Application Of Liquid Chromatography-mass Spectrometry Research Articles

Focus on analytical science in Spain (JAI 2008)

Every 3 years Barcelona celebrates the EXPOQUIMIA, the largest chemical exhibition in southern Europe. On this occasion a major Conference on Instrumental Analysis (Jornadas de Analisis Instrumental, JAI) is held that takes advantage of the synergies generated by the simultaneous presence of scientists and technical staff working in analytical chemistry, commercial exhibitors of instrumentation, and companies whose main activities are related to chemistry. From October 21 to October 23, 2008, JAI celebrated its 12th anniversary. It was organized by the Spanish Society of Chromatography and Related Techniques (SECyTA), the Society of Analytical Chemistry, the Society of Mass Spectrometry (SEEM), and Society of Proteomics and Optics, the Society of Applied Spectroscopy, and the Association of Environmental Sciences and Techniques. The conference was attended by 580 registered participants. A total of 444 communications were given, 71 in oral form and 373 as posters. A large proportion of these covered environmental applications (122) and food quality and safety (107). Others were related to developments in instrumental analysis (41), pharmaceutical products (21), clinical analysis (21), metal speciation (17), chemometrics and theoretical developments (12), nanotechnology (10), and several other topics. In addition, interesting lectures were given by invited speakers such as Kurt Wuthrich, a Nobel laureate in chemistry (2002), from the Scripps Research Institute (La Jolla, California, USA) and the Institute of Molecular Biology and Biophysics (ETH Zurich, Switzerland), Yoshinobu Baba from the Plasma Nanotechnology Research Center of Nagoya University (Japan), Detlef Gunther from the Institute of Inorganic Chemistry (ETH Zurich, Switzerland), Philip J. Marriott from the School of Applied Sciences of RMIT University (Melbourne, Australia), and Cameron McLeod from the Centre for Analytical Sciences of the University of Sheffield (UK). Several awards were given to the participating students. There were 11 best poster prizes, some of them for specific subjects and others without topic restriction. As customary during previous JAI meetings, Analytical and Bioanalytical Chemistry was present and two ABC poster prizes (on bioanalytics and on chemical speciation) were awarded on behalf of the journal. There were also two awards for the two best oral communications in chromatography (awarded by SECyTA) and for the two best papers in mass spectrometry (awarded by SEEM). The special issue is a collection of a few of the presentations given at the 12th JAI conference, devoted to instrumental analysis, for example, gas chromatography– mass spectrometry (GC-MS) and liquid chromatography– mass spectrometry (LC-MS) applications to determinations of trace organic compounds in environmental samples and technical formulas. Applications of GC-MS, LC-MS, and selective electrodes to the analysis of drugs and metabolites in human samples are covered. Studies of atomic fluorescence spectrometry for total determinations and speciation of hydride-forming elements in garlic still show continuing Anal Bioanal Chem (2009) 394:1515–1516 DOI 10.1007/s00216-009-2845-2

The expanding role of LC-MS in analyzing metabolites and degradation products of food contaminants

Liquid chromatography-mass spectrometry (LC-MS) has contributed significantly in advancing research in the analysis of metabolites and degradation products of food contaminants. Of particular interest is the comprehensive application of LC-MS to discovery of degradation products and metabolites. This review, covering research published between 2003 and 2008, describes how LC-MS has been used in this field, with the majority of work dealing with target-metabolite analysis and only a small fraction using LC-MS comprehensively. In considering the significance of this topic and the potential interest in it, we briefly describe state-of-the art mass analyzers applied for it (QtrAP, QqTOF, and Orbitrap). We detail the challenges and the achievements of LC-MS in this field of analysis, with emphasis on the latest developments in the technique. We also discuss how some of the key features of LC-MS are exploited to identify, to characterize and to determine some metabolites and degradation products of residues and food contaminants. Finally, we critically evaluate the prospects for, and the limitations of, LC-MS in this field, including identification of degradation products, quantitative methods and metabolite profiling.

A Review of Recent Trends in Applications of Liquid Chromatography-Mass Spectrometry for Determination of Mycotoxins

Monitoring, control, risk assessment, and prevention of contaminants in food and in feed are important issues associated with public health, agricultural production, food processing, and trade. Food and feed safety, as well as carry over of contaminants into animal tissue, are of major public concern nowadays, especially if considering the global challenge and world trade liberalization. Mycotoxins are toxic secondary metabolites of moulds and one of the major contaminants of agricultural products. Their presence in food and feed is harmful to the health of humans and animals. Therefore, analytical methods for the identification and determination of mycotoxins need to be sensitive, selective, and robust to provide accurate data especially for monitoring, risk assessment, quality control, and research. The application of hyphenated techniques especially HPLC-MS and HPLC-MS-MS has, in many cases, revolutionized the analysis of mycotoxins. The LC-MS methods offer a new tool for the sensitive, selective, and accurate analysis of contaminants in agricultural commodities. Tandem mass spectrometry provides the maximum scale of confidence in analyte identification. However, LC-MS-MS is definitely not a trouble free solution for the analysis of mycotoxins in complex biological matrices. Sample clean-up and chromatography still remain the important and necessary steps for obtaining reliable analytical results. This paper provides some general aspects regarding mycotoxins in food and emphasizes the analytical techniques with regard to LC-MS technology.

Lipidomics in triacylglycerol and cholesteryl ester oxidation

Although direct mass spectrometry is capable of identification the major molecular species of lipids in crude total lipid extracts, prior chromatographic isolation is necessary for detection and identification of the minor components. This is especially important for the analysis of the oxolipids, which usually occur in trace amounts in the total lipid extract, and require prior isolation for detailed analysis. Both thin-layer chromatography and adsorption cartridges provide effective means for isolation and enrichment of lipid classes, while gas-liquid chromatography and high performance liquid chromatography with on-line mass spectrometry permit further separation and identification of molecular species. Prior chromatographic resolution is absolutely necessary for the identification of isobaric and chiral molecules, which mass spectrometry/mass spectrometry (MS/MS) cannot distinguish. Both gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry applications may require the preparation of derivatives in order to improve the chromatographic and mass spectrometric properties of the oxolipids which is a small inconvenience for securing analytical reliability. The following chapter reviews the advantages and necessity of combined chromatographic-mass spectrometric approaches to successful identification and quantification of molecular species of oxoacylglycerols and oxocholesteryl esters in in-vitro model studies of lipid peroxidation and in the analyses of oxolipids recovered from tissues.

Recent trends in liquid chromatography-tandem mass spectrometry to determine pesticides and their metabolites in food

The applications of liquid chromatography-mass spectrometry (LC-MS) have exploded in innumerable analytical fields, including pesticide-residue determination. There is no doubt that LC-MS is currently competing with gas chromatography (GC)-MS for the status of ‘reference’ analytical technique to determine pesticide residues and that its ever-increasing application is bound to the evolution of modern instruments and their growing performance qualities. We highlight the large number and variety of pesticides that can be readily determined using such instruments, the respective merits of the different mass analyzers, and the improvements brought about by tandem MS (MS 2). We also discuss new applications of LC-MS in this field, such as “non-target” screening procedures and unknown identification by MS or MS n presenting the different solutions proposed to solve this challenging problem. Finally, we address the opportunities afforded by the most recent instrument designs.

Critical review of the application of liquid chromatography/mass spectrometry to the determination of pesticide residues in biological samples

A critical review is made on the use of hyphenated liquid chromatography/mass spectrometry (LC-MS) for the identification and quantification of pesticides and their metabolites in human biosamples (whole blood, plasma, serum and urine). The first applications of LC-MS in this field began in the early 1990s. Since then, increasing interest has been shown in applying this powerful technique, with most applications dealing with the determination of a variety of chemically diverse metabolites in urine. The use of different LC-MS interfaces and mass spectral detection modes are discussed. Special attention is given to tandem mass spectrometry (MS/MS) due to its inherent advantages of increased sensitivity and selectivity, as well as its advantages for identification and confirmation of analytes in samples. Quantification can be severely affected by matrix effects, the most common being inhibition of the ionisation of analytes in the mass spectrometer, which leads to unacceptable errors if no correction is made. Different approaches can be employed to minimise this undesirable matrix effect, the preferred being the use of labelled internal standards (when available) in isotope dilution methods or the application of an efficient clean-up, performed off-line or automated on-line. Adequate criteria for confirming the identities of residues detected are required in order to avoid false positives. The criterion most commonly used with a triple quadrupole instrument is the monitoring of two MS/MS transitions together with the ion abundance ratio. TOF mass analysers are seldom used in pesticide residue analysis despite their improved resolution and mass accuracy characteristics, which makes them very suitable for confirmation purposes. The main reasons for the relative unpopularity of TOF MS in residue analysis are its limited sensitivity and its high acquisition cost. In this paper, we present a critical assessment on current techniques, trends and future developments, and give illustrative examples to point out the main characteristics of LC-MS for pesticide residue analysis in biological fluids.

Measuring DNA Nucleobase Adducts Using Neutral Hydrolysis and Liquid Chromatography-Mass Spectrometry

The detection and identification of DNA adducts is important for predicting human cancer risk posed by chemicals and for uncovering potential genotoxicity of new drug and agricultural chemical candidates. For compounds that react with DNA to form N7-guanine and/or N3-adenine adducts, neutral thermal hydrolysis provides a simple procedure for sample preparation. The N7-guanine and N3-adenine adducts are selectively ejected from the DNA chain, resulting in a clean sample matrix enriched in nucleobase adducts. Coupling neutral thermal hydrolysis with liquid chromatography-mass spectrometry (LC-MS) provides sensitive methods to detect and quantitate DNA adducts, and structural information is provided by MS. Combining these technologies with capillary liquid chromatography sample preconcentration systems can provide exquisitely sensitive detection. In this review, we first summarize the chemistry of nucleobase adduct formation, briefly summarize modern methods to detect DNA adducts, and then describe neutral thermal hydrolysis coupled to LC-MS/MS and some of its applications to DNA damage studies. Finally, we review recent applications of neutral thermal hydrolysis and LC-MS to toxicity screening of chemicals.

Analysis and fate of surfactants in sludge and sludge-amended soils

Surfactants are among the most prevalent organic pollutants of anthropogenic origin with the potential to enter the environment through the discharge of wastewater and sewage sludge. We give an overview of analytical methods currently in use for the determination of different classes of surfactants in sewage sludge and soil. The main focus is on the application of liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS), discussing various aspects of these two techniques, including sample preparation. We give an overview of data on the occurrence of sludge and sludge-amended soils, and we draw conclusions about the fate of surfactants and their metabolites in sludge-amended soils. Finally, we briefly discuss the current European legislation relating to the use of sludge in agriculture.

Liquid Chromatography-Mass Spectrometry: An Introduction. Robert E. Ardrey. Huddersfield, UK: Wiley, 2003, 276 pp., $110.00, hardcover. ISBN 0-471-49799-1.

This book covers the diverse and rapidly expanding topic of liquid chromatography–mass spectrometry (LC-MS). The first half of the text (Chapters 1–4) covers chromatographic theory in some depth and provides an overview of MS methods that are applicable to LC-MS. Chapter 5 comprises the second half of the book and contains applications of LC-MS and MS techniques to small molecules and biopolymers. The text contains a bibliography, an appendix of physical constants, and a complete glossary of terms specific for LC-MS. This book is written especially for self-study and for in-house training sessions. Each chapter includes learning objectives, pertinent references, a summary, and self-assessment questions. Following a brief introductory chapter, Chapter 2 contains basic LC theory …

Increasing the throughput and productivity of Caco-2 cell permeability assays using liquid chromatography-mass spectrometry: application to resveratrol absorption and metabolism.

The Caco-2 cell monolayer permeability assay has become a standard model of human intestinal absorption and transport. This paper reviews recent progress in increasing the throughput of Caco-2 cell monolayer assays and in expanding the scope of this assay to include modeling intestinal drug metabolism. The state-of-the-art in Caco-2 cell monolayer permeability assays combines multi-well plates fitted with semi-permeable inserts on which Caco-2 cells have been cultured with liquid chromatography-mass spectrometry (LC-MS) or LC-tandem mass spectrometry (LC-MS-MS) for the quantitative analysis of test compounds and the identification of their intestinal metabolites. After reviewing the progress in increasing the throughput of Caco-2 cell monolayer assays for both modeling human intestinal permeability or transport and the metabolism of xenobiotic compounds, we demonstrate the application of LC-MS and LC-MS-MS to the measurement of resveratrol permeability and metabolism in the Caco-2 model. trans-Resveratrol (trans-3,5,4'-trihydroxystilbene) is a polyphenolic compound occurring in grapes, peanuts and other food sources, that is under investigation as a cancer chemoprevention agent. The apparent permeability coefficient for apical (AP) to basolateral (BL) movement of resveratrol was 2.0 x 10(-5)cm/sec. Resveratrol was not a substrate for P-glycoprotein or the multi-drug resistance associated proteins (MRP). No phase I metabolites were observed, but the phase II conjugates resveratrol-3-glucuronide and resveratrol-3-sulfate was identified based on LC-MS and LC-MS-MS analysis and comparison with synthetic standards. Although these data indicate that resveratrol diffuses rapidly across the intestinal epithelium, extensive phase II metabolism during absorption might reduce resveratrol bioavailability.

The use of hyphenated techniques in comparative phytochemical studies of legumes

The coupling of instruments performing chromatographic separations to those providing structural data has had an enormous impact in analytical chemistry. These ‘hyphenated techniques’ are enabling compounds to be detected in plant extracts more effectively than ever before. At the same time, the rapid development of DNA sequencing technology and cladistic data analysis have provided taxonomists with the means to produce testable systematic hypotheses. These parallel developments in analytical chemistry and systematics have transformed the often criticised discipline of chemotaxonomy into modern integrated studies in comparative phytochemistry that aim to test cladistic hypotheses or gain insights into the biochemical evolution of plants. In this paper the key developments in the main hyphenated techniques, gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS), are considered together with some of the challenges facing the further development of capillary electrophoresis-mass spectrometry (CE-MS) and liquid chromatography-nuclear magnetic resonance spectroscopy (LC-NMR). The application of GC-MS and LC-MS in comparative phytochemical studies in legumes is reviewed both from selected research in the literature and from the authors’ own experiences, with an emphasis on nitrogen-containing and phenolic compounds. The use of GC-MS has provided an extensive data set on the occurrence of quinolizidine alkaloids in legumes and this character is now assuming taxonomic significance at a high level. GC-MS also provides the means to separate the numerous isomeric forms of polyhydroxyalkaloids and hydroxypipecolic acids as their volatile trimethylsilyl derivatives and surveys of these compounds are supporting systematic work at lower taxonomic levels. LC-MS is enabling the metabolic profiles of intact flavonoid glycosides to be obtained from small fragments of material while recent methods to analyse non-protein amino acids by LC-MS without derivatisation hold much promise in surveys of these important taxonomic characters. Tandem mass spectrometry (MS/MS) provides a rapid means of sequencing peptides and so, as we enter the era of proteomics, LC-MS/MS is likely to play a central role in the analysis of legume proteins.

LC-MS-MS identification of drug metabolites obtained by metalloporphyrin mediated oxidation

In this paper we report the application of liquid chromatography-mass spectrometry (LC-MS-MS) to the identification of the products formed by oxidation of albendazole and disopyramide with metalloporphyrins in dichloroethane, using iodosylbenzene as an oxygen donor. Our results show that LC-MS-MS is a powerful tool to study the in vitro metabolism of drugs, allowing the identification of known and unknown metabolites. In addition, it was observed that the catalyst system used resulted in the formation of the same metabolites as obtained in vivo, although for disopyramide other products were also observed.

Introduction to quantitative liquid chromatography-tandem mass spectrometry (LC-MS-MS)

The paper is a brief summary of a one-hour tutorial focusing on practical aspects for newcomers to the field of quantitative liquid chromatography-mass spectrometry (LC-MS), rather than on theoretical aspects. An introduction to atmospheric-pressure ionization (API), ion sources, and tandem mass spectrometry (MS-MS) was give. So-called matrix effects, their sources, investigation, and methods of avoidance, selection of an appropriate internal standard, and selectivity limitations were discussed in detail. The potential and limitations of LC-MS were shown. In this paper no applications are presented, because many applications of LC-MS(MS) have been published in the literature.

Progress of liquid chromatography-mass spectrometry in clinical and forensic toxicology.

The use of liquid chromatography-mass spectrometry (LC-MS) has recently exploded in various analytic fields, including toxicology and therapeutic drug monitoring (although still far behind pharmacokinetics). There is no doubt that LC-MS is currently competing with gas chromatography (GC)-MS for the status of the reference analytic technique in toxicology. This review presents, for the nonspecialist reader, the principles, advantages, and drawbacks of LC-MS systems using atmospheric pressure interfaces. It also gives an overview of the analytic methods for xenobiotics that could be set up with these instruments for clinical or forensic toxicology. In particular, as far as quantitative techniques are concerned, this review tries to underline the large number and variety of drugs or classes of drugs (drugs of abuse, therapeutic drugs) or toxic compounds (e.g., pesticides) that can be readily determined using such instruments, the respective merits of the different ionization sources, and the improvements brought about by tandem MS. It also discusses new applications of LC-MS in the field of toxicology, such as "general unknown" screening procedures and mass spectral libraries using LC-atmospheric pressure ionization (API)-MS or MS-MS, presenting the different solutions proposed to overcome the naturally low fragmentation power of API sources. Finally, the opportunities afforded by the most recent or proposed instrument designs are addressed.

Current developments in LC-MS for pharmaceutical analysis.

The current developments in liquid chromatography-mass spectrometry (LC-MS) and its applications to the analysis of pharmaceuticals are reviewed. Various mass spectrometric techniques, including electrospray and nanospray ionization, atmospheric pressure chemical ionization and photoionization and their interface with liquid chromatographic techniques are described. These include high performance liquid chromatography, capillary electrophoresis and capillary electrochromatography and the advantages and disadvantages of each technique are discussed. The applications of LC-MS to the studies of in vitro and in vivo drug metabolism, identification and characterization of impurities in pharmaceuticals, analysis of chiral impurities in drug substances and high-throughput LC-MS-MS systems for applications in the "accelerated drug discovery" process are described.

A mass spectrometric method for quantitation of intact insulin in blood samples.

An analytical method was developed for the quantitation of intact insulin in blood samples. Solid-phase extraction (SPE) was used to purify and concentrate the protein after the plasma is separated. Analysis is performed by electrospray liquid chromatography-mass spectrometry (LC-MS) using a trifluoroacetic acid mobile phase. The limit of quantitation of the SPE LC-MS method has been determined to be 1.0 ng/mL for endogenous levels of insulin. Base levels of human insulin in plasma have been quantitated, and values ranging from 1.0 to 1.4 ng/mL were observed. In a single analysis, the method can determine human, porcine, and bovine insulin. Reproducibility was tested for both blood samples and aqueous standards and produced relative standard deviations of approximately 10% and lower. Calibration curves were constructed corresponding to plasma levels of 0.4 to 80 ng/mL and found to be linear with R2 values greater than 0.99. Stability studies of human and porcine insulin were performed over a period of 21 days for whole human blood samples stored at both room temperature and 4 degrees C. Hemolyzed blood samples were also analyzed using the developed method and were found to produce quantitatable levels of insulin. The advantage of the application of SPE and LC-MS for the quantitation of insulin is the high specificity compared to other techniques such as radioimmunoassay (RIA). In addition, the developed LC-MS method is not subject to interferences that cause problems with RIA, such as hemolysis. The method is efficient and rapid and produces results more specific than those obtained with RIA.

Liquid chromatography-mass spectrometry in the study of the metabolism of drugs and other xenobiotics.

The application of liquid chromatography-mass spectrometry (LC/MS) to the study of metabolism of drugs and other xenobiotics is reviewed. Original research papers covering the period from 1998 to early 2000 and concerning the use of LC/MS in the study of xenobiotic metabolism in humans and other mammalian species are reviewed. LC/MS interfaces, sample preparation steps, column types, mobile phases and additives, and the type of metabolites detected are summarized and discussed in an attempt to identify the current and future trends in the use of LC/MS for metabolism studies. Applications are listed according to the parent xenobiotic type and include substances used in therapeutics, drug candidates, compounds being evaluated in clinical trials, environmental pollutants, adulterants and naturally occurring substances.

Analytical techniques for trace organic compounds - VI. Application of liquid chromatography-mass spectrometry (Technical Report)

Abstract

Metalloporphyrins in coal 5. Analysis of porphyrins in coal extracts using liquid chromatography-mass spectrometry

The application of liquid chromatography-mass spectrometry to the separation and identification of porphyrin homologues from coal is demonstrated using a moving belt interface. In this way C 32, C 31, C 30 and C 29 polyalkylporphyrins are shown to be present as ligands in the haem fraction isolated from an immature lignite (Canakkale-Can).

Metabolism of magnolol from magnoliae cortex. I. Application of liquid chromatography-mass spectrometry to the analysis of metabolites of magnolol in rats.

As a part of our studies on the metabolism of active components from traditional Chinese medicines, magnolol was orally administered to rats. The urinary and fecal metabolites were analyzed by high-performance liquid chromatography and liquid chromatography-mass spectrometry, and their structures were determined to be tetrahydromagnolol (M1), 5-(1-propen-1 (E)-yl)-5'-propyl-2, 2'-dihydroxybiphenyl (M2), 5-allyl-5'-propyl-2, 2'-dihydroxybiphenyl (M3), isomagnolol (5, 5'-di (1-propen-1 (E)-yl)-2, 2'-dihydroxybiphenyl) (M4), 5-allyl-5'-(1-propen-1 (E)-yl)-2, 2'-dihydroxybiphenyl (M5). On the other hand, magnolol was transformed to M4 and M5 together with small amounts of M2 and M3 by anaerobic incubation with rat feces. This suggests that the isomerization of magnolol in the rat could be carried out by the action of intestinal bacteria.