Investigating the Extraction Efficiency of Dioxins in Several Types of Aqueous Matrices by Automated Solid Phase Extraction Utilizing Disks

Transcription

1 Investigating the Extraction Efficiency of Dioxins in Several Types of Aqueous Matrices by Automated Solid Phase Extraction Utilizing Disks James Fenster and Michael Ebitson, Horizon Technology, Inc., Salem, NH USA Key Words Dioxins, SPE, Solid Phase Extraction, POPs Introduction Dioxins are of great environmental concern due to their teratogenic, mutagenic, and carcinogenic impact. These lipophilic compounds bioaccumulate in humans and wildlife and can have half lives of up to 132 years, making them persistent organic pollutants (POPs). Traditional SPE requires a filtration step to remove particulates when using SPE cartridges, because of clogging issues. The filtered particulates then require a separate extraction step, such as soxhlet extraction. Liquid-liquid Extraction (LLE) often has issues with emulsions that can adversely affect the proper extraction of the particulate matter. Using the automated 47-mm SPE-disk approach allows for the extraction to take place without the problems such as clogging, filtration or emulsions. The SPE disk allows for the dioxin compounds in water to be retained on divinylbenzene (DVB) disk packing while the water passes through. It also allows the particulate matter to sit on the top of the disk. This way, when the elution solvents are delivered to extract the disk, they also extract any dioxin compounds that may have attached to suspended particulates or sediment, allowing for extraction of the whole sample. Disks combine fast flow rates without compound breakthrough, allowing efficient extraction of particulate laden samples larger than 1 liter with excellent recoveries that result in lower detection limits. This application will focus on SPE extraction techniques, results and recoveries of dioxins in deionized water, particulate-laden river water samples and wastewater. Experimental SPE-DEX 4790 Automated Extraction System Extractions of samples were accomplished using the automated SPE-DEX 4790 with the Envision platform controller (Horizon Technology, Inc.). SPE extraction disks were Atlantic DVB disks (47 mm), and pre-filters. Extraction solvents were methylene chloride, acetone, methanol, reagent water, hexane, and nonane. Samples were dried using sodium sulfate and then cleaned up using a coupling column, containing silica gel, alumina and Florisil. Samples were concentrated on a mivac Evaporator (Genevac), and analytical analysis was carried out by high resolution gas chromatography (HRGC)/high resolution mass spectroscopy (HRMS). The samples and characterization information are summarized in Table 1.

2 Table 1. Summary of Samples Prepared Sample Type Number of Samples Sample Volume ml Disk Type ph Prefilter Large Particulates Fine Particulates Sediment DI ( LCS) DVB 2 No No No No River Water DVB 2 Yes No Yes No River Water DVB 2 Yes Yes Yes Yes Wastewater DVB 2 Yes Yes Yes No Results and Discussion Due to the persistent nature of these compounds great care needs to be taken to ensure all glassware and extraction system components are clean in order to assure no cross contamination between samples or interferences in method blanks or low level samples. A cleaning procedure was developed using organic solvents and mild detergent that assures the extractor s liquid flow path is free of contaminants between samples. Twelve samples as described in Table 1, were prepared, extracted, and analyzed in order to demonstrate the effectiveness of the SPE method and to compare matrix effects. The samples represent a variety of matrices, including distilled water, very fine particulate laden river samples, river samples containing fine particles and sediment, and finally two wastewater influent samples. All sample sizes were reduced compared to the usual 1 L of sample taken due to the use of the 47 mm extraction disks in the smaller holder. If larger samples were required for detection limit criteria, larger particulated samples could be run using the EZ Flow disk holder which allow the layering of filters above the SPE disk so the particles are retained on the surface of the filter for rinsing with the elution solvent, but flow through the SPE disk is not compromised. Dioxins and furans are known to bind to sediment or suspended particles so these types of samples were ideal as reference matrix spikes. Each of the 12 samples were spiked with 25 µl of a 20 pg/µl solution containing CDDs and CDFs and a 40 pg/µl for OCDD and OCDF. As specified in USEPA Method 1613 the samples were allowed to sit for 3 hours to equilibrate and become more representative of a native sample. The method in Table 2 was programmed into the SPE-DEX 4790 Envision controller for a 47mm disk and was used for all of the extraction runs in this study. P a ge 2 Table 2. SPE-DEX 4790 Extraction Method Steps Solvent Soak Air-Dry Pre-Wet 1 DCM 1 Min 1 Min Pre-Wet 2 Acetone 1 Min 1 Min Pre-Wet 3 MeoH 1 Min 4 sec Pre-Wet 4 Water 5 sec 2 sec Pre-Wet 5 Water 0 sec 0 sec Sample Introduction Air-Dry Time 5 min Rinse 1 Acetone 1 min 30 sec 30 sec Rinse 2 DCM 1 min 30 sec 30 sec Rinse 3 DCM 1 min 30 sec 30 sec Rinse 4 DCM 1 min 30 sec 30 sec Rinse 5 DCM 1 min 30 sec 1 min

3 The clean LCS samples were processed very quickly and passed through the disk at speeds up to 150 ml/min. A sample pre-filter was used with the particulate-laden river samples and the sediment-laden samples. The flow rates through these samples were slower than the LCS samples. Additionally, it was determined that increasing the soak times with the multiple rinse steps in the particulate-laden samples will optimize the extraction efficiency of the automated extractor. One of the unique features in the design of this extraction system is that the original sample bottle is automatically rinsed. Twenty-five milliliters of extract consisting of methylene chloride and acetone 80:20 was collected, dried with sodium sulfate and concentrated to 100 µl on the evaporation system. Solvent extracts were exchanged with 3.0 ml of hexane, twice to ensure complete solvent exchange takes place. The sample extracts were then brought up to 1 ml volume and cleanup was carried out with a coupling column with silica gel, alumina and florisil. Final concentration was carried out on the evaporation system to a volume of 100 µl, 25 µl of nonane is added and placed back on the concentrator until a final volume of 25 µl is reached. Results for these samples are shown in tables 4, 5, 6, and 7. Samples were analyzed by HRGC/HRMS under the following conditions. Instrument Condition HRGC/MS Column DB5 (60 m) Flow 1mL/min Column Temperature 180 o C to 190 o C at 2 o C/min then 190 o C to 240 o at 5 o C/min Sample Injection Volume 1.8 µl Run Time 52 minutes In order to know how much recovery would be lost to the drying and concentration steps, 25 ml methylene chloride was spiked with 25 µl of a 20 pg/µl solution containing CDDs and CDFs and a 40 pg/µl for OCDD and OCDF. These spikes were dried, treated with florisil, silica gel, and alumina and concentrated. The following table reports losses in recovery associated with these steps. Results for the concentrated methylene chloride spike is shown in Table 3. Losses were fairly small for these final cleanup and concentration steps with the exception of the hepta and octa chlorinated furans. The results show that recovery losses may occur in the clean-up and evaporation steps, even if the extraction step provides a high recovery. Care must be taken in each step to ensure the best overall recovery of analyte. Several different types of water samples were examined to see if significant differences in recovery were observed. Samples with suspended particles yielded higher recoveries (Table 5) than the LCS (Table 4) by a small amount. Table 6 shows results for samples with both particulate and sediment, providing an increasingly challenging matrix. The suspended particles and sediment in the bottle did lower the recoveries due to the compounds natural tendency to adhere to soil particles. Wastewater influent samples, a challenging matrix, were analyzed and the results shown in (Table 6). Even in this matrix most of the compounds showed a reasonable recovery and good precision. Page 3

4 Table 3. Methylene Chloride Spike (Dried, Treated and Concentrated) Compounds %Recovery % Loss 2,3,7,8-TCDF ,2,3,7,8-PeCDF ,3,4,7,8-PeCDF ,2,3,4,7,8-HxCDF ,2,3,6,7,8-HxCDF ,3,4,6,7,8-HxCDF ,2,3,7,8,9-HxCDF ,2,3,4,6,7,8-HpCDF ,2,3,4,7,8,9-HpCDF OCDF ,3,7,8-TCDD ,2,3,7,8-PeCDD ,2,3,4,7,8-HxCDD ,2,3,6,7,8-HxCDD ,2,3,4,6,7,8-HpCDD OCDD Table 4. Results -DI Water LCS Compounds Sample 1 %Recovery Sample 2 %Recovery SD 2,3,7,8-TCDF ,2,3,7,8-PeCDF ,3,4,7,8-PeCDF ,2,3,4,7,8-HxCDF ,2,3,6,7,8-HxCDF ,3,4,6,7,8-HxCDF ,2,3,7,8,9-HxCDF ,2,3,4,6,7,8-HpCDF ,2,3,4,7,8,9-HpCDF OCDF ,3,7,8-TCDD ,2,3,7,8-PeCDD ,2,3,4,7,8-HxCDD ,2,3,6,7,8-HxCDD ,2,3,4,6,7,8-HpCDD OCDD Page 4

5 Table 5. Results - River Water with Fine Particulates Compounds 1 %Recovery 2 %Recovery 3 %Recovery 4 %Recovery 5 %Recovery 6 %Recovery Average SD 2,3,7,8-TCDF ,2,3,7,8-PeCDF ,3,4,7,8-PeCDF ,2,3,4,7,8-HxCDF ,2,3,6,7,8-HxCDF ,3,4,6,7,8-HxCDF ,2,3,7,8,9-HxCDF ,2,3,4,6,7,8-HpCDF ,2,3,4,7,8,9-HpCDF OCDF ,3,7,8-TCDD ,2,3,7,8-PeCDD ,2,3,4,7,8-HxCDD ,2,3,6,7,8-HxCDD ,2,3,4,6,7,8-HpCDD Table 6. Results - Fine Particulate and Sediment-Laden River Water Compounds Sample 1 %Recovery Sample 2 %Recovery SD 2,3,7,8-TCDF ,2,3,7,8-PeCDF ,3,4,7,8-PeCDF ,2,3,4,7,8-HxCDF ,2,3,6,7,8-HxCDF ,3,4,6,7,8-HxCDF ,2,3,7,8,9-HxCDF ,2,3,4,6,7,8-HpCDF ,2,3,4,7,8,9-HpCDF OCDF ,3,7,8-TCDD ,2,3,7,8-PeCDD ,2,3,4,7,8-HxCDD ,2,3,6,7,8-HxCDD ,2,3,4,6,7,8-HpCDD OCDD Page 5

6 Table 7. Results - Wastewater Influent Samples Compounds Sample 1 %Recovery Sample 2 %Recovery SD 2,3,7,8-TCDF ,2,3,7,8-PeCDF ,3,4,7,8-PeCDF ,2,3,4,7,8-HxCDF ,2,3,6,7,8-HxCDF ,3,4,6,7,8-HxCDF ,2,3,7,8,9-HxCDF ,2,3,4,6,7,8-HpCDF ,2,3,4,7,8,9-HpCDF OCDF ,3,7,8-TCDD ,2,3,7,8-PeCDD ,2,3,4,7,8-HxCDD ,2,3,6,7,8-HxCDD ,2,3,4,6,7,8-HpCDD OCDD Conclusion We were able to demonstrate an efficient SPE disk technology for the extraction of several types of known water matrices for the detection of tetra through octa-chlorinated dioxins and furans with analytical sensitivities to ppt (ng/l) levels. We were able to achieve acceptable recoveries with particulate-laden water samples without the means of another extraction apparatus such as SDS (Soxhlet/Dean-Stark extractor). Automated SPE extraction, using the SPE-DEX 4790, is very efficient, and provides a fast method of extracting these difficult compounds from water matrices. Future work on these compounds will involve the extraction of larger volumes of samples (1 L or greater) using the EZ Flow Disk Holder. These studies will enable the analysis of samples with heavy particulate matter to be processed in a timely and efficient manor while lowering detection limits to the range of ppq (pg/l). Acknowledgements: Horizon Technology, Inc. gratefully acknowledges the CARSO Group France. References: 1. EPA Method 1613, Tetra- through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS, Revision B, October ISO Method 18073:2004 Determination of Tetra- through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS, reviewed and confirmed in AN _01 16 Northwestern Drive, Salem, NH USA Tel: (603) Support-Service@horizontechinc.com