723
Anal. Chem. 1906, 58,723-725
associated with HgClz treated soils than with untreated soils (5.2%). The difference of 1.4% due to HgClz was significant for the soil residues but was too small to have produced a significant effect in the extract. There was also a significant interaction term between PAH and PAH concentration. The highest percentage of bound 14C (9.3%) occurred with benzo[a]pyrene with the 5 pg/g treatment and the smallest percentage (3.8%) occurred with benzo[a]pyrene at the 50 pg/g treatment. The difference in bound 14Cwas much less pronounced for anthracene where the soil residue contained 7.0% of 14Cat the low concentration and 4.2% at the high concentration and was consistent for both extraction procedures. The mechanism for this effect is not clear because the effect of PAH is confounded with differences in experimental conditions such as the length of incubation time. Although the PAH main effect was not significant, the significant interaction term between type of PAH and concentration could have been caused by differences in experimental conditions. Recovery of PAH's from environmental matrices is influenced by many factors. Results of this study indicate that PAH concentrations are likely to be underestimated and that the degree of underestimation is likely to be greater for low than for high concentrations. Underestimation should be minimized by using the most efficient extraction technique, in this case the Soxhlet method. The most efficient technique
should be determined for each sample matrix.
ACKNOWLEDGMENT The authors thank Kevin Hosler for preparing the contaminated soil samples and David Ide for his work on the extractions and TLC. Registry No. Benzo[a]pyrene, 50-32-8;anthracene, 120-12-7. LITERATURE CITED (1) Bulman, T. L.; Lesage, S.; Fowlie, P. J. A.; Webber, M. D. "The Persistence of Polynuclear Aromatic Hydrocarbons in Soil"; Petroleum Assoclatlon for Conservation of the Canadian Environment (PACE), Report No. 85-2, Ottawa, Ontario, November 1985. (2) MacDougall, D.; Crummett, W. Anal. Chem. 1980, 52, 2242-2249. (3) Haddock, J. D.; Landrum, P. F.; Giesy, J. P. Anal. Chem. 1983, 55, 1197-1200. (4) Maybury, R. "Laboratory Manual for Pesticlde Residue Analysis in Agricultural Products", Food Production and Inspection Branch, Agriculture Canada, Revised 1984. (5) Afghan, B. K.; Wilkinson, R. J. "Method for Determination of Polynuclear Aromatic Hydrocarbons in Environmental Samples (HPLC-multidetectlon system); Environment Canada, Manuscrlpt 20-AMD-3-81BKA, 1981. (6) Harrison, F. L.; Bishop, D. J.; Mallon, B. J. Environ. Sci. Techno/. 1985, 19, 186-193.
RECEIVED for review July 15, 1985. Accepted October 24, 1985. This work was supported by the Petroleum Association for Conservation of the Canadian Environment (PACE) and the Great Lakes Water Quality Program.
Determination of Munitions in Water Using Macroreticular Resins J. J. Richard and G. A. Junk*
USDOE,Ames Laboratory, Ames, Iowa 50011
A simple procedure has been developed for the determlnatlon of munltlons present In water at levels as low as 0.1 pg/L. The method uses 60-80 mesh XAD-4 for extraction, followed by elutlon with 20 mL of ethyl acetate, concentration of the eluate, separation by caplllary GC, and detectlon using electron capture. Contrived and fleld samples contalnlng nltrobenzene, 1,3-dlnltrobenzene, 1,3,5-trlnltrobenzene, 2,4-dlnltrotoluene, 2,6dlnltrotduene, 2,4,&trlnltrotoluene (TNT), and 1,3,5-trlnltrohexahydro-1,3,5-trlarlne (RDX) have been tested successfully. The XAD-4 extractlon In the field reduced the cost of transporting water samples to the laboratory where addltlonal savlngs occurred because less solvent was used to elute the resln than was required for solvent extractlon. Adsorptlon onto partlculate matter, assoclatlon with humlc adds, resln capaclty, resln polarity, and Incomplete dlssolutlon were examlned as the most likely causes of the low recoverles for RDX when XAD-2 and XAD-7 resins were used.
Nitrated organic compounds are introduced into the environment from the production, storage, transport, and disposal of munitions. Wastewater from munitions production and contaminated surface water and groundwater from the disposal of munitions are of greatest concern. The nitrated organic compounds in these waters are usually isolated by liquid-liquid extraction (I-@, and the concentrated extracts me analyzed by some form of chromatography. The extraction 0003-2700/86/0358-0723$01 S O / O
procedure is best accomplished in the laboratory; consequently transport of water samples in cooled containers is the normal procedure. The costly transport can be avoided by sorbing the organic compounds onto a macroreticular resin in the field and then transporting the small column of resin at ambient temperature to the laboratory for further processing. This advantage of resins has not been exploited in the reports of their use for the isolation of nitrated organic compounds (6-9). Resin use has been limited to XAD-2 for the cleanup of wastewaters from the manufacture of trinitrotoluene (6))a mixture of XAD-4 and XAD-8 to remove nitrated compounds from river water (7), and XAD-4 and Porapaks, R and S, to extract various explosives from surface waters (8, 9). This paper describes a convenient procedure for the efficient recovery of two munitions, 1,3,5-trinitrohexahydro-l,3,5-triazine (RDX) and 2,4,6-trinitrotoluene (TNT), from water using the macroreticular resin XAD-4. Also discussed are the recovery results for related compounds, 2,4-dinitrotoluene (2,4-DNT),2,6-dinitrotoluene (2,6-DNT),1,3,5-trinitrobenzene (1,3,5-TNB),1,3-dinitrobenzene(1,3-DNB),and nitrobenzene (NB), from both contrived and groundwater samples.
EXPERIMENTAL SECTION Reagents and Chemicals. All solvents were reagent grade and distilled prior to use. The nitrobenzenes and nitrotoluenes were obtained from Chem Service (West Chester, PA). The RDX was obtained from Army Ordinance. The XAD-2, XAD-4, and XAD-7 solid sorbents are macroreticular resins obtained from 0 1986 American Chemical Soclety
724
ANALYTICAL CHEMISTRY, VOL. 58, NO. 4, APRIL 1986
Table I. Recovery of Nitrosubstituted Compounds Spiked into Tap Water at the 4 wg/L - Level Using - 20-50 Mesh XAD-2 and XAD-4
Table 11. Recovery of Nitro-Substituted Comnounds Spiked into Water-at the 0.1 pg/L Level Using 20-50 Mesh XAD-2
% recovery
compd
XAD-2
XAD-4
NB 1,3-DNB 2,6-DNT 2,4-DNT 1,3,5-TNB 2,4,6-TNT RDX
89 f 8= 84 f 8 99 f I 102 f 9 81 f 8 95 f I 65 f I
86 f 9 81 f 9
100 f 6 96 f 5 14 f 8 95 f 8 66 f I
Standard deviation calculated from four to six runs.
Rohm and Haas (Philadelphia,PA) and purified by the procedure of Junk et al. (IO). The 60-80 mesh fraction of XAD-4 was obtained by sieving the resin that has been ground in a Staub Co. Model 4E grinding mill (Philadelphia, PA). All water samples were filtered through a 0.45-pm membrane filter. Standard solutions, used to spike the waters for test purposes, contained 4.0 and 0.1 pg of each test compound/mL of organic solvent, either acetone or ethyl acetate. Extraction Procedure. One milliliter of the standard spiking solution was added to 1L of water, which was then passed through a 5-mL XAD column, at a flow rate of 15 mL/min. Most of the residual water in the column was removed by aspirating for 5 min. The column was then eluted by using 2 X 10-mL portions of organic solvent that were collected in a 60-mL separatory funnel. This eluate was freed of small amounts of residual water by use of anhydrous magnesium sulfate. The eluate was filtered through a fritted glass funnel into a concentrator flask, and most of the solvent was removed with a rotary evaporator at 35-40 "C. The concentrated eluate was diluted to appropriate volume for analysis. Analysis. Gas chromatographic analysis of the concentrated extract was performed on a Carlo Erba Fractovap (Peabody,MA) equipped with an electron capture detector (ECD). A 30 m X 0.32 mm DB-5 fused silica capillary column from J&W (Rancho Cordova, CA) and hydrogen carrier gas were used for separating the nitro compounds. On-column injection at 40 O C was employed followed by a 2-min hold before temperature programming at 7.5 OC/min to 205 "C.
-
RESULTS AND DISCUSSION Eluting Solvent. The initial recovery tests were run by using diethyl ether to elute the resin columns. Less than 10% of the RDX was recovered by this standard procedure (IO). The low recovery was attributed to RDX solubility problems when hexane was added to the diethyl ether to aid in the removal of residual water. Since RDX is known to be more soluble in polar solvents, acetone, methyl ethyl ketone, and ethyl acetate were studied as solvents for eluting the resin columns. In order to remove the residual water from the ketone solvents, it was necessary to add a water-insoluble solvent, such as benzene. This step was cumbersome and had some of the same solubility problems observed with diethyl ether and hexane. These problems do not occur with ethyl acetate, which wets the resin well, elutes the nitrated compounds efficiently, has low water solubility, and can be freed of small amounts of residual water by shaking with anhydrous magnesium sulfate. Therefore ethyl acetate was used to obtain all the results reported in the following tables. Recovery Results. Table I gives the recovery results for nitrobenzenes, nitrotoluenes, and RDX from 1L of tap water whose raw water source was a shallow well. Both XAD-2 and XAD-4 a t 20-50 mesh sizes were used for these tests. The exhaust waters from the XAD-2 and XAD-4 columns . were collected and solvent extracted. The analyses of these extracts showed 1,3-DNB, 1,3,5-TNB, and RDX to be present. Failure of the resins to remove these compounds could be
(I
compd
% recovery
compd
NB 1,3-DNB 2,6-DNT 2,4-DNT
18 f 6" 88 f 10 91 f 6 98 f 2
1,3,5-TNB 2,4,6-TNT RDX
%
recovery
89 f 4 91 f 11 90 f 6
Standard deviation calculated from four to six runs.
Table 111. Recovery of Nitro-Substituted Compounds Level Using 20-50 Mesh Spiked into Water at the 4 .ug/L XAD-7 compd
% recovery
compd
% recovery
NB 1,S-DNB 2,6-DNT 2,4-DNT
IO" 80
1,3,5-TNB 2,4,6-TNT RDX
80 80
88 89
70
Average deviation of f7% calculated from only two runs. caused by their adsorption onto particulate matter or their association with humic material present in the water; other causes could be incomplete dissolution or problems with resin capacity and polarity. All these probable causes were investigated. Test studies using organic-free water, both commercial and freshly distilled, and water fiitered through a 0.2-pm filter gave recoveries similar to those reported in Table I. These results showed that adsorption on particulate matter and association with humic material were not the cause of poor recoveries. Comparative results a t different concentrations confirm this conclusion. If adsorption or association, or both, are operable, lower recoveries should be obtained as the concentration of solutes is decreased. This was not observed as is evident from comparing the very favorable results in Table I1 for tests at 0.1 pg/L to the less favorable results in Table I, where the higher concentration of 4 pg/L was investigated. The results in Table I11 where XAD-7, a more polar resin than XAD-4 and XAD-2, was used would suggest that polarity is not a significant factor. Resin capacity based on surface area is not the explanation for low recoveries, since XAD-2 with 350 m2/g gave recoveries equivalent to XAD-4 with 780 m2/g. The higher recoveries observed for RDX at the lower concentration of 0.1 pg/L compared to the results a t 4.0 pg/L (see Tables I and 11)suggest that incomplete dissolution could be occurring at the higher concentration, thus leading to lower recoveries. Alternative spiking procedures intended to improve the dissolution, and hence the recoveries, were investigated. The tested procedures were as follows: (1)the spike solution was added, with stirring, to water a t 50 O C , before cooling and passing the spiked water through the resin; (2) the spiked water was agitated for 15 min with a sonic bath before passage through the XAD column; (3) the spike solution was diluted with 50 mL of acetone, which was added to the water before passage through the resin; and (4) procedure 3 was repeated with 50 mL of methanol. All experiments gave results similar to those reported in Table I where recovery of RDX and 1,3,5-TNB are abnormally low. Recoveries also were checked by using smaller particle sizes in the resin column. The nearly quantitative recoveries given in Table IV were obtained by using XAD-4 ground to 60-80 mesh. When the recovery tests were repeated with 60-80 mesh spherical beads of XAD-4 similar high recoveries were obtained. These results at 4 pg/L, and the comparable high recoveries given in Table I1 for tests at 0.1 pg/L, suggest that
Anal. Chem. 1986, 58,725-727
Table IV Recoveries of Nitro-Substituted Compounds Spiked into Water at the 4 wg/L Level Using 60-80 Mesh XAD-4
compd NB
1,3-DNB 2,6-DNT 2,4-DNT a
% recovery
*
97 7" 99 3 99 A 6 98 f 6
*
compd
% recovery
1,3,5-TNB 2,4,6-TNT RDX
98 f 5 91 f 3 97 f 5
Standard deviation calculated from four to six runs.
Table V. RDX in Groundwaters by Three Different Procedures
groundwater no. 1 2 3
4 5 6
I
amt of RDX, wg/L CHzClz extraction XAD-2 XAD-4 23 35 29 0.8
42 13 NDb
13"
24
22
40
14
30
0.7 29 6.2
1.6 47 15 1.8
1.0
"All values uncorrected for recovery efficiency. bND, not determined.
formation of microparticles of the test compounds is the probable cause of low recoveries. The exact explanation for higher recoveries when smaller mesh resin is used cannot be given from existing data, but the probable reason is effective filtration of microparticles of the test compounds combined with more efficient contact of the test compounds with exposed resin surfaces. Our preliminary data using XAD-2 and XAD-4 of different shapes and sizes lend support to incomplete dissolution being the explanation for low recoveries of some compounds when solid sorbents are used for the extraction. Field Sample Results. RDX was extracted from groundwater samples taken from monitor wells a t a munition disposal site. The traditional solvent extraction with CHzClz and extraction by the resin sorption procedure were employed using both 20-50 mesh XAD-2 and 60-80 mesh XAD-4. Results are given in Table V. The lower results, using XAD-2, confirm the -65% recovery established from tests of con-
725
trived samples. The agreements of the XAD-4 and the CHzClz solvent extraction results for these field samples, and the nearly 100% recovery when XAD-4 was used for contrived samples, establish the validity of the resin sorption procedure as described in this report.
CONCLUSION The test data for contrived samples and the results given in Table V for field samples show that 60-80 mesh XAD-4 can be used to determine accurately the nitrated organic compounds in environmental waters. The same results are obtained as those for use of the recommended methylene chloride extraction, but with much less time per determination and at very reduced solvent and transportation costs. ACKNOWLEDGMENT We are grateful for the technical assistance of Roy Spalding, John Fulton, and Mike Avery and the administrative assistance and encouragement of V. A. Fassel and R. W. Fisher. LITERATURE CITED Hoffsommer, J. C.; Rosen, J. M. Bull. Environ.
Contam. Toxicol.
1972, 7, 177-181. Chandler, C. D.; Gibson, G. R.; Bolleter, W. T. J . Chromatogr. 1974, 100, 185-168. Pereira, W. E.; Short, D. L.; Manigold, D. 6.; Roscio, P. K. Bull. Environ. Contam. TOxicol. 1979, 21, 554-562. Spangoord, R. J.; Gibson, 6. W.; Keck, R. G.; Thomas, D.W. Environ. Sci. T6ChnOl. 1982, 1 6 , 229-232. Phillips, J. H.; Coraor, R. J.; Prescott, S. R . Anal. Chem. 1983, 55, 889-892. Walsh, J. T.; Chalk, R. C.; Merrit, C. Anal. Chem. 1973, 4 5 , 1215-1220. Fan, T. Y.; Ross, R.; Fine, D. H. Environ. Sci. Techno/. 1978, 12, 692-695. Anspach, G. L.; Jones, W. E.;Kitchens, J. F. "Evaluation of Solid Sorbents for Sampling and Analysis of Explosives from Water"; NTIS Publication AD-A117541,1982. Maskarinec, M. P.; Manning, D. L.; Harvey, R. W.; Griest, W. H.; Tomkins, B. A. J . Chromatogr. 1984, 302,51-63. Junk, G. A.; Richard, J. J.; Grieser, M. D.; Witiak, D.;Witiak, J. L.; Arguello, M. D.; Svec, H. J.; Fritz, J. S.;Calder, G. V. J . Chromatogr. 1974, 99, 745-762.
RECEIVEDfor review October 25, 1985. Accepted December 12,1985. This work was performed in the laboratories of the US. Department of Energy and supported under Contract W-7405-Eng-82. The work was supported by the Office of Health and Environmental Research, Office of Energy Research, and the Assistant Secretary for Fossil Energy, Division of Coal Utilization, through the Morgantown Energy Technology Center.
Characterization of Functional Group Complexation of a Poly(dit hiocar bamat e) Chelating Resin Zs. HorvBth' and Ramon M. Barnes* Department of Chemistry, GRC Towers, University of Massachusetts, Amherst, Massachusetts 01003-0035 Alteration of chelating efficiency of a poiy(dithiocarbamate) resln caused by thiocyanate contamination was evaluated for transition metals. The resin capacity for Cu, Co, and Fe( I I I ) was inversely related to the thiocyanate concentration. When synthesized by the reaction of carbon disulfide and a polyamine-poiyurea resin in pyridine instead of ammonium hydroxide, the resin capacity was maximized by elimination of thiocyanate.
Permanent address: L. Eotvos University, Institute for Inorganic and Analytical Chemistry, P.O. Box 123,H-1443 Budapest,Hungary.
The poly(dithi0carbamate) (PDTC) resin is effective as a chelate ion exchanger for separation and preconcentration in trace analyses with atomic spectroscopy (1,2). The resin is formed by the reaction of carbon disulfide with a polyamine-polyurea resin (3). Infrared spectra of the poly(dithiocarbamate) resin indicated the presence of both dithiocarbamate and isothiocyanate groups. However, direct analysis failed to establish the actual dithiocarbamate content. The existence of an inner salt structure as opposed to the expected ammonium salt was inferred from the ammonium concentration ( 4 ) . When the resin capacity was determined
0003-2700/86/0358-0725$01.50/0 0 1986 American Chemical Society
