. Food and Drug Administration has purchased seven of its 4000 QTRAP Systems for the analysis of potential harmful pesticides in the U.S. food supply. These systems will be deployed at FDA field offices in Jefferson, AR.; Irvine, CA.; Lenexa, KA.; Jamaica, NY; Bothell, WA.; Atlanta, GA; and College Park, MD.

Proxeon (Denmark) has announced it has integrated the software for its liquid chromatography platform with Thermo Fisher Scientific?s (San Jose, CA) mass spectrometry data-management system.

Very short columns filled with 1.9 µm particles were evaluated for the ultra-fast analysis of pharmaceutical formulations. Local anæsthetic, mydriatic and anti-hypertensive agents were chosen as analytes and a method was developed and validated for each of these substances, according to ICH guidelines. Excellent quantitative performance was obtained using an optimized chromatographic system that reduces the importance of extra-column effects and cuts the analysis time to less than 15 s.

Microemulsion liquid chromatography (MELC) is a recent development offering reduced sample preparation times for complex samples and generic separation conditions applicable to a wide range of solutes. This article introduces the concepts of MELC and discusses the possible benefits and future applications.