Jessika Hagberg

Alkaline Degradation of Cellulose: Mechanisms and Kinetics

Cellulose powder and softwood sawdust were subjected to alkaline degradation under conditions representative of a cementitious environment for periods of 7 and 3 years, respectively. During the first 3 years, sampling was frequent, and data on the degradation of cellulose and production of isosaccharinic acid was used for establishing long-term prediction models. Samples after an additional period of 4 years were compared to the predicted values. The total rate of degradation was measured as the increase in total organic carbon (TOC) in corresponding solutions. A previously published theoretical model of degradation kinetics gave a good approximation of the present experimental data. Peeling-off, stopping, and alkaline hydrolysis reaction rate constants were obtained as model parameters, and the results suggested that the transformation of the glucose end group is the rate-limiting step in the cellulose peeling-off reaction and also determines the pH dependence of that reaction. After 3 years, isosaccharinic (ISA) acid represented 70–85% of all degradation products as quantified by capillary zone electrophoresis. The long-term prediction model indicated that all of the cellulose would be degraded after only 150–550 years. The control sampling after 7 years points toward a lower degradation of cellulose and production of ISA than predicted by the model, reflecting either a degradation of ISA that was faster than the production or a termination of the ISA production.

Analysis of POPs in human samples reveal a contribution of brominated dioxin of up to 15% of the total dioxin TEQ

Polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) were analyzed in both human adipose tissue and plasma from nine individuals, from the Swedish general population, using high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). In addition, several other persistent organic pollutants (POPs) were determined in the same samples, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and perfluorinated chemicals (PFCs). Polybrominated dibenzofurans were detected in all of the human adipose tissue samples confirming their presence in the Swedish population. The highest concentration was found for 2,3,7,8-TeBDF, ranging from 0.27 to 2.4 pg g(-1) lipid, followed by 1,2,3,7,8-PeBDF, 0.23-0.89pgg(-1) lipid, 2,3,4,7,8-PeBDF, 0.44-0.54 pg g(-1) lipid, and 2,7/2,8-DiBDF, 0.19-0.30 pg g(-1) lipid. No PBDDs could be detected above the limit of detection (<0.02-<0.21 pg g(-1) lipid) in any of the samples. The levels of PCDD/Fs were in the range 1.79-31.5pg toxic equivalents (TEQ)g(-1) lipid, and PBDEs were found in the 1.16-7.46 ng g(-1) lipid range. The measured chlorinated dioxins indicate decreasing human concentrations in Sweden. The toxicity equivalents (TEQ) for PBDD/Fs (0.2-0.8 pg TEQg(-1) lipid) were found to contribute 1-15% of the total dioxin TEQ of the chlorinated dioxins and furans (5-18 pg TEQg(-1) lipid) depending on the individual. Also PBDEs concentrations are decreasing compared to 1997-2000, but most noteworthy a shift in BDE pattern where BDE#47 is surpassed by BDE#153. The levels of PFCs are in the same range as the highest levels of the traditional POPs (sum of 60 PCBs) based on volume. These findings illustrate the importance of continuous monitoring of brominated compounds in both human and the environment.

Analysis of low-molecular-mass organic acids using capillary zone electrophoresis-electrospray ionization mass spectrometry

A capillary zone electrophoresis-electrospray ionization-mass spectrometry (CZE-ESI-MS) method was developed to facilitate identification and determination of eleven low-molecular-mass (LMW) organic acids (i.e. oxalic, lactic, malonic, maleic, citric, tartaric, adipic, glutaric, gluconic, isosaccharinic and succinic acid) in different sample matrices. This CZE method was adapted to suit MS conditions. Sheath liquid, sheath flow and MS parameters were optimized to achieve high mass spectrometric sensitivity. The CZE-ESI-MS procedure showed good sensitivity (limit of detection of < 0.05-0.7 mg/l for all acids), linearity (r2 = 0.9925-0.9998) and reproducibility (2.09-5.34% RSD). The applicability of the CZE-ESI-MS was demonstrated on LMW organic acids in an ale sample. In addition the (here presented) method also provided quantification of fumaric, galacturonic and 2-ketoglutaric acid with high sensitivity.

Determination of 2,4,6-Trichloroanisole and 2,4,6-Tribromoanisole in Wine Using Microextraction in Packed Syringe and Gas Chromatography-Mass Spectrometry

A selective and fast method for the quantitative determination of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA) in wine was developed. Microextraction in packed syringe (MEPS) was optimized for the extraction and preconcentration of the analytes using extremely small volume samples (0.1-1 mL). For GC-EI-MS, the limit of detection (LOD) for red and white wine was in the range 0.17-0.49 microg L(-1) for TCA and TBA. In addition to GC-EI-MS both GC-NCI-MS and GC-HRMS were used to further improve both selectivity and sensitivity. The lowest LODs were achieved using GC-HRMS in the EI mode. In red and white wine samples the LODs were between 0.22-0.75 ng L(-1) for TCA and TBA. The reproducibility and linearity for the GC-HRMS method was good, with RSD-values of 4-10% for spiked red wine samples at 1 ng L(-1) and linearity with R (2) > 0.962 over a concentration range of 1 to 100 ng L(-1).

Chemical and bioanalytical characterisation of PAHs in risk assessment of remediated PAH-contaminated soils

Polycyclic aromatic hydrocarbons (PAHs) are common contaminants in soil at former industrial areas; and in Sweden, some of the most contaminated sites are being remediated. Generic guideline values for soil use after so-called successful remediation actions of PAH-contaminated soil are based on the 16 EPA priority pollutants, which only constitute a small part of the complex cocktail of toxicants in many contaminated soils. The aim of the study was to elucidate if the actual toxicological risks of soil samples from successful remediation projects could be reflected by chemical determination of these PAHs. We compared chemical analysis (GC-MS) and bioassay analysis (H4IIE-luc) of a number of remediated PAH-contaminated soils. The H4IIE-luc bioassay is an aryl hydrocarbon (Ah) receptor-based assay that detects compounds that activate the Ah receptor, one important mechanism for PAH toxicity. Comparison of the results showed that the bioassay-determined toxicity in the remediated soil samples could only be explained to a minor extent by the concentrations of the 16 priority PAHs. The current risk assessment method for PAH-contaminated soil in use in Sweden along with other countries, based on chemical analysis of selected PAHs, is missing toxicologically relevant PAHs and other similar substances. It is therefore reasonable to include bioassays in risk assessment and in the classification of remediated PAH-contaminated soils. This could minimise environmental and human health risks and enable greater safety in subsequent reuse of remediated soils.

Determination of nitrate and other water quality parameters in groundwater from UV/Vis spectra employing partial least squares regression

The use of UV/Vis spectroscopy in combination with partial least squares (PLS) regression for the simultaneous prediction of nitrate and non-purgeable organic carbon (NPOC) in groundwaters was evaluated. A model of high quality was obtained using first order derivative spectra in the range 200-300 nm. Inclusion of non-UV-absorbing constituents in the modeling procedure, i.e., chloride, sulfate, fluoride, total carbon (TC), inorganic carbon (IC), alkalinity, pH and conductivity was also evaluated. This model seemed to be useful for prediction of chloride, TC, IC, alkalinity and conductivity, while its ability to predict sulfate, fluoride and pH was poor. In conclusion, application of PLS regression, which requires neither filtration of samples nor addition of chemicals, is a promising alternative for fast interpretation of geochemical patterns of groundwater quality.

Atmospheric-Pressure Chemical Ionization Tandem Mass Spectrometry (APGC/MS/MS) an Alternative to High-Resolution Mass Spectrometry (HRGC/HRMS) for the Determination of Dioxins

The use of a new atmospheric-pressure chemical ionization source for gas chromatography (APGC) coupled with a tandem quadrupole mass spectrometry (MS/MS) system, as an alternative to high-resolution mass spectrometry (HRMS), for the determination of PCDDs/PCDFs is described. The potential of using atmospheric-pressure chemical ionization (APCI) coupled to a tandem quadrupole analyzer has been validated for the identification and quantification of dioxins and furans in different complex matrices. The main advantage of using the APCI source is the soft ionization at atmospheric pressure, which results in very limited fragmentation. APCI mass spectra are dominated by the molecular ion cluster, in contrast with the high energy ionization process under electron ionization (EI). The use of the molecular ion as the precursor ion in MS/MS enhances selectivity and, consequently, sensitivity by increasing the signal-to-noise ratios (S/N). For standard solutions of 2,3,7,8-TCDD, injections of 10 fg in the splitless mode on 30- or 60-m-length, 0.25 mm inner diameter (id), and 25 μm film thickness low-polarity capillary columns (DB5MS type), signal-to-noise (S/N) ratios of >10:1 were routinely obtained. Linearity was achieved in the region (correlation coefficient of r(2) > 0.998) for calibration curves ranging from 100 fg/μL to 1000 pg/μL. The results from a wide variety of complex samples, including certified and standard reference materials and samples from several QA/QC studies, which were previously analyzed by EI HRGC/HRMS, were compared with the results from the APGC/MS/MS system. Results between instruments showed good agreement both in individual congeners and toxic equivalence factors (TEQs). The data show that the use of APGC in combination with MS/MS for the analysis of dioxins has the same potential, in terms of sensitivity and selectivity, as the traditional HRMS instrumentation used for this analysis. However, the APCI/MS/MS system, as a benchtop system, is much easier to use.

Time-dependent relative potency factors for polycyclic aromatic hydrocarbons and their derivatives in the H4IIE-luc bioassay

The H4IIE-luc transactivation bioassay for aryl hydrocarbon receptor (AhR) agonists was used to investigate the relative potency factors (REPs) of 22 individual polycyclic aromatic hydrocarbons (PAHs) and their oxygenated-, methylated-, and N-containing derivatives (azaarenes), which are often present in PAH-contaminated soils. Naphthacene and dibenz[ah]acridine exhibited greater AhR-mediated potency, whereas lesser molecular-weight azaarenes were less potent AhR agonists. Six oxygenated PAHs had calculable REPs, but their potencies were less than their parent PAHs. Unlike the parent, unsubstituted PAHs, oxidation of methylated PAHs seemed to increase the AhR-mediated potency of the compounds, with 2-methylanthracene-9,10-dione being almost 2 times more potent than 2-methylanthracene. Both bioassay and gas chromatography-mass spectrometry analysis were used to examine the exposure time-dependent effects on the REPs at 24 h, 48 h, and 72 h of exposure in the H4IIE-luc transactivation bioassay. Changes in concentrations of 5 compounds including the model reference 2,3,7,8-tetrachlorodibenzo-p-dioxin in the cell culture wells were measured, and the amounts in the cell medium, in the cells, and adsorbed to the wells was determined and the influence on the REPs was studied. Declining REP values with increased duration of exposure were shown for all compounds, which we concluded were a consequence of the metabolism of PAHs and PAH derivatives in H4IIe-luc cells. The present study provides new knowledge regarding the degradation and distribution of compounds in the wells during exposure.

Analysis of brominated dioxins and furans by high resolution gas chromatography/high resolution mass spectrometry.

This article reviews the available literature on the analysis of brominated dibenzo-p dioxins and furans (PBDD/Fs) by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). Sample extraction and clean up, injection techniques, chromatographic separation, labelled standards and QA/QC works are discussed. Furthermore, full separation of PBDD/Fs from polybrominated diphenyl ethers (PBDEs) during clean up and control of possible chromatographic interference of PBDEs during instrumental analysis as well as possible actions to further enhance the quality of published data are discussed in detail.

Determination of dissociation constants of low molecular weight organic acids by capillary zone electrophoresis and indirect UV detection

SummaryA capillary zone electrophoretic (CZE) method has been developed to determine dissociation constants (pKa) for anionic, non-UV absorbing species in the range 3.3–4.3. The procedure was evaluated by determining the pKa for two well-characterised low molecular weight organic acids: formic and lactic acids. The results correspond well with literature values (in parentheses): formic acid 3.71 (3.75) and lactic acid 3.84 (3.85). The pKa of two polyhydroxycarboxylic acids were also determined, namely 3.64 for gluconic acid and 3.87 for isosaccharinic acid (only poorly described in the literature).