Anal. Chem. 1988, 60,696-698 Tong, W. G.; Shaw, R. W. Appl. Spectrosc. 1988, 40, 494. Nippoldt, M. A.; Green, R. B. Appl. Opt. 1981, 2 0 , 3206. Keller, R. A.; Engleman, R., Jr.; Zalewski, E. F. J. Opt. SOC. Am. 1979, 6 9 , 738. Travis, J. C.; Turk, G. C.; Green, R. B. Anal. Chem. 1982, 5 4 , 1006A. Green, R. B.; Havrilla, G. J.: Trask. T. 0.Appl. Spectrosc. 1980, 3 4 , 561. Goldsmith, J. E. M.; Lawler, J. E. Contemp. Phys. 1981, 22, 235. King, D. S . ; Schenck. P. K. Laser Focus Fiberopt. Commun. 1982, March, 50. Penning, F. M. Physica (The Hague) 1928, 8 , 137. Smyth. K. C.; Schenck, P. K. Chem. Phys. Lett. 1978, 5 5 , 466. Smyth. K. C.; Keller, R. A.; Crim, F. F. Chem. Phys. Lett 1978, 5 5 , 473. Smyth, K. C.; Bentz, B. L.; Bruhn, C. G.;Harrison, W. W. J. Am. Chem. SOC. 1979, 101, 797.
(28) Zaiewski, E. F.; Keller, R. A.; Engleman, R., Jr. J. Chem. Phys. 1979, 7 0 , 1015. (29) Eckstein, E. W.; Coburn, J. W.; Kay, E. I n t . J. Mass Spectrom. Ion Phys. 1975, 17, 129. (30) Penning, F. M. 2.Phys. 1929, 57, 723. (31) Loving, T. J.; Harrison, W. W. Anal. Chem. 1983, 5 4 , 1526. (32) Keefe, R. B. Ph.D. Dissertation, University of Virginia, Charlottesville, VA. 1983. (33) Velazco, J. C.; Kolts. J. H.; Setser, J. W. J. Chem. Phys. 1978, 6 9 , 4357.
RECEIVED for review August 5, 1987. Accepted December 7, 1987. Support for this research by the Department of Energy, Division of Basic Energy Sciences, is gratefully acknowledged.
Determination of Tributyltin in Tissues and Sediments by Graphite Furnace Atomic Absorption Spectrometry Mark D. Stephenson* and Donald R. Smith
Moss Landing Marine Laboratories, California Department of Fish and Game, Moss Landing, California 95039
A method for the determlnation of trlbutyitin (TBT) In tissue and sedbnents has been developed for environmental Sampies. The technique Involves extraction wlth methylene chlorlde and Isolation of TBT from mono- and dlbutyltln wlth a sodlum hydroxide wash. The TBT Is then back extracted and converted to elemental Sn wlth nltrlc acid. Analysis Is by Zeeman graphite furnace atomic absorption spectrophotometry. Recoverles of spiked samples were between 99 % and 111% for mussel and fish tlssues and 72% and 99% for various sediments. The llmlt of quantlflcatlon was 0.0025 pg/g for tissue (on a wet weight basis). This technlque was developed in response to our need to process large numbers of environmental samples with a mlnlmum time investment.
Tributyltin (TBT) has recently come under the scrutiny of environmental scientists because of its increased use in antifouling boat bottom paint and its extreme toxicity to nontarget organisms. Consequently, determining levels of TBT in seawater, sediment, and biological samples is necessary in order to assess if environmental contamination is occurring. Analytical techniques for determining T B T in seawater are well established (see Blair et al. ( I ) ) , but for tissue and sediment the techniques are less well developed. Stephenson et al. (2) found that laboratories agreed within a factor of 2 or 3 in an intercomparison of seven laboratories. Several studies have reported analytical techniques for determining TBT concentrations in tissues. Tsuda et al. (3) extracted TBT with HC1 and ethyl acetate-hexane with a subsequent hydrogenation with sodium borohydride and analyzed with electron capture detection gas chromatography (ECGC). Dooley (4) compared extraction solvents (ethyl acetate and chloroform/methanol/water) followed by derivatization with pentylmagnesium bromide (PeMgBr) and analyzed with gas chromatography/mass spectrometry (GCMS). Maguire et al. (5) extracted T B T with hexane and HCl followed by derivatization with PeMgBr and analyzed with gas chromatography with atomic absorption spectrometry (AA) as a detector. Short and Thrower (6) extracted tissue with hexane only and analyzed with graphite furnace atomic absorption spectrometry (GFAA). Bryan et al. (7) extracted TBT with hexane and HCl with a subsequent separation of TBT from other alkyltins with
1N sodium hydroxide solution and analyzed with GFAA. The reported percent TBT recovered in these studies varied widely: >88% (3),31% to 85% ( 4 ) ,94% ( 5 ) ,and 55% (6). There are also several reported analytical techniques for determining T B T in sediment. Tsuda et al. (3) used a HCl and hexane extraction and analyzed with ECGC. Randall et ai. (8)used a 2.5 M calcium chloride and 2.5 M HC1 extraction and analyzed with hydride generation atomic absorption spectrometry (HGAA). Muller (9) used a HC1 and diethyl ether extraction followed by methylation with methylmagnesium chloride and analyzed with flame photometric gas chromatography (FPGC) and GC/MS. Hattori et al. (10) used methanolic hydrochloric acid and benzene extraction and analyzed with ECGC. Valkirs et al. (11)mixed sediment with seawater and analyzed with HGAA. Maguire et al. (5) used HC1, tropolone, and benzene to extract, followed by PeMgBr derivatization and analysis with FPGC. Waldock and Miller (12) used HBr, methylene chloride, and tropolone to extract with a MeMgBr derivatization and GC/MS analysis or used a toluene HC1 extraction followed by a sodium hydroxide wash and GFAA analysis. Percent recoveries of T B T in these studies were 98% (3), 97% (81, 93% (IO),and 100% (5). Recoveries were greater than 70% and 95% for GC/MS and GFAA analysis, respectively, by Waldock and Miller (12). Many of these methods are very time-consuming and require complex chemical reactions (Grignard derivitization) and necessitate the use of expensive instrumentation (i.e. GC/MS). The purpose of this study is to report a method for determining concentrations of TBT in sediment and tissue that is rapid, inexpensive, and quantitative for TBT.
EXPERIMENTAL SECTION Reagents. Reagent grade methylene chloride, hexane, sodium hydroxide, and hydrochloric acid and Ultrex grade nitric acid were purchased from Van Waters and Rogers. Bis(tributy1tin) oxide, dibutyltin dichloride, and n-butyltin trichloride were obtained from Alfa Ventron (Danvers, MA). Apparatus. The extraction apparatus is a 30 cm diameter vertical rotator capable of accommodating 12 50-mL centrifuge tubes. The samples were analyzed on a Perkin-Elmer 5000 atomic absorption spectrophotometer equipped with a Model 600 HGA Zeeman graphite furnace and AS60 autosampler. Procedure. Five to ten grams of wet tissue or 0.3 to 0.4 g of freeze-dried tissue was placed in a 50-mL centrifuge tube fitted with a Teflon-lined cap. Samples with or without spikes were
0003-2700/88/0360-0696$01.50/0 (C 1988 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 60,
Table I. Zeeman HGA 500 Graphite Furnace Parameters Used for Analysis of Tributyltin in Mussel, Oyster, Fish, and Sediment Samples recorder, step temp, “C ramp, s hold, s read, s 1 2 3 4
5 6
130 800 20 2100 2650 20
5
30
10
20
1 0 1 2
4
5 2
8
0
s
-3 0
int gas, mL/min 300 300 0 0 300 300
then mixed on a vortex mixer for 10 s. Mussel tissue and freeze-dried oyster tissue were not diluted before homogenation. Fish tissue was diluted 50/50 with 18-MQ deionized water to facilitate extraction and mixing with spikes. Ten milliliters of 6 N HC1 was added and the sample was mixed on a vortex mixer for 10 s. Twenty grams of methylene chloride was added and the sample was placed on the rotator set at 6 rpm for 12-16 h. The sample was subsequently centrifuged for 5 min at 403 g. Ten to eighteen milliliters of methylene chloride was pipetted into a 125-mL Erlenmeyer flask and evaporated to dryness by placing in a 30 “C water bath and blowing air into the flask through an air manifold. The residue was redissolved in 4 mL of hexane. Three milliliters of this residue-hexane mixture was placed in a 13 X 100 mm glass culture tube fitted with a Teflon-lined cap. Three milliliters of 3% NaOH was added to the culture tube and the tube was mixed on a vortex mixer for 1 min. The tubes were centrifuged for 5 min at 403g. Two milliliters of hexane was placed in an acidcleaned 30-mL glass beaker and evaporated down under a stream of air. One milliliter of concentrated Ultrex nitric acid was added and the beaker was heated to digest the residue. The acid was evaporated and 1 mL of 3 N nitric acid was added and subsequently poured into autosampler cups for analysis. For Zeeman analysis the 286.3-nm Sn wavelength was used. Pyrolytically coated graphite tubes fitted with L’vov platforms were employed for all analyses. Ten microliters of sample was coinjected with 10 p L of matrix modifier (100 pg of PO4 plus 10 pg of Mg(NO& per injection). The Zeeman HGA 500 furnace parameters are given in Table I. Peak area integration was used for signal quantification for an interval of 5 s during vaporization. Argon was used as the internal purge gas. The analysis and instrument parameters listed here are collectively referred to as the stabilized temperature platform furnace (STPF) (13). The computed characteristic mass of prepared standard solutions was routinely compared with the expected value (13) and was always within 10%.
RESULTS AND DISCUSSION Recoveries of TBT were between 99% and 111% for tissue and 72% and 99% for sediments (Table 11). The coefficients of variation ranged from 8.8% to 24% in these samples (Table 111). These recoveries and coefficients of variation are within the range of previously reported methods (ref 3-12). The sample detection limit (2 times the standard deviation of the sample blank) is 0.0025 pg of TBT/g. This is adequate for most environmental samples. The NaOH wash as used by others (2, 7) is reported to exclude mono- and dibutyltins. Samples spiked with these compounds yielded no detectable concentrations, confirming their selective removal with the NaOH wash. The digestion of organometallic compounds dissolved in organic solvent with acid has been used successfully for determinations of organically bound elements (14). This technique is advantageous since injection of organic matrices into graphite furnaces has been reported to be complicated by severe matrix interferences and in this study matrix modification techniques could not be used successfully when the sample was in an organic matrix. The results from samples analyzed by using matrix modification were compared to results from method of additions and were found to be slightly
NO. 7, APRIL
1, 1988
697
Table 11. Percent Recovery of Tributyltin in Spiked Tissue and Sediment Samples mass of spike added, pg of sample mussel tissue shelter I, channel marker
oyster tissue ICES standard fish tissue salmon tissue sediments outer harbor inner harbor
TBT
% recovery
2.5 7.5
100 f 1.1
7.5
111 f 1.1
2.5
106 f 12.6
2.5
72 f 9.8 82 f 6.6 99 f 4.1
2.5 7.5
99 f 8.0
Table 111. Coefficients of Variation of Tributyltin in Tissue and Sediment Samples Based on Individual Analyses of Five Replicate Samplesa tissue or sediment
mussel tissue outer harbor oyster tissue sediments inner harbor outer harbor
concn
YC coeff of variation
0.989
8.8
5.900*
24.0
0.478
8.9 24.0
0.424
OConcentrations reported as pg of TBT/g wet weight. *Concentration based on dry weight basis. lower (14% f 4%, mean f standard deviation). This is a small difference when compared to errors involved with analyzing samples dissolved in organic solvents by method of additions. This demonstrates that the S T P F technique (matrix modifier in combination with pyrolytically coated graphite tubes fitted with L’vov platforms, Zeeman background correction, and rapid temperature ramp during atomization) (13) produces results similar to the method of additions. This is advantageous because of the substantial savings in instrument time required for analysis with the method of additions. The results from this technique have been compared to other techniques (2). The reported values from this technique compared favorably with those obtained by using Grignard derivatization. In order to determine if the detection limit of this technique was low enough to successfully conduct environmental studies, we analyzed two mussel samples-one from a well-flushed harbor where there were few vessels (Humboldt Bay, CA) and one from a harbor with over 7000 vessels (Marina del Rey, CA). Since T B T has been shown to occur in substantially elevated concentrations in harbors hosting large numbers of vessels, we intended these two areas to represent an extreme range in environmental levels of TBT. The Humboldt Bay sample (0.2 pg of TBT/g dry weight) exhibited T B T levels that were more than 85 times lower than the Marina del Rey sample (17.1 of pg TBT/g dry weight). This demonstrates the usefulness of this analytical technique in detecting current levels of T B T in environmental samples. The analytical procedure described here has several advantages over other existing techniques. Many of the techniques reported to date are very tedious and require a large time investment. Those involving derivitization by Grignard reactions are especially so. In the current procedure there is no need to derivatize since T B T can be analyzed on GFAA after isolation with a NaOH wash. Also, there is no need to inject solvents into the graphite furnace since the T B T is digested and oxidized to elemental tin with HN03. And there
698
Anal. Chem. 1988, 60,698-702
is no need to employ method of additions for analysis since the use of STPF techniques removes interfering compounds in the sample matrix thus saving analytical instrument time. These advantages make this technique very preferable for determining TBT in environmental samples where rapid analysis is desired. For example, one person can analyze 100 samples per week (including preparing the glass- and plasticware) by using this technique. This is in contrast to one person using Grignard derivatization techniques and analyzing 10-20 samples per week (Jeff Short, personal communication).
ACKNOWLEDGMENT The authors thank Carol Dooley for helping in the design of the initial analytical protocols and Gary Ichikawa and Jon Goetzl for carrying out much of the experimental work. Registry No. TBT, 36643-28-4. LITERATURE CITED (1) Blair, W. R.; Olson, G. J.; Brinckman, F. E.; Paule, R. C.; Becker, D. A. "An International Butyltin Measurement Methods Intercomparison: Sample Preparation and Results of Analysis". National Bureau of Standards Report NBSIR-3321, 1986; 57 pp.
(2) Stephenson, M. D.; Smith, D. R.; Hall, L. W., Jr.; Johnson, W. E.; Michel, P.; Short, J.: Waldock, M.; Huggett, R. J.; Seligman, P.; Kola, S. OCenaS 87 Symposium. Vol. 4, Organotin Symposium, Halifax, Nova Scotia, 1987. (3) Tsuda, T.; Nakanishi, H.; Morita, T.; Takebayashi, J. J. Assoc. Off. Anal. Chem. 1986, 69, 981-984. (4) Dooley, C. A. "Butyltin Compounds in Tissues"; Naval Oceans System Technical Report 1089, 1986; 21 pp. (5) Maguire, R. J.; Tkacz, R. J.; Chau, Y. K.; Bengart, G. A,; Wong, P. T. S. Chemosphere 1986, 3, 253-274. (6) Short, J. W.; Thrower, F. P. Mar. Pollut. Bull. 1986, 17, 542-545. (7) Bryan, G. W.; Gibbs, P. E.; Hummerstone, L. G.; Burt, G. R. J. Mar. Biol. Assoc. U . K . 1986, 66, 611-640. (8) Randall, L.; Han. J. S.;Weber, J. H. Environ. Techno/. Lett. 1966, 7 ,
571-576. (9) Muelier, M. D. Fresenius' Z.Anal. Chem. 1984, 3 1 7 , 32-36.
(IO) Hattori, Y.; Kobayashi, A.; Takemoto, S.; Takami. K.; Kuge, Y.; Sugi-
mae, A.; Nakamoto, M. J. Chromatogr. 1984, 3 1 5 , 341-349. (11) Valkirs, A. 0.; Seligman, P. F.; Vafa, G.; Stang, P. M.; Homer, V.; Lieberman, S. H. Naval Ocean Systems Center Technical Report No. 1037, 1985. (12) Waldock, M. J.; Miller, D. ICES Paper CM. 1983. E:12 (mimeograph). International Council for the Exploration of the Sea, Copenhagen. (13) Slavin, W.; Carnrick, G. R.; Manning, D. C.; Pruszkowska, E. At. Spectrosc. 1983. 4(3), 69-86. (14) Magnusson, B.; Westerlund, S. Anal. Chim. Acta 1981, 137, 63-72.
RECEIVED for review June 8,1987. Accepted December 7,1987.
In Situ Fluorescence Detection of Polycyclic Aromatic Hydrocarbons following Preconcentration on Alkylated Silica Adsorbents J. W. Cam' and J. M. Harris* Department of Chemistry, University of Utah, Salt Lake City, U t a h 84112
I n situ detection of analytes sorbed to alkylated silica is proposed as a sensitive and quantitative method for the determination of trace concentration levels of PAH compounds in aqueous solution. The concept is evaluated by using pyrene as a model analyte preconcentrated from methanoiwater solutions onto C18 chromatographic silica, a material that is compatible with in Snu fluorescence detection of sorbed species. Adjustment of solution phase cornposition is shown to control the preconcentratlon factor by 3 orders of magnitude, predictable by chromatographic retention results. Sensitivity increases for fluorescence detection of pyrene within practical limits were as large as 245, leading to a 200-fold reduction in detectable solution concentrations to levels as low as 0.17 parts per trllilon. I n situ fluorescence detection has also been found to be suitable for determining the retention of solutes in regions of solvent composition where chromatographk measurements would prove difficuit.
Sample preconcentration as a means of decreasing concentration detection limits is a well-established technique in the trace analysis of both organic and inorganic substances (1-3). Traditional methods of sample preconcentration involve liquid-liquid extraction, solvent evaporation, or both, followed by separation and analysis (2). Drawbacks to this approach include loss of volatile components during evaporation (3)and Present address: Heights, NY 10596.
IBM Watson Regearch Center, Yorktown
incomplete extraction of trace materials from solution. More recently, trace materials have been removed from gas (4) or liquid matrices (5-8) by surface adsorption onto a variety of solid supports including cellulose (9),carbon (4, 10-13), fiberglass (14), zeolites (15), membrane filters (16),Chelex 100 (17),XAD (18-20), and Tenex (21) resins and glass or silica gel derivatized with C18 (5,8,22) and other functional groups (17,23,24). Analytes have been adsorbed to a surface either by direct means (4,6, 7,15-19) or in conjunction with chelating agents (5,8, 22, 25). In other applications, sorption occurs through chemically specific interactions with chelating agents immobilized on the surface of a glass support (9, 17, 20,23, 24). For the most part, trace materials preconcentrated through surface sorption are stripped from the support material before analysis. The extracted sample, often containing a number of components, is chromatographically resolved before detection. In situ detection of preconcentrated analytes on the surface of an adsorbent has been demonstrated by using electron spectroscopy and X-ray fluorescence (13,24). Advantages of in situ detection of preconcentrated analyte include the reduction in losses that might occur during sample stripping and the simplification of the analytical method by eliminating a step in the procedure. In addition, removal of analyte from the adsorbent by a solvent washing step will increase the volume in which the sample is dispersed, reversing to some degree the benefits of preconcentration. In this work, the concept of in situ detection of preconcentrated analytes is extended to fluorescence spectroscopy; trace levels of a model PAH compound (pyrene) are preconcentrated from methanol-water solutions by sorption onto a
0Y~5-~/00/88/0~60-0698$01.50/0 62 1988 American Chemical Society
