Preparation and Analysis of a Frozen Mussel Tissue Reference Material for the Determination of Trace Organic Constituents Stephen A. Wise,” Bruce A. Benner, Jr., Richard G. Christensen, Barbara J. Koster, Joachlm Kurz,t Mlchele M. Schantz, and Rolf Zelsler
Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
A new mussel tissue Standard Reference Material (SRM) has been prepared and analyzed for trace organic and inorganic constituents. SRM 1974 [Organics in Mussel Tissue (Mytilus edulis)] is a frozen mussel tissue homogenate that has been certified for the concentrations of nine polycyclic aromatic hydrocarbons (PAHs) from results obtained from gas chromatography-mass spectrometry and reversed-phase liquid chromatography with fluorescence detection. Noncertified concentrations for 19 additional PAHs are also reported. Gas chromatography with electron capture detection and gas chromatography with mass spectrometric detection were used to provide noncertified concentrations for 13 polychlorinated biphenyl congeners and 9 chlorinated pesticides. In addition to the organic contaminants, noncertified concentrations for 36 trace elements were determined primarily by instrumental neutron activation analysis. SRM 1974 is the first frozen tissue SRM for environmental measurements of organic and inorganic constituents.
Introduction Certified reference materials (CRMs) are used by many laboratories in their analytical quality assurance programs to validate analytical procedures and to continuously monitor these procedures to verify that they remain in control. For the marine analytical chemistry community, a number of CRMs for marine tissues are available; the majority of these CRMs are intended as control materials for the determination of trace element composition. CRMs issued by the National Institute of Standards and Technology (NIST) (formerly the National Bureau of Standards) are known as Standard Reference Materials (SRMs). One of the earliest NIST SRMs for the determination of trace elements in marine tissue was SRM 1566 (Oyster Tissue) ( I ) . This material was first issued in 1979, and a renewal oyster material was issued in 1989 as SRM 1566a (2). Mussel tissue reference materials for trace element determinations are available from several sources including the following: the National Institute of Environmental Studies (NIES; Tsukuba, Japan), the Community Bureau of Reference (BCR; Brussels, Belgium), and the International Atomic Energy Agency (IAEA; Vienna, Austria) Permanent address: Department of Analytical and Environmental Chemistry, University of Ulm, 7900 Ulm, Federal Republic of Germany.
(3-7). The Marine Analytical Chemistry Standards Program of the National Research Council Canada (NRCC) has produced several biological tissue materials certified for trace element content including lobster hepatopancreas, dogfish liver, and dogfish muscle (8, 9). At present only the IAEA provides marine tissue reference materials (Copepoda, fish flesh, and shrimp homogenate) with certified concentrations of selected organic contaminants, Le., several chlorinated pesticides and polychlorinated biphenyl (PCB) congeners. With the increasing interest in monitoring organic pollutants in the marine environment, there is a need for certified reference materials of marine samples that have been characterized for a large number of organic contaminants including PCBs (individual congeners), chlorinated pesticide residues, and polycyclic aromatic hydrocarbons (PAHs). All of the biological tissue reference materials mentioned above are distributed as lyophilized (freeze-dried)matrices. In recent years some limitations of these “classical” biological and environmental CRMs have been recognized. The requirements for physical and/or chemical stability, stable dry weight, and sterility have restricted the matrices that can be used as reference materials or have necessitated sample preparation that often significantly alters the physical or chemical properties of the material. Sample preparation procedures for biological marine reference materials have included freeze-drying, fat extraction, radiation sterilization, or more extreme measures such as cooking. The physical characteristics of these materials are, in many instances, significantly different from the sample matrix actually analyzed (this is particularly t w e for samples analyzed for trace organic constituents); thus the value of these materials as quality control samples is often limited. Several new approaches to the preparation of ‘%Fond generation” reference materials (i.e., materials that are similar to the fresh samples routinely analyzed) have‘been reported. The NRCC has prepared dogfish liver and muscle reference materials by subjecting the materials to lipid extraction. This process provides a partially “defatted” matrix to prevent rancidity and to produce a stable material (8). Recently, Berman et al. (9) advocated the use of “high-pressure emulsification” to prepare biological reference materials whose physical and chemical characteristics are very similar to those of the original fresh material. In this process the tissue is slurry homogenized, stabilized against rancidity by the addition of an anti-
Not subject to U S . Copyright. Published 1991 by the American Chemical Society
Environ. Sci. Technol., Vol. 25, No. 10, 1991 1695
oxidant, adjusted to 85% moisture, subjected to highpressure emulsification, hermetically sealed in polypropylene bottles, and finally heat sterilized. Stoeppler et al. (IO)prepared cryogenically homogenized frozen tissue as “second generation” reference materials for use in their Environmental Specimen Bank program; however, these materials are not readily available as reference materials to the scientific community. To meet the need for a natural matrix marine tissue CRM for organic contaminants, NIST has issued SRM 1974 [Organics in Mussel Tissue (Mytilus edulis)]. This material is provided as a frozen tissue homogenate that has only been subjected to cryogenic grinding for sample preparation, thereby providing a matrix similar to the sample matrices typically encountered in marine tissue analyses. Certified concentrations of nine PAHs are based on the combination of measurements by gas chromatography-mass spectrometry (GC-MS) and reversed-phase liquid chromatography with fluorescence detection (LCFL). Noncertified concentrations of selected PCB congeners and chlorinated pesticides are based on measurements by gas chromatography with electron capture detection (GC-ECD)and GC-MS. Even though this material was developed primarily for organic constituents, noncertified concentrations of 36 trace elements are reported, thereby providing a reference material that satisfies the matrix requirements of inorganic analysts who routinely analyze fresh tissue samples. Experimental Section Collection and Preparation of SRM 1974. (a) Sample Collection. The mussels (Mytilus edulis) used for the preparation of SRM 1974 were collected on December 1, 1988, from Dorchester Bay within Boston Harbor, MA (42’18.25’ N, 71’02.31’ W). Approximately 2400 individual mussels were collected by hand a t low tide. The samples were transported to the Battelle New England Laboratory (Duxbury, MA) where the mussels were rinsed in a tank supplied with pumped seawater. The mussels were placed in insulated, Teflon-lined wooden containers, frozen, and transported to NIST on dry ice. At NIST the mussels were transferred to Teflon bags (60-70 mussels/bag) and stored in a liquid nitrogen vapor freezer (-120 ‘C) until they were shucked. (b) Preparation of SRM 1974. The mussel tissue was removed from the shells by the following procedure. After the mussels were allowed to warm to -0 OC to avoid breaking the shell, the mussels were opened with a titanium knife and the tissue removed with a second titanium knife. The tissue was placed in a Teflon bag (-1 kg/bag) and immediately returned to the liquid nitrogen freezer. Approximately 28 kg of mussel tissue was prepared for use as the SRM. The frozen mussel tissue was pulverized in batches of -150 g each by use of a cryogenic grinding procedure described previously (11). The total 28 kg of frozen pulverized material was then combined in an aluminum mixing drum (59 cm x 73 cm). The drum was placed inside a liquid nitrogen vapor freezer and motordriven to rotate a t 20 rpm about its horizontal axis. Interior vanes a t an angle to the axis of rotation provided a longitudinal component of mixing. After mixing for 2 h, subsamples (15-20 g) of the mussel tissue homogenate were aliquoted into clean, precooled glass bottles. All of the subsampling manipulations were performed with Teflon implements to avoid contamination and in the liquid nitrogen freezer to avoid warming of the samples or moisture condensation on the frozen material. The bottles of SRM 1974 have been stored since preparation a t -80 OC. 1696 Envlron. Sci. Technol., Vol. 25, No. 10, 1991
15 g SRM 1974 wet welght (-88% moisture)
f
f
Soxhlet Extraction (Methylene Chloride)
Soxhlet Extraction (HexanelAcetone 1 :1)
J-
J-
Gel Permeailon Chromatography (GPC)
Amino Solid Phase
Extraction (SPE)
J-
Silica SPE
J-
Normal-Phase LC (“1)
PCB and 4,4‘-DDE
Normal-Phase LC (”2)
ore Polar Pesticides
I** GC-MS (PAHs)
GC-ECD (DB-5 and C18)
GC-MS (08.5)
GC-ECD (DB-5 and C18)
GC-MS (DE-5)
.1
Reversed-Phase LC-Fluorescence (PAHs)
Figure 1. Analytical scheme for the analysis of SRM 1974 for organic constituents.
Materials. SRM 1491 (Aromatic Hydrocarbons in Hexane/Toluene), SRM 1647a (Priority Pollutant PAH in Acetonitrile), SRM 2261 (Concentrated Chlorinated Pesticides in Hexane), SRM 2262 (Concentrated PCB Congeners in Iso-octane), SRM 1588 (Organics in Cod Liver Oil), and SRM 1566a (Oyster Tissue) were obtained from the Standard Reference Materials Program, National Institute of Standards and Technology (Gaithersburg, MD); NIES CRM No. 6 (Mussel Tissue) was obtained from the National Institute of Environmental Studies (Tsukuba, Japan). All solvents were HPLC grade. Conversion to Dry Weight Basis. The amount of moisture in the frozen mussel homogenate was determined by measuring the weight loss after freeze-drying. Twenty bottles of SRM 1974 were selected according to a stratified randomization scheme for the drying study. The entire contents of each bottle were transferred to a Teflon jar and dried for 5 days at 1Pa with a -10 “C shelf temperature and a -50 OC condenser temperature. Based on these studies, a 95% prediction interval for the moisture content of a new bottle of SRM 1974 is 87.65 f 0.17% Analytical results for organic and inorganic constituents are reported on a dry weight basis for the convenience of the users. The results for the organic constituents were determined on a wet weight basis; they were converted to a dry weight basis by dividing by the conversion factor of 0.1235. Determination of Organic Constituents. The analytical scheme for the determination of the organic constituents in SRM 1974 is shown in Figure 1. The SRM was analyzed for selected PAHs by reversed-phase LC-FL and GC-MS. The PCBs and chlorinated pesticides were determined by using GC-ECD and GC-MS after isolation by gel permeation chromatography (GPC) and normalphase LC. (a) LC Analysis for PAHs. For the LC-FL analyses, 14-18-g (wet weight) portions of mussel homogenate from six randomly selected bottles were mixed with 100 g of preextracted sodium sulfate; these mixtures were then placed in glass extraction thimbles, spiked with an internal standard solution (see below), and Soxhlet extracted for 18 h with 250 mL of hexane/acetone (1:l v/v). The extracts were concentrated to -30 mL in a rotary evaporator and then further concentrated under a stream of nitrogen to 1mL. About 0.5 mL of methylene chloride was added to the extract to redissolve some of the hexane-insoluble material, and the extract was then passed through a precleaned aminosilane solid-phase extraction (SPE) cartridge and eluted with 15 mL of 10% methylene chloride in n-
-
-
hexane. The eluant from the SPE cartridge was concentrated to -1 mL, and the SPE procedure was repeated a second and third time. After the third SPE cleanup, the eluant was concentrated to -0.5 mL and injected onto a semipreparative aminosilane column (9 mm i.d. X 30 cm) to isolate the total PAH fraction by normal-phase LC using 2% methylene chloride in n-hexane at 5 mL/min (12,13). The isolated PAH fraction (- 190 mL) was then concentrated to -0.5 mL and the solvent changed to acetonitrile for the reversed-phase LC analysis. Reversed-phase LC analysis of the PAH fraction was performed on a polymeric octadecylsilane (CIE)column (Vydac 201TP, The Separations Group, Hesperia, CA; 4.6 mm i.d. X 25 cm, 5-pm particle size) using gradient elution from 50% acetonitrile in water to 100% acetonitrile at l%/min with a flow rate of 1.5 mL/min. Fluorescence detection with wavelength programming, as described previously (14, 15) was used to monitor the LC separation. For LC-FL measurements, perdeuterated PAHs were utilized as the internal standards (phenanthrene-d,,, fluoranthene-d,,, and perylene-d,,) (16). Calibration response factors for the analytes relative to the internal standards were determined by analyzing SRM 1647a [Polycyclic Aromatic Hydrocarbons (in Acetonitrile)]. (b) GC-MS Analysis for PAHs. For the GC-MS analyses, 13-26-g (wet weight) portions of the mussel homogenate from 12 randomly selected bottles were prepared and extracted with methylene chloride as described above. Gel permeation chromatography (GPC) on a semipreparative divin lbenzene-polystyrene column (10-pm particle size, 100- pore size, 2.5 cm i.d. X 60 cm, PL-Gel; Polymer Labs, Inc., Amherst, MA) was used to remove the majority of the lipid and biogenic materials from the concentrated extract (27). The GPC separation was performed using methylene chloride at a flow rate of 9.9 mL/min. The majority of the lipid and biogenic material elutes immediately after the void volume of the column, and the PAHs (as well as the PCBs and pesticides) are retained longer. The eluant (-70 mL) was concentrated to -0.3 mL and then placed on a silica SPE cartridge and eluted with 12 mL of 10% methylene chloride in n-pentane as the final cleanup step prior to GC-MS analysis, GC-MS analyses were performed using a 0.25 mm X 60 m fused-silica capillary column with a 5% phenyl-substituted methylpolysiloxane phase (DB-5; 0.25-pm film thickness). The column temperature was programmed from 37 to 150 "C at 30 "C/min and then from 150 to 300 "C at 2 "C/min with a 32-min hold at the final temperature. Selected ions were monitored during the run for the analytes of interest and the internal standards. For these GC-MS measurements, the following perdeuterated PAHs were utilized as the internal standards: naphthalene-&, acenaphthene-d,,, phenanthrene-dlo, pyrene-d,,, benz[alanthracene-d12,benzo[e]pyrene-d,,, and benzo[ghi]perylene-d,,. Calibration response factors for the analytes relative to the internal standards were determined by analyzing SRM 1491 (Aromatic Hydrocarbons in Hexane/Toluene). (c) GC-ECD and GC-MS Analysis for PCBs and Chlorinated Pesticides. Subsamples from five bottles of SRM 1974 were extracted and the extracts processed through the GPC as described above for the GC-MS analysis. Following the GPC, normal-phase LC on the semipreparative aminosilane column was used to isolate two fractions containing (1)the PCBs and lower polarity chlorinated pesticides and (2) the more polar chlorinated pesticides. For the normal-phase LC fractionation, hexane was used as the mobile phase for the isolation of the PCB
K
and lower polarity pesticides, and 5% methylene chloride in n-hexane was used for the isolation of the second fraction. GC-ECD and GC-MS analyses were performed on a column similar to the one used for the GC-MS-determination of the PAHs. For GC-ECD analysis of the two fractions, the column was temperature programmed from 200 (for 30 min) to 270 "C at 2 "C/min and then held for 10 min. PCB 103, PCB 198, and 4,4'-DDT-dEwere used as internal standards. GC-ECD analyses of the two chlorinated compound fractions were also performed using a second column, a 0.25 mm X 50 m fused-silica capillary column coated with a 0.2-pm film of CP SIL 8 (SE-54) PIUS 10% methyl-clEincorporated (Chrompack International Middelburg, The Netherlands). For both fractions the column was temperature programmed from 60 (for 3 min) to 170 "C at 20 "C/min and then at 1.5 "C/min to 270 "C (for 10 min). For the GC-MS analysis of the first fraction (PCB fraction), the column was temperature programmed from 50 (for 2 min) to 170 "C at 40 "C/min and then at 1.5 "C/min to 290 "C (for 5 min). For the GC-MS analysis of the second (more polar pesticide) fraction, the column was temperature programmed at 40 "C/min from 68 (for 1min) to 200 "C (for 30 min) and then at 2 "C/min to 270 "C (for 10 rnin). For measurement of the PCBs, selected ions were monitored for each of the 10 degrees of chlorination (two ions per degree of chlorination, the molecular ion and the M + 2 ion). For the chlorinated pesticides the major ion was monitored. For the GC-ECD and GC-MS analyses, calibration response factors for the analytes relative to the internal standards were determined by processing diluted solutions of SRM 2261 and 2262 and the internal standards. Two subsamples of SRM 1588 (Organics in Cod Liver Oil) were processed as extracts and analyzed with the mussel Samples as control materials. The data obtained for the various control materials did not reveal any significant bias compared to the certified values. Determination of Inorganic Constituents. Inorganic constituents were determined by using instrumental neutron activation analysis (INAA), differential pulse anodic stripping voltammetry (DPASV), and cold vapor atomic absorption spectrometry (CVAAS). INAA was performed using the approach described previously for the analysis of marine bivalves (18). The contents of six randomly selected bottles of SRM 1974 were freeze-dried and three pellets were formed from each bottle. Certified biological reference materials NIES CRM No. 6 (Mussel Tissue) and SRM 1566a (Oyster Tissue) were prepared in the same manner and included in the INAA scheme as controls. The sequential determination via short-lived and long-lived nuclides was carried out on only one pellet, the second pellet was used only with a short irradiation, and the third pellet was used with a long irradiation. Hence, the reported values are based on 12 determinations for each of the elements determined by INAA. For the assay of short-lived nuclides, the samples and controls were irradiated, one each together with one of the standards, for 30 s in the NIST reactor pneumatic facility RT-4 (19)at 20-MW reactor power. After the short irradiation, the samples and controls underwent a long irradiation. For the assay of intermediate- and long-lived nuclides, the samples, controls, and standards were irradiated in two sets for 16 h at 15-MW reactor power. Samples were counted after 6 days of decay to assay for nuclides with intermediate half-lives and again after 4-8weeks decay to assay for longer lived nuclides. Quantitative evaluation was performed by the comparator method, utilizing all standards from the individual irradiaEnviron. Sci. Technol., Vol. 25, No. 10, 1991
1607
Table I. Summary of Analytical Results and Certified Concentrations for PAHs in SRM 1974 compound phenanthrene anthracene fluoranthene pyrene perylene benzo[ b] fluoranthene benzo[a]pyrene benzo[ghi]perylene indeno[ 1,2,3-cd]pyrene
concn,” ng/g dry weight LC-FL GC-MS 44.6 f 2.7 5.97 f 0.52 289 f 10 294 f 10 8.56 f 0.35 55.9 f 2.2 20.1 f 2.3 19.6 f 1.4 15.6 f 1.4
45.3 f 7.3 6.14 f 0.72 255 f 21 259 f 12 8.5 f 1.7 48.7 f 5.2 17.1 f 2.2 20.3 f 2.3 13.6 f 1.4
certified concn,b~c ng/g dry wt wet wt 45 f 11 6.1 f 1.7 272 f 47 276 f 30 8.5 f 2.4 52.3 f 9.4 18.6 f 3.8 20.0 i 2.3 14.6 f 2.7
5.6 A 1.4 0.75 f 0.21 33.6 f 5.8 34.1 f 3.7 1.05 f 0.29 6.5 f 1.2 2.29 f 0.47 2.47 f 0.28 1.80 f 0.33
Uncertainties are one standard deviation of a single measurement, treating all measurements as statistically independent and identically distributed. *Certified values were determined on a wet weight basis; concentrations were converted to a dry weight basis for user convenience. CThecertified values are equally weighted means of results from two analytical techniques. The uncertainty is obtained from a 95% prediction interval plus an allowance for systematic error between the methods used. In the absence of systematic error, the resulting uncertainty limits will cover the concentration of approximately 95% of samples of this SRM having a minimum sample size of 15 g (wet weight).
tions. The peak search and activation analysis software was used to calculate specific activities of the nuclides in standards, Le., “standard constants”, and to calculate the unknown concentrations in the samples. The standard constants of the 12 irradiations for the standards showed no deviations exceeding counting statistics (0.2-2% relative uncertainty depending on the nuclide). Therefore, all standards and samples were treated for quantitation as if they were from one irradiation, corrected for the individual decay times. The data obtained for the various control materials did not reveal any significant bias compared to certified or well-known literature values. Three portions from one bottle of the freeze-dried SRM were analyzed at KFA Julich by DPASV to determine Co, Ni, Zn, Cu, Cd, and Pb, and by CVAAS to determine Hg. The voltammetric determinations were carried out according to previously published procedures for biological and environmental samples (20),after high-pressure ashing digestion with nitric acid (21). CVAAS was performed after wet digestion in completely closed quartz vessels (22). The reported values for CVAAS and DPASV are based on three sample dissolutions, which were each analyzed in duplicate. The reported values for Co and Zn are the combined results from measurements by INAA and DPASV. Results and Discussion SRM 1974 [Organics in Mussel Tissue (Mytilus edulis)] was prepared to meet the need for a marine tissue CRM that had been characterized with respect to PAHs, PCB congeners, chlorinated pesticides, and trace elements. The mussel tissue for this SRM was cryogenically pulverized and homogenized by a procedure previously developed and used in the NIST/U.S. Environmental Protection Agency Environmental Specimen Bank Program (11,23). This cryogenic homogenization procedure has been shown to provide frozen mussel tissue homogenate with 99% of the material having a particle size smaller than 0.42 mm, and the bulk of the material (-70%) with particle sizes less than 0.15 mm (24). The tissue homogenate can be handled easily as the frozen powder in preparation for organic or inorganic analyses. Organic Constituents. (a) Determination of PAHs. The results from at least two independent analytical procedures are generally used at NIST to determine the “certified concentrations of the analytes in environmental SRMs. When only one analytical technique is used (and the technique is not a definitive method), then the concentrations are reported as “noncertified” values rather than certified values. The analytical approach for the 1698
Environ. Sci. Technol., Vol. 25, No. 10, 1991
measurement of the organic contaminants in SRM 1974 is shown in Figure 1. Two analytical techniques were used for the determination of PAHs, Le., GC-MS and reversed-phase LC-FL. These two techniques have been used extensively at NIST for the measurement of PAHs in environmental samples (25). Recently, the results of GC-MS and LC-FL analyses of several SRMs and reference samples were summarized, and the comparability of the two techniques was discussed in detail (26). For the two approaches used in the determination of PAHs (see Figure l),different sample extraction solvents and cleanup steps were employed. For both approaches it was necessary to remove the majority of the lipid and biogenic material from the extract prior to GC or LC analysis. GPC and SPE on a silica column were used to cleanup the extract prior to GC-MS analysis. For the samples analyzed by LC-FL, the bulk of the lipids and polar biogenic materials was removed from the extracts by using a series of amino SPE cartridges, and then the PAH fraction was isolated by using normal-phase LC on an aminosilane column. The analytical results for the determination of nine PAHs, using both LC-FL and GC-MS, are summarized and compared in Table I. As shown in Table I, there is generally good agreement between the LC-FL and GC-MS determinations. Differences in the mean values for the two techniques were 1-4% for phenanthrene, anthracene, perylene, and benzo[ghi]perylene; 12% for fluoranthene and pyrene; and 13-15% for benzo[a]pyrene, benzo[b]fluoranthene, and indeno[ 1,2,3-cd]pyrene. Based on the results from these two techniques, certified concentrations of these nine PAHs were determined and are summarized in Table I. The results for additional PAHs, measured by only one analytical technique (either GC-MS or LC-FL), are summarized in Table I1 and are provided as noncertified values. (b) Determination of PCBs and Chlorinated Pesticides. The results for the determination of 13 PCB congeners and 9 chlorinated pesticide residues in SRM 1974 are summarized in Tables I11 and IV, respectively. The PCB congeners and chlorinated pesticides were determined by using GC-ECD on two stationary phases with different selectivity (DB-5 and C-18) and GC-MS. HOWever, since only one cleanup procedure was used (i.e. GPC followed by normal-phase LC), as shown in Figure 1, the combined results are provided only as noncertified values. The normal-phase LC on the aminosilane column, which separates on the basis of polarity, is used to separate the PCB congeners and lower polarity pesticides, in this case 2,4’-DDE, and 4,4’-DDE, from the more polar pesticides
0
5
10
15
30
25
20
35
40
45
50
55
Time (min) Figure 2. GC-ECD analysis on DB-5 column of PCB and lower polarity chlorinated pesticide fraction isolated from SRM 1974.
Table 11. Noncertified Concentrations of PAHs i n SRM 1974 compound 2-methylnaphthalenebjc l-methylnaphthaleneb~c fluorenebPC 9-methyl- and 4 - m e t h ~ l p h e n a n t h r e n e ~ l-methylphenanthrenebsc 2- and 9-ethylphenanthrenes and 3,6-dimethylphenanthrenebzd 2,6-dimeth~lphanthrene~ 2,7-dimeth~lphenanthrene~ 1,3-, 2,lO-, 3,9-, and 3,10-dimethylphenanthrenesbsc 1,6- and 2,9-dimethylphenanthrene~~>~ 1,7-dimeth~lphenanthrene~ benz[a]anthraceneb chrysene/ triphenylenebsd benzo[a]fluorantheneb benzo~]fluoranthene/benz~[k]fluoranthene~~~ benzo [ k]fluoranthenee benzo[ e ] pyreneb indeno[ 1,2,3-cd] fluorantheneb dibenzo[a,h]anthracenee
wig dry wta 17 f 4 9 f 2 12 f 2 22 f 5 19 f 5 34 f 8 37 f 7 35 f 9 91 f 17 47 f 11 42 f 9 37 f 3 124 f 11 4.1 f 1.2 35 f 6 24 f 1 81 f 6 3.9 o.6 2.8 o.l
*
Uncertainties are one standard deviation of a single measurement, treating all measurements as statistically independent and identically distributed. Results reported in dry weight may be converted to wet weight by multiplying by 0.1235. bConcentration was determined by GC-MS. Three bottles were analyzed for these compounds; 9-12 bottles were analyzed for all other compounds determined by GC-MS, 6 bottles were analyzed for compounds determined by LC-FL. dRepresents the coelution of two or more compounds. e Concentration was determined by LC-FL.
(17). The use of such a polarity separation minimizes possible interferences between the pesticides and PCBs
IS,internal standard.
during the GC-ECD analysis. Chromatograms from the GC-ECD analyses for these two fractions on the methylphenylpolysiloxane (DB-5) column, which is the most commonly used column for these analyses, are shown in Figures 2 and 3. The C-18 column provides different selectivity, particularly for the di- to heptachlorobiphenyls, which is similar to a C-8 polysiloxane phase (27, 28). Several of the PCB congeners listed in Table I11 coelute with each other in the commonly used GC-ECD analysis on a DB-5 or similar column (29). For the 13 PCB congeners listed in Table 111, 5 congeners may have some contribution from coeluting congeners, e.g., PCB 15 with PCB 18, PCB 95 with PCB 66, PCB 90 with PCB 101, PCB 164 and PCB 163 with PCB 138, and PCB 159 and PCB 182 with PCB 187 (see Figure 2). The extent of the contribution of the coeluting congeners has been shown to vary in marine samples (31). For example, PCBs 163 and 164 generally contribute only 10% to the concentration of PCB 138 (31). Despite these coelution problems, PCBs 28,52,101, 138,153, and 180 (i.e., the peaks eluting at the retention of these standard compounds including any coeluting congeners) are widely used as representative congeners for quantitation of complex PCB mixtures (31). To assess the contribution of coeluting congeners, the were by GC-ECD On a second with different selectivity and by GC-MS. The GC-MS analysis discriminates between coeluting peaks with differences of an odd number of chlorines (Le., 1, 3, 5, and so on). Therefore, the GC-MS can discriminate between PCB 15 and PCB 18, PCB 95 and PCB 66, and PCB 159 and PCB 187. The agreement is good between the GC-MS and GC-ECD analyses for PCB 18 and PCB 187, which suggests very little contribution from PCB 15 and PCB 159, respectively. For the measurement of PCB 66, the Environ. Sci. Technol., Vol. 25, No. 10, 1991
1609
3. w
0 0
z
dK
4
$
3,
+& n
$
0 0
Br
s
z 0 z
I
I
0
I
5
I
10
I
15
20I
25I
301
351
401
Time (min) Flgure 3. GC-ECD analysls on DB-5 column of the more polar chlorinated pesticide fraction isolated from SRM 1974.
results from the C-18column, which separates PCB 95 from PCB 66, were in good agreement with the GC-MS results, which selectively measures PCB 66 (tetrachloro 1700
Environ. Sci. Technol., Vol. 25, No. 10, 1991
IS,internal standard.
substitution) in the presence of PCB 95 (pentachloro substitution). The difference indicates the presence of -20 ng/g PCB 95. The C-18 column was also able to
Table IV. Summary of Analytical Results and Noncertified Concentrations of Selected Chlorinated Pesticides in SRM 1974 chlorinated pesticides cis-chlordane (a-chlordane) trans-nonachlor dieldrin 2,4’-DDE 4,4’-DDE 2,4’-DDD 4,4’-DDD 2,4’-DDT 4,4’-DDT
GC-ECD (DB-5)
concnP nale dry w t GC-ECD GC-MS noncertified ((2-18) (DB-5) valuesb
26 f 3
25 f 2
26 f 2
19 f 1 21 f 2 22 k 1 7.7 f 0.8 7.1 f 0.9 10 f 2 5.6 f 0.2 5.8 f 0.2 6.0 f 0.4 47f3 48f2 49f4 20f2 23f3 17f2 64f6 69f6 70f6 3.1 f 0.4 4.1 f 0.3 3.4 f 0.4 2.0 f 0.2 3.7 f 0.2 2.3 f 0.3
26 f 1 21 f 5 8f4 5.8 f 0.6 48f2 20f7 68f3 4f1 3f2
“Uncertainties are f one standard deviation of a single measurement, treating all measurements as statistically independent and identically distributed. Samples from five samples were extracted; each extract was analyzed in triplicate for the GC-ECD analyses and analyzed once for the GC-MS analyses. Results reported in dry weight may be converted to wet weight by multiplying by 0.1235. Noncertified concentrations are mean values from the three methods with uncertainties expressed as 95% confidence intervals.
separate PCB 101 and PCB 90, which are both pentachloro substituted. The temperature program used for the GCMS analysis provided a separation of PCB 163 and PCB 138, which explains the lower concentration for PCB 138 determined from GC-MS. PCB 28 and PCB 31, however, did coelute in the GC-MS analyses, as indicated by the higher concentrations compared to the two GC-ECD methods (see Table 111). Based on the three techniques, the recommended noncertified values are summarized in Table 111. The results of the GC-ECD and GC-MS analyses for the chlorinated pesticides are summarized in Table IV. In general, there were no significant differences in the results obtained from the three techniques. Therefore, the results were combined to provide the noncertified concentrations. The relative concentrations of DDT and its metabolites are somewhat unusual in this sample. In the technical DDT mixture used until the early 19709, the ratio of 4,4’-DDT to 2,4’-DDT was 4 1 (32);however, in this sample, the ratio of 4,4’-DDT to 2,4’-DDT is 0.7:l. On the basis of the results from the Mussel Watch Project of the National Oceanic and Atmospheric Administration’s National Status and Trends Program (33),4,4’-DDE was the major metabolite found in mussel tissue from over 180 U S . coastal sites during 1986-1988. In SRM 1974 the metabolite 4,4’-DDD is high relative to 4,4’-DDE (about 2:l). Elevated levels of 4,4’-DDD, which is a typical algae metabolite (34),have been seen in other mussel samples from the Mussel Watch Project, particularly those from the Atlantic and Gulf of Mexico coasts. The other group of chlorinated pesticides found to be abundant in this material are the chlordanes, cis-chlordane, and trans-nonachlor. The use of chlordane was stopped in the mid1970s; however, it is still found as an important residue in marine samples. (c) Comparison of Organic Contaminant Levels in SRM 1974 with Other Mussel Samples. The mussels used for SRM 1974 were collected in Boston Harbor to provide a sample typical of an urban site with relatively high concentrations of organic contaminants. The DorChester Bay site in Boston Harbor was selected on the basis of contaminant data from the 1986 collection of the Mussel Watch Project of the NOAA National Status and Trends Program (35). Of particular interest in the selection of a
Table V. Noncertified Concentrations of Inorganic Constituents in SRM 1974 element”
pg/g dry wtb
0.876 f 0.025c Li 31.3 0.7c B 3.29 f 0.09 Na (70) 0.48 f 0.03 Mg (%) A1 503 f 46 6.04 f 0.17 C1 (70) 1.10 f 0.33 K (70) 0.085 f 0.009 sc V 1.55 f 0.29 Cr 2.61 & 0.21 10.2 f 1.2 Mn 500 f 27 Fe 0.38 f O.Old co 1.00 f 0.08e Ni cu 9.2 f 1.9e 91.6 f 3.8d Zn 9.72 f 0.35 As 2.00 f 0.06 Se
*
element
wg/g dry wtb
Br Rb Sr Mo Ag Cd Sb Cs La Ce Sm Eu Hf Ta Au Hg Pb Th
373 f 18 5.67 f 0.16 60 f 14 2.0 f 0.5 0.854 f 0.021 1.4 f 0.4e 0.0262 f 0.0002 0.040 f 0.003 0.35 f 0.08 0.53 f 0.13 0.064 f 0.014 0.012 f 0.002 0.05 f 0.03 0.018 f 0.003 0.0476 f 0.0010 0.194 f 0.014 9.7 f 0.6e 0.07 f 0.02
=Elements listed in order of increasing atomic number. buncertainties are one standard deviation of a single measurement, assuming all measurements are statistically independent and identically distributed. For INAA results, samples from six bottles were analyzed in duplicate. Results reported in dry weight may be converted to wet weight by multiplying by 0.1235. ‘Results for B and Li were determined by neutron activation-mass spectrometry (NA-MS) (36) and have been reported previously (37). dValue is the combination of the INAA and DPASV results, Le.: Co, 0.36 (INAA) and 0.40 (DPASV) pg/g dry weight; Zn, 91.5 (INAA) and 91.8 (DPASV) pg/g dry weight. eValue determined by DPASV at KFA Julich; three subsamples from one bottle of SRM 1974 analyzed in duplicate. fValue determined by CVAAS at KFA Julich; three subsamples from one bottle of SRM 1974 analyzed in duplicate.
site for the collection of the proposed SRM were the concentrations of PAHs. According to the 1986 data from the Mussel Watch Project (35),Dorchester Bay ranked as the fifth highest site out of approximately 180 U S . coastal sites. The actual mussel material used for SRM 1974 was found to have levels of PAHs 2-3 times lower than the 1986 Mussel Watch Project results indicated. However, when compared to the NOAA Mussel Watch results for 1988 (the year in which mussels for SRM 1974 were collected), the concentrations of the PAHs, PCBs, and chlorinated pesticides in SRM 1974 are higher than mussel samples from -85% of the 180 sites in the Mussel Watch Project (33). Inorganic Constituents. Even though the primary aim in the production of SRM 1974 was for the determination of organic contaminants, a number of inorganic elements have also been determined. The results of these inorganic analyses will (1)more completely characterize the composition and the homogeneity of the material, (2) offer a fresh frozen matrix rather than a freeze-dried matrix for inorganic methods research and evaluation, and (3) provide a NIST SRM marine tissue for inorganic studies that has analyate levels different from previously issued materials (i.e., oyster tissues). INAA was selected for the inorganic analyses because of its ability to extensively characterize marine tissues; however, some elements (notably Cu, Ni, Cd, and Hg) cannot be determined instrumentally with NAA in marine tissues, and Pb is not determined via NAA. Hence, INAA was complemented previously with X-ray fluorescence (XRF) and prompt y-activation analysis (PGAA) for the characterization of more than 40 elements in marine bivalve molluscs (18). However, in this work we selected differential pulse anodic stripping voltammetry to deterEnviron. Scl. Technol., Vol. 25, No. 10, 1991
1701
Table VI. Comparison of Selected Trace Element Concentrations in SRM 1974 and Other Bivalve Mollusc Reference Materials
SRM 1974 mussela 3.29 0.48 503 6.04 1.10 0.085 1.55 2.61 10.2 500 0.38 1.00 9.2 91.6 9.72 2.00 5.67 60 1.96 0.854 1.4 0.0262 0.35 0.194 9.71
element Na ( % ) Mg (7%) A1 Cl(%) K (%) S V Cr Mn Fe co Ni cu Zn As Se Rb Sr Mo Ag Cd Sb La Hg Pb
NIES CRM musselb
concn, pg/g dry wt IAEA-MA-M-2ITM musselc
1.00 0.21 (220) [[1.7llf 0.54 [0.044] 0.63 16.3 158 (0.37) 0.93 4.9 106 9.2 (1.5) l2.51
POI
[ D.21I’
0.027 0.82 [ [0.0115]]f [0.22] (0.05) 0.91
4.55 0.59 (8.71) (0.48) (0.045) 1.25 67.1 256 (0.88) 7.96 156 12.8 2.27 6.96 101 (0.054) 1.32 (0.027) (0.95) (1.92)
BCR CRM 278 musse1
SRM 1566a oystere
(2.0) (0.14) (70) (3.1) 0.790 (0.018)
0.417 0.118 202 0.829
0.80 7.3 133 (0.33) (1.2)
9.60 76 5.9 1.66 (2.7) (14) (0.35) ((0.118)) 0.34 0.188 1.91
(0.06) 4.68 1.43 12.3 539 0.57 2.25 66.3 830 14 2.21 3.29 11.1 (0.3) 1.68 4.15 (0.01) (0.3) 0.0642 0.371
Values for SRM 1974 are noncertified concentrations. Certified and noncertified values from ref 7, values in parentheses are noncertified; values in brackets were determined at NIST by INAA when used as a control material during the analysis of SRM 1974. Certified and noncertified values from ref 4; values in parentheses are noncertified. dCertified and noncertified values from ref 3; values in parentheses are noncertified. e Certified and noncertified values from ref 2; values in parentheses are noncertified. f Values determined by INAA and reDorted in ref 18.
mine Ni, Co, Cu, Zn, Cd, and P b (20,21) and cold vapor atomic absorption spectrometry to determine Hg (22). The simultaneous multielement determinations with both INAA and DPASV resulted in independent procedures for Co and Zn and also provided the opportunity to deduce whether any gross errors occurred in the determinations of the other elements. This combination of techniques resulted in “noncertified” concentrations for 36 elements. These results are summarized in Table v ; the results for Co and Zn are the combination of the results from the two techniques (INAA and DPASV). Most of the elements have been determined with high precision (relative uncertainty less than 2%) due to good counting statistics and reproducibility of irradiation and counting instrumentation. With this precision, larger observed uncertainties may be due to inhomogeneities in the material. Al, Sc, Cr, and rare earth elements show relative uncertainties of -lo%, which may indicate a somewhat inhomogeneous distribution of elements that may not be intrinsic components of the tissue at the observed levels. Other elements (e.g., Na, C1, Zn, and Se) exhibit very small uncertainties, which indicate that the material has been homogenized sufficiently to provide reproducible portions of approximately 2 g wet weight with uncertainties due to inhomogeneity smaller than 2 % Analysts involved in inorganic analyses of marine bivalves will find this material useful because of its fresh frozen status, which is similar to the actual field samples analyzed, Le., including fluids, lipids, and other unaltered constituents. Cryogenic homogenization and cryopresevation may also preserve elemental species (e.g., organometallic species) in their original form. Although elemental species have not been determined in this material, its availability will help to foster the development of methods I
1702
Environ. Sci. Technol., Vol. 25, No. 10, 1991
for the determination of elemental species in marine tissues. Comparison of SRM 1974 with Other Mussel/ Oyster Reference Materials for Trace Element Determinations. SRM 1974 complements existing mussel/oyster tissue reference materials for the determination of trace elements. SRM 1566a (Oyster Tissue), available from NIST, has certified concentrations for 26 elements and noncertified concentrations for 13 additional elements. Three different mussle tissue reference materials are available from other sources: NIES CRM No. 6, mussel (13 certified and 6 reference values); BCR CRM 278, mussel tissue (9 certified and 15 noncertified values); and IAEA MA-M-B/TM, mussel homogenate (16 certified and 6 noncertified values). All of these reference materials are freeze-dried matrices. The concentrations of selected elements in these four mussel/oyster tissue reference materials are listed in Table VI for comparison with the elemental concentrations in SRM 1974. As mentioned above, both mussel and oyster reference materials are necessary since oysters accumulate certain elements (Cu, Zn, and Ag) to significantly higher levels than mussels (31) (see Table VI). When compared with the three other mussel SRMs, the concentrations of several of the common pollutants elements in SRM 1974 are higher, e.g., Al, Cr, Fe, Mo, Ag, Cd, Hg, and Pb. The concentrations of most of the pollutant elements in SRM 1974 would rank in the upper 10% of the mussel samples collected and analyzed as part of the NOAA Mussel Watch Project (33). Acknowledgments
The mussels used for SRM 1974 were collected with the assistance of S. Freitas of Battelle New England Research
Laboratory, Duxbury, MA. The measurementa of selected inorganic constituents by voltammetry and cold vapor atomic absorption spectroscopy were performed at the Nuclear Research Center in Julich, Federal Republic of Germany, by P. Ostapczuk, K. May, and M. Stoeppler. Consultation on the statistical design of the experimental work and evaluation of the data were provided by W. F. Guthrie, S. B. Schiller, and K. R. Eberhardt (NIST). The support aspects involved in the preparation, certification, and issuance of this Standard Reference Material were coordinated through the NIST Standard Reference Materials Program by R. Alvarez. We thank J. c. Buijten (Chrompack Internationl) for the gift of the C-18 GC column. Registry No. PCB 28, 7012-37-5; PCB 44,41464-39-5; PCB 52,35693-99-3; PCB 66,32598-10-0; PCB 101,37680-73-2;PCB 90,68194-07-0; PCB 105,32598-14-4; PCB 118,31508-00-6; PCB 128,38380-07-3;PCB 138,35065-28-2;PCB 163,74472-44-9 PCB 164,74472-45-0;PCB 153,35065-27-1;PCB 180,35065-29-3;PCB 187, 52663-68-0; PCB 182, 60145-23-5; 2,4’-DDE, 3424-82-6; 4,4’-DDE, 72-55-9; 2,4’-DDD, 53-19-0; 4,4’-DDD, 72-54-8; 2,4’-DDT, 789-02-6; 4,4’-DDT, 50-29-3; Li, 7439-93-2; B, 7440-42-8; Na, 7440-23-5; Mg, 7439-95-4; Al, 7429-90-5; C1, 16887-00-6; K, 7440-09-7; Sc, 7440-20-2; V, 7440-62-2; Cr, 7440-47-3; Mn, 743996-5; Fe, 7439-89-6; Co, 7440-48-4; Ni, 7440-02-0; Cu, 7440-50-8; Zn, 7440-66-6; AS, 7440-38-2; Se, 7782-49-2; S, 7704-34-9; Rb, 7440-17-7; Sr, 7440-24-6; Mo, 7439-98-7; Ag, 7440-22-4; Cd, 7440-43-9; Sb, 7440-36-0; La, 7439-91-0; Hg, 7439-97-6; Pb, 7439-92-1; phenanthrene, 85-01-8; anthracene, 120-12-7; fluoranthene, 206-44-0; pyrene, 129-00-0; perylene, 198-55-0; benzo[ blfluoranthene, 205-99-2; benzo[a]pyrene, 50-32-8; benzo[ghi]perylene, 191-24-2; indeno[ 1,2,3-cd]pyrene,193-39-5; 2-methylnaphthalene, 91-57-6; 1-methylnaphthalene, 90-12-0; fluorene, 86-73-7; 4-methylphenanthrene, 832-64-4; 9-methylphenanthrene, 883-20-5; 1-methylphenanthrene,832-69-9; 9-ethylphenanthrene, 3674-75-7; 3,6-dimethylphenanthrene, 1576-67-6; 2-ethylphenanthrene, 3674-74-6; 2,6-dimethylphenanthrene,17980-16-4; 2,7-dimethylphenanthrene, 1576-69-8;3,10-dimethylphenanthrene, 66291-33-6; 2,9-dimethylphenanthrene,17980-09-5; 1,6-dimethylphenanthrene, 20291-74-1; 1,7-dimethylphenanthrene, 483-87-4; benz[a]anthracene, 56-55-3; chrysene, 218-01-9; triphenylene, 217-59-4; benzo[a]fluoranthene, 203-33-8; benzo[i]fluoranthene, 205-82-3; benzo[k]fluoranthene, 207-08-9; benzo[elpyrene, 192-97-2; indeno[ 1,2,3-cd]fluoranthene,193-43-1; dibenz[a,h]anthracene, 53-70-3; 1,3-dimethylphenanthrene, 16664-45-2; 2,10-dimethylphenanthrene,2497-54-3; 3,9-dimethylphenanthrene, 66291-32-5; cis-chlordane, 5103-71-9; trans-nonachlor, 39765-80-5; dieldrin, 60-57-1. Literature Cited Certificate of Analysis; SRM 1566 Oyster Tissue; National Bureau of Standards, Gaithersburg, MD, 1979. Certificate of Analysis; SRM 1566a Oyster Tissue; National Institute of Standards and Technology, Gaithersburg, MD, 1989. Griepink, B.; Muntau, H. The Certification of the Contents (Mass Fractions) of As, Cd, Cr, Cu, Fe, Hg, Mn, Pb, Se and Zn in Mussel Tissue (Mytilus edulis) CRM No 278; EUR 11838, Commission of the European Communities, Luxembourg, 1988. Report No. 26, Zntercalibration of Analytical Methods on Marine Environmental Samples-Trace Element Measurements on Mussel Homogenate (MA-M-BITM); International Atomic Energy Agency, Laboratory of Marine Radioactivity, MC 98000 Monaco, 1985. Parr, R. M.; Schelenz, R.; Ballestra, S.Fresenius Z . Anal. Chem. 1988,332, 518-523. Okamoto, K.; Fuwa, K. Analyst 1985, 110, 785-789. NIES Certified Reference Material No. 6 “Mussel”; National Institute for Environmental Studies, Tsukuba, Japan, 1984. Berman, S. S.; Sturgeon, R. E. Fresenius 2. Anal. Chem. 1987, 326, 712-715.
(9) Berman, S. S.; Sturgeon, R. E. Fresenius 2.Anal. Chem. 1988, 332, 546-548. (10) Schladot, J. D.; Backhaus, F. In Progress in Environmental Specimen Banking; Wise, S. A., Zeisler, R., Goldstein, G. M., Eds. NBS Spec. Publ. (U.S.) 1988, No. 740, 184-193. (11) Zeisler, R.; Langland, J. K.; Harrison, S.H. Anal. Chem. 1983,55, 2431-2434. (12) Wise, S. A,; Cheder, S.N.; Hertz, H. S.; Hilpert, L. R.; May, W. E. Anal. Chem. 1977,49, 2306-2310. (13) May, W. E.; Wise, S.A. Anal. Chem. 1984, 56, 225-232. (14) Wise, S. A,; Benner, B. A., Jr.; Byrd, G. D.; Cheder, S. N.; Rebbert, R. E.; Schantz, M. M. Anal. Chem. 1988, 60, 887-894. (15) Schantz, M. M.; Benner, B. A. Jr.; Cheder, S. N.; Koster, B. J.; Hehn, K. E.; Stone, S. F.; Kelly, W. R.; Zeisler, R.; Wise, S. A. Fresenius J . Anal. Chem. 1990,338,501-514. (16) Kline, W. F.; Wise, S.A.; May, W. E. J.Liq. Chromatogr. 1985,8, 223-237. (17) Parris, R. M.; Cheder, S.N.; Wise, S. A. In Progress in Environmental Specimen Banking; Wise, S. A., Zeisler, R., Goldstein, G. M., Eds. NBS Spec. Publ. (U.S.) 1988, No. 740, 74-81. (18) Zeisler, R.; Stone, S. F.; Sanders, R. W. Anal. Chem. 1988, 60, 2760-2765. (19) Becker, D. A. J . Radioanal. Chem. 1987, 110, 393-401. (20) Ostapczuk, P.; Valenta, P.; Niirnberg, H. W. J.Electroanal. Chem. 1986,214, 51-64. (21) Ostapczuk, P.; Froning, M.; Stoeppler, M. Fresenius Z . Anal. Chem. 1989,334,661. (22) May, K.; Stoeppler, M. Fresenius Z . Anal. Chem. 1984,317, 248-251. (23) Wise, S.A.; Koster, B. J.; Parris, R. M.; Schantz, M. M.; Stone, S. F.; Zeisler, R. Int. J.Environ. Anal. Chem. 1989, 37, 91-106. (24) Kratochvil, B. G. Recommended Procedures for the Collection, Shipment, Shucking, Storage, and Cryogenic Grinding of Mussels for Use in the NESB Pilot Program at National Bureau of Standards, Report to Center for Analytical Chemistry. National Bureau of Standards, Gaithersburg, MD, Oct 1981. (25) Wise, S. A,; Hilpert, L. R.; Rebbert, R. E.; Sander, L. C.; Schantz, M. M.; Cheder, S. N.; May, W. E. Fresenius 2. Anal. Chem. 1988,332,573-582. Wise, S. A.; Hilpert, L. R.; Byrd, G. D.; May, W. E. Polycyclic Aromat. Compd. 1990, I , 81-98. Fischer, R.; Ballschmiter, K. Fresenius 2.Anal. Chem. 1988, 332, 441-446. Fischer, R.; Ballschmiter, K. Fresenius 2.Anal. Chem. 1989, 335, 457-463. Ballschmiter, K.; Schuer, W.; Buchert, H. Fresenius Z. Anal. Chem. 1987, 326, 253-257. Ballschmiter, K.; Zell, M. Fresenius 2. Anal. Chem. 1980, 302, 20-31. Duinker, J. C.; Schultz, D. E.; Petrick, G. Mar. Pollut. Bull. 1988, 19(1), 19-25. Ballschmiter, K.; Zell,M. Int. J.Environ. Anal. Chem. 1980, 8, 15-35. National Status a n d Trends Program for Marine Environmental Quality-Progress Report-A Summary of Data on Tissue Contamination from the First Three Years (1986-1989) of the Mussel Watch Project; NOAA Technical Memorandum NOS OMA 49; Rockville, MD, 1989. Ballschmiter, K.; Buchert, H.; Bihler, S.; Zell, M. Fresenius 2.Anal. Chem. 1981,306, 323-339. National Status a n d Trends Program for Marine Environmental Quality-Progress Report-A Summary of Selected Data on Chemical Contaminants in Tissues Collected During 1984,1985, and 1986; NOAA Technical Memorandum NOS OMA 38; Rockville, MD, 1987. Clarke, W. B.; Koekebakker, M.; Barr, R. D.; Downing, R. G.; Fleming, R. F. Appl. Radiat. Isot. 1987, 38, 735-743. Iyengar, G. V.; Clarke, W. B.; Downing, R. G. Fresenius J . Anal. Chem. 1990,338, 562-566. Received for review November 26, 1990. Revised manuscript received May 15,1991. Accepted May 28,1991. This work was Environ. Sci. Technol., Vol. 25, No. 10, 1991
1703
Environ. Sci. Technol. 1991, 25, 1704-1708
supported in part by the Ocean Assessments Division, National Oceanic a n d Atmospheric Administration (NOAA); the Office of the Chief of Naval Operations, Department of the Navy; the Minerals Management Service, Department of the Interior; and Environmental Monitoring Systems Laboratory (Las Vegas), Environmental Protection Agency. Certain commercial equip-
ment, instruments, or materials are identified in this report to specify adequately the experimental procedure. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are the best available for the purpose.
Determination of Trace Metals in Saline Irrigation Drainage Waters with Inductively Coupled Plasma Optical Emission Spectrometry after Preconcentration by Chelation-Solvent Extraction Gordon R. Bradford* and Darlush Bakhtar Department of Soil and Environmental Sciences, University of California, Riverside, California 9252 1
Preconcentration of Fe, Mn, Cu, Zn, Cd, Pb, V, Mo, Ni, Co, Cr, T1, Ga, Au, U, Hg, Se, As, Sn,Sb, Bi, and Te from saline water is described using multielement chelation with ammonium pyrrolidinedithiocarbamate extracted into chloroform. Extract residues were taken up in dilute nitric acid solution for analysis by simultaneous multielement inductively coupled plasma optical emission spectrometry (ICP-OES). Recovery percentages of elements at low microgram per liter levels in spiked saline samples ranged from 92 to 102 5%. Saline agricultural drainage and evaporation pond water samples from the San Joaquin Valley, CA, were analyzed by this method. In the case of U, the accuracy of the combined procedure was confirmed by an independent method. Introduction
Direct determination of low microgram per liter concentrations of many trace elements by inductively coupled plasma optical emission spectrometry (ICP-OES) in saline waters is not feasible due to insufficient instrumental sensitivity and/or interferences from a highly saline matrix. Liquid-liquid extraction, (1)coprecipitation, (2) chelating ion exchange, (3)solvent evaporation, ( 4 ) hydride generation, (5) and chelation-solvent extraction (6-10) have been used for preconcentration. Cresser (11) cited several hundred papers published between 1955 and 1975 on single-element analyses by atomic absorption spectrometry (AAS) following chelation and solvent extraction. More recently, multielement extractions have been reported (7-9) for analyses by AAS. Sugiyama et al. (12) reported on chelation of 13 elements and direct analyses of their organic solvent extract by ICP-OES. However, interchanging ICP-OES parameters from pneumatic nebulization of aqueous to organic solvents is difficult. Therefore, a method fully adapted to simultaneously concentrate as many as 22 trace elements for analyses by ICP-OES using direct pneumatic a q u e o u s nebulization is attractive. As recently as 1986, Thompson (13) wrote, "Several applications of pre-concentration to geochemical analyses by ICP-OES have been reported, the materials being water, rocks, soils and sediments. However, it is clear that a good, general-purpose, rapid, multi-element pre-concentration method which is selective against interfering matrix elements (Al, Ca, Mg, Fe, Na, K) is still lacking and would easily repay the considerable thought and investment in development time". Particularly, dithiocarbamates have been used to complex many metals for extraction into an organic phase with 1704
Environ. Sci. Technol., Vol. 25, No. 10, 1991
Table I. ICAP-OES Wavelengths and Instrumental Detection Limits" element
wavelength, nm
arsenic antimony barium bismuth boron cadmium chromium cobalt copper gold gallium iron lead lithium manganese mercury molybdenum nickel selenium tellurium thallium tin strontium uranium vanadium zinc
193.69 206.83 493.40 249.67' 223.06a 228.80" 267.71 286.61 324.25 242.80 417.21 259.94 220.35 670.70 257.61 253.65 202.03" 231.60 196.02 214.20" 190.86" 284.00 421.50 385.96 292.40 2O6.2Oa
Second-order lines. NA, not applicable. a
detection limits, m d L instrumental preconcn 0.001b 0.001b 0.002 0.001b 0.005 0.004 0.002 0.005 0.010 0.005 0.020 0.005 0.020 0.005 0.005 0.001*
0.008 0.010 0.001b 0.001b 0.100 0.10 0.20 0.10 0.010 0.005
0.001 0.001 NAc 0.001 NAc 0.001 0.001 0.001 0.002 0.001 0.001 0.003 0.003 NAc 0.002 0.001 0.001 0.001 0.001 0.001 0.001 0.001 NAc 0.003 0.001 0.002
Continuous-flow hydride generation.
high distribution ratios.(6-10, 12, 14, 15) A typical structural formula for a metal (M) complex of ammonium pyrrolidinedithiocarbamate (APDC) is shown in Figure 1. In this paper, a simultaneous preconcentration method for 22 elements with large enrichment factors by extraction of APDC metal complexes into chloroform is reported. It has application for trace element analyses of waters, soil extracts, soil-exchange solutions, and agricultural drainage waters containing a wide concentration range of cations (Ca, Mg, Na, K)and anions (Cl-, SO4"). The procedure is relatively simple, rapid, and adaptable to aqueous pneumatic nebulization with ICP-OES. Accordingly, one laboratory worker can extract 20-25 samples per 8-h working period. Experimental S e c t i o n Apparatus. A Jarrell-Ash Atomcomp 800 series spectrometer with computer-controlled background correction including spectral line overlap correction and other timing
0013-936X/91/0925-1704$02.50/0
0 1991 American Chemical Society
