Anal. Chem. 1989, 6 1 , 1298-1300
1298
various methodologies for a single soil sample. In summary, these results indicate that DEq/GFAA is a promising method for measuring soil solution extract complexa'ion capacities. Registry No. Cu, 7440-50-8;Cd, 7440-43-9. LITERATURE C I T E D (1) Bertha, E. L.: Chopin, G. R . J . Inorg. Nucl. Chem. 1979, 4 0 , 655-658. (2) Choppin, G. R.; Nash, K. L. J . Inorg. Nucl. Chem. 1981, 4 3 , 357-359. (3) Nash, K. L.; Choppin, G. R . J . Inorg. Nucl. Chem. 1980, 42. 1045- 1050. (4) Miller, M. H.; Ohlroaae, -- A. J. Soil Sci. SOC.Am. R o c . 1958. 20. 225-228. (5) Hodgson, J. F.; Geering, H. R.; Norvell. W. A. Soil Sci. SOC. Am. Proc. 1965, 28. 665-669. (6) Hodgson, J. F.; Lindsay, W. L.; Trierweiier. J. F. Soil Sci. SOC.Am. Proc. 1966, 3 0 , 723-726. (7) Geering. H. R.; Hodgson. J. F. Soil Sci. SOC.Am R o c . 1969, 3 3 , 54-59. (8) Crosser, M. L.; Allen, H. E. Soil Sci. 1977, i 2 3 , 176-181. (9) Fitch, A.; Stevenson. F. J. 1986 I n Interactions of Soil Minerals with Natural Organics and Microbes; Soil Science Society of America, Special Publication 17; Soil Science Society of America: Madison, WI, 1986; pp 29-58. (10) Lampert, J. K. Ph.D. Thesis, University of Wisconsin-Madison, 1982. (11) Minnich, M. M.; McBride. M. B. Soil Sci. SOC. Am J . 1987. 5 1 , 568-572. (12) Blaedel,W. J.; Christensen, E. L. Anal. Chem. 1967, 3 9 , 1262-1265. (13) Blaedel, W. J.; Haupert, T. J.; Evenson. M A. Anal. Chem. 1969, 4 1 , 583-590.
(14) Cox, J. A.: Kuo-Hsien, C. Anal. Chem. 1978. 5 0 , 601-602. (15) Cox, J. A.; Twardowski, 2. Anal. Chem. 1980, 5 2 , 1503-1505. (16) Cox, J. A.: Olbrych, E.; Brajter, K . Anal. Chem. 1981, 5 3 , 1309- 1311, (17) Cox, J. A.; Gajek, R.; Litwinski, G. R.; Carnahan. J.. Trochimczuk, W. Anal. Chem. 1982, 5 4 , 1153-1157. (18) Cox, J. A.; DiNunzio. J. E. Anal. Chem. 1977, 4 9 , 1272-1275. (19) Murrman, R . P.; Koutz, F. R . Special Report 171. U.S. Cold Regions Research & Engineering Lab, Hanover. NH, 1972; pp 48-74. (20) Cavaliaro, N.; McBride, M. 6 . Soil Sci. SOC. Am. J . 1980, 4 4 , 881-882. (21) Cavallaro, N.; McBride, M. 6 . Soil Sci. SOC. Am. J . 1980, 4 4 , 729-752. (22) Fitch. A.; Stevenson, F. J.; Chen, Y . Org. Geochem. 1986, 9 , 109- 116.
Alanah Fitch* Department of Chemistry Loyola University of Chicago 6525 North Sheridan Road Chicago, Illinois 60626 P h i l i p A. Helmke Department of Soil Science University of Wisconsin Madison, Wisconsin 53706 RECEIVED for review May 26, 1988. Resubmitted March 6, 1989. Accepted March 13, 1989. This work was supported by EPA Grant R8046140.
Influence of the Vessel Materials and Solvents on the Stability of Mixtures of Bis(2,4,6-trichlorophenyl) Oxalate and Hydrogen Peroxide for Peroxyoxalate Chemiluminescence Sir: The peroxyoxalate chemiluminescence (PO-CL) method has been widely acknowledged as an ultrasensitive detection technique in high-performance liquid chromatography (HPLC) ( I ) and flow injection analysis ( 2 ) . The greatest advantage of this technique is that extremely high sensitivity can be attained with a very simple detection device. For example, subfemtomole levels of Dns-amino acids were measured by HPLC with a PO-CL detector consisting of a simple flow cell placed in front of a photomultiplier tube (3). One problem in the application of this method to an actual detection system is that many factors can affect the intensity and/or the lifetime of PO-CL reactions and, consequently, make the response of the detector unstable. These factors also make it difficult to determine the optimum conditions for measurements of the highest sensitivity. Therefore, we have focused our efforts on elucidating the sources of disturbance. In a previous paper ( 4 ) ,we discussed the measuring conditions that influence the intensity and the lifetime of PO-CL reactions. In this communication, we report on two other factors that can cause deterioration in the stability of a mixture of oxalate and HzOz,the materials of the reservoir bottles and the solvents. In 1967, Rauhut et al. measured the deactivation rate of the mixture of bis(2,4-dinitrophenyl) oxalate (DNPO) and H2OZdissolved in dimethyl phthalate and determined the half-life to be ca. 70 min, but they did not mention what type of material they used as a reservoir for the solution (5). Sigvardson and Birks referred t o the decomposition of bis(2,4,6-trichlorophenyl) oxalate (TCPO) in their 1983 paper (6). They found that TCPO in acetone stored in an amber soda-lime glass bottle decomposed by half in 6 h, but was quite stable in a borosilicate glass bottle. 0003-2700/89/0361-1298$01.50/0
In this work, we measured the dependence of the decomposition rates of TCPO and the deactivation rates of TCPO/HZO2mixtures on the reservoir materials and the solvents. We observed the highest rate of deactivation of a TCPO/H202 mixture in acetone stored in soda-lime glass bottles. I t was stable in a Pyrex or sodium borosilicate glass bottle or a Teflon vessel when acetonitrile was used as a solvent. The cleaning procedure of the reservoirs also affected the deactivation rates of the mixture. From the results of these experiments, it was suspected that metal oxides contained in soda-lime glass caused the deactivation, and their influence was also measured. In every combination of the reservoir material and the solvent, the TCPO solutions were quite stable. EXPERIMENTAL S E C T I O N The materials of the reservoir bottles tested were clear soda-lime glass, amber soda-lime glass, Pyrex borosilicate glass, sodium borosilicate glass, Teflon, and stainless steel. Solvent effects were measured in acetonitrile, acetone, or ethyl acetate. A bottle of each material was purchased from American Scientific Products, McGaw Park, IL. All the chemicals were the same as those in the previous paper ( 4 ) or of reagent grade. Cleaning Procedure of the Vessels. Two procedures were tested. (1) The vessels were soaked in a solution of detergent (MICRO, International Products Corp., diluted according to the manufacturer's instructions) for at least 1 day and rinsed with water purified by the Barnstead NANOpure I1 system (Sybron Barnstead, Boston, MA). (2) After procedure 1,the vessels were soaked in 1M NaOH and 1 M HNOBsolutions in turn for 1 day each and rinsed with purified water. Measurements of the Decomposition of TCPO. The same HPLC system as that in the previous report ( 4 ) was used. The compositions of all the solutions including the sample were also C 1989 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 61, NO. 11, JUNE 1, 1989
Table I. Residual Activities of PO-CL3 h after Mixing TCPO and H202"
reservoir clear soda-lime amber soda-lime Pyrex borosilicate sodium borosilicate Teflon stainless steel
residual activities of the mixture in the following solvents as percentage of original activity acetonitrile acetone ethyl acetate 75 (96) 67 (90) 100 (100) 100 (100) 96b (100) 88 (92)
38 (50) 30 (48) 55 (56) 54 (56) 55 (54) 50 (53)
60 (66) 57 (67) 72 (72) 70 (71) 70 (73) 65 (70)
OCleaning procedure 1 was applied to all the vessels. Residual activities in vessels washed by procedure 2 are shown in parentheses as a percentage of initial activity. *The average of the rates in three vessels out of five where deactivation was observed. No deactivation was observed in the other two. the same. A Pyrex borosilicate glass bottle was used to dissolve TCPO in each solvent because TCPO was found in advance to be stable in any solvent in this bottle. The solution was then transferred into a bottle of each material tested, and the decomposition rates of TCPO were determined by measuring a sample peak height every 30 min. Measurements of the Deactivation of the TCPO/H2OZ Mixture. An HPLC system with two pumps was constructed by eliminating a pump, a mixer, and solution 3 from the system mentioned above. The TCPO and H202solutions were prepared separately in Pyrex bottles. Their concentrations were 1.0 and 10 mM, respectively. For the testa of the influence of acetonitrile and acetone, TCPO and H202were dissolved in each solvent. For the ethyl acetate measurement, TCPO was dissolved in ethyl acetate, but H202was dissolved in acetonitrile because ethyl acetate is immiscible with H 2 0 in the mobile phase without the addition of acetonitrile. The same amount of TCPO and HzOz solutions was mixed in the vessel tested. For the influence of concentration, the measured ranges of TCPO and H20zconcentrations were 0.3-2.0 and 3.0-20.0 mM, respectively. Each TCPO solution was mixed with 10 mM HzOz solution, and each HzOz solution with 1 mM TCPO solution. Acetonitrile and Pyrex glass bottles were used for these measurements. The procedure for determination of the deactivation rates of the mixtures was also the same as above. The flow rate of the mixture solution was 1 mL/min. Measurements of the Effects of the Metal Oxides. A 100-mg sample of either CaO or MgO was added to 500 mL of the TCPO/H202/CH3CNmixture in a Pyrex glass bottle washed as in procedure 2, and the solution was stirred with a micro stirring bar (8 mm X 1mm). A suction filter was suspended in the middle of the reservoir bottle so as not to aspirate the metal oxide powder. The deactivation of the mixtures was observed in the same manner as above. All measurementswere done at room temperature ( - 2 2 "C).
RESULTS AND DISCUSSION Decomposition of TCPO. TCPO was stable in every kind of solvent and vessel for a t least 6 h. We repeated the measurements three times in acetone stored in an amber soda-lime glass bottle, but no deactivation was observed. This result is contradictory to that of Sigvardson e t al. (6). This may be due to differences in the composition of the glasses. Deactivation of the Mixture. The residual activities of the mixture of TCPO and HzOZ3 h after mixing them in each solvent and each vessel are shown in Table I. The vessels were cleaned by procedure 1. The activities after 3 h when cleaning procedure 2 was applied are shown in parentheses. Each type of vessel and solvent was examined three to five times. The reproducibility of these measurements was within *5% of the value reported. Among the solvents tested, acetonitrile was the best; no deactivation was observed for a t least 6 h in this solvent in
1299
a Pyrex borosilicate or sodium borosilicate glass bottle. The measurements were repeated five times to confirm that there was no deactivation. However, the mixture deactivated a t a rather high rate even in acetonitrile when stored in a soda-lime glass bottle. With the other solvents, high rates of deactivation were observed even in borosilicate glass, and the worst combination of solvent and reservoir for maintaining the activity was acetone and amber soda-lime glass, where 70% of the activity was lost after 3 h. In a test of concentration dependence, no deactivation was observed in the concentration range of 0.5-2.0 mM TCPO or 3.0-15 mM HzOz. However, a slight decrease of activity (-5%) was measured a t 0.3 mM TCPO or 20 mM Hz02. I t was confirmed in every case by comparing each of the data with one obtained in a dark room that no photolysis of the mixture occurred. The effect of Teflon was measured five times in different Teflon vessels with CH3CN used as a solvent. Slow deactivation was observed in three vessels and no deactivation in two vessels when cleaning procedure 1 was applied. The average of these three deactivation rates was N 4 % . When procedure 2 was applied, no deactivation was observed in any vessels. This may be due to differences in the efficiency of wash-up of the contaminant adsorbed on the bottles. Deactivation (12% on average) was observed in all five stainless steel reservoirs washed with procedure I, and the rates were decreased slightly by using procedure 2. This also may be attributed to the different cleaning efficiency or to metal impurities that cause the mixture to deactivate and dissolve in the acid or base solution. Larger deactivation rates were observed in soda-lime glass bottles than in borosilicate glass, but a drastic decrease of these rates was attained by applying procedure 2. These facts cannot be accounted for by the different cleaning efficiency of adsorbed contaminant alone. One of the strongest possibilities is the differences in the composition of the materials. Soda-lime glass contains certain metal oxides that borosilicate glass does not (7). It is quite possible that these metal oxides cause deactivation of the mixture and, when cleaning procedure 2 was employed, these metal oxides were leached into the acid and alkali (8). T o provide a perspective on this possibility, the deactivation of the TCPO/H2O2mixture by metal oxides was tested. Deactivation of the Mixture by Metal Oxides. The differences in the composition of soda-lime, sodium borosilicate, and Pyrex borosilicate glasses are the amounts of Bz03, NazO, MgO, and CaO present (7). Among these oxides, B203 was eliminated from consideration, because it is not present in soda-lime glass. The influence of NazO was not measured because of its extreme reactivity. Addition of 100 mg of either CaO or MgO to 500 mL of a TCPO/H2OZmixture (in CH3CN stored in a Pyrex bottle) caused deactivations of 30% and 33%, respectively, over a 3-h period; no deactivation was observed when the same amounts of these metal oxides were added to either TCPO or H z 0 2solution alone. These results strongly suggest the possibility that metal oxides in soda-lime glass deactivate the mixture.
CONCLUSION The conclusions derived from this study are as follows: (1) Almost any vessel and solvent can be used to store TCPO and HzOzif they are not mixed. (2) When the solutions are mixed, the vessel material and solvent affect the deactivation rate of the mixture. The mixtures are stable for a t least 6 h in acetonitrile when stored in a borosilicate glass bottle. No deactivation was observed in Teflon when cleaning procedure 2 was applied. Other vessel materials and solvents cause deactivation t o a greater or lesser degree. (3) Photolysis of
1300
Anal. Chem. 1989, 67, 1300-1302
the mixtures does not occur under normal conditions. (4) The materials that cause the mixtures to deactivate are not only those adsorbed on the bottles, but the constituents of the bottles themselves. When one is using a new vessel, its influence on decomposition rates must be checked before use.
LITERATURE CITED (1) Imai, K.; Weinberger, R. TrAC, Trends Anal. Chem. (Pers, Ed.) 1985,
4, 170-175. (2) Honda, K.; Sekino, J.; Imai, K. Anal. Chem. 1983, 55,940-943. (3) Miyaguchi, K.; Honda. K.; Imai, K. J. Chromafogr. 1984, 316, 501-505. (4) Hanaoka, N.; Givens, R. S.; Schowen, R. L.; Kuwana. T. Anal. Chem. 1988, 60, 2193-2197. (5) Rauhut, M. M.; Bollyky, L. J.; Roberts, B. G.; Loy, M.; Whitman, R . H.;
Iannotta, A. V.: Semsel, A. M.; Clarke, R. A. J , Am. Chem. SOC. 1967,89, 6515-6522. (6) Sigvardson. K. W.; Birks, J. W. Anal. Chem. 1983, 55,432-435. (7) Bansal, N. P.; Doremus, R. H. Handbook of Glass Properties; Academic Press: New York, 1986; Table 3.1. (8) McLellan, G. W.; Shand, E. B. Glass Engineering Handbook; McGrawHill: New York, 1984; Chapter 3.
Nobuaki Hanaoka Shirnadzu-Kansas Research Laboratory 2095 Constant Avenue Kansas 66046
RECEIVED for review November 14, 1988. Accepted March 10, 1989.
TECHNICAL NOTES Fractionation of Polychlorinated Biphenyls, Polychlorinated Dibenzo-p-dioxins, and Polychlorinated Dibenzofurans on Porous Graphitic Carbon’ Colin S. Creaser* and Ameera Al-Haddad School of Chemical Sciences, University of E a s t Anglia, Norwich NR4 7TJ. U.K Activated carbon (1,2) and Carbopack (3)have been widely used for the separation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from polychlorinated biphenyls (PCBs) and other halogenated aromatic compounds. Fractionation of halogenated aromatic compounds on these two types of carbon requires the sample t o be eluted with complex solvent mixtures. Environmental and biological samples cleaned by such carbons typically require elution with cyclohexane/dichloromethane t o elute ortho-chlorine-substitutedPCBs and halogenated pesticides. Non-ortho-chlorine-containing PCBs are then eluted with benzene in ethyl acetate and finally the strongly retained PCDDs and PCDFs are recovered by back flushing the column with toluene. Although many environmental and biological samples have been successfully cleaned u p by activated and Carbopack carbons, the cleanup procedure is lengthy and the inhomogeneity of the active sites on activated carbon results in broad and tailing solute elution profiles. Porous graphitic carbon (PGC) is a novel chromatographic material ( 4 ) consisting of porous carbon spheres whose size can, in principle, be chosen from a few micrometers to a few hundred micrometers. It has a surface area of about 150 m2/g, a mean pore volume of 2.0 cm3/g, and a particle porosity of 70%. PGC is the only carbon that can be used as a packing material for HPLC, because of its strength and ability to withstand the high-pressure gradients used in HPLC and in HPLC slurry packing procedures. The efficiency of PGC is comparable t o that obtained with bonded phase silica gel for many compounds such as methylbenzenes, phenols, ethers, monosubstituted benzenes, amines, and acids ( 4 ) . In this paper, we report the fractionation of chlorinated aromatic compounds including PCBs, PCDFs, PCDDs, and pesticides using porous graphitic carbon. A back-flushing procedure has been used for the cleanup of soil samples for the determination of PCDDs and PCDFs.
EXPERIMENTAL SECTION Porous Graphitic Carbon HPLC Column. A 4.7 X 50 mm
This paper is dedicated to the memory of Dr. Roger Beale Homer (1940-1988). 0003-2700/89/0361-1300$01.50/0
porous graphitic carbon column (Hypercarb, Shandon Scientific, Ltd., Cheshire WA7 lPR, England, 7-pm particle size) was used for the fractionation of halogenated aromatic compounds and for the cleanup of soil extracts for the determination of PCDDs and PCDFs. The HPLC equipment consisted of a Waters Model 501 solvent delivery system, Waters Model 455 UV variable wavelength detector, and a Rheodyne Model 7125 syringe loading sample injector with a 100- or 20-pL sample loop. The PGC column was fitted with a 7040 Rheodyne switching valve to enable back flushing of the column. Pesticide grade (BDH) hexane was used as the eluting solvent. The flow rate was 5 mL/min with a back pressure of 1500-2000 psi. The porous graphitic carbon column was conditioned by eluting with about 100 mL of hexane. A mixture of Aroclors (1254 and 1260) in hexane was spiked with a range of PCDDs, PCDFs, pesticides (Figure l),and nonortho PCBs a t 1 yg/g prior to chromatography on PGC. The pesticides tested were parathion, malathion, heptachlor, aldrin, dieldrin, heptaclor epoxide, @-benzenehexachloride (@-BHC), a-benzene hexachloride ((Y BHC), lindane, l,l,l-trichloro-2,2bis(4-chloropheny1)ethane (p,p’-DDT). l,l,l-trichloro-2-(2chlorophenyl)-2-(4-chlorophenyl)ethane (o,p’-DDT), 1,l-dichloro-2,2-bis(4-chlorophenyl)ethylene(p,p’-DDE), 1,l-dichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethylene (o,p’-DDE), 1,l-dichloro-2,2-bis(4-chlorophenyl)ethane ( p , p’-DDD), and 1,ldichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane (o,p’-DDD). The column was eluted first with 100 mL of hexane (PCBs and pesticides fraction), then back flushed with a further 200 mL of the same solvent (PCDDs and PCDFs fraction). The PCBs and pesticides were detected by a UV detection at 245 nm, while the PCDDs and PCDFs were determined by collection of fractions and analysis by gas chromatography-electron capture detection (GC-ECD). PCDD and PCDF recoveries for the PGC cleanup were determined for a selected range of isomers (100 ng each), by comparing the ECD response before and after the PGC fractionation. Commercial PCB mixtures (Aroclor 1242,1254, and 1260)were chromatographed using 8020 (v/v) acetonitrile/water as an eluent, at a flow rate of 1 mL/min and a pressure of ca. 2000 psi. Collection and Cleanup of Soils. Soil samples were collected to a depth of 5 cm, air-dried, and sieved through a 2-mm mesh. The samples (250 g) were spiked with [13Clz]2,3,7,8-TCDDand [13C12]1,2,3,4,6,7,8-H7CDDand then Soxhlet extracted with hexane/acetone (41:59) for 8 h ( 5 ) . The extracted organic phase was applied to a multilayer column (420 mm X 25 mm i.d.1 packed 0 1989 American Chemical Society
