Leonard P. Sarna

Aqueous solubility of polychlorinated dibenzo-p-dioxins determined by high pressure liquid chromatography

Abstract Water solubilities (SW) determined by the HPLC generator column method are reported for a series of chlorinated dibenzo- p -dioxins (PCDDs) with SW ranging from 0.4 ng/L (ppt) for octa-chlorodibenzo- p -dioxin to 430 ng/L for 1,2,3,7-tetrachlorodibenzo- p -dioxin at 20°C. A correlation is demonstrated between SW and HPLC capacity factors (k′) for these extremely hydrophobic compounds, allowing calculation of SW of PCDDs from k′ and melting point data.

Environmental fate modelling of chlorodioxins: Determination of physical constants

Environmental fate modelling of polychlorinated dibenzo-p-dioxins (PCDDs) requires knowledge of a number of fundamental physical parameters of these compounds, viz., octanol-water partition coefficient (Kow), solubility in water (Sw), vapor pressure (p), and Henrys constant (H). Classical methodology for determination of these parameters is often not suitable for use with compounds as hydrophobic as PCDDs, Methods have been developed or refined to enable these properties to be measured.

Solid-phase microextraction of the herbicide metolachlor in runoff and tile-drainage water samples

The new rapid solid-phase microextraction (SPME) technique developed in Canada by Pawliszyn and co-workers has been used in the analysis of water for pesticide residues in laboratory studies. SPME used with gas chromatography and electron-capture detection (GC-ECD) of metolachlor in runoff water showed linear response over a wide range. The lowest concentration analyzed was 0.002 μg/1 (2 ppt), and the highest was 20 000 μg/1 (20 ppm). Over this span of seven orders of magnitude, the standard curve had an R2 of 0.9954 for ten data points, each of which was averaged over three or more trials. The curve below 200 μg/1, or 0.20 ppm had a slightly different slope (R2 0.9996). Earlier analyses by automated SPME-GC and flame ionization detection (FID) in distilled water showed linear response over the range 180 to 180 000 μg/1. A 100-μm polydimethylsiloxane-coated fibre was used; metolachlor residues in the runoff water were 0.17 to 50.7 μg/1. This is the first time, to our knowledge, that SPME has been used in the analysis of herbicide residues in runoff water.

Dissolved organic matter mediated aquatic transport of chlorinated dioxins

Abstract The bioavailability and environmental fate of extremely hydrophobic environmental contaminants such as chlorinated dioxins is linked to their solubility characteristics in water. Solubilities of three chlorinated dioxins, viz., 1,2,3,7-T4CDD, 1,2,3,4,7-P5CDD, and 1,2,3,4,7,8-H6CDD, were determined in pure water using a glass bead generator column technique, and their enhanced solubilities in the presence of several dissolved humic fractions quantified at 20, 30 and 40°C. The strengths of these interactions between chlorodioxins and the dissolved humic substances, viz., a fulvic acid, a humic acid, and Aldrich humic acid, were examined using simple thermodynamic calculations. A new partition/association coefficient, Koc (mobile) is defined.

Vapor pressure determination for several polychlorodioxins by two gas saturation methods

Abstract Vapor pressures of several individual chlorodioxins are determined by two gas saturation methods, one using 2 – 3 mg of unlabelled material with GC-FID analysis (Method 1), and the other, 10 – 100 ug of 14 C-compounds (Method 2). Values from Method 1 can be used for calculation of thermodynamic parameters, but those from method 2 are adequate for environmental modelling. The temperature ranges were chosen (a) Method 1: to allow extrapolation of vapor pressures over a wide temperature range, and (b) Method 2: for environmental relevance.

Analysis of the petroleum components benzene, toluene, ethyl benzene and the xylenes in water by commercially available solid-phase microextraction and carbon-layer open tubular capillary column gas chromatography

Extraction of the petroleum components benzene, toluene, ethyl benzene and the xylenes (BTEX) from water is described using a commercially available poly(dimethylsiloxane) solid-phase microextraction fibre assembly with separation and quantification by carbon-layer open tubular capillary column gas chromatography and flame ionization detection. All components of BTEX are resolved. No cryofocussing is required.

Vapor pressure measurements on halogenated dibenzo-p-dioxins and dibenzofurans. An extended data set for a correlation method

Vapor pressures are important parameters for the modelling of the environmental fate and incineration behavior of halogenated dibenzo-dioxins and dibenzofurans (1). Correlation methods play an important role in the determination of thermal properties of polyhalogenated dioxins and furans (2,3) as there are hundreds of homologs and isomers whose synthesis in their pure form can be very difficult. Many of the compounds are highly toxic and their impact on the environment must be considered. The hazards associated with 2,3,7,8-T4CDD are well known. The measurement of thermal properties is involved for safety reasons, and the required quantities of these substances often fall within the milligram range. Correlation methods permit the estimation of the substance properties of hundreds of compounds from a limited set of measurements on the least toxic species. The correlation method (2,3) has in the past been used a) to predict enthalpies of fusion and boiling points from a set of vapor pressure results from polychloro dibenzo-dioxins, dibenzofurans and xanthenes; b) to test the self consistency of this set of measured vapor pressures; c) to predict the vapor pressures of solid 2,3,7,8-T4CDD and d) predict vapor pressures for twenty-nine halogenated dibenzo-dioxins and for fifty-five polychloro dibenzofurans (3). The correlation method was based on experimental vapor pressure data for one to four chlorinated congeners and on the octachloro dibenzo- p-dioxins and furans. We are presently extending the data set by including pentahexa- and heptachloro dibenzo-p-dioxins (1,2,3,4,7-P5CDD, 1,2,3,4,7,8-H6CDD, 1,2,3,4,6,7,8-H7CDD) and dibenzofurans (1,2,3,4,8-P5CDF, 1,2,4,7,8-P5CDF, 1,2,3,4,7,8-H6CDF, 1,2,4,6,7,8-H6CDF, 1,2,4,6,8,9-H6CDF, 1,2,3,4,6,7,8-H7CDF, 1,2,3,4,6,7,9-H7CDF, 1,2,3,4,6,8,9-H7CDF). The influence of exchanging chlorine against bromine has also been studied by recording vapor pressure curves on the following brominated dibenzo-p-dioxin congeners: 2,3,-D2BDD, 1,2,3,4-T4BDD and 1234678-H7BDF.