Extractability of dioxins from soil: II. Effects of acid or alkaline pretreatment on the extractability of dioxin homologues from soil samples

The effects of sample pretreatment on the extractability of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CoPCBs) from three suburban soil samples were evaluated. The samples were treated with 0.1?M HCl or 0.1?M NaOH and extracted by pressurized liquid extraction (PLE) with toluene. In addition, untreated soil samples were subjected to PLE with acetone. The extractability values were compared to values obtained by toluene extraction without pretreatment. Alkaline pretreatment increased the extractability of higher-chlorinated CDDs (HiCDDs), whereas acid pretreatment slightly decreased their extractability. No change in extractability was observed for higher-chlorinated CDFs under any conditions. The extractability of lower-chlorinated CDD/Fs (LoCDD/Fs) and CoPCBs was increased only by acetone extraction. PCDD/F homologue profiles in soil humic acid fractions and those in dead leaves, a major raw material of soil humus, were also determined. These results suggest that the variations in the extractability of dioxin homologues are due mainly to variations in their physical state in the soil, especially their interactions with soil humus.     

Extractability of dioxins from suspended substances in distributed water

The extractability of dioxins from suspended substances (SS) in distributed water was evaluated. Dioxins adsorbed on the collected SS were extracted by pressurized liquid extraction with various solvents. High-polarity solvents (acetone, alcohols) extracted considerably higher amounts of some lower-chlorinated dibenzo-p-dioxins (LoCDDs) than did low-polarity solvents (dichloromethane, toluene), whereas the extracted amounts of higher-chlorinated dibenzo-p-dioxins (HiCDDs) were roughly the same, regardless of the solvent. The extractability of the LoCDDs depended on the isomer. Daily variations in quantities for PCDDs, organic matter (OM), and iron in the SS were examined, and the results suggested that in the SS, LoCDDs and HiCDDs were associated, respectively, with raw water-derived organic matter and microparticles sequestered in iron oxy(hydr)oxide floc. It was also suggested that the low extractability of certain congeners was not attributable to the enormously coexisting ferric compounds but was probably attributable to OM with which they strongly associate.     

Pressurized liquid extraction of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls from contaminated soil

Extraction solvents for pressurized liquid extraction (PLE) used to extract polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs) from contaminated soil were investigated. The PCDD/PCDFs and Co-PCBs in Certified Reference Material: CRM 0422 (Forest soil) were extracted using toluene, n-hexane, acetone, acetone/toluene and acetone/n-hexane (1:1, v/v). Soxhlet extraction was the reference method. Results demonstrated that PLE using mixed solvents produced better analyte recoveries than the single solvents. However, these results were lower than those for Soxhlet extraction. Additional extraction cycles using mixed solvents achieved better recovery results. Mixed solvents and several extraction cycles were necessary for satisfactory extraction of more tightly bound PCDD/PCDFs and Co-PCBs from soil.     

Influence of the characteristics of soil and fly ash on the supercritical carbon dioxide extraction of dioxins.

Several investigations on the extraction of dioxins from soil and fly ash with supercritical fluid have been reported; however, few of them describe the influence of components on the extraction. We extracted dioxins from eight samples with different values of organic carbon content and surface area with supercritical CO(2) at a temperature of 463 K, a pressure of 40 MPa, and using 10% toluene as an entrainer. We researched the influence of the characteristics of soil and fly ash on supercritical CO(2) extraction of dioxins. The results revealed that the extraction efficiencies of PCDD/DFs and PCBs were high for all soil samples, while that of fly ash samples decreased with the increase in organic carbon content and surface area. The extraction efficiencies of dioxins from four standard samples, activated carbon, humic acid, alumina, and florisil, were also examined. The results revealed that the extraction efficiencies were strongly influenced by activated carbon like components present in the samples.     

Simultaneous extraction of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls from contaminated soil using pressurized liquid extraction

Pressurized liquid extraction (PLE) was studied for simultaneous extractions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDFs), and of coplanar polychlorinated biphenyls (Co-PCBs) from a tightly bounded condition in the soil matrix. Temperatures were maintained at 175 and 200 degrees C, respectively, and two or three static cycles for single PLE with toluene and acetone/n-hexane were studied using a certified reference material to compare the effects of those conditions on recoveries. A single PLE with two static cycles at 150 degrees C and the repeated single PLE (additional PLE) were reference methods. Satisfactory recoveries were not obtained using tested single PLE (2,3,7,8-substituted PCDD/PCDFs and Co-PCBs average, average (avg.) 79-103%), but they were achieved using additional PLE (acetone/n-hexane, avg. 115-128%; toluene, avg. 111-132%). In addition, these methods and additional PLE of the reference method using acetone/n-hexane were not markedly different (avg. 123-128%). That fact suggests that the use of mixed solvents and additional PLE were more important factors than temperatures and static cycles of single PLE for quantitative and simultaneous extractions of those compounds from the soil.     

Extraction of Residues of Dyfonate-ring-14C from Soil

Abstract

Residues of Dyfonate-ring-¹⁴C were extracted from a clay loam soil with various solvents under a variety of conditions. Recovery of radioactivity from the soil was not related to the polarity (dipole moment) or the dielectric constant of the solvents. Commonly used solvents such as acetone, methanol, ethanol, and hexane/acetone (1:1) extracted only 28, 44, 27, and 25%, respectively, of the residues from the air-dried soil. The extraction efficiencies were increased to 46, 60, 54, and 49%, respectively, when 20% water was added to the soil prior to extraction with these solvents. The amount of water added to the soil and time of contact with water also affected the recovery of radioactivity from the soil. Any of the solvents or methods investigated failed to recover more than 60% of the radioactivity in the soil, indicating that residues of Dyfonate were strongly bound to the soil and were difficult to recover.     

Supercritical fluid extraction of polychlorinated dibenzo-p-dioxins from municipal incinerator fly ash

The supercritical fluid extraction of polychlorinated dibenzo-p-dioxins from an incinerator fly ash sample has been investigated; supercritical nitrous oxide and its mixtures with methanol and toluene were employed as mobile phases. Recoveries of individual polychlorinated dibenzo-p-dioxins congeners were calculated from results of analysis of ¹³C-labeled dioxins by high resolution GC-MS employing selected ion monitoring. The extraction procedure was compared with extraction in a Soxhlet apparatus, which is currently used as a standard method for removing chlorinated dibenzo-p-dioxins from fly ash samples: the results indicated that the time required for the extraction and clean-up can be reduced from 24 to 2.5 hours/sample. Quantitative recovery of the chlorinated dibenzo-p-dioxins was achieved at μg/kg levels, the relative standard deviation was between 1.8 and 5.8%. The use of a virtually inert fluid such as pure nitrous oxide provides significant improvement over conventional extraction procedures because no solvent residue is left in the processed extract.     

Determination of 26 polychlorinated biphenyls congeners in soil samples using microwave-assisted extraction with open vessel and gas chromatography

A procedure focused on microwave-assisted extraction in open vessel (MAE-OV) and gas chromatography with electron capture detection (GC-ECD) was used for the determination of 26 congeners of polychlorinated biphenyls (PCBs) in soil samples. The limit of detection (LOD) and limit of quantification (LOQ) were evaluated for commercial PCBs mixture Aroclor1260. LOD and LOQ were calculated for each PCB congener, in the ranges (0.03–0.27?ng?g^?1) and (0.11–0.70?ng?g^?1), respectively. After optimization, 26 PCBs congeners were successfully extracted from soil samples with recovery amounts ranging between 84.7% and 117.3% for all PCBs congeners. The evaluated method of MAE-OV showed good separation and extraction of all PCBs congeners from soil samples. Extraction parameters such as solvent choice, power and extraction time were investigated. This study indicated that MAE-OV could be an interesting alternative method to extract PCBs from soils, since it is economical, easy, fast and requires low amounts of solvents.     

Optimization of pressurized liquid extraction (PLE) of dioxin-furans and dioxin-like PCBs from environmental samples

Pressurized liquid extraction (PLE) applying three extraction cycles, temperature and pressure, improved the efficiency of solvent extraction when compared with the classical Soxhlet extraction. Polychlorinated-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like PCBs (coplanar polychlorinated biphenyls (Co-PCBs)) in two Certified Reference Materials [DX-1 (sediment) and BCR 529 (soil)] and in two contaminated environmental samples (sediment and soil) were extracted by ASE and Soxhlet methods. Unlike data previously reported by other authors, results demonstrated that ASE using n-hexane as solvent and three extraction cycles, 12.4 MPa (1800 psi) and 150 degrees C achieves similar recovery results than the classical Soxhlet extraction for PCDFs and Co-PCBs, and better recovery results for PCDDs. ASE extraction, performed in less time and with less solvent proved to be, under optimized conditions, an excellent extraction technique for the simultaneous analysis of PCDD/PCDFs and Co-PCBs from environmental samples. Such fast analytical methodology, having the best cost-efficiency ratio, will improve the control and will provide more information about the occurrence of dioxins and the levels of toxicity and thereby will contribute to increase human health.     

Comparison of Different Extraction Techniques of Polychlorinated Biphenyls from Sediments Samples

In this work, problems that may occur during determination of trace levels of polychlorinated biphenyls in sediment samples are described. Main error sources are connected with extraction of analytes prior to final determination.

During model studies, polychlorinated biphenyls have been extracted from sediment reference material (METRANAL 2) with the use of different solvents (dichloromethane, hexsane, and toluene); the process has been enhanced by mechanical shaking or ultrasounds. Seven selected PCBs (PCB 28, 52, 101, 118, 138, 153, and 180 – according to IUPAC) were determined in extracts samples by GC–MS technique.

During the studies, two calculation methods were applied to determine the amount of analytes introduced to the chromatographic column. The first approach assumes that the recovery of PCBs that contained a small amount of chlorine atoms in the molecule is similar to the recovery of ¹³C₁₂PCB28 standard, whereas compounds with greater number of chlorine atoms in the molecule will be recovered from the sediment similarly to the recovery of ¹³C₁₂PCB180 standard. The second approach assumes that the recovery of PCB 138 and PCB 153 is similar to the average value of ¹³C₁₂PCB28 and ¹³C₁₂PCB180 standards.

In the case of shaking assisted extraction, 55–90% PCB recoveries were achieved when toluene was used as a solvent, while 71–86% recovery was achieved when dichloromethane was used. When hexsane was used as solvent, recovery ranged 43–107%. In the case of ultrasounds assisted extraction, PCB recoveries of 50–108% were achieved when toluene was used as solvent, while 44–101% recovery was achieved when dichloromethane was applied. When hexsane was used as solvent, recovery reached 57–95%.

Studies have also shown that, when applying different isolation techniques and different solvents, the recovery of applied ¹³C₁₂PCB28 and ¹³C₁₂PCB180 standards is different. Recovery of ¹³C₁₂PCB28 standard was from 5% (for hexane tenfold extraction assisted by shaking) to 57% (for toluene tenfold extraction assisted by shaking). However, recovery of ¹³C₁₂PCB180 standard was from 9% (for hexane tenfold extraction assisted by shaking) to 82% (for toluene tenfold extraction assisted by shaking). This is due to the differences of their binding to the sludge matrix. Standard with a greater number of chlorine atoms in the molecule (¹³C₁₂PCB180) is more weakly associated with sediment than ¹³C₁₂PCB28 standard. In order to improve the accuracy of the results obtained, it is necessary to use labeled PCB compounds.     

Development and validation of a method for analyzing polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in sewage sludge samples

Summary A method has been developed for the analysis of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) in sewage sludge samples. It was found that PCDD/F are best Soxhlet extracted from the matrix with toluene for 24h, after having tested other solvents (dichloromethane and hexane/acetone 41/59) and other extraction times. Several clean up steps (sulfuric acid, multilayer silica and Florisl columns) and concentration are required prior to analysis of the extract by high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS). The complete procedure has been validated and the accuracy and precision data (repeatability and reproducibility) are given. The method is linear in the range studied and the limit of detection ranges between 0.2 and 2.2 pg g⁻¹ of dry matter for the 2,3,7,8-substituted congeners. Moreover, the suitability of the method has been checked in an international interlaboratory comparison. The successful application of this method to several samples from Catalan and Dutch urban wastewater treatment plants was demonstrated.     

Recovery of some common solvents from protective clothing breakthrough indicator pads by microwave-solvent extraction and gas chromatography

The efficiency of solvent adsorption using Permea-Tec general solvent pads, used for the detection of chemical breakthrough of protective clothing, was determined for methanol, acetone, ethyl methyl ketone, trichloroethylene (TriCE), tetrachloroethylene (TetCE), toluene, m-xylene, and D-limonene. Known volumes of single or mixed solvents were added to pads in the range 0.2-5.0 microliters (0.16-8.13 micrograms). After microwave-solvent extraction (ME) into hexan-1-ol, the samples (0.5-3.0 microliters) of the filtered and extracted solutions were analyzed by gas chromatography. All solvents exhibited > 97% adsorption on the pads at spiking levels of 0.48-0.98 microgram for each solvent. The solvent recovery for the system was calculated for each solvent, with solvents with boiling points below 110 degrees C showing recoveries of > 90%, and with solvents with boiling points above 110 degrees C showing recoveries from 80 to 90%. The recovery precision was good (RSD < or = 4%) for all solvents over the range 1.0-2.5 microliters of applied solvents to pads for ME and 1.0 microliter of extracted solutions for GC analysis.     

Enhancement of phenols on ion-pair extraction of chromium(VI) with tetraphenylarsonium

The effect of phenols on the ion-pair extraction of chromium(VI) as chromate anion (HCrO ₄ ^– ) with tetraphenylarsonium cation (TPA⁺) has been investigated. By using TPACl, chromate is extracted as an ion-pair, TPA⁺·HCrO ₄ ^– , into organic solvents, but its extractability into nonpolar solvents such as carbon tetrachloride is very low. The addition of several phenols greatly enhances the extractability, e.g., the distribution ratio of chromium(VI) between carbon tetrachloride and water rises 5500-fold in the presence of 0.020M 3,5-dichlorophenol in the organic phase. The enhancement was larger when using more acidic phenols and less polar solvents. From the analysis of the extraction data for the 3,5-dichlorophenol-carbon tetrachloride system, it was shown that one molecule of chromate is extracted together with one TPA⁺ and 1–3 phenol molecules and the extraction constants were determined. The UV spectrum indicated the extracted species including chromate ester to the TPA⁺·ArOCrO ₃ ^– ·mArOH (m=1,2).     

Improved Method for the Determination of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) in Sanitary Napkins

Abstract

An improved method was developed for determining highly toxic 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-p-furans (PCDD/Fs) in sanitary napkins. Samples were extracted by Soxhlet (50% dichloromethane/hexane) and sonication (hexane), and a multi-layer silica column was used for clean-up after acetone precipitation to separate the superabsorbent polymers. Improved separation efficiency of PCDD/Fs from sanitary napkins with a high level of superabsorbent polymers was achieved using the acetone precipitation method. Hexane was then applied as an alternative solvent to remove residual interfering substances including sticky components contained on sanitary napkins via alumina column chromatography in the second clean-up step. Recoveries approached 100% with an average relative standard deviation of less than 15%, and recoveries of internal standards were from 70.5 to 114.8% and 0.6 to 13.6% for the two extraction methods. The mean method detection limit was 0.075–0.968?pg/g for Soxhlet extraction and 0.0032–0.091?pg/g for sonication extraction. The established method meets the quality criteria for the screening of dioxins stated in EU Regulations 589/2014 and 709/2014, and therefore provides a suitable alternative for the determination of dioxins in sanitary napkins containing superabsorbent polymers.     

Optimisation and comparison of microwave-assisted extraction and Soxhlet extraction for the determination of polychlorinated biphenyls in soil samples using an experimental design approach

Optimisation of microwave-assisted extraction (MAE) for the extraction of polychlorinated biphenyls (PCBs) from soil samples has been accomplished using an experimental design approach. Variables studied have been: percentage of acetone (v/v) in an acetone:n-hexane mixture, solvent volume, extraction time, microwave power and pressure inside the extraction vessel. Five samples of a certified soil (CRM 481) have been extracted under the optimum conditions of the developed method and the results have been compared to those obtained by Soxhlet extraction. Good recoveries (>95%) have been obtained for all the PCBs studied. All extracts have been analysed by gas chromatography/mass spectrometry (GC/MS) and an optimum determination method for the electron impact mass spectrometric (EIMS) has also been developed.     

Pyrethroid soil extraction,properties of mixed solvents and time profiles using GC/MS-NICI analysis

Ultrasonic extraction was used to develop a suitable binary solvent system for the analysis of synthetic pyrethroid pesticides and mirex on soil. The analysis was carried out by gas chromatography with negative ion chemical ionization mass spectrometry (GC/MS-NICI). In the initial experiments, accurately weighed soil samples were spiked with a mixture of standard solution pyrethroids and mirex and shaken for 24?h to ensure homogeneity, then extracted with solvent. The extracts were evaporated to dryness before the volumetric internal standard was added.

The binary solvents used in this study were various mixtures of hexane?:?acetone, hexane?:?dichloromethane (DCM), isooctane?:?acetone and isooctane?:?dichloromethane, representing different classes of polarity. The recoveries of all pyrethroids and mirex were satisfactory over three solvent systems: hexane?:?acetone, hexane?:?DCM and isooctane?:?acetone, but results of isooctane?:?DCM produced low recoveries. The average recovery increased with the extraction time, but the increase was not statistically significant. A 30-min optimum extraction was deemed sufficient for recovering pyrethroids from soil. After 30?min, extraction decreased owing to the re-distribution of the analyte on the soil matrix.     

The determination of polychlorinated biphenyl in small samples of monkey milk and tissues. II. Extraction efficiency

The extraction efficiency of benzene, toluene, dichloromethane, acetone:hexane and chloroform:methanol with respect to lipids and polychlorinated biphenyls was investigated using small samples of monkey adipose tissue, liver, kidney, brain, skin, feces and milk. The most efficient solvents were: acetone:hexane and chloroform:methanol for brain, feces, kidney, liver and milk; acetone:hexane and dichloromethane for adipose tissue; acetone:hexane and toluene for blood and dichloromethane for skin tissue. Within these solvent pairs acetone:hexane was the most outstanding with respect to an average of 90% PCB recoveries from fortified samples in the range of 0.02-2 ppm. In addition, a comparison was made between the lipid determination before and after Florisil column chromatography. Only adipose and blood lipids were sufficiently recovered from Florisil to make a lipid determination after chromatography feasible.     

Comparison of solvent mixtures for pressurized solvent extraction of soil fatty acid biomarkers

The extraction and transesterification of soil lipids into fatty acid methyl esters (FAMEs) is a useful technique for studying soil microbial communities. The objective of this study was to find the best solvent mixture to extract soil lipids with a pressurized solvent extractor system. Four solvent mixtures were selected for testing: chloroform:methanol:phosphate buffer (1:2:0.8, v/v/v), chloroform:methanol (1:2, v/v), hexane:2-propanol (3:2, v/v) and acetone. Soils were from agricultural fields and had a wide range of clay, organic matter and microbial biomass contents. Total lipid fatty acid methyl esters (TL-FAMEs) were the extractable soil lipids identified and quantified with gas chromatography and flame ionization detection. Concentrations of TL-FAMEs ranged from 57.3 to 542.2 n mole g⁻¹ soil (dry weight basis). The highest concentrations of TL-FAMEs were extracted with chloroform:methanol:buffer or chloroform:methanol mixtures than with the hexane:2-propanol or acetone solvents. The concentrations of TL-FAMEs in chemical groups, including saturated, branched, mono- and poly-unsaturated and hydroxy fatty acids were assessed, and biological groups (soil bacteria, mycorrhizal fungi, saprophytic fungi and higher plants) was distinguished. The extraction efficiency for the chemical and biological groups followed the general trend of: chloroform:methanol:buffer ≥ chloroform:methanol > hexane:2-propanol = acetone. Discriminant analysis revealed differences in TL-FAME profiles based on the solvent mixture and the soil type. Although solvent mixtures containing chloroform and methanol were the most efficient for extracting lipids from the agricultural soils in this study, soil properties and the lipid groups to be studied should be considered when selecting a solvent mixture. According to our knowledge, this is the first report of soil lipid extraction with hexane:2-propanol or acetone in a pressurized solvent extraction system.     

Selective pressurized liquid extraction of estrogenic compounds in soil and analysis by gas chromatography-mass spectrometry

A selective pressurized liquid extraction (SPLE) method, followed by gas chromatography–mass spectrometry (GC–MS), for the simultaneous extraction and clean-up of estrone (E1), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), estriol (E3) and bisphenol A (BPA) from soil samples is described. The on-line clean-up of soil by SPLE was achieved using different organic matter retainers, including silica, alumina and Florisil, the most effective being silica. Thus, different amounts of silica, in conjunction with different extraction solvents (acetone, ethyl acetate, isohexane and dichloromethane), either alone or in combination, were used to extract the target chemicals from spiked soil samples. It was shown that 3 g silica resulted in satisfactory rates of recovery of target compounds and acetone:dichloromethane (1:3, v/v) was efficient in extracting and eluting estrogenic compounds for SPLE. Variables affecting the SPLE efficiency, including temperature and pressure were studied; the optimum parameters were 60 °C and 1500 psi, respectively. The limits of detection (LODs) of the proposed method were 0.02–0.37 ng g⁻¹ for the different estrogenic chemicals studied. The outputs using the proposed method were linear over the range from 0.1 to 120 ng g⁻¹ for E1, E2, EE2, 0.2–120 ng g⁻¹ for E3, and 0.5–120 ng g⁻¹ for BPA. The optimized method was further verified by performing spiking experiments in natural soil matrices; good rates of recovery and reproducibility were achieved for all selected compounds and the method was successfully applied to soil samples from Northeast Scotland, for the determination of the target compounds.     

Validation of methods for measuring polychlorinated dibenzo- p -dioxins and furans,and dioxin-like polychlorinated biphenyls in flue gas

Method validation was performed on the collection and extraction procedures for an analysis of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DLPCBs) in flue gas. The adoption of the rapid pressurized liquid extraction (PLE) technique was evaluated for extraction from polyurethane foam plugs (PUFPs) and fly ash. With respect to extraction from PUFPs, dichloromethane PLE showed an extraction efficiency equivalent to that of conventional acetone Soxhlet, while toluene PLE was found to have a lower extraction efficiency from fly ash than toluene Soxhlet. The collection ability of three sampling methods, employed in the Japanese standard analytical method JIS K0311 (revised in 2005) was evaluated by evaluating the distribution of gaseous PCDD/Fs and DLPCBs in each collection compartment in sampling trains. A DiOANA® fibrous alumina filter and a PUFP, newly employed trapping devices in the revised JIS method, were found to trap gaseous analytes effectively. The validation of the two newly employed sampling methods (DiOANA and PUFP) was tested by parallel measurements of the methods with a conventional five-impinger method, and good agreements on the PCDD/Fs and DLPCBs quantities were demonstrated.