The Science of the Total Environment, 104 (1991) 1-7 Elsevier Science Publishers B.V., Amsterdam
Standard Reference Materials for dioxins and other environmental pollutants Robert Alvarez Standard Reference Materials Program, National Institute of Standards & Technology, Gaithersburg, MD 20899, USA
ABSTRACT The National Institute of Standards and Technology issues approximately 1100 Standard Reference Materials (SRMs) certified for chemical composition or physical properties. A number of these SRMs has been developed to assist chemists in analyzing environmental samples more reliably for chlorinated dioxins and other organic pollutants. Certification of the pollutant concentration in a natural matrix SRM is based on concordant analyses by the NIST Organic Analytical Research Division using at least two independent methods. For a calibration solution, such as SRM 1614, Dioxin (2,3,7,8-TCDD) in Isooctane, certification is based on agreement of the calculated concentration based on the gravimetric preparation and the concentration as determined experimentally. SRM 1614 also includes a m3C-labeled 2,3,7,8TCDD for use as an internal standard in methods based on gas chromatography/mass spectrometry. The certified concentrations (ng g-m) are 98.3 + 3.3 for the unlabeled dioxin and 95.6 + 1.5 for the labeled dioxin. The certificates for SRM 1588, Organics in Cod Liver Oil, and SRM 1589, Polychlorinated Biphenyls (as Arocior 1260) in Human Serum, provide noncertified concentrations of dioxins. Concentrations of chlorinated dioxins in two urban particulate SRMs have been reported in the literature.
INTRODUCTION T h e reliable d e t e r m i n a t i o n o f dioxins in e n v i r o n m e n t a l materials is necessary to establish a c c u r a t e baseline c o n c e n t r a t i o n s ; to assemble reliable d a t a o n the emission a n d t r a n s p o r t o f dioxins; to d e t e r m i n e effectiveness o f c o n t r o l measures; to c o r r e l a t e h e a l t h effects with c o n c e n t r a t i o n s o f dioxins; a n d to issue e n v i r o n m e n t a l r e g u l a t i o n s for dioxins based o n s o u n d experim e n t a l data. T h e same c o n s i d e r a t i o n s a p p l y to the d e t e r m i n a t i o n o f o t h e r p o l l u t a n t s , such as pesticides, p o l y c h l o r i n a t e d biphenyls, polycyclic a r o m a t i c h y d r o c a r b o n s , a n d especially, c o m p o u n d s classified as p r i o r i t y p o l l u t a n t s by g o v e r n m e n t a l r e g u l a t o r y agencies, such as the E n v i r o n m e n t a l P r o t e c t i o n A g e n c y in the U n i t e d States.
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However, when laboratories analyze homogeneous materials for dioxins and other pollutants, the analytical results often disagree seriously. Discrepant data may result from poor methodology, improper instrument calibration, faulty experimental techniques, or from a combination of these TABLE 1 Standard Reference Materials certified for organic pollutants SRM No.
SRM name
Certification
1491 1492 1580
Aromatic Hydrocarbons in Hexane Chlorinated Pesticides in Hexane Organics in Shale Oil
1581 1582 1583
Polychlorinated Biphenyls in Oils Petroleum Crude Oil Chlorinated Pesticides in 2,2,4Trimethylpentane Priority Pollutant Phenols in Methanol Chlorinated Biphenyls in 2,2,4trimethylpentane Isotopically Labeled and Unlabeled Priority Pollutants in Methanol Nitrated Polycyclic Aromatic Hydrocarbons in Methanol Organics in Cod Liver Oil PCBs (as Aroclor 1260) in Human Serum Dinitropyrene Isomers and l-Nitropyrene in CH2 C12 Complex Mixture of PAHs from Coal Tar Dioxins (2,3,7,8-TCDD) in Isooctane Halocarbons in Methanol Polynuclear Aromatic Hydrocarbon Generator Columns Priority Pollutant Polynuclear Aromatic Hydrocarbons in Acetonitrile Urban Dust/Organics Diesel Particulate Matter PCBs in River Sediment Organics in Marine Sediment
Twenty-three aromatic hydrocarbons Fifteen pesticides Five PAHsa; three phenols + one additional compound Aroclors 1242 and 1260 in two oils Five PAHs plus dibenzothiophene
1584 1585 1586 1587 1588 1589 1596 1597 1614 1639 1644b 1647a
1649 1650 1939 1941
Five pesticides Ten phenols Eight chlorinated biphenyls Ten isotopically labeled compounds; 10 unlabeled compounds Six nitrated PAHs Ten pesticides, five PCBs, ~-tocopherol Aroclor 1260 Four nitropyrenes Twelve PAHs 2,3,7,8-TCDD; 2,3,7,8-TCDD -~3C Seven halocarbons Anthracene, benz[a]anthracene, and benzo[a]pyrene
Sixteen PAHs Five PAHs Five PAHs + 1-nitropyrene Three PCBs Eleven PAHs
aPolycyclic aromatic hydrocarbons. bSRM 1644 generates known concentrations of three PAHs in water.
STANDARD REFERENCE MATERIALS
factors. Lack of information on the purity of dioxins adversely affects instrument calibration. One approach towards obtaining accurate data is through the use of certified reference materials such as the Standard Reference Materials issued by the National Institute of Standards and Technology under Federal statutes. ENVIRONMENTAL STANDARD REFERENCE MATERIALS Standard Reference Materials are homogeneous, stable materials with certified chemical or physical properties for use in calibrating instruments, validating laboratory data, developing methods of known accuracy, and referring data from different laboratories to a common base. Of the approximately 1100 SRMs listed in the current NIST SRM catalog [1], over 50 have been developed for use in improving the accuracy of environmental analyses for inorganic and organic pollutants. For matrix SRMs, certified concentrations are based on agreement of results by two or more independent methods. For solution calibrator SRMs, such as SRM 1614, Dioxin (2,3,7,8-TCDD in Isooctane), certification is based on the concentration calculated by adding a known mass of the organic analyte to a known mass of solvent and also on the results of a chemical analysis. A listing of Standard Reference Materials certified for the concentrations of organic pollutants is shown in Table 1. SRM 1614 consists of separate solutions of unlabeled and labeled 2,3,7,8tetrachlorodibenzo-p-dioxins (2,3,7,8-TCDD) in 2,2,4-trimethylpentane (Isooctane). It is intended primarily for use in determining instrumental response factors for the calibration of chromatographs. It can also be used for adding known amounts of 2,3,7,8-TCDD to environmental samples for determination of this analyte in a matrix by the method of additions. The 13C-labeled 2,3,7,8-TCDD can serve as an internal standard in methods based on gas chromatography/mass spectrometry. A copy of the Certificate of Analysis is included in the Appendix. Two SRMs are available that have noncertified concentrations for dioxins based on the mass of each dioxin added to the mass of the matrix. At present, these concentrations have not been certified because of insufficient demand for their certification. The SRMs are SRM 1588, Organics in Cod Liver Oil, and SRM 1589, Polychlorinated Biphenyls (as Aroclor 1260) in Human Serum. The Certificate of Analysis for SRM 1588, Organics in Cod Liver Oil, provides noncertified concentrations of six dioxins, ranging from 0.21 ng gfor 2,3,7,8-tetrachlorodibenzo-p-dioxin to 1.01 ng g-~ for octachlorodibenzop-dioxin. The four other compounds are the 1,2,7-trichloro, the 1,2,3,4-tetrachloro, the 1,2,3,6,7,8-hexachloro, and the 1,2,3,7,8,9-hexachloro forms of dibenzo-p-dioxin. SRM 1588 was developed primarily to provide certified
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concentrations o f 10 chlorinated pesticides and five polychlorinated biphenyls in a cod liver oil matrix. The Certificate o f Analysis for S R M 1589 provides noncertified concentrations for 1,2,3,4-TCDD and 2,3,7,8-TCDD, of 0.156 and 0.083ngml -~, respectively, in the reconstituted serum. SRM 1589 was developed primarily to provide certified concentrations and uncertainties for Aroclor 1260 in h u m a n serum. In discussing analytical methodology for the determination o f dioxins in environmental samples, C r u m m e t t et al. [2] indicate that a major limitation to attempting these analyses is the limited availability o f chlorinated dioxins in pure form. The authors further state that even when such compounds are available and added to a matrix, their recovery cannot be assured to be equivalent to the recovery o f the same compounds present naturally. Accordingly, they cite a proposal o f Nestrick et al. [3] to use SRMs, 1648 (Urban Particulate Matter) and 1649 (Urban Dust/Organics), for demonstrating ability to remove and measure the dioxins present on particulate matter and tabulate the concentrations o f 2,3,7,8,-TCDD and other chlorinated dioxins in the two SRMs. REFERENCES 1 Catalog of NIST Standard Reference Materials, 1990-91, NIST Special Publication 260, U.S. Government Printing Office, Washington, DC. 2 W.B. Crummett, T.J. Nestrick and L.L. Lamparski, Analytical methodology for the determination of PCDDs in environmental samples: an overview and critique, in M.A. Kamrin and P.W. Rodgers (Eds), Dioxins in the Environment, Hemisphere Publishing Co., Washington, DC, 1985, Chapt. 6, p. 75. 3 T.J. Nestrick, L.L. Lamparski and W.B. Crummett, Proposed Adoption of National Bureau of Standards SRM's 1648 and 1649 as "Reference Particulate Matrices" for Analytical Methodology Quality Assurance in CDDs/CDFs Determination, Presented before the 186th National American Chemical Society Meeting, August 29, 1983.
STANDARD REFERENCE MATERIALS
APPENDIX ~,,
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QIertificate of
nal sis
Standard Reference Material 1614 Dioxin (2,3,7,8-TCDD in Isooctane)
Standard Reference Material (SRM) 1614 consists of separate solutions of unlabeled and labeled 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in 2,2,4-trimethyipentane (isooctane). Three ampoules contain approximately 1.2 mL each of an isooctane solution of unlabeled 2,3,7,8-TCDD, and three ampoules contain approximately 1.2 mL each of an isooctane solution of I3C-laheled 2,3,7,8-TCDD. This SRM is intended primarily for use in the evnluation of analytical methods used in the determination of 2,3,7,8;TCDD. It can also be used to fortify samples with known amounts of 2,3,7,8-TCDD. The 13C-iaheled 2,3,7,8-TCDD can be used as an internal standard in methods based on gas chromatography/ mass spectrometry (GC/MS). Certified Concentrations of 2,3,7,8-TCDD The certified concentrations and estimated uncertainties of the unlabeled and 13C-laheled 2,3,7,8-TCDD solutions are given in Table I. The concentration values are certified in ng/g units, but are also reported in ng/mL units for user convenience. The 13C-labeled solution is certified for the total concentration of all isotopic forms of 2 3 7 8-TCDD. • . • 13 • . + 13 ' ' ' The motovtc purity of the C*laheled material was determmed to he 98.2 _ 0. i atom percent C by mass spectrometry. 13 13 The fully C-laheled compound, 2,3,7,8-TCDD- Cl2, accounts for 80.7 + 0.5 percent of the 2,3,7,8-TCDD molecules in the sample. The certified values are the weighted averages of 8ravimetric values, based on the concentration calculated from the mass of 2,3,7,8-TCDD added to a known mass of isooctane and on the analytical results obtained using capillary gas chromatography with electron capture detection (GC/ECD). The uncertainties are two standard deviations of the certified values. These uncertainties include the gravimetric and GC measurement variability and any observed material heterogeneity. NOTICE AND WARNING TO USERS Handling The toxicity and/or carcinogenicity of 2,3,7,8-TCDD has not been precisely defined; however, this material should be treated as a potential health hazard. Ampoules should be opened and the contents used only by persons trained in proper handling techniques. Techniques used in handling radioactive and infections materials are applicable to 2,3,7,8-TCDD. Users in the United States should contact their regional offices of the U.S. Environmental Protection Agency for information regarding proper disposal of these materials; in other countries, they should contact the appropriate organization responsible for public health or environmental control. Trimethylpentane (isooctane), used as a diluent in this S RM, is stable when stored in closed containers at room temperature. It will not undergo hazardous polymerization. However, it is highly flammable and should be kept away from oxidizing agents. Gaithersburg, MD 20899 July 8, 1985
Stanley D. Rasberry, Chief Office of Standard Reference Materials (over)
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Table I Certified Concentrations of 2,3,7,8-TCDD" in SRM 1614 Concentrationb Compound
ng/g
ng/mL ¢, 23 ° C
2,3,7,8-TCDD
98.3 +3.3
67.8 + 2.3
2,3,7,8-TCDD-13cd
95.6 + 1.5
65.9 + 1.0
*CAS Registry Numbers: 2,3,7,8-TCDD-12C12: 1746-01-6; 2,3,7,8-TCDD-13CI2: 76523-40-5, Chemical Abstracts, Tenth Collective Index, Index Guide, American Chemical Society, Columbus, Ohio, 1982. bThe uncertainties given represent two standard deviations oftbe certified values. These uncertainties include the gravimetric and GC/ECD 2,3,7,8-TCDD measurement variability, the trichlorodibenzo-p-dioxin measurement variability, and, for the unlabeled 2,3,7,8-TCDD, the observed sample heterogeneity. : The concentration and uncertainty expressed in mass / volume units are applicable for use of this material at 23.0 oC. Since the density of 2,2,4-trimethyipentane changes with temperature, the concentration will change at temperatures other than 23.0 "C. The concentration will change by less than I percent of the value listed if the SRM is used at temperatures in the 15 to 31 °C range. dThe concentrations given represent the tots/concentrations for all isotopic forms of 2,3,7,8-TCDD in the solution. The fully 13C-labeled 2,3,7,8-TCDD accounts for 80.7 ± 0.5 perccnt of the 2,3,7,8-TCDD molccules in the sample. This value is provided for information only.
Preparation and Analysis Samples of the unlabeled 2,3,7,8-TCDD and 13C-2,3,7,8-TCDD used in the preparation of SRM 1614 were donated by R. Mitchum, National Center for Toxicological Research, Jefferson AK. The unlabeled 2,3,7,8-TCDD was originally obtained from ECO Control, Inc., Cambridge, MA; and the 13C-labeled 2,3,7,8-TCDD from Midwest Research Institute, Kansas City, MO. The purities of the labeled and unlabeled 2,3,7,8-TCDD used in the preparation of this SRM were determined at NBS using mass spectrometry, nuclear magnetic resonance spectrometry, and GC with flame ionization detection. The purities were found to be greater than 95%. Solutions of the unlabeled 2,3,7,8-TCDD and the 13C-labeled 2,3,7,8-TCDD were prepared at NBS by weighing and mixing the appropriate compound and isooctane. Each solution was dispensed into 2-mL amber ampoules which were then flame sealed. Aliquots from randomly selected ampoules were analyzed with a gas chromatograph equipped for split injection and a 30m x 0.25mm i.d. wall-coated open-tubular column with a 0.25 tzm film of a non-polar, immobilized phase. A constant current electron capture detector (S3Ni) was used for these analyses. Quantitative results were obtained through the use of 2,2',4,4',5,5'-hexachlorobiphenyl as an internal standard. Calibration solutions consisting of weighed amounts of the analyse and the internal standard compound in isooctane were analyzed chromatographically to determine response factors. A trichlorodibenzo-p-dioxin impurity present in both solutions was quantified using GC/MS with electron impact ionization, selected ion monitoring, and the method of standard additions. Standard additions of unlabeled 2,3,7trichlorodibenzo-p-dioxin were made to the unlabeled and 13C-labeled 2,3,7,8-TCDD solutions, and although the retention time of the trichlorodibenzo-p-dioxin impurity was coincident with that of the 2,3,7-isomer, this was not sufficient to positively identify which isomer was present. Concentrations of the trichlorodibenzo-p-dioxin in the SRM solutions are provided, for information only, in Table 2. Expiration of Certification This certification is valid within the specified limit of uncertainty for one year from the date of purchase. In the event that the certification should become invalid before then, purchasers will be notified by NBS. Storage Sealed ampoules, as received, should be stored in the dark at temperatures between 10 and 30 oC. It is recommended that these materials be stored in a secure area in a double-scaled container.
STANDARD REFERENCE MATERIALS
Solution Unlabeled
Labeled (3C)
Table 2 Concentrations of Trichlorodibenzo-p-dioxin in SRM 1614 --Concentration'~ Compound na/~
trichlorodibenzo=p=diomn- 12C12 . . . . 13CI2 tnchlorodtbenzo-p=dtomn•
(1.5) (3.9)
(1.0) (2.7)
aValuea not certified; provided for information only.
Us.__ee Samples of the SRM should be withdrawn from ampoules (at 23 _+8 °C) immediately after opening and used without delay for the certified values listed in Table ! to be valid within the stated uncertainties. Certified values are not applicable to material in ampoules stored after opening, even if they are resealed. Preparation and analytical determinations were performed in the NBS Organic Analytical Research Division by S.N. Chesler, B. Coxon, L.R. Hilpert, R.M. Parris, R.E. Rebbert, M.J. Welch, and E. White, V. Consultation on the statistical design of the experimental work and evaluation of the data was provided by R.C. Paule of the NBS National Measurement Laboratory. The coordination of the technical measurements leading to the certification of SRM 1614 was under the direction of L.R. Hilpert, R.M. Pards, and W.E. May. The technical and support aspects involved in the preparation, certification, and issuance of this SRM were coordinated through the Office of Standard Reference Materials by T.E. Gills.
Standard Reference Materials for dioxins and other environmental pollutants Robert Alvarez Standard Reference Materials Program, National Institute of Standards & Technology, Gaithersburg, MD 20899, USA
ABSTRACT The National Institute of Standards and Technology issues approximately 1100 Standard Reference Materials (SRMs) certified for chemical composition or physical properties. A number of these SRMs has been developed to assist chemists in analyzing environmental samples more reliably for chlorinated dioxins and other organic pollutants. Certification of the pollutant concentration in a natural matrix SRM is based on concordant analyses by the NIST Organic Analytical Research Division using at least two independent methods. For a calibration solution, such as SRM 1614, Dioxin (2,3,7,8-TCDD) in Isooctane, certification is based on agreement of the calculated concentration based on the gravimetric preparation and the concentration as determined experimentally. SRM 1614 also includes a m3C-labeled 2,3,7,8TCDD for use as an internal standard in methods based on gas chromatography/mass spectrometry. The certified concentrations (ng g-m) are 98.3 + 3.3 for the unlabeled dioxin and 95.6 + 1.5 for the labeled dioxin. The certificates for SRM 1588, Organics in Cod Liver Oil, and SRM 1589, Polychlorinated Biphenyls (as Arocior 1260) in Human Serum, provide noncertified concentrations of dioxins. Concentrations of chlorinated dioxins in two urban particulate SRMs have been reported in the literature.
INTRODUCTION T h e reliable d e t e r m i n a t i o n o f dioxins in e n v i r o n m e n t a l materials is necessary to establish a c c u r a t e baseline c o n c e n t r a t i o n s ; to assemble reliable d a t a o n the emission a n d t r a n s p o r t o f dioxins; to d e t e r m i n e effectiveness o f c o n t r o l measures; to c o r r e l a t e h e a l t h effects with c o n c e n t r a t i o n s o f dioxins; a n d to issue e n v i r o n m e n t a l r e g u l a t i o n s for dioxins based o n s o u n d experim e n t a l data. T h e same c o n s i d e r a t i o n s a p p l y to the d e t e r m i n a t i o n o f o t h e r p o l l u t a n t s , such as pesticides, p o l y c h l o r i n a t e d biphenyls, polycyclic a r o m a t i c h y d r o c a r b o n s , a n d especially, c o m p o u n d s classified as p r i o r i t y p o l l u t a n t s by g o v e r n m e n t a l r e g u l a t o r y agencies, such as the E n v i r o n m e n t a l P r o t e c t i o n A g e n c y in the U n i t e d States.
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However, when laboratories analyze homogeneous materials for dioxins and other pollutants, the analytical results often disagree seriously. Discrepant data may result from poor methodology, improper instrument calibration, faulty experimental techniques, or from a combination of these TABLE 1 Standard Reference Materials certified for organic pollutants SRM No.
SRM name
Certification
1491 1492 1580
Aromatic Hydrocarbons in Hexane Chlorinated Pesticides in Hexane Organics in Shale Oil
1581 1582 1583
Polychlorinated Biphenyls in Oils Petroleum Crude Oil Chlorinated Pesticides in 2,2,4Trimethylpentane Priority Pollutant Phenols in Methanol Chlorinated Biphenyls in 2,2,4trimethylpentane Isotopically Labeled and Unlabeled Priority Pollutants in Methanol Nitrated Polycyclic Aromatic Hydrocarbons in Methanol Organics in Cod Liver Oil PCBs (as Aroclor 1260) in Human Serum Dinitropyrene Isomers and l-Nitropyrene in CH2 C12 Complex Mixture of PAHs from Coal Tar Dioxins (2,3,7,8-TCDD) in Isooctane Halocarbons in Methanol Polynuclear Aromatic Hydrocarbon Generator Columns Priority Pollutant Polynuclear Aromatic Hydrocarbons in Acetonitrile Urban Dust/Organics Diesel Particulate Matter PCBs in River Sediment Organics in Marine Sediment
Twenty-three aromatic hydrocarbons Fifteen pesticides Five PAHsa; three phenols + one additional compound Aroclors 1242 and 1260 in two oils Five PAHs plus dibenzothiophene
1584 1585 1586 1587 1588 1589 1596 1597 1614 1639 1644b 1647a
1649 1650 1939 1941
Five pesticides Ten phenols Eight chlorinated biphenyls Ten isotopically labeled compounds; 10 unlabeled compounds Six nitrated PAHs Ten pesticides, five PCBs, ~-tocopherol Aroclor 1260 Four nitropyrenes Twelve PAHs 2,3,7,8-TCDD; 2,3,7,8-TCDD -~3C Seven halocarbons Anthracene, benz[a]anthracene, and benzo[a]pyrene
Sixteen PAHs Five PAHs Five PAHs + 1-nitropyrene Three PCBs Eleven PAHs
aPolycyclic aromatic hydrocarbons. bSRM 1644 generates known concentrations of three PAHs in water.
STANDARD REFERENCE MATERIALS
factors. Lack of information on the purity of dioxins adversely affects instrument calibration. One approach towards obtaining accurate data is through the use of certified reference materials such as the Standard Reference Materials issued by the National Institute of Standards and Technology under Federal statutes. ENVIRONMENTAL STANDARD REFERENCE MATERIALS Standard Reference Materials are homogeneous, stable materials with certified chemical or physical properties for use in calibrating instruments, validating laboratory data, developing methods of known accuracy, and referring data from different laboratories to a common base. Of the approximately 1100 SRMs listed in the current NIST SRM catalog [1], over 50 have been developed for use in improving the accuracy of environmental analyses for inorganic and organic pollutants. For matrix SRMs, certified concentrations are based on agreement of results by two or more independent methods. For solution calibrator SRMs, such as SRM 1614, Dioxin (2,3,7,8-TCDD in Isooctane), certification is based on the concentration calculated by adding a known mass of the organic analyte to a known mass of solvent and also on the results of a chemical analysis. A listing of Standard Reference Materials certified for the concentrations of organic pollutants is shown in Table 1. SRM 1614 consists of separate solutions of unlabeled and labeled 2,3,7,8tetrachlorodibenzo-p-dioxins (2,3,7,8-TCDD) in 2,2,4-trimethylpentane (Isooctane). It is intended primarily for use in determining instrumental response factors for the calibration of chromatographs. It can also be used for adding known amounts of 2,3,7,8-TCDD to environmental samples for determination of this analyte in a matrix by the method of additions. The 13C-labeled 2,3,7,8-TCDD can serve as an internal standard in methods based on gas chromatography/mass spectrometry. A copy of the Certificate of Analysis is included in the Appendix. Two SRMs are available that have noncertified concentrations for dioxins based on the mass of each dioxin added to the mass of the matrix. At present, these concentrations have not been certified because of insufficient demand for their certification. The SRMs are SRM 1588, Organics in Cod Liver Oil, and SRM 1589, Polychlorinated Biphenyls (as Aroclor 1260) in Human Serum. The Certificate of Analysis for SRM 1588, Organics in Cod Liver Oil, provides noncertified concentrations of six dioxins, ranging from 0.21 ng gfor 2,3,7,8-tetrachlorodibenzo-p-dioxin to 1.01 ng g-~ for octachlorodibenzop-dioxin. The four other compounds are the 1,2,7-trichloro, the 1,2,3,4-tetrachloro, the 1,2,3,6,7,8-hexachloro, and the 1,2,3,7,8,9-hexachloro forms of dibenzo-p-dioxin. SRM 1588 was developed primarily to provide certified
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concentrations o f 10 chlorinated pesticides and five polychlorinated biphenyls in a cod liver oil matrix. The Certificate o f Analysis for S R M 1589 provides noncertified concentrations for 1,2,3,4-TCDD and 2,3,7,8-TCDD, of 0.156 and 0.083ngml -~, respectively, in the reconstituted serum. SRM 1589 was developed primarily to provide certified concentrations and uncertainties for Aroclor 1260 in h u m a n serum. In discussing analytical methodology for the determination o f dioxins in environmental samples, C r u m m e t t et al. [2] indicate that a major limitation to attempting these analyses is the limited availability o f chlorinated dioxins in pure form. The authors further state that even when such compounds are available and added to a matrix, their recovery cannot be assured to be equivalent to the recovery o f the same compounds present naturally. Accordingly, they cite a proposal o f Nestrick et al. [3] to use SRMs, 1648 (Urban Particulate Matter) and 1649 (Urban Dust/Organics), for demonstrating ability to remove and measure the dioxins present on particulate matter and tabulate the concentrations o f 2,3,7,8,-TCDD and other chlorinated dioxins in the two SRMs. REFERENCES 1 Catalog of NIST Standard Reference Materials, 1990-91, NIST Special Publication 260, U.S. Government Printing Office, Washington, DC. 2 W.B. Crummett, T.J. Nestrick and L.L. Lamparski, Analytical methodology for the determination of PCDDs in environmental samples: an overview and critique, in M.A. Kamrin and P.W. Rodgers (Eds), Dioxins in the Environment, Hemisphere Publishing Co., Washington, DC, 1985, Chapt. 6, p. 75. 3 T.J. Nestrick, L.L. Lamparski and W.B. Crummett, Proposed Adoption of National Bureau of Standards SRM's 1648 and 1649 as "Reference Particulate Matrices" for Analytical Methodology Quality Assurance in CDDs/CDFs Determination, Presented before the 186th National American Chemical Society Meeting, August 29, 1983.
STANDARD REFERENCE MATERIALS
APPENDIX ~,,
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M alc°elnJt~rld/rig¢
Naltonal
~=':'~"'
QIertificate of
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Standard Reference Material 1614 Dioxin (2,3,7,8-TCDD in Isooctane)
Standard Reference Material (SRM) 1614 consists of separate solutions of unlabeled and labeled 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in 2,2,4-trimethyipentane (isooctane). Three ampoules contain approximately 1.2 mL each of an isooctane solution of unlabeled 2,3,7,8-TCDD, and three ampoules contain approximately 1.2 mL each of an isooctane solution of I3C-laheled 2,3,7,8-TCDD. This SRM is intended primarily for use in the evnluation of analytical methods used in the determination of 2,3,7,8;TCDD. It can also be used to fortify samples with known amounts of 2,3,7,8-TCDD. The 13C-iaheled 2,3,7,8-TCDD can be used as an internal standard in methods based on gas chromatography/ mass spectrometry (GC/MS). Certified Concentrations of 2,3,7,8-TCDD The certified concentrations and estimated uncertainties of the unlabeled and 13C-laheled 2,3,7,8-TCDD solutions are given in Table I. The concentration values are certified in ng/g units, but are also reported in ng/mL units for user convenience. The 13C-labeled solution is certified for the total concentration of all isotopic forms of 2 3 7 8-TCDD. • . • 13 • . + 13 ' ' ' The motovtc purity of the C*laheled material was determmed to he 98.2 _ 0. i atom percent C by mass spectrometry. 13 13 The fully C-laheled compound, 2,3,7,8-TCDD- Cl2, accounts for 80.7 + 0.5 percent of the 2,3,7,8-TCDD molecules in the sample. The certified values are the weighted averages of 8ravimetric values, based on the concentration calculated from the mass of 2,3,7,8-TCDD added to a known mass of isooctane and on the analytical results obtained using capillary gas chromatography with electron capture detection (GC/ECD). The uncertainties are two standard deviations of the certified values. These uncertainties include the gravimetric and GC measurement variability and any observed material heterogeneity. NOTICE AND WARNING TO USERS Handling The toxicity and/or carcinogenicity of 2,3,7,8-TCDD has not been precisely defined; however, this material should be treated as a potential health hazard. Ampoules should be opened and the contents used only by persons trained in proper handling techniques. Techniques used in handling radioactive and infections materials are applicable to 2,3,7,8-TCDD. Users in the United States should contact their regional offices of the U.S. Environmental Protection Agency for information regarding proper disposal of these materials; in other countries, they should contact the appropriate organization responsible for public health or environmental control. Trimethylpentane (isooctane), used as a diluent in this S RM, is stable when stored in closed containers at room temperature. It will not undergo hazardous polymerization. However, it is highly flammable and should be kept away from oxidizing agents. Gaithersburg, MD 20899 July 8, 1985
Stanley D. Rasberry, Chief Office of Standard Reference Materials (over)
6
R. ALVAREZ
Table I Certified Concentrations of 2,3,7,8-TCDD" in SRM 1614 Concentrationb Compound
ng/g
ng/mL ¢, 23 ° C
2,3,7,8-TCDD
98.3 +3.3
67.8 + 2.3
2,3,7,8-TCDD-13cd
95.6 + 1.5
65.9 + 1.0
*CAS Registry Numbers: 2,3,7,8-TCDD-12C12: 1746-01-6; 2,3,7,8-TCDD-13CI2: 76523-40-5, Chemical Abstracts, Tenth Collective Index, Index Guide, American Chemical Society, Columbus, Ohio, 1982. bThe uncertainties given represent two standard deviations oftbe certified values. These uncertainties include the gravimetric and GC/ECD 2,3,7,8-TCDD measurement variability, the trichlorodibenzo-p-dioxin measurement variability, and, for the unlabeled 2,3,7,8-TCDD, the observed sample heterogeneity. : The concentration and uncertainty expressed in mass / volume units are applicable for use of this material at 23.0 oC. Since the density of 2,2,4-trimethyipentane changes with temperature, the concentration will change at temperatures other than 23.0 "C. The concentration will change by less than I percent of the value listed if the SRM is used at temperatures in the 15 to 31 °C range. dThe concentrations given represent the tots/concentrations for all isotopic forms of 2,3,7,8-TCDD in the solution. The fully 13C-labeled 2,3,7,8-TCDD accounts for 80.7 ± 0.5 perccnt of the 2,3,7,8-TCDD molccules in the sample. This value is provided for information only.
Preparation and Analysis Samples of the unlabeled 2,3,7,8-TCDD and 13C-2,3,7,8-TCDD used in the preparation of SRM 1614 were donated by R. Mitchum, National Center for Toxicological Research, Jefferson AK. The unlabeled 2,3,7,8-TCDD was originally obtained from ECO Control, Inc., Cambridge, MA; and the 13C-labeled 2,3,7,8-TCDD from Midwest Research Institute, Kansas City, MO. The purities of the labeled and unlabeled 2,3,7,8-TCDD used in the preparation of this SRM were determined at NBS using mass spectrometry, nuclear magnetic resonance spectrometry, and GC with flame ionization detection. The purities were found to be greater than 95%. Solutions of the unlabeled 2,3,7,8-TCDD and the 13C-labeled 2,3,7,8-TCDD were prepared at NBS by weighing and mixing the appropriate compound and isooctane. Each solution was dispensed into 2-mL amber ampoules which were then flame sealed. Aliquots from randomly selected ampoules were analyzed with a gas chromatograph equipped for split injection and a 30m x 0.25mm i.d. wall-coated open-tubular column with a 0.25 tzm film of a non-polar, immobilized phase. A constant current electron capture detector (S3Ni) was used for these analyses. Quantitative results were obtained through the use of 2,2',4,4',5,5'-hexachlorobiphenyl as an internal standard. Calibration solutions consisting of weighed amounts of the analyse and the internal standard compound in isooctane were analyzed chromatographically to determine response factors. A trichlorodibenzo-p-dioxin impurity present in both solutions was quantified using GC/MS with electron impact ionization, selected ion monitoring, and the method of standard additions. Standard additions of unlabeled 2,3,7trichlorodibenzo-p-dioxin were made to the unlabeled and 13C-labeled 2,3,7,8-TCDD solutions, and although the retention time of the trichlorodibenzo-p-dioxin impurity was coincident with that of the 2,3,7-isomer, this was not sufficient to positively identify which isomer was present. Concentrations of the trichlorodibenzo-p-dioxin in the SRM solutions are provided, for information only, in Table 2. Expiration of Certification This certification is valid within the specified limit of uncertainty for one year from the date of purchase. In the event that the certification should become invalid before then, purchasers will be notified by NBS. Storage Sealed ampoules, as received, should be stored in the dark at temperatures between 10 and 30 oC. It is recommended that these materials be stored in a secure area in a double-scaled container.
STANDARD REFERENCE MATERIALS
Solution Unlabeled
Labeled (3C)
Table 2 Concentrations of Trichlorodibenzo-p-dioxin in SRM 1614 --Concentration'~ Compound na/~
trichlorodibenzo=p=diomn- 12C12 . . . . 13CI2 tnchlorodtbenzo-p=dtomn•
(1.5) (3.9)
(1.0) (2.7)
aValuea not certified; provided for information only.
Us.__ee Samples of the SRM should be withdrawn from ampoules (at 23 _+8 °C) immediately after opening and used without delay for the certified values listed in Table ! to be valid within the stated uncertainties. Certified values are not applicable to material in ampoules stored after opening, even if they are resealed. Preparation and analytical determinations were performed in the NBS Organic Analytical Research Division by S.N. Chesler, B. Coxon, L.R. Hilpert, R.M. Parris, R.E. Rebbert, M.J. Welch, and E. White, V. Consultation on the statistical design of the experimental work and evaluation of the data was provided by R.C. Paule of the NBS National Measurement Laboratory. The coordination of the technical measurements leading to the certification of SRM 1614 was under the direction of L.R. Hilpert, R.M. Pards, and W.E. May. The technical and support aspects involved in the preparation, certification, and issuance of this SRM were coordinated through the Office of Standard Reference Materials by T.E. Gills.
