Identification of organic compounds in atmospheric aerosol particles by on-line supercritical fluid extraction–liquid chromatography–gas chromatography–mass spectrometry

Polycyclic aromatic hydrocarbons in bone homeostasis

Prolonged exposure to polycyclic aromatic hydrocarbons (PAHs) may result in autoimmune diseases, such as rheumatoid arthritis (RA) and osteoporosis (OP), which are based on an imbalance in bone homeostasis. These diseases are characterized by bone erosion and even a disruption in homeostasis, including in osteoblasts and osteoclasts. Current evidence indicates that multiple factors affect the progression of bone homeostasis, such as genetic susceptibility and epigenetic modifications. However, environmental factors, especially PAHs from various sources, have been shown to play an increasingly prominent role in the progression of bone homeostasis. Hence, it is essential to investigate the effects and pathogenesis of PAHs in bone homeostasis. In this review, recent progress is summarized concerning the effects and mechanisms of PAHs and their ligands and receptors in bone homeostasis. Moreover, strategies based on the effects and mechanisms of PAHs in the regulation of the bone balance and alleviation of bone destruction are also reviewed. We further discuss the future challenges and perspectives regarding the roles of PAHs in autoimmune diseases based on bone homeostasis.

Application of supercritical fluids in cholesterol extraction from foodstuffs: a review

Various innovations have so far been devised to extract cholesterol from foods. Achieving a supercritical fluid is perhaps one of the greatest human successes in the field of extraction from foodstuffs in last 2 decades. Supercritical fluid extraction (SFE) offers a rapid, environment-friendly and selective method for extracting cholesterol from foods. This review aims at investigating the application of supercritical fluids in extraction of cholesterol. Various factors affecting the SFE, collection systems, examples of cholesterol extraction and SFE benefits are some of the issues discussed in this study.

Decreasing Aerosol Water Is Consistent with OC Trends in the Southeast U.S

Water is a ubiquitous and abundant component of atmospheric aerosols. It influences light scattering, the hydrological cycle, atmospheric chemistry, and secondary particulate matter (PM) formation. Despite the critical importance of aerosol liquid water, mass concentrations are not well-known. Using speciated ion and meteorological data from the Southeastern Aerosol Research and Characterization network, we employ the thermodynamic model ISORROPIAv2.1 to estimate water mass concentrations and evaluate trends from 2001 to 2012 in urban and rural locations. The purpose of this study is to better understand the historical trends of aerosol liquid water in the southeast U.S. in the context of improved air quality and recently noted reductions in particulate organic carbon (OC). Aerosol water mass concentrations decrease by ∼79% from 2001 to 2012 in the region. Decreases are more prominent in rural than in urban areas. Fractional contribution of water to PM also decreases during the same time period, and this is consistent with recently noted improvements in visibility. These findings agree with the hypotheses that aerosol liquid water facilitates formation of biogenic secondary organic aerosol (SOA) and that biogenically derived SOA is modulated in the presence of anthropogenic perturbations.

Polycyclic aromatic hydrocarbon concentrations in gas and particle phases and source determination in atmospheric samples from a semiurban area of Dourados, Brazil

A headspace solid-phase microextraction (HS-SPME) procedure that employs a PDMS/DVB fiber was developed for the analysis of gas-phase polycyclic aromatic hydrocarbons (PAHs) collected in polyurethane foam (PUF) by gas chromatography (GC) mass spectrometry. The method exhibited good linearity (R (2) > 0.99) and repeatability (4.9-25 %) as well as an impressive detection limit that ranged from 1.1 to 3.3 ng. Twenty-two air samples were collected by high-volume samplers from January to November 2007 in a semiurban area of Dourados (Brazil) and were analyzed for their content of total suspended particulates and PAHs. The PAHs were extracted from the PUF samples using the developed procedure (HS-SPME), and PAHs adsorbed on particulate matter were extracted with dichloromethane/methanol (4:1 [v/v]) in an ultrasonic bath. The values of the total daily concentrations of 16 PAHs determined in the samples ranged from 0.375 to 8.407 ng m(-3). In addition, diagnostic ratios were calculated, showing that the PAHs in the atmosphere at the sampling site originated predominantly from vehicle emissions and the combustion of grass and wood. Hierarchical cluster analysis and principal component analysis were performed as well, the results of which indicated (1) the same sources of PAH identified by the diagnostic ratios and (2) that the sampling days could be categorized into three groups depending on the atmospheric conditions. GC retention indices were also used to identify PAHs, biphenyl (phenylbenzene), and heterocyclic organic compounds (benzofurans) in some of the samples.

Ambient air levels and health risk assessment of benzo(a)pyrene in atmospheric particulate matter samples from low-polluted areas: application of an optimized microwave extraction and HPLC-FL methodology

A new methodology involving a simple and fast pretreatment of the samples by microwave-assisted extraction and concentration by N2 stream, followed by HPLC with fluorescence detection, was used for determining the concentration of benzo(a)pyrene (BaP) in atmospheric particulate matter (PM10 fraction). Obtained LOD, 1.0 × 10(-3) ng/m(3), was adequate for the analysis of benzo(a)pyrene in the samples, and BaP recovery from PAH in Fine Dust (PM10-like) certified reference material was nearly quantitative (86%). The validated procedure was applied for analyzing 115 PM10 samples collected at different sampling locations in the low-polluted area of Extremadura (Southwest Spain) during a monitoring campaign carried out in 2011-2012. BaP spatial variations and seasonal variability were investigated as well as the influence of meteorological conditions and different air pollutants concentrations. A normalized protocol for health risk assessment was applied to estimate lifetime cancer risk due to BaP inhalation in the sampling areas, finding that around eight inhabitants per million people may develop lung cancer due to the exposition to BaP in atmospheric particulates emitted by the investigated sources.

Atmospheric reactions of 9,10-anthraquinone

The probably carcinogenic compound 9,10-anthraquinone is mainly existing in the atmosphere in the particulate phase and is often detected and measured among other oxygenated PAHs in atmospheric samples. Its fate, once released or formed in the atmosphere, still remains unknown. In this work, heterogeneous chemical oxidation processes of 9,10-anthraquinone were investigated with ozone (O3), nitrogen dioxide (NO2) and hydroxyl radical (OH). The study of 9,10-anthraquinone adsorbed on silica particles showed no reactivity with O3 and NO2. On the other hand, the reaction with OH radicals was observed and led to the formation of 1-hydroxy-9,10-anthraquinone, another oxidation product recognized as possibly carcinogenic to humans. This study showed that reactions with ozone and nitrogen dioxide are unlikely to contribute to atmospheric degradation of 9,10-anthraquinone, whereas reactions with OH radicals could be involved in 9,10-anthraquinone degradation processes, even if such reaction is probably very slow under ambient conditions.

Green bioanalysis: some innovative ideas towards green analytical techniques

The key target of green chemistry is to make compounds and materials available to mankind, while causing no harm to the environment. In the 21st century analytical scientists are more concerned about green analytical method development. The number of literatures on green chemistry has undergone a dramatic increase in the new millennium. Green bioanalytical techniques aim to minimize or eliminate the hazardous waste associated with bioanalytical methods. An efficient and sincere approach towards bioanalytical method development has an enormous contribution towards green analysis. The selection of organic constituents of the mobile phase, choice of sample extraction process, adoption of an appropriate separation procedure and a few others, control the green chemistry approach of the bioanalytical method. In routine practice, UHPLC–MS can be the most suitable approach, while supercritical fluid chromatography is one of the best available techniques for green bioanalytical methods. Nevertheless, there always remains great scope of further research on green bioanalytical methods.

[Analysis of volatile and semi-volatile compounds in tobacco using off-line combination of liquid chromatography and capillary gas chromatography-mass spectrometry]

A method of off-line combination of liquid chromatography and capillary gas chromatography-mass spectrometry (LC-CGC/MS) was established for the analysis of volatile and semi-volatile compounds in tobacco. The separation mechanism of volatile and semi-volatile compounds was studied. An LC column of 250 mm x 2.0 mm packed with 5 microm amino-bonded silica was used as stationary phase for the separation. n-Hexane/dichloromethane/acetonitrile (90: 6.6: 3.4, v/v/v) was used as mobile phase. Five fractions from one LC run were collected in five nitrogen-blowing flasks, separately. The same fractions from 10 LC runs were combined together and concentrated to 1 mL by nitrogen blowing, and then were analyzed by CGC/MS. The column of DB-5MS (60 m x 0.25 mm x 0.25 microm) was used for CGC/MS analysis. Comparing with direct CGC/MS analysis of the same sample, the LC-CGC/MS system is suitable for a complex sample, and has a higher reliability of qualitative analysis.

Classification of organic and biological materials with deep ultraviolet excitation

We show that native fluorescence can be used to differentiate classes or groups of organic molecules and biological materials when excitation occurs at specific excitation wavelengths in the deep ultraviolet (UV) region. Native fluorescence excitation-emission maps (EEMs) of pure organic materials, microbiological samples, and environmental background materials were compared using excitation wavelengths between 200-400 nm with emission wavelengths from 270 to 500 nm. These samples included polycyclic aromatic hydrocarbons (PAHs), nitrogen- and sulfur-bearing organic heterocycles, bacterial spores, and bacterial vegetative whole cells (both Gram positive and Gram negative). Each sample was categorized into ten distinct groups based on fluorescence properties. Emission spectra at each of 40 excitation wavelengths were analyzed using principal component analysis (PCA). Optimum excitation wavelengths for differentiating groups were determined using two metrics. We show that deep UV excitation at 235 (+/-2) nm optimally separates all organic and biological groups within our dataset with >90% confidence. For the specific case of separation of bacterial spores from all other samples in the database, excitation at wavelengths less than 250 nm provides maximum separation with >6sigma confidence.

Sample preparation

A panorama of sample preparation methods has been composed from 481 references, with a highlight of some promising methods fast developed during recent years and a somewhat brief introduction on most of the well-developed methods. All the samples were commonly referred to molecular composition, being extendable to particles including cells but not to organs, tissues and larger bodies. Some criteria to evaluate or validate a sample preparation method were proposed for reference. Strategy for integration of several methods to prepare complicated protein samples for proteomic studies was illustrated and discussed.

Optimization of a novel method for the organic chemical characterization of atmospheric aerosols based on microwave-assisted extraction combined with stir bar sorptive extraction

A practical analytical methodology based on coupling microwave-assisted extraction-stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry (MAE-SBSE-TD-GC-MS) was developed and validated for the characterization of several SVOC in atmospheric particulate matter (PM). The high enrichment capacity of SBSE makes it a powerful tool for improving detection limits and MAE has been useful for overcoming the long extraction times and high volumes of extraction solvent used in traditional methodologies. Relative to Soxhlet extraction followed by GC-MS analysis (EPA Methods 3540 and 8270C), the MAE-SBSE-TD-GC-MS methodology resulted with approximately 10(4) times better detection limits. Detection limits ranged from 0.3 to 8.3 pg m(-3) for pp'-DDD and decachlorobyphenyl, respectively in PM2.5, 24 m3 air sample. The performance of the optimized methodology gave good precisions, with R.S.D. less than 30% for most of the standards, and linearity within the range tested of 0.1-15 microg L(-1). Analysis of real PM samples resulted in the identification of compounds in the ng L(-1) range.

Principles, developments and applications of on-line coupling of extraction with chromatography

On-line coupling of extraction and chromatographic separation allows the whole analysis to be performed in a closed system. On-line systems are particularly useful when the analytes are labile, the amount of sample is limited, or very high sensitivity is required. Many on-line systems have been developed both for liquid and for solid samples. This review discusses the different instruments that have been constructed and the factors that need to be considered in the coupling. Selected illustrative applications are described to illustrate the potential of the on-line systems.

Characterisation of polycyclic aromatic hydrocarbons in atmospheric aerosols by gas chromatography–mass spectrometry

An accurate and reliable method for determining polycyclic aromatic hydrocarbons (PAHs) in atmospheric aerosols is described. This optimised gas chromatography-mass spectrometry (GC-MS) method permits a wide range of concentrations to be analysed without the influence of interferences. Pre-treatment comparison of four kinds of aerosol collector filters determined that quartz and glass fibre filters were the most suitable. Solvents like cyclohexane, toluene, acetonitrile and dichloromethane were evaluated for their PAH-extraction capacity. Ultrasonic extraction using CH2Cl2 was selected because it is rapid and easy; moreover, this solvent increases the sample-throughput capacity. PAH compounds were quantitatively collected and ultrasonically extracted twice using 15 mL of CH2Cl2 for 15 min for each replicate. Rotavapor concentration, fractionation and dissolution were also optimised. A certified standard mixture (16 EPA PAHs), a deuterated compound and precision recovery assays were used for validating the proposed methodology. Adequate analytical parameters were obtained. Detection limits were (1.6-26.3) x 10(-5) ng and quantification limits were (5.2-87.6) x 10(-5) ng. Analysis of the environmental samples detected 4-10 EPA list PAH compounds. In addition, 2-11 tentative compounds were found, and their molecular structures were described for the first time. Our study of both Youden method and the standard addition method has shown that the proposed determination of PAHs in environmental samples is free of systematic errors. In conclusion, this unbiased methodology improves the identification and quantification of PAH compounds. High sensitivity as well as acceptable detection and quantification limits were obtained for the environmental applications.

Development of analytical methods for polycyclic aromatic hydrocarbons (PAHs) in airborne particulates: a review

In the present work, the different sample collection, pretreatment and analytical methods for polycyclic aromatic hydrocarbons (PAHs) in airborne particulates is systematacially reviewed, and the applications of these pretreatment and analytical methods for PAHs are compared in detail. Some comments on the future expectation are also presented.

Analysis of polycyclic aromatic hydrocarbons (PAHs) in environmental samples: a critical review of gas chromatographic (GC) methods

Polycyclic aromatic hydrocarbons (PAHs) are frequently measured in the atmosphere for air quality assessment, in biological tissues for health-effects monitoring, in sediments and mollusks for environmental monitoring, and in foodstuffs for safety reasons. In contemporary analysis of these complex matrices, gas chromatography (GC), rather than liquid chromatography (LC), is often the preferred approach for separation, identification, and quantification of PAHs, largely because GC generally affords greater selectivity, resolution, and sensitivity than LC. This article reviews modern-day GC and state-of-the-art GC techniques used for the determination of PAHs in environmental samples. Standard test methods are discussed. GC separations of PAHs on a variety of capillary columns are examined, and the properties and uses of selected mass spectrometric (MS) techniques are presented. PAH literature on GC with MS techniques, including chemical ionization, ion-trap MS, time-of-flight MS (TOF-MS), and isotope-ratio mass spectrometry (IRMS), is reviewed. Enhancements to GC, for example large-volume injection, thermal desorption, fast GC, and coupling of GC to LC, are also discussed with regard to the determination of PAHs in an effort to demonstrate the vigor and robustness GC continues to achieve in the analytical sciences.

Development of a supercritical fluid extraction-gas chromatography-mass spectrometry method for the identification of highly polar compounds in secondary organic aerosols formed from biogenic hydrocarbons in smog chamber experiments

A new one-step method for the analysis of highly polar components of secondary organic aerosols (SOA) has been developed. This method should lead to a better understanding of SOA formation and evolution since it enables the compounds responsible for SOA formation to be identified. Since it is based on supercritical fluid extraction coupled to gas chromatography-mass spectrometry, it minimizes the analysis time and significantly enhances sensitivity, which makes it suitable for trace-level compounds, which are constituents of SOA. One of the key features of this method is the in situ derivatisation step: an online silylation allowing the measurement of highly polar, polyfunctional compounds, which is a prerequisite for the elucidation of chemical mechanisms. This paper presents the development of this analytical method and highlights its ability to address this major atmospheric issue through the analysis of SOA formed from the ozonolysis of a biogenic hydrocarbon (sabinene). Ozonolysis of sabinene was performed in a 6 m3 Teflon chamber. The aerosol components were derivatised in situ. More than thirty products, such as sabinaketone, sabinic acid and other multifunctional compounds including dicarboxylic acids and oxoacids, were measured. Nine of them were identified and quantified. The sensitivity and the linearity (0.91<R<0.98) of the method were both good and detection limits ranged from 1.2 to 6.4 ng for the investigated compounds.

Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry in the identification of organic compounds in atmospheric aerosols from coniferous forest

Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOF-MS) was applied in the identification of organic compounds in atmospheric aerosols from coniferous forest. The samples were collected at Hyytiälä, Finland, as part of the QUEST campaign, in Spring 2003. Manual and automated search procedures were compared in the identification. An automated procedure is preferable when a large number of data files need to be processed; but manual search was more accurate with the present samples, where the number of compounds was large and most of the compounds of interest were present at trace level. Altogether, about 50 compounds were identified on the basis of mass spectra and linear retention indices. The identified compounds included oxidised monoterpenes, acyclic alkanes, alkenes, ketones and aldehydes, as well as a few alcohols, acids, and aromatic compounds.

Characterization of organic compounds in aerosol particles from a coniferous forest by GC-MS

Atmospheric aerosol particles were collected in a Finnish Scots pine forest as part of a European Union project. Sampling was done in March-April 2003 with a high-volume sampler. Dynamic ultrasonic-assisted solvent extraction and gas chromatography-mass spectrometry (GC-MS) were applied to the analysis of aerosol samples for analytes such as n-alkanes, polycyclic aromatic hydrocarbons (PAH), oxidized polycyclic aromatic hydrocarbons (oxy-PAHs), sesquiterpenes (SQT) and oxidized sesquiterpenes (oxy-SQT). The highest concentrations were found for the n-alkanes, which were present in a wide range (C11-C32) indicating both biogenic and anthropogenic sources. PAH compounds were found in every sample while oxy-PAH compounds were present in low concentrations in a few samples. A few oxidized monoterpenes, most notably (-)-verbenone and pinonaldehyde, were found in several samples in concentrations clearly exceeding the PAH concentrations. The effect of temperature could be seen in most samples, where the concentrations of n-alkanes declined with decreasing temperatures. Particle formation events were accompanied by higher concentrations of heavy n-alkanes, verbenone and pinonaldehyde.

Optimization of Supercritical Fluid Extraction by Carbon Dioxide with Organic Modifiers of Polycyclic Aromatic Hydrocarbons from Urban Particulate Matter

The main advantages of using supercritical fluids for the extractions of organic pollutants from environmental matrix is that they are inexpensive, contaminant free, and less costly to dispose safely than organic solvents. In this work, a series of extraction experiments were carried out using CO2 as supercritical fluid on a certified sample of "Urban dust" (NIST S.R.M. 1649a) to optimize the analytical parameters with the aim of investigating the extraction limit of organic pollutant by using an almost "organic solvent-free" technique. The certified sample contains small concentrations of several organic pollutants, as PAH and PCB. The initial tests of extraction were carried out with only CO2 in supercritical phase, by maintaining the temperature at 50 degrees C and 80 degrees C and by making the pressure vary between 230 bar and 600 bar. The effect of three organic modifiers (methanol, n-hexane and toluene), added at 5% in volume, has been considered. The yield of recovery has been estimated for anthracene, fluoranthene, chrysene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene by GC-MS according to the increasing molecular weight.