PCDFs extraction

PLE pressurized liquid extraction, SPE solid phase extraction, UE ultrasonic extraction, DSPE dispersive solid phase extraction, SBSE stir bar sorptive extraction, TD-GC-MS thermal desorption-gas chromatography-mass spectrometry, LAS linear alkylbenzene sulfonates, CDEAs coconut diethanol amides, NPEOs nonylphenol ethoxylates, DP degradation products, SPC sulphenyl carboxylates, PCDD dibenzo-p-dioxins (PCDD), PCDF dibenzofurans, PCBs biphenyls... 

Also the production of specific Abs for PCDDs/PCDFs has been directed toward the development of immunoaffinity procedures [248,249]. Shelver et al. reported several works regarding the use of IAC to selectively extract and analyze these compounds from complex matrices such as milk or serum [250-253]. Moreover, a separation of very similar dioxin congeners (i.e., 1,3,7,8-TCDD and 2,3,7,8-TCDD) was also examined [254]. 

For the determination of the intralaboratory repeatability of the DR CALUX bioassay for sediment samples, two sediment extracts were analyzed 10 times. Each analysis was performed in triplicate. As a prerequisite for a correct triplicate analysis, the percentage standard deviation in the triplicate determination should be below 15%. This is in accordance with the harmonized quality criteria for eell-based bioassay analyses of PCDDs/PCDFs in feed and food as formulated by Behnisch et al. (Behnisch et al, 2001 a) and as detailed in European Union directive 2002/69/ EC and direetive 2002/70/EC. The repeatability for the low-2,3,7,8-TCDD-content sediment... 

Opperhuizen, A., Wagenaar, W.J., Van der Wielen, F.W.M., Van den Berg, M., Olie, K., O. Hutzinger, O., Gobas, F.A.P.C. (1986) Uptake and elimination of PCDD/PCDF congeners by fish after aqueous exposure to a fly ash extract from a municipal incinerator. Chemosphere 15, 2049-2053. 

DeRoos FL, Bicking MKL. 1990. Supercritical fluid extraction for the determination of PCDDs and PCDFs in soil. Chemosphere 20 1355-1362. 

Forst C, Stieglitz L, Zwick G. 1988. Isomer-specific determination of PCDD/PCDF in oil extracts from water leachate of a waste landfill. Chemosphere 17 1935-1944. 

Patterson DG Jr, Fiirst P, Alexander LR, et al. 1989b. Analysis of human serum for PCDDs/PCDFs A comparison of three extraction procedures. Chemosphere 19 89-96. 

Van den Berg M, Meerman L, Olie K, et al. 1986a. Retention of PCDDs and PCDFs in the liver of the rat and hamster after oral administration of a municipal incinerator fly ash extract. Toxicol Environ Chem 12 267-284. 

CEN-Norm-Entwurf Dioxine (2/1992), CEN/TC 264/WG 1.. .Determination of the mass concentration of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) - Stationary source emissions - (a) Sampling (b) Extraction and clean-up", European Committee for Normalization (CEN)... 

Lindstrdm G, van Bavel B, Karlsson MJL, Rappe C, Hardell L (1995), Organohalogen Compounds 23 27-30. The use of supercritical fluid extraction (SFE) as a sample preparation method in the analyses of PCDD, PCDF and PCB in human tissue", Eds. Dioxin 95 Secretariat, Edmonton, Kanada ISBN 3-928379-13-5... 

Onuska FI, Terry KA (1991), HRC CC 14 829-834.. .Supercritical fluid extraction of polychlorinated dibenzo-p-dioxins from municipal incinerator fly ash" van Bavel B, Hartonen K, Riekkola ML, Rappe C (1992), Organohalogen Compounds 8 15-18.. .Optimization of supercritical fluid extraction of PCDD/PCDFs and PCBs from fly ash", Eds. Finnish Institute of Occupational Health, Helsinki, Finnland ISBN 951-801-932-0... 

The identification of PCDD/PCDF isomers is based on the simultaneous detection of the two most abundant ions in the molecular ion regions and the H-COC1 ion. In addition, the identification of OCDD and five of the 2,3,7,8-substituted isomers, for which a 13C-labeled standard is available in the internal standard and recovery standard solutions, is based on their exact retention time (-1 to 3 seconds from the respective internal or recovery standard signal). The 2,3,7,8-substituted isomers for which 13C-labeled standards are not available in the sample extracts are identified by the relative retention times of the isomer in the daily standard as compared to the appropriate internal standard. 

The PCDDs/PCDFs are quantitated by comparing the MS response of the detected analyte relative to the MS response of the appropriate 13C labeled internal standard (Table 2). The responses of both the ions monitored for each analyte are used for quantitation. The labeled internal standards are added prior to sample extraction. Thus, the quantitative results for the native analytes are corrected for the recovery of the internal standards, based on the assumption that losses of the internal standards during sample preparation and analysis are equal to the losses of the unlabeled PCDDs/PCDFs. 

If the concentration of any PCDD/PCDF exceeds the calibration range of the instrument, a dilution must be performed to bring that concentration within range. Additional recovery standard solution is added to the diluted sample extract immediately prior to reanalysis (see Section 10.4). 

Isomer specificity for all 2,3,7,8-substituted PCDDs/PCDFs cannot be achieved on the 60 m DB-5 column. In order to determine the concentration of the individual 2,3,7,8-substituted isomers, if the toxicity equivalence is greater than 0.7 ppb (solids), 7 ppt (aqueous), or 7 ppb (chemical waste), the sample extract shall be reanalyzed on a 60 m SP-2330 or SP-2331 (or equivalent) GC column. 

The combination of a Soxhlet extractor and a Dean Stark moisture trap is used for the removal of water and extraction of PCDDs/PCDFs from samples of fly ash, soil/sediment, and che particulate fraction of water samples. The combination consists of a Soxhlet extractor body with a Dean Stark moisture trap fitted between the extractor and the condenser. 

Partition the concentrated extract against 40 mL of 20 percent (w/v) potassium hydroxide (KOH). Shake for two minutes. Remove and discard the base layer (bottom). Repeat the base washes until color is not visible in the bottom layer (perform base washes a maximum of four times). Strong base (KOH) is known to degrade certain PCDDs/PCDFs therefore, contact time should be minimized. 

Remove the extract of the sample or blank from storage. Gently swirl the solvent on the lower portion of the vial to ensure complete dissolution of the PCDDs/PCDFs. 

In order to assure that retention time shifts do not adversely affect the identification of PCDDs/PCDFs, the absolute retention times of the two recovery standards added to every sample extract immediately prior to analysis may not shift by more than 10 seconds from their retention times in the continuing calibration standard (see Paragraph 17.1.4). 

If the area of any internal standard in a diluted sample is less than 10 percent of the area of that internal standard in the continuing calibration standard, then the unlabeled PCDD/PCDF concentrations in the sample shall be estimated using the recovery standard, using the formulae that follow. The purpose is to ensure that there is an adequate MS response for quantitation in a diluted sample. While use of a smaller aliquot of the sample might require smaller dilutions and therefore yield a larger area for the internal standard in the diluted extract, this practice leads to other concerns about the homogeneity of the sample and the representativeness of the aliquot taken for extraction. 

The sample extract may be analyzed on a single GC column capable of resolving all 2,3,7,8-substituted PCDDs/PCDFs from other isomers, but not necessarily resolving all the non-2,3,7,8-substituted isomers from one another. 

If the calculated concentration of the unlabeled PCDDs/PCDFs exceeded the initial calibration range, the sample extract shall be diluted and reanalyzed (see Section 10.4). Such sample dilutions are billable under the contract... 

Properties of PCDEs, including physicochemical ones, are not well known as the literature reviews of PCDEs have shown [4, 11,40,46]. PCDEs resemble PCBs structurally and in their chemical and physical properties, which, like PCDDs, PCDFs, and related compounds, are known to be stable and resistant to breakdown by heat, hydrolysis, bases, and acids. PCBs are also quite stable to oxidation under moderate conditions [3], but there is not much data about PCDEs concerning their stability. There is some evidence that PCDEs are resistant to bases and acids and the occurrence of PCDEs in the environment indicates that PCDEs are persistent and bioaccumulating compounds. The study of Firestone et al. [37] already showed that PCDEs are quite stable, since PCDEs could be measured in chlorophenol extracts after sulfuric acid treatment. Tetra- and octachlorinated PCDE congeners were later proven resistant in treatment with... 

PCDEs are converted to toxic PCDFs in photochemical reactions [71] and metabolism of PCDEs could in theory also lead to the formation of PCDDs when both 2- and 2 -positions are hydroxylated and then dehydrated. No PCDDs and PCDFs, however, were detected in the urinary and fecal extracts of rats fed with PCDEs [18]. Metabolic formation of PCDDs or PCDFs was neither observed in the case of a predioxin, Triclosan. 

Soxhlet extraction is a preferred method for extraction of PCDDs and PCDFs in particulates [111] and has been applied to extract PCDEs from sediment [33]. Koistinen et al. [33] extracted sediments for analyses of PCDEs, PCDDs, and PCDFs with toluene for 48 h. Coburn and Comba [115] used ultrasonic extraction with a mixture of hexane acetone (1 1). Suspended particulates were extracted with dichloromethane for 2 h [51]. 

As with sediment, Soxhlet extraction has been preferred for extraction of PCDEs from fly ash. Before extraction of fly ash, acid treatment with HC1 increases the recoveries of PCDDs and PCDFs, and was applied by Kurz and Ballschmiter [43], Koistinen et al. [57] did not use pretreatment with HCl when they extracted a fly ash for analysis of PCDEs. 

During extraction and cleanup, concentration of sample extracts can be performed using similar techniques as in the analysis of organochlorines, PCDDs, and PCDFs [1, 111]. Vacuum evaporation and evaporation under nitrogen flow are also typical concentration techniques in PCDE analyses. 

Kuehl et al. [116] have used Celite-545 coated with concentrated sulfuric acid for lipid removal. They eluted fish extract using hexane through this column to a cesium silicate column. Acid treated silica gel is a common material for lipid removal of biota and abiota samples for PCDD/PCDF analyses [111, 112] and has been applied to human adipose tissue extracts for analysis of PCDE [132]. Silica impregnated with concentrated sulfuric acid packed on silica gel in a column has been applied as a second cleanup step [43,120,132]. A multi-silica gel column consisting of layers of silica (silica gel 60), silica impregnated with sulfuric acid (44%), silica, silica impregnated with sodium hydroxide (1 mol 1 ), silica, silica with silver nitrate (10%), and silica has been used for fish extracts by Birkholz et al. [120], The extract was eluted with 2% dichloromethane in hexane and was further purified on Florisil. 

Silica gel has mostly been used for bulk matrix removal, but it has also been used to fractionate PCDE-containing extracts [51,119,121,129]. When silica gel chromatography is used for fractionation of PCDE-containing extracts, PCBs are often eluted with PCDEs. Lake et al. [51] eluted PCDEs from a silica column (deactivated with 5% water) together with PCBs using pentane (50 ml) as an eluent. A 2-( 1 -pyrenyl)ethyldimethylsilylated silica column has been used to separate PCDEs and PCBs from PCDDs and PCDFs [43],... 

Ryan et al. [134] have used a 1.5 g column of Florisil (60-100 mesh activated at 130°C for 24 h) for separation of PCDEs from PCDDs and PCDFs. They eluted first PCDEs and PCBs with 2% hexane in dichloromethane (20 ml) and then PCDD/PCDFs with dichloromethane (35 ml). They further fractionated the extract on a silica column. 

Koistinen et al. [58] have applied a Florisil cleanup which uses a partially deactivated (1.25%) Florisil microcolumn (1 g) to separate PCDEs from PCDDs and PCDFs in abiota and biota extracts [33,57,113,114,123-125]. After sulfuric acid cleanup, PCDEs are eluted through a Florisil column together with PCBs using hexane (15 ml). PCDDs and PCDFs are retained in the column and can be eluted with dichloromethane (12 ml). 

Activated alumina (260 °C) column has been used for isolation of PCDEs, PCDDs, and PCDFs from chlorophenol extracts [37,38]. Four fractions were collected from an alumina column (50 g) petroleum ether (400 ml), 5% ethyl ether in petroleum ether (200 ml), 25% ethyl ether in petroleum ether (400 ml), and ethyl ether (400 ml). PCDEs, PCDDs, and PCDFs were determined in the third and fourth fractions after sulfuric acid cleanup. 

The use of isotope-labeled internal standards, which is recommended in the mass spectrometric analysis of PCDDs and PCDFs, to monitor the efficiency of extraction and cleanup has not been common in PCDE analyses due to the limited number of commercially available labeled standards. A D5-labeled pentaCDE has been used as an internal standard in Finnish studies [33,113,114, 123-125,139] and 13Cl2-labeled PCDEs have been used only in few studies [120, 131]. Labeled compounds behave hke the corresponding endogenous compounds during cleanup steps and would be the best internal standards for reliable results in PCDE analysis. 

It is difficult to conclude what the best analytical method is for PCDEs but, based on the literature, microcolumns such as Florisil [57] seem to be effective in separation of PCDEs from PCDDs and PCDFs. Furthermore they are fast and inexpensive. Before PCDEs can be analyzed by MS, however, an additional cleanup step is needed. This has been performed using column chromatography on carbon, since silica gel and neutral alumina microcolumns have not worked well with fish extracts for this purpose [57]. Activated silica and alumina microcolumns, however, could possibly be alternatives for a carbon column. An activated silica column has been used an additional cleanup step after Florisil and carbon column chromatography in the case of mussel extracts [123]. It is not necessary to separate PCBs from PCDEs, since PCBs have been reported not to interfere in the MS analysis of PCDEs [57,130],... 

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