Overview of Analytical Methodologies for Dioxin Analysis

Statistical comparison for assessing agreement between two mass spectrometric methods for the analysis of polychlorinated dibenzo-p-dioxins and furans (PCDDs/Fs) in contaminated soils

A gas chromatography coupled to high-resolution mass spectrometry (GC-HR/MS) has been used as the standard method for the quantification of polychlorinated dibenzo-p-dioxins and furans (PCDDs/Fs), which are regulated at screening and action levels in the environment. However, several alternative methods have been attempted due to the disadvantage of its high cost. Although a gas chromatography with triple quadrupole mass spectrometry (GC-QqQ-MS/MS) has been used in a wide variety of sample matrices, showing that they are interchangeable, there has been a lack of comprehensive studies on statistical agreement with GC-HR/MS. In this study, a pairwise comparison of the total concentrations of PCDDs/Fs in 90 soil field samples obtained by two mass spectrometric methods was performed using the Passing-Bablok (P&B) regression and Bland-Altman (B&A) analysis for the method comparison. According to the result of the B&A analysis, the concentration range of PCDDs/Fs was between 98.2 and 1760 pg/g showed good agreement between two methods at the 95 % confidence level (CL). Although there was a large discrepancy between the two methods in the low concentrations (<16.5 pg/g of PCDDs/Fs), this result was similar to the P&B regression analysis. As the verification results by B&A and P&B regression analysis, the interchangeable concentration range between the two methods was confirmed to be adequate for the monitoring of PCDDs/Fs regulating levels in soils.

Comparative analyses of catalytic degradation of PCDD/Fs in the laboratory vs. industrial conditions

This study investigates the efficiencies and mechanisms of the catalytic degradation of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) first, in simulated laboratory conditions and then, in a commercial municipal solid waste incineration (MSWI) plant. Five commercially available V₂O₅-WO₃/TiO₂ (VWTi) catalysts were tested. The degradation efficiency of PCDD/Fs in the simulated flue gas ranged 22.8-91.7% and was generally higher than that in the MSWI flue gas of 8.0-85.4%. The degradation efficiency of PCDD/Fs in the real flue gas of the MSWI plant was largely hindered by the complex composition of the flue gas, which could not be completely reproduced in the simulated laboratory conditions. Furthermore, the degradation of the higher chlorinated PCDD/Fs was easier compared to the lower chlorinated ones in the presence of the VWTi catalysts, which was primarily driven by the tendency of the higher chlorinated PCDD/Fs to be adsorbed on the surface of the catalyst and further destructed due to their lower vapor pressure. In addition, powdered catalysts should be preferred over the honeycomb shaped ones as they exposed higher PCDD/Fs degradation efficiencies under equal reaction conditions. The chemical composition and a range of the relevant to the study properties of the catalysts, such as surface area, crystallinity, oxidation ability, and surface acidity, were analyzed. The study ultimately supports the identification of the preferred characteristics of the VWTi catalysts for the most efficient degradation of toxic PCDD/Fs and elucidates the corresponding deactivation reasons of the catalysts.

PCDD/Fs-induced oxidative damage and antioxidant system responses in tobacco cell suspension cultures

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are ubiquitous contaminants and can be considerably accumulated by natural plants. In order to elucidate the biochemical and physiological responses of plant to PCDD/Fs, tobacco Bright Yellow-2 (BY-2) cells were selected as model plant and treated with time- and concentration-dependent PCDD/Fs. The toxic effect and oxidative stress caused by PCDD/Fs were evident, which could be indicted by the reduction in fresh mass, the increase in malondialdehyde (MDA) content, and the damage of tobacco cell ultrastructure. PCDD/Fs tolerance was correlated with changes in antioxidant system and hormones of tobacco cells. Superoxide dismutase (SOD) and peroxidase (POD) exhibited peak enzyme activities at the PCDD/Fs concentration of 1000ng WHO(98)-TEQg(-1)fresh weight. Glutathione reductase (GR) enzyme activity increased monotonically at high level PCDD/Fs, but the activity of catalase (CAT) was only slightly affected at all treatment. Meanwhile, the exposure to PCDD/Fs resulted in the changes of hormones content. With the increase of exposure concentration of PCDD/Fs, the levels of indole-3-acetic acid (IAA) and abscisic acid (ABA) increased, whereas the concentration of jasmonates (JAs) decreased. The above results suggest that tobacco cells had the ability to cope with the oxidative stress induced by low concentration of PCDD/Fs through increasing the activities of antioxidant enzymes and alternating plant hormones levels. However, oxidative stress and toxicity would burst out when plant cells were exposed to the high levels of PCDD/Fs.

The analysis of dioxins and related compounds

The analysis of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated biphenyls, and other related compounds requires complex sample preparation and analytical procedures using highly sensitive and selective state-of-the-art instrumentation to meet very stringent data quality objectives. The analytical procedures (extraction, sample preparation), instrumentation (chromatographic separation and detection by mass spectrometry) and screening techniques for the determination of dioxins, furans, dioxin-like polychlorinated biphenyls and related compounds with a focus on new approaches and alternate techniques to standard regulatory methods are reviewed.

Analysis of Polychlorinated Dibenzo-p-Dioxins and Polychlorinated Dibenzofurans in Soil and Sediment

This review presents methods for the analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), called dioxins, in soil and sediment. These compounds are produced as by-products of different combustion processes, and because of their persistency and toxicity they present a threat for animal and human health. Due to their high organic matter content, soil and sediment can accumulate dioxins and have become important secondary emission sources. Determining dioxins in these samples is complex because dioxins are present in trace levels and have to be separated from interferences whereas other classes of organic contaminants are present in higher concentrations. After sampling, follows extraction of compounds with a suitable solvent, extract clean-up from unwanted compounds, and qualitative and quantitative analysis. At the end of this review, we gave levels of PCDD/PCDFs found in soil and sediment samples.

An enzyme-linked immunosorbent assay for the determination of dioxins in contaminated sediment and soil samples

A 96-microwell enzyme-linked immunosorbent assay (ELISA) method was evaluated to determine PCDDs/PCDFs in sediment and soil samples from an EPA Superfund site. Samples were prepared and analyzed by both the ELISA and a gas chromatography/high resolution mass spectrometry (GC/HRMS) method. Comparable method precision, accuracy, and detection level (8 ng kg(-1)) were achieved by the ELISA method with respect to GC/HRMS. However, the extraction and cleanup method developed for the ELISA requires refinement for the soil type that yielded a waxy residue after sample processing. Four types of statistical analyses (Pearson correlation coefficient, paired t-test, nonparametric tests, and McNemar's test of association) were performed to determine whether the two methods produced statistically different results. The log-transformed ELISA-derived 2,3,7,8-tetrachlorodibenzo-p-dioxin values and log-transformed GC/HRMS-derived TEQ values were significantly correlated (r=0.79) at the 0.05 level. The median difference in values between ELISA and GC/HRMS was not significant at the 0.05 level. Low false negative and false positive rates (<10%) were observed for the ELISA when compared to the GC/HRMS at 1,000 ng TEQ kg(-1). The findings suggest that immunochemical technology could be a complementary monitoring tool for determining concentrations at the 1,000 ng TEQ kg(-1) action level for contaminated sediment and soil. The ELISA could also be used in an analytical triage approach to screen and rank samples prior to instrumental analysis.