Gas chromatography of essential oil: State-of-the-art, recent advances, and perspectives.

This review is an overview of the recent advances of gas chromatography in essential oil analysis; in particular, it focuses on both the new stationary phases and the advanced analytical methods and instrumentations. A paragraph is dedicated to ionic liquids as gas chromatography stationary phases, showing that, thanks to their peculiar selectivity, they can offer a complementary contribution to conventional stationary phases for the analysis of complex essential oils and the separation of critical pairs of components. Strategies to speed-up the analysis time, thus answering to the ever increasing request for routine essential oils quality control, are also discussed. Last but not least, a paragraph is dedicated to recent developments in column miniaturization in particular that based on microelectromechanical-system technology in a perspective of developing micro-gas chromatographic systems to optimize the energy consumption as well as the instrumentation dimensions. A number of applications in the essential oil field is also included.

Recent advances and applications of gas chromatography vacuum ultraviolet spectroscopy.

The vacuum ultraviolet spectrophotometer was developed recently as an alternative to existing gas chromatography detectors. This detector measures the absorption of gas-phase chemical species in the range of 120-240 nm, where all chemical compounds present unique absorption spectra. Therefore, qualitative analysis can be performed and quantification follows standard Beer-Lambert law principles. Different fields of application, such as petrochemical, food, and environmental analysis have been explored. Commonly demonstrated is the capability for facile deconvolution of co-eluting analytes. The concept of additive absorption for co-eluting analytes has also been advanced for classification and speciation of complex mixtures using a data treatment procedure termed time interval deconvolution. Furthermore, pseudo-absolute quantitation can be performed for system diagnosis, as well as potentially calibrationless quantitation. In this manuscript an overview of these features, the vacuum ultraviolet spectrophotometer instrumentation, and performance capabilities are given. A discussion of the applications of the vacuum ultraviolet detector is provided by describing and discussing the papers published thus far since 2014.

New and Evolving Techniques for the Characterization of Peptide Therapeutics.

Advances in technologies related to the design and manufacture of therapeutic peptides have enabled researchers to overcome the biological and technological challenges that have limited their application in the past. As a result, peptides of increasing complexity have become progressively important against a variety of disease targets. Developing peptide drug products brings with it unique scientific challenges consistent with the unique physicochemical properties of peptide molecules. The identification of the proper characterization tools is required in order to develop peptide formulations with the appropriate stability, manufacturability, and bioperformance characteristics. This knowledge supports the build of critical quality attributes and, ultimately, regulatory specifications. The purpose of this review article is to provide an overview of the techniques that are employed for analytical characterization of peptide drug products. The techniques covered are highlighted in the context of peptide drug product understanding and include chemical and biophysical approaches. Emphasis is placed on summarizing the recent literature experience in the field. Finally, the authors provide regulatory perspective on these characterization approaches and discuss some potential areas for further research in the field.

Analytical characterization of cyclodextrins: History, official methods and recommended new techniques.

The main goal of this review is to provide a comprehensive overview on the methods used for analysis of cyclodextrins (CDs) and CD-derivatives. The paper intends to act as a guide for the readers in looking around the classical and modern instrumental analytical methods suitable for identification, characterization and determination of CDs themselves, CDs in finished products or even in biological samples. At present, in the European and United States Pharmacopoeias, the three parent CDs and two synthetic derivatives, namely the (2-hydroxypropyl)-beta-CD and sulfobutylether-beta-CD Na salt are official. Besides these modified CDs, two other derivatives are approved as excipients in human pharmaceutical products: the (2-hydroxypropyl)-gamma-CD and the randomly methylated-beta-CD. Although most of the official analysis methods in the pharmacopoeias have been well used for decades, new aspects of the functional excipient CD characterization suggest a need to revisit compendial methods. Comparison of strengths and weaknesses of current official methods with new improved techniques intends to help analysts to decide on changing traditional analytical methods with improved new ones. This review also deals with the analytical aspects of the first single isomer CD derivative approved as a drug active (Sugammadex/Bridion®) as well as analytical considerations of using CDs themselves as active pharmaceutical ingredients. Stability-indicating instrumental methods suitable to adequately follow chemical- and enzymatic degradation of CDs will also be discussed. Challenges in the determination of CDs in different biological matrices will be illustrated on real pharmaco- and toxicokinetic studies of CD-enabled drug formulations.

Tissue fatty acid composition and secretory phospholipase-A2 activity in oral squamous cell carcinoma

Purpose: Oral squamous cell carcinoma (OSCC) is a remarkable health problem worldwide, but its pathogenesis remains unknown. The aim of this study was to compare fat composition and secretory phospholipase-A2 (sPLA2) activity between the malignant and adjacent normal squamous tissues in patients with OSCC. Methods: Paired samples of malignant squamous and adjacent normal-appearing tissues were collected from 27 patients with OSCC. The fatty acid composition in the obtained tissues was determined by gas liquid chromatography. Tissue enzyme activities of sPLA2 were measured using the standard assay with Diheptanoyl Thio-Phosphatidylcholine as substrate. Results: In the OSCC tissue, the level of stearic acid (18:0) and activity of sPLA2 were higher (P < 0.001), and the levels of oleic acid (18:1n-9) and linoleic acid (18:2n-6) were lower than that in the adjacent normal-appearing squamous tissue (P < 0.001). The activity of sPLA2 in OSCC was strongly negatively correlated with the amount of 18:2n-6 (r = −0.41, P < 0.001). Negative significant associations were observed between the OSCC invasion and tissue levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHE). Conclusion: The changes in the fatty acid composition and sPLA2 activity may be regarded as indicators of altered lipid metabolism occurring in vivo during squamous cell carcinogenesis (AU)

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Recent applications of microchip electrophoresis to biomedical analysis.

Many separation methods have been developed for biomedical analysis, including chromatographic (e.g. high performance liquid chromatography (HPLC) and gas chromatography (GC)) and electrophoretic methods (e.g. gel electrophoresis and capillary electrophoresis (CE)). Among these techniques, CE provides advantages in terms of high separation efficiency, simplicity, low sample and solvent volume consumption, short analysis time and applicability to a wide range of biomedically important substances. Microchip electrophoresis (ME) is a miniaturized platform of CE and is now considered as a simpler and more convenient alternative, which has demonstrated potential in analytical chemistry. High-throughput, cost-effective and portable analysis systems can be developed using ME. The current review describes different separation modes and detectors that have been employed in ME to analyze various classes of biomedical analytes (e.g. pharmaceuticals and related substances, nucleic acids, amino acids, peptides, proteins, antibodies and antigens, carbohydrates, cells, cell components and lysates). Recent applications (during 2010-2014) in these areas are presented in tables and some significant findings are highlighted.

Presence and composition of cathinone derivatives in drug samples taken from a drug test service in Spain (2010-2012).

OBJECTIVE: The aim of this study was to describe the presence and composition of cathinone derivatives (CDs) in drug samples analyzed at a Drug Testing Service. MATERIAL AND METHODS: Data provided by the Drug Testing Service at Energy Control (a Spanish organization working in risk reduction among recreational drug users) were obtained from samples delivered as, or containing CDs, between January 2010 and June 2012. Specimens were identified by combining thin layer chromatography and gas chromatography associated with mass spectrometry. RESULTS: Two hundred and thirty-seven (3.8%) of the 6199 samples were delivered as, or contained CDs. 22 different CDs were detected, alone or in different combinations. Methylone (24.9%), mephedrone (24.5%), 4-methylethcathinone (9.28%), and methylenedioxypyrovalerone (6.8%) were the most common CDs. These substances were also found in 80 (1.3%) of 6042 samples delivered allegedly containing drugs different from CDs (such as 3,4-methylenedioxy-N-methylamphetamine (MDMA), amphetamines, ketamine…). CONCLUSIONS: Cathinone derivatives were markedly present in the Spanish drug market during the studied period. There is no evidence to conclude that use of CDs will become widespread or relevant for public health, but the phenomenon must be followed, as the potential risks of these new drugs of abuse are substantial.

Advances in analytical methods to study cholesterol metabolism: the determination of serum noncholesterol sterols.

Cholesterol biosynthesis precursors and plant sterols are noncholesterol sterols currently used as relative surrogate markers of cholesterol synthesis and absorption, respectively. Its determination in serum samples is a way of diagnosing inherited disorders and also a tool for health evaluation during lipid-lowering lifestyle/drug therapy monitoring. This approach is the only one that can be used for large-scale clinical trials or population based studies, but, nevertheless, there is no reference method for the quantification of noncholesterol sterols in human serum samples and only analysis by GC-FID and GC-MS has been reported to be completely validated. Although there has been a wider use of noncholesterol sterols for the measurement and characterization of cholesterol metabolism, there is a lack of harmonization of measurements and of standardization of the methodology, which is essential for routine measurements of diagnostic utility. New recent advances in analytical methods for the determination of serum noncholesterol sterols are highlighted, focusing on the sample preparation, separation and detection techniques, which will enhance the range of applications in clinical practice.

Current-day employment of the micro-bore open-tubular capillary column in the gas chromatography field.

The present contribution is focused on the exploitation of the micro-bore (MB) open-tubular column (ID≤0.18 mm), in current-day gas chromatography. The vast majority of GC methods involve the use of MB columns, from a variety of one-dimensional techniques (conventional and high speed), to different forms of heart-cutting and comprehensive multidimensional methodologies. Various aspects related to the use of MB open-tubular capillaries will be described and critically discussed, along with a series of pertinent applications. A series of works from the past have also been cited, essentially because many approaches today-applied, derive from the ideas of the past. Obviously, the present contribution does not review the entire history of the micro-bore capillary (more than one book would be necessary); rather, it intends to portray the great contribution that such analytical tools provide in enhancing two fundamental GC features, namely separation power and speed.

Gas chromatographic enantioseparation of derivatized α-amino acids on chiral stationary phases--past and present.

The historical development of the enantioseparation of derivatized α-amino acids by high-resolution capillary gas chromatography on chiral stationary phases derived from α-amino acid-derivatives and modified cyclodextrins is described. The pioneering work emerging from Emanuel Gil-Av and his associates at the Weizmann Institute of Science is reviewed. A bridge to more recent developments is spanned aimed at helping to select appropriate tools for contemporary chiral α-amino acid analysis by gas chromatography in different research areas.

Polycyclic aromatic hydrocarbons in food and beverages. Analytical methods and trends.

Polycyclic aromatic hydrocarbons (PAHs) are compounds widespread in the environment, many of them showing carcinogenic effects. These compounds can reach the food chain by different ways and, therefore, the analysis of PAHs in food is a matter of concern. This article reviews the extraction methodologies together with the separation and detection techniques which are currently applied in the determination of PAHs in food and beverages. Specific extraction conditions, performance characteristics, chromatographic and detection parameters are discussed. A review of the occurrence of these compounds in the matrixes under study is also provided.

Recent trends in the advanced analysis of bioactive fatty acids.

The consumption of dietary fats have been long associated to chronic diseases such as obesity, diabetes, cancer, arthritis, asthma, and cardiovascular disease; although some controversy still exists in the role of dietary fats in human health, certain fats have demonstrated their positive effect in the modulation of abnormal fatty acid and eicosanoid metabolism, both of them associated to chronic diseases. Among the different fats, some fatty acids can be used as functional ingredients such as alpha-linolenic acid (ALA), arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), gamma-linolenic acid (GLA), stearidonic acid (STA) and conjugated linoleic acid (CLA), among others. The present review is focused on recent developments in FAs analysis, covering sample preparation methods such as extraction, fractionation and derivatization as well as new advances in chromatographic methods such as GC and HPLC. Special attention is paid to trans fatty acids due its increasing interest for the food industry.

Advances and developments in membrane extraction for gas chromatography: Techniques and applications.

This review article focuses on advances and technical developments of the realm of membrane extraction techniques for the analytes that are (made) amenable to gas chromatographic analysis, and sheds light on the analytical applications to biological and environmental samples. In this review, the state of the art in this growing area of membrane extraction for gas chromatography is presented and several selected examples from our work and that of other groups are discussed. The published articles on the techniques and their applications, found in the scientific literature between the years 2000 and May 2007 and cited in over than 100 references, are perused and commented. A good deal of light will be thrown on the novelty of the techniques, instrumentations and applications. The mentioned techniques are mainly microporous membrane liquid-liquid extraction, extracting syringe, two-phase hollow-fibre-protected liquid-phase microextraction and its modifications, and membrane extraction with sorbent interface and its variants. The merits and demerits of the techniques will be highlighted.

Advances in the gas chromatographic determination of persistent organic pollutants in the aquatic environment.

Environmental chemists have been challenged for over 30 years to analyse complex mixtures of halogenated organic pollutants like polychlorinated biphenyls (PCBs), polychlorinated alkanes (PCAs), polybrominated diphenyl ethers (PBDEs) and polychlorinated dibenzo-p-dioxins and polychlorinated furans (PCDD/Fs). Gas chromatography (GC) often proved to be the method of choice because of its high resolution. The recent developments in the field of comprehensive two-dimensional GC (GCxGC) show that this technique can provide much more information than conventional (single-column) GC. Large volume injection (e.g. by programmed temperature vaporiser, or on-column injection) can be employed for the injection of tens of microliters of sample extract, in that way substantially improving the detection limits. Electron-capture detection (ECD) is a sensitive detection method but unambiguous identification is not possible and misidentification easily occurs. Mass spectrometric (MS) detection substantially improves the identification and the better the resolution (as with MS/MS, time-of-flight (TOF) MS and high-resolution (HR)MS), the lower the chances of misidentification are. Unfortunately, this comes only with substantially higher investments and maintenance costs. Co-extracted lipids, sulphur and other interferences can disturb the GC separation and detection leading to unreliable results. Extraction, and more so, sample clean-up and fractionation, are crucial steps prior to the GC analysis of these pollutants. Recent developments in sample extraction and clean-up show that selective pressurised liquid extraction (PLE) is an effective and efficient extraction and clean-up technique that enables processing of multiple samples in less than 1h. Quality assurance tools such as interlaboratory studies and reference materials are very well established for PCDD/Fs and PCBs but the improvement of that infrastructure is needed for brominated flame retardants, PCAs and toxaphene.

Recent developments in the application of comprehensive two-dimensional gas chromatography.

The literature on comprehensive two-dimensional gas chromatography (GC x GC) is reviewed, with emphasis on application-oriented studies published in the period 2004-2006. The various strategies that can be used in such studies, the state-of-the-art analytical performance and the high potential of GC x GC combined with time-of-flight mass spectrometric detection are highlighted.