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134 HAMILTON ET AL. IlaziorMck Bar N t [;]11 ANI! Utah '. I 4 IIIILII I , IICIl.DIIITIIllI FIG. 1. Map of Green River providing location of sampling sites for light trapping of larval razorback sucker. preserved in ethanol, and held in 20-ml glass vials at room temperature. Determination of Selenium in Larvae Selenium concentrations were measured in 10 razorback sucker larvae from each of the five sites on the Green River. Selenium was determined by neutron activation analysis of composites of the larvae. Some analyses were accomplished on one larva and other analyses on composites of 2 to 10 larvae. Larvae samples were prepared and analyzed at the Environmental and Contaminants Research Center (ECRC) and at the University of Missouri Research Reactor (MURR), both in Columbia, Missouri. Neutron activation was used for the analysis of larvae because of the extremely small sample mass. All sample preparation prior (0 neutron activation analysis is described in Waddell and May (1995). Samples were transported to MURR for the determination of the radio nuclide Se --m (McKown and Morris, 1978). The method is briefly de- scribed in Waddell and May (1995) and the only exception was that samples and standards were successively placed in a shuttle rabbit and irradiated for 5 s at a thermal neutron flux of about 8 x 1014 n x cm - Z x sec - 1, instead of 1 x 1014 n x cm - 2 X sec -1. Selenium standards and quality control samples were analyzed in the same manner. National Insti- tute of Standards and Technology (NIST) 1577 (bovine liver) standard reference material was analyzed by M URR as quality control checks on accuracy and precision. Sel- enium values in micrograms were obtained by direct com- parison of peak areas obtained for the samples to the average peak areas obtained for a set of standards. Samples of the ethanol used to preserve larvae during storage and a composite sample of larval razorback suckers were analyzed for 61 elements by inductively coupled plasma-mass spectrometry (ICP-MS). Seven vials contain- ing ethanol only (no larvae) were combined, referred to as clean ethanol, and analyzed as one sample. Ethanol from the 26 vials that originally contained larvae was combined, referred to as dirty ethanol, and analyzed as one sample. One composite of 279 razorback suckers was formed from larvae collected between May 19 and June 6 at Stewart Lake Drain. Guts and otoliths of these larvae were removed and retained at the Larval Fish Laboratory for other deter- minations. The larval composite was placed in a 20-ml scintillation vial and lyophilized to a constant dry weight. The clean and dirty ethanol samples were each placed into a 250-ml Zymark Turbo Yap I12 tube and the samples evaporated with a Turbo Vap water bath at 50T and nitrogen vortexing to approximately a I-ml endpoint. Each ethanol liquid was transferred to a Questron bomb vessel (Teflon) by rinsing with 5 ml concentrated nitric acid. The lyophilized fish larvae composite sample (0.091 g) was also transferred to a Questron bomb to which 5 ml concentrated nitric acid was added. The bombs were sealed and placed in a CEM microwave oven which proceeded through a six- step program to acid-digest the samples. After the bombs were cooled for 2 h in a freezer, the resulting digestate liquid was transferred to a polyethylene bottle and diluted to 100 m!. The diluted digestate matrix was 5% nitric acid. Quality control samples carried through the procedure in- cluded ethanol blanks, spiked ethanol, four nitric acid diges- tion blanks, and spiked nitric acid blank. All digestates were analyzed for elements using aPE' SCIEX Elan 6000 ICP-MS. The operation was conducted in TotalQuant mode, which is an exhaustive semiquantitative 2 References to trade names. commercial products. or manufacturers do not imply or constitute governmental endorsement or recommendation for use.