Determination of levoglucosan in atmospheric aerosols using high performance liquid chromatography with aerosol charge detection

A sensitive method for analysis of levoglucosan (1,6-anhydro-beta,d-glucopyranose) and other monosaccharide anhydrides, compounds present in biomass combustion smoke, was investigated employing high-performance liquid chromatography (HPLC) with recently developed aerosol charge detection. Aerosol charge detection involves the conversion of the column effluent to an aerosol, which is charged to produce a current. Use of a cation-exchange column and a pure water eluent was found to separate levoglucosan and mannosan from other aerosol components with a detection limit of about 90 ng mL(-1) for levoglucosan or 5 ng injected. This method was demonstrated by successful analysis of aerosol filter samples from three locations.     

Methods for the determination of levoglucosan and other sugar anhydrides as biomass burning tracers in environmental samples – A review

Nowadays, there is a great pressure on finding an alternative source of energy. One such source is biomass combustion. Biomass is any organic matter such as wood, crops, seaweed, and animal wastes that during combustion emits energy but also smoke and solid residue. Biomass burning tracers, such as levoglucosan, mannosan and galactosan, are sugar anhydrides produced during burning of biomass that contain cellulose and hemicellulose. Analysis of environmental samples for tracers is the source of information about the type of biofuel burned. In this article, a literature review of the preparation and determination of biomass burning tracers for environmental samples was presented. The review discusses the preparation of different samples (particulate matter, soils, sediments, biological samples), extraction, derivatization, and determination. Amongst determination methods the most popular was gas chromatography with mass spectrometry but other techniques were also used, such as high‐performance liquid chromatography with aerosol charge detection, capillary electrophoresis with pulsed amperometric detection, and ion chromatography with pulsed amperometric detection.     

Simultaneous Determination of Levoglucosan,Mannosan and Galactosan at Trace Levels in Snow Samples by GC/MS

A method for the simultaneous determination of levoglucosan, mannosan and galactosan at trace levels in snow samples is reported by using GC/MS. This method is an improvement on previous aerosol studies. The required sample volume for this method is a mere 5.00 mL of melt water. Discrimination of three isomers is analyzed on the basis of different retention time and fragmentation patterns. The limit of detection is 0.070, 0.058 and 0.046 ng mL^?1 ice melt water for three isomers. This method has the advantage of simultaneous determination of three monosaccharide anhydrides at trace concentration levels in small sample volumes. The relatively high extraction efficiency and low limit of detection will facilitate further studies on biomass burning recorded in snow and ice samples.     

Derivatization procedures and determination of levoglucosan and related monosaccharide anhydrides in atmospheric aerosols by gas chromatography-mass spectrometry

This study evaluated the derivatization procedures for detecting the three most commonly monosaccharide anhydrides (MAs) (levoglucosan, mannosan and galactosan) in atmospheric aerosols using gas chromatography-mass spectrometry (GC-MS). Various silylating agents, mainly trimethylsilylating agents (TMS), were compared and the effects of various contents of trimethylchlorosilane (TMCS, as a stimulator) were evaluated to optimize the conditions for detecting these compounds in aerosol samples. Differences among the abundances of the derivatives were caused by the sterical hindrance of three hydroxyl groups in the structures of monosaccharide anhydrides. The effects of the reaction time and temperature were also examined. The optimal reaction time and temperature were 60 min and 80 °C with 1% TMCS plus 0.2% 1,4-dithioerythritol (DTE). Under these conditions, the percentages of formation of bis-O-TMS derivatives (as by-products) were 23, 29 and 10% for galactosan, mannosan and levoglucosan, respectively. The concentrations of galactosan, mannosan and levoglucosan in particles of smoke samples ranged from 29 to 88, 23 to 69 and 77 to 380 ng/m³, respectively; and in particles of atmospheric aerosols ranged from 0.06 to 0.75, n.d. to 0.49 and 1.6 to 132 ng/m³, respectively. Levoglucosan was the dominant MAs detected in both type of samples. Less than 10% quantitation difference was obtained when bis-O-TMS derivatives were included in the calculation.     

High-performance anion-exchange chromatography–mass spectrometry method for determination of levoglucosan, mannosan, and galactosan in atmospheric fine particulate matter

Biomass burning has a strong influence on the atmospheric aerosol composition through particulate organic, inorganic, and soot emissions. When biomass burns, cellulose and hemicelluloses degrade, producing monosaccharide anhydrides (MAs) such as levoglucosan, mannosan, and galactosan. Therefore, these compounds have been commonly used as tracers for biomass burning. In this study, a fast water-based method was developed for the routine analysis of MAs, based on high-performance anion-exchange chromatography with electrospray ionization mass spectrometry detection. This method combines simple sample preparation, fast separation, and the advantages of the selective detection with MS. Analysis run was optimized to the maximum separation of levoglucosan, mannosan, and galactosan with 15-min analysis. The validation results indicated that the method showed good applicability for determination of MA isomer concentrations in ambient samples. The limit of detection was 100 pg for levoglucosan and 50 pg for mannosan and galactosan. Wide determination ranges enabled the analysis of samples of different concentration levels. The method showed good precision, both for standard solutions (3.9–5.9% RSD) and for fine particle samples (4.3–8.5% RSD). Co-elution of internal standard (carbon-13-labeled levoglucosan) and sugar alcohols with levoglucosan decreased the sensitivity of levoglucosan determination. The method was used to determine the MA concentrations in ambient fine particle samples from urban background (Helsinki) and rural background (Hyytiälä) in Finland. The average levoglucosan, mannosan, and galactosan concentrations were 77, 8.8, and 4.2 ng?m^?3 in Helsinki (winter 2008–2009) and 17, 2.3, and 1.4 ng?m^?3 in Hyytiälä (spring 2007), respectively. The interrelation of the three MA isomers was fairly constant in the ambient fine particle samples.     

Hydrophilic interaction chromatography with Fourier transform mass spectrometry of monosaccharide anhydrides

A fast, selective, and sensitive method for the determination of three monosaccharide anhydrides (galactosan, mannosan, levoglucosan), based on hydrophilic interaction chromatography and Fourier transform mass spectrometry, was successfully developed. The simple experimental stationary phase and mass spectrometry performance screening allowed the selection of the best available chromatographic and mass spectrometry conditions. Thus, the chromatographic separation was performed on a highly selective stationary phase containing a zwitterionic phosphorylcholine group and the monosaccharide anhydrides were detected as [M+HCOO]^? adduct in the negative mode. The method showed accuracy in the range of 84–111 and 89–102% with interbatch precision expressed as relative standard deviations of 5.6–15.4 and 5.0–9.0% for the aerosol extract and snow samples, respectively. The limit of quantification in absolute values ranged from 10 to 30 pg, the limit of quantification, expressed as concentration, ranged was 0.3–0.9 ng/m³ for aerosol and 10–20 ng/mL for snow samples. The method was successfully applied for the determination of monosaccharide anhydrides in aerosol and snow samples.     

A comparative study on the pyrolysis of metal- and ash-enriched wood and the combustion properties of the gained char

This study aims to investigate the pyrolysis behaviour of metal-contaminated wood and the combustion properties of char derived from wood pyrolysis. Seven metals (Na, Mg, Ca, Zn, Cd, Pb and Fe(III)) were introduced to willow in cation form by ion-exchange and the thermal behaviour of demineralised samples and samples with additional ash were also investigated.The results show that the char yield increased from 21% to 24–28% and levoglucosan yield in vapour phase decreased from 88% to 62–29% after the addition of inorganic compounds, even though the metal binding capacity of wood varied from one metal ion to another. While char yield seems to be effected mainly by the concentration of the metal ions, levoglucosan yield was more dependent on the ionic species especially when sodium ions were present. When combustion experiments were carried out with char made of the metal enriched wood, two consecutive steps were observed, both effected by the presence of inorganic compounds. The first step was identified as the release and combustion of volatiles, while the second peak of the burning profile is the actual combustion of the fixed carbon. The burnout temperatures, estimated ignition indices and the conversion indicate that the type and not the amount of metal ions were the determining factors during the second step of combustion.     

The influence of fine structure on the pyrolysis of cellulose. II. Pyrolysis in air

The pyrolysis of purified celluloses in air at 251°C was studied. The pyrolysis was found to obey first-order kinetics, and the rate constants correlated with the crystallinities, orientations and accessibilities of the samples. The results are interpreted in terms of an oxygen-catalyzed decomposition, with the accessibility of oxygen to the cellulose determining the rate of pyrolysis. The production of levoglucosan under conditions approaching combustion was shown to be a function of the crystallinity and orientation of cellulose. Some levoglucosan appears to be produced from the less ordered regions.     

Development of a gas chromatographic/ion trap mass spectrometric method for the determination of levoglucosan and saccharidic compounds in atmospheric aerosols. Application to urban aerosols

We developed and validated a gas chromatographic/ion trap mass spectrometric method for the determination of levoglucosan and the related monosaccharide anhydrides, mannosan, galactosan and 1,6-anhydro-beta-D-glucofuranose in urban atmospheric aerosols collected on quartz fiber filters. The method is based on extraction with dichloromethane-methanol (80 : 20, v/v), trimethylsilylation, multiple reaction monitoring in the tandem mass spectrometric mode using the ion at m/z 217, and the use of an internal standard calibration procedure with the structurally related compound methyl beta-L-arabinopyranoside. In addition, the method allows the quantification of other saccharidic compounds, arabitol, mannitol, glucose, fructose, inositol and sucrose, which were found to be important in summer aerosols. The recovery of levoglucosan was estimated by spiking blank filters and was better than 90%. The precision evaluated by analyzing parts of the same filters was about 2% for the monosaccharide anhydrides and 7% for the other saccharidic compounds in the case of a winter aerosol sample, and the corresponding values for a summer aerosol sample were 5% and 8%. The method was applied to urban PM(10) (particulate matter of <10 microm aerodynamic diameter) aerosols collected at Ghent, Belgium, during a 2000-2001 winter and a 2001 summer episode and revealed interesting seasonal variations. While monosaccharide anhydrides were relatively more important during the winter season owing to wood burning, the other saccharidic compounds were more prevalent during the summer season, with some of them, if not all, originating from the vegetation.     

Experimental and theoretical study of thermodynamic properties of levoglucosan

The heat capacity of levoglucosan was measured over the temperature range (5 to 370) K by adiabatic calorimetry. The temperatures and enthalpies of a solid-phase transition and fusion for the compound were found by DSC. The obtained results allowed us to calculate thermodynamic properties of crystalline levoglucosan in the temperature range (0 to 384) K. The enthalpy of sublimation for the low-temperature crystal phase was found from the temperature-dependent saturated vapor pressures determined by the Knudsen effusion method. The thermodynamic properties of gaseous levoglucosan were calculated by methods of statistical thermodynamics using the molecular parameters from quantum chemical calculations. The enthalpy of formation of the crystalline compound was found from the experiments in a combustion calorimeter. The gas-phase enthalpy of formation was also obtained at the G4 level of theory. The thermodynamic analysis of equilibria of levoglucosan formation from cellulose, starch, and glucose was conducted.     

Effect of long-range transport of air mass on the ionic components in radiation fog in northern Japan.

Water samples from radiation and upslope types of fog were collected at Takanosu Basin and Hachimantai mountain range of Akita Prefecture in northern Japan, respectively. The effect of the long-range transport of pollutants from the Asian Continent to the basin and the mountain range on the chemical characteristics of two types of fog was studied using chemical analysis data for the water samples as well as the back-trajectories of the air mass. In particular, non-sea-salt (nss)-SO4(2-) of radiation fog provided a much higher concentration than that of upslope fog, which suggests that nss-SO4(2-) might be transported mainly from the Asian Continent. The transport and uptake mechanism of pollutants in the radiation fog water were explained based on their accumulation in the basin due to anticyclonic subsidence and by the long-lasting fog behavior.     

Determination of saccharides in atmospheric aerosol using anion-exchange high-performance liquid chromatography and pulsed-amperometric detection

An improved method is described for the quantification of primary sugars, sugar alcohols and anhydrosugars in atmospheric aerosols, making use of separation by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD). Quartz fibre filters from high-volume samplers were extracted with water and the extract injected directly. Repeatability is typically 4% RSD, for e.g. levoglucosan at 50 ng m(-3) in air, better for winter levels around 700 ng m(-3). Limits of detection for individual sugars are in the range 0.02-0.05 microg mL(-1) in solution, corresponding to 2-5 ng m(-3) from a 20 m(3) air sample. The overlap of arabitol and levogluocosan is overcome by using a Dionex PA-1 column, with appropriate control of eluent composition, and peak deconvolution software, allowing quantification of both sugars in difficult summer samples containing low-levels of levoglucosan. Analysis of a set of ambient aerosol samples by both GC-flame ionization detection and HPAEC-PAD shows good agreement. The new method has the advantage of requiring no sample pretreatment or derivatization and is thus well suited to handling large numbers of samples.     

Wetting and self-cleaning properties of artificial superhydrophobic surfaces

The wetting and the self-cleaning properties (the latter is often called the "Lotus-Effect") of three types of superhydrophobic surfaces have been investigated: silicon wafer specimens with different regular arrays of spikes hydrophobized by chemical treatment, replicates of water-repellent leaves of plants, and commercially available metal foils which were additionally hydrophobized by means of a fluorinated agent. Water droplets rolled off easily from those silicon samples which had a microstructure consisting of rather slender spikes with narrow pitches. Such samples could be cleaned almost completely from artificial particulate contaminations by a fog consisting of water droplets (diameter range, 8-20 microm). Some metal foils and some replicates had two levels of roughening. Because of this, a complete removal of all particles was not possible using artificial fog. However, water drops with some amount of kinetic impact energy were able to clean these surfaces perfectly. A substrate where pronounced structures in the range below 5 microm were lacking could not be cleaned by means of fog because this treatment resulted in a continuous water film on the samples.     

High performance thin layer chromatography determination of cellobiosan and levoglucosan in bio-oil obtained by fast pyrolysis of sawdust

In this work, high performance thin layer liquid chromatography (HTPLC) is applied to the determination of sugars in fast pyrolysis liquids (bio-oil) and fractions thereof. The proposed procedure allows the separation of anhydrosugar levoglucosan and cellobiosan, as well as glucose, arabinose, xylose and cellobiose. Pre-treatment and derivatization of samples are not necessary and volatile compounds present in bio-oil do not interfere with sugar analysis. The detrimental effect of the complex bio-oil matrix on columns and detector lifetime is avoided by using disposable HTPLC plates. Prior screening of glucose, present especially in aged and aqueous bio-oil fractions, is required to quantify cellobiosan without interference. Concentrations of levoglucosan and cellobiosan in bio-oil samples obtained from Pinus radiata sawdust were ranged between 1.27-2.26% and 0.98-1.96% respectively, while a bio-oil sample obtained from native wood contained a higher levoglucosan concentration.     

Discrimination of ionic pollutants except condensation nuclei of acid fog using an ultrasonic humidifier.

Fog droplets in the atmosphere are first produced by the activation of cloud condensation nuclei (CCN), which are originally some ionic compound. Subsequently, the nuclei grow by vapor diffusion. Fog droplets are polluted through the activation process and successive diffusion growth and residence (post activation). We cannot distinguish the effects of the two pollution processes of natural fog water samples. We found that fog droplets can be produced artificially without CCN using an ultrasonic humidifier. Because the artificial fog droplets are not polluted by CCN, the movement of the fog droplets in natural air will take up some pollutants in the air. Consequently, the two pollution processes of fog (the activation of CCN and the post activation process) can be discriminated using data from field experiments. This sampling analytical method is extremely important for further research regarding fog, clouds and environmental chemistry.     

Determination of fatty alcohol ethoxylates with diphenic anhydride derivatization and liquid chromatography with spectrophotometric detection: A comparative study with other anhydrides

A method for the determination of fatty alcohol ethoxylates (FAEs) using diphenic anhydride as derivatization reagent and RP-HPLC separation with UV–vis detection is presented and compared to derivatization with maleic, phthalic, and other cyclic anhydrides. With these anhydrides, the reaction rates increased when urea was added to the reaction medium, and the yields did not decrease when the samples contained moderate amounts of water. Gradient elution on a C8 column was performed with water/acetonitrile in the presence of 0.1% acetic acid. The use of diphenic anhydride was advantageous for both the chromatographic separation and the detection. Specifically, sensitivity at 200 and 220 nm was significantly better for the FAE diphenates, resulting in lower limits of detection at both wavelengths for the diphenates than for the maleates and phthalates (up to 30 and 4.3 times lower at 220 nm, respectively). Response factors for the diphenates decreased less than those of the phthalates when the number of ethylene oxide units, m, increased, reaching a constant value of ca. 0.62 when m > 3. Peak symmetries and efficiencies were also better than those found for the other anhydrides. The optimized procedure was applied to the characterization and determination of FAEs in the effluent of a wastewater treatment plant and in sea water.     

Analysis of some anhydrides as their corresponding acids by capillary electrophoresis

Summary The potential of capillary electrophoresis for the indirect determination of anhydrides was demonstrated by the analysis of five closely-related anhydrides as their corresponding acids. Direct analysis of such substances is generally difficult because of their susceptibility to hydrolysis. In this work anhydrides were first hydrolyzed in water, hydrolysis being monitored using micellar electrokinetic chromatography (MEKC) which separated neutral anhydrides and anions of corresponding acids. After hydrolysis, separation of the acids was quickly achieved within two minutes by reversed electroosmotic-flow, capillary electrophoresis (REF-CE), with UV detection at 210 nm.     

左旋葡聚糖的制备与在生物技术领域的应用

左旋葡聚糖(LGA)作为一种极具潜力的新糖源,既可以加酸水解为葡萄糖后间接用于微生物发酵,也可以被真菌或细菌甚至构造的基因工程菌直接代谢,目前已经在发酵上展现出良好的应用前景。此外,LGA还可作为碳源,生产生物乙醇、丁二酸等。目前制备LGA普遍采用生物质热解法,该方法存在能耗高、产率低、产物难以提取等缺点,应努力发展在溶剂体系中分解纤维素制备LGA的方法以提高产率。今后的研究应致力于开发微生物代谢LGA的新过程、新方法、新菌种,为LGA的高效利用提供坚实基础。     

Capillary GC Determination of Short-Chain Dicarboxylic Acids in Rain,Fog, and Mist

Abstract

A capillary GC and GC-MS method, employing dibutyl esters is described for determining short-chain dicarboxylic acids in rain, fog and mist samples collected in the Los Angeles area. Approximately twenty dicarboxylic acids (C₂-C₁₀) were identified in the water samples, including cis (maleic) and trans (fumaric) unsaturated, saturated, normal, branched and aromatic. Oxalic acid is the dominant acid, followed by succinic and malonic acids. The total concentrations measured are 2.9–51μM, 64–66 μM and 12 μM for rain, fog and mist samples, respectively. These diacids are probably produced by photooxidation of anthropogenic and possibly biogenic organic compounds in the atmosphere.     

Evaluation of ionic pollutants of acid fog and rain using a factor analysis and back trajectories.

Fog and rain water samples were collected at the same time in the Akita Hachimantai mountain range in northern Japan from June to September in 1998 and 1999. The various ion concentrations in these samples were analyzed, and the fog droplet sizes were measured for each fog event. As the fog droplet size increased, the ion concentration decreased. The slope of log-log plots of the concentration versus the droplet size differed with the kind of ion. In order to characterize the air pollutant, moreover, these data were quantitatively analyzed by an oblique rotational factor analysis. We found that three factors were extracted as the air pollutant source: (NH4)2SO4, acids (HNO3 + H2SO4) and sea-salt. Combining the factor analysis with the 72 h back-trajectory at 850 hPa level, we found that the contribution of each factor varied with the transport pattern of air masses.