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Geochemical & Environmental Research Group (GERG) Laboratory Methods Select one of the links blelow to display the method descriptions associated with GERG.
Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 001 Tissue Organics The tissue samples were extracted by the NOAA Status and Trends Method (MacLeod et al., 1985) with minor revisions (Brooks et al., 1989; Wade et al., 1988). Briefly, the tissue samples were homogenized with a Teckmar Tissumizer. A 1 to 10-gram sample (wet weight) was extracted with the Teckmar Tissumizer by adding surrogate standards, Na2SO4, and methylene chloride in a centrifuge tube. The tissue extracts were purified by silica/alumina column chromatography to isolate the aliphatic and PAH/pesticide/PCB fractions. The PAH/pesticide/PCB fraction was further purified by HPLC in order to remove interfering lipids. The quantitative analyses were performed by capillary gas chromatography (CGC) with a flame ionization detector for aliphatic hydrocarbons, CGC with electron capture detector for pesticides and PCB's, and a mass spectrometer detector in the SIM mode for aromatic hydrocarbons (Wade et al., 1988). There are specific cases where analytes requested for the pesticide and PCB analyses and are known to co-elute with other analytes in the normal CGC with electron capture. These include the pesticide Endosulfan I and the PCB congeners 114 and 157. In these cases, the samples will be analyzed by CGC with a mass spectrometer detector in the SIM mode. References 1. Brooks, J.M., T.L. Wade, E.L. Atlas, M.C. Kennicutt II, B.J. 2. MacLeod, W.D., D.W. Brown, A.J. Friedman, D.G. Burrow, O. Mayes, 3. Wade, T.L., E.L. Atlas, J.M. Brooks, M.C. Kennicutt II, R.G. Fox, Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 002 Tissue, Sediment and Water Mercury Mercury was determined by EPA method 245.5 with minor revisions. Sediment samples can be analyzed either freeze dried or on a wet basis. Sediment samples are homogenized by mixing before subsampling. The tissue samples were homogenized in the original sample containers with a Tekar Tissumizer and subsampled. Water samples are acidified (0.5% v/v with high purity nitric acid, HNO3) in the original sample bottle. For sediments a 0.5 to 1.0 gram sample (dry weight) was used. For tissues a 1.5 to 2.0 gram sample (wet weight) was used. For water the sample size is 20 ml. For tissue and sediment, the sample is weighed into a 50 ml polypropylene centrifuge tube. 2.5 ml of concentrated sulfuric acid (H2SO4) and 1.5 ml of concentrated nitric acid (HNO3) were added and the samples heated in a water bath at 90 C for 15 min. After cooling 10 ml of distilled water and 15 ml of mixture of 3.3% (w/w) potassium permanganate (KMnO4), and 1.7% (w/w) potassium persulfate (K2S2O8) were added to each tube and the samples heated in a water bath at 90 C for 30 min. After cooling 5 ml of 10% (w/w) hydroxylamine hydrochloride (NH2OH HC1) was added to reduce excess permanganate and the volume brought to 35 ml with distilled water. For water samples, the sample is weighed into a 50 ml polypropylene centrifuge tube, 1 ml of concentrated H2SO4 is added and the solution mixed vigorously with a vortex stirrer. Then 4.5 ml of the KMnOr/K2S2O8 is added and the resulting mixture heated in a 90 C water bath for 2 hours. After cooling, 1.5 ml of a 10% (w/w) hydroxylamine hydrochloride (NH2OH HC1) solution is added, sample volume adjusted to a constant volume with distilled water and the resulting solution mixed vigorously. Mercury is determined by a modification of the method of Hatch and Ott (1968). A portion of the digest solution is placed in a sealed container. To this is added 0.4 ml of 10% (w/w) stannous chloride (SnCl2). Mercury is reduced to the elemental state and aerated from solution into an atomic absorption spectrophotometer where its concentration is measured. References 1. "USEPA Contract Laboratory Program Statement of Work for Inorganic 2. "Interim Method for the Sampling and Analysis of Priority 3. Hatch, W.R. and Ott, W.L., "Determination of Sub-Microgram Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 003 % Dry Weight Approximately 1 gram of wet sample is weighed into a clean, labeled, preweighed 10 ml beaker. The beaker is placed in a forced air oven at approximately 75 degrees Celsius for 24 hours. The beaker with the dry sample is then weighed and the % dry weight is calculated by the formula: (wt. dry sample and beaker) - (wt. beaker) (100) (wt. wet sample and beaker) - (wt. beaker) Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 004 Sediments Organic/Pesticide The sediment samples were freeze-dried and extracted in a Soxhlet extraction apparatus. Briefly, the freeze-dried sediment samples were homogenized and a 10-gram sample was weighed into the extraction thimble. Surrogate standards and methylene chloride were added and the samples extracted for 12 hrs. The extracts were treated with copper to remove sulfur and were purified by silica/alumina column chromatography (MacLeod et al., 1985; Brooks et al., 1989) to isolate the aliphatic and aromatic/pesticide/PCB fractions. The quantitative analyses were performed by capillary gas chromatography (CGC) with a flame ionization detector for aliphatic hydrocarbons, CGC with electron capture detector for pesticides and PCB's, and a mass spectrometer detector in the SIM mode for aromatic hydrocarbons (Wade et al., 1988). There are specific cases where analytes requested for the pesticide and PCB analyses and are known to co-elute with other analytes in the normal CGC with electron capture. These include the pesticide Endosulfan I and the PCB congeners 114 and 157. In these cases, the samples will be analyzed by CGC with a mass spectrometer detector in the SIM mode. References: 1. Brooks, J.M., T.L. Wade, E.L. Atlas, M.C. Kennicutt II, B.J. 2. MacLeod, W.D., D.W. Brown, A.J. Friedman, D.G. Burrow, O. Mayes, 3. Wade, T.L., E.L. Atlas, J.M. Brooks, M.C. Kennicutt II, R.G. Fox, Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 005 Aromatic Hydrocarbon Metabolites in Bile SAMPLE PRESERVATION AND STORAGE Upon arrival at the laboratory sample vials are inspected, logged in, and unique laboratory identification numbers are assigned. Chain-of- custody protocols are followed. INSTRUMENT ANALYSIS Five ul of the sample is injected onto the IIPLC system using an autosampler. Instrument settings are: Column Oven Temperature 50 plus/minus 1 C SAMPLE ANALYSIS Once optimal HPLC operating parameters have been established and the instrument is functioning according to specifications (see above), 5 ul of each sample/standard are injected directly onto the HPLC system using an autosampler. The response of the fluorescence detector is recorded with a HP-1000 computer for 35 minutes at naphthalene, phenanthrene and benzo[a]pyrene excitation/emission wavelength paris. Peak areas are integrated for those peaks eluting between 5 and 28 minutes for naphthalene and between 5 and 28 minutes. These times are approximate and are based on times reported in the NOAA Technical Memorandum, NMFS F/NWC-102 and are verified for each system. Chromatographic conditions are selected so that no aromatic hydrocarbon metabolites elute before 5 minutes and solvent contaminants elute after 28 minutes for naphthalene, phenanthrene and benzo[a]pyrene metabolites. CALCULATIONS Phenanthrene and naphthalene peaks are identified from the calibration standards. The retention times are recorded and the areas of the reference standards are integrated. The mean response factor (ng/integration unit) is used to calculate sample analyte concentrations. The approximate retention times for naphthalene, phenanthrene, and benzo[a]pyrene are approximately 15, 17, and 21 minutes, respectively under the given analytical conditions. STANDARDS Standard concentrations are approximately: naphthalene 4 ng/ul, phenanthrene 2 ng/ul, and benzo[a]pyrene 0.3 ng/ul. Standards are prepared in methanol under yellow lights and stored at 20 C in amber vials. CALIBRATION Three calibration standards are analyzed at the beginning of each sample run and must agree within an RSD of plus/minus 10% before proceeding. During the sample run standards will comprise at least 10% of the run and must agree within an RSD of 10% of the mean calibration value. REFERENCE BILE A reference bile (provided by Dr. Margaret Krahn) is analyzed and reported for each sample run and must have an RSD of no more than plus/minus 15% of the previous value and not exceed an RSD of plus/minus 25% for each batch. REFERENCES 1. Krahn, M.M., M.S. Meyers, D.G. Burrows, and D.C. Malins. 1984. 2. Krahn, M.M., L.K. Moore, and W.D. MacLeod, Jr. 1986. Standard 3. Krahn, M.M., L.D. Rhode, M.S. Myers, L.K. Moore, W.D. MacLeod, Jr., Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 006 Grain Size A small aliquot of sediment is treated with 30% hydrogen peroxide to remove organic coating from grains. A dispersing agent is then added to the sample. The sand/mud fractions are then separated using a 63 micron sieve. The sand fraction (>63 microns) is retained on the screen and the mud fraction (silt and clay <63 microns) is washed into a 1 (one) liter volumetric cylinder. The sand fraction is dried, sieved on a 63 micron screen and weighed. The sediment which passes through the screen a second time is added to the 1 liter cylinder. The mud fraction is analyzed by stirring the cylinder and sampling 20 ml aliquots at 4 and 8 phi intervals. The 4 and 8 phi samples are dried and weighed. The % sand, silt, and clay fractions are determined on a dry weight basis. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 007 Trace Metal-Sediment Sediments are digested with aqua regia (3:1 HCl:HNO3) in glass beakers on a hotplate and diluted to volume with distilled water. Metals in the digestate are determined by 3 techniques, depending upon concentration and element. Mercury is determined by cold vapor atomic absorption spectrometry (AAS), in which Sn2+ is used to reduce Hg0. Arsenic, selenium, cadmium, and lead are determined by graphite furnace AAS, in which electrical heating is used to produce an atomic cloud. Remaining elements (and Cd or Pb when in high concentration) are determined by atomic emission using an argon plasma. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 008 Trace Metal SEM-Sediment Sediments are digested with 1N HC1 in glass beakers on a hotplate and diluted to volume with distilled water. Metals in the digestate are determined by 3 techniques, depending upon concentration and element. Mercury is determined by cold vapor atomic absorption spectrometry (AAS), in which Sn2+ is used to reduce Hg0. Arsenic, selenium, cadmium, and lead are determined by graphite furnace AAS, in which electrical heating is used to produce an atomic cloud. Remaining elements (and Cd or Pb when in high concentration) are determined by atomic emission using an argon plasma. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 009 Total Organic Carbon-Leco TOC contents are analyzed by two methods. The first method (Leco method) burns acidified freeze dried sediment using a LECO Model 523-300 induction furnace under an oxygen environment. The resultant carbon dioxide gas is detected and quantified with a Horiba PIR-2000 infrared detector. The output signal from the Horiba is sent to an HP 3396A integrator which reports the quantity of carbon dioxide as a peak area. If it is necessary to calculate inorganic carbon, an unacidified sample is also analyzed and the difference between the acidified sample (Total Organic Carbon) and the nonacidified sample (Total Carbon) is the inorganic carbon. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 010 Total Organic Carbon-Coulometrics The second method (Coulometrics) also burns sediment under an oxygen atmosphere to produce carbon dioxide gas. This gas is bubbled through an electrochemical cell, where a reaction between the CO2 and the cell solution produces a color change. This solution is then electrically backtitrated to the endpoint. The amount of electricity (coulombs) used to reach this endpoint is directly proportional to the amount of organic carbon in the sample. The concentration of inorganic carbon is determined using the same detector, but the CO2 is produced by acidifying the sample in a closed environment. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 011 Oil and Grease Follow Method number 001 or Method number 004 for the extraction of sediments or tissues. Before the extract is concentrated for silica gel/alumina column, mark the level of extract on the flask then remove 20 ml and rotovap to dryness. Bring the volume of the dry aliquot to 1 ml with methylene chloride, and weigh a 100 microliter aliquot. Measure the volume of the original extract. The concentration of Oil and Grease is calculated by the formula: (wt. 100 ul aliquot) (total volume) (sample wt.) (20) Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 012 Total Petroleum Hydrocarbons Follow Method number 001 or Method number 004 for the extraction of sediment or tissues. After the extract has passed through an alumina column remove a known volume and rotovap to dryness. Bring the volume of the dried aliquot to 1 ml with methylene chloride and weigh a 100 microliter aliquot. The concentration of Total Petroleum Hydrocarbons is calculated by the formula: (wt. / 100 ul aliquot) (total volume) (sample wt.) (% removed for aliquot) Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 013 Acid Volume Sulfide (AVS) Acid volatile sulfide (AVS) is defined as sulfides that are converted to H2S upon exposure to 1N HCl at room temperature for 1 hour. Approximately 10 grams of wet sediment are acidified with 1N HCl, and reactive sulfides that are converted to gaseous H2S are trapped as Ag2S and measured gravimetrically. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 014 Trace Metal-Tissue Tissues are either digested with nitric acid or dry ashed in a muffle furnace. Metals are determined by 3 techniques, depending upon concentration and element. Mercury is determined by cold vapor atomic absorption spectrometry (AAS), in which Sn2+ is used to reduce Hg0. Arsenic, selenium, cadmium, and lead are determined by graphite furnace AAS, in which electrical heating is used to produce an atomic cloud. Remaining elements (and Cd or Pb when in high concentration) are determined by atomic emission using an argon plasma. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 015 Trace Metal (except Hg) - Water The water sample is kept in the bottle in which originally received for the entire procedure to minimize the possibility of contamination. If not acidified prior to receipt, the sample is acidified with high purity nitric acid to achieve a 0.5% (v/v) acid concentration. After acidification the sample is stored at room temperature for at least 24 hours prior to analysis. Metals are determined by 3 techniques to achieve maximum sensitivity for all elements of interest. Mercury is determined by cold vapor atomic absorption spectrophotometry (AAS, see method code 002). Typically B, Ba, Be, Mg, Mo and Sr are determined by argon plasma atomic emission spectroscopy using undiluted acidified sample. Remaining elements are determined, also using undiluted sample, by graphite furnace AAS, in which electrical heating is used to produce an atomic cloud. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 016 Determination of Benzene, Toluene, Ethylbenzene and M,P,O - Xylene By Gas Chromatography/Mass Spectrometry (Btex) INTRODUCTION The method described quantitatively determines Benzene, Toluene, Ethyl-benzene, and M,P,O Xylene (BTEX) in a variety of matrices. This method is applicable to nearly all types of samples including water, sediments, soils, waste solvents, sludges, and industrial wastes. Quantitation is performed by gas chromatography/mass spectrometry (GC/MS) in the full scan mode. The BTEX compounds are introduced into the gas chromatograph by a purge and trap technique and detected using a mass spectrometer, which provides both qualitative and quantitative information. The GC/MS system is operated to obtain separation of the analytes of interest from any interferences. SAMPLE PREPARATION Water samples: Water is carefully drawn into a syringe and the volume adjusted to either 5 or 25 ml. Once the volume has been adjusted the surrogate and internal standards are added. A second aliquot is removed at this time to protect the integrity of the sample. The sample is then introduced into the purging device. The second sample is maintained only until such time when the first sample has been properly analyzed. If necessary the second sample must be analyzed within 24 hours. After the sample and appropriate standards have been transferred to the purging device the purging program is initiated. The samples are purged with purified helium at a flow of 40 ml.min for 11 min at a temperature of 75 C. The purged analytes are trapped on a 0.31 x 25 cm stainless steel column packed with 8 cm each of Tenax-GC, Silican gel, and Charcoal. The trap is held at ambient temperatures (25 C). After purging is completed the analytes are backflushed for two minutes from the trap to the head of the analytical capillary column which has been cooled to -160 C. After the desorb step is completed the analytes are analyzed by GC/MS. Units are reported in mg/L for water. Units are reported in ng/g for sediments. Results are reported to three (3) significant figures. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 017 Water Organic Water samples are extracted after acidified to a pH of 2 or less with HCl. Surrogate standards are added and the water is extracted with methylene chloride in a separatory funnel. The water is extracted three times and the extracts are combine. The organic phase is concentrated to -10-15 ml in a round bottom flask equipped with a three-ball Snyder condenser. The extract is concentrated further and exchanged into 2 ml of hexane in a 25 ml Kuderna-Danish (KD) receiver in a water bath (60 C). Extracts are now ready for purification by column chromatography or analyses directly by GC. Separation of aliphatic hydrocarbons from aromatic and chlorinated hydrocarbons is accomplished by alumina/silica gel chromatography. Silica gel (20 g, 170 /12 hrs, deactivated 5% with water) is slurry packed in CH2Cl2 over alumina (10 g 400 C/4 hrs, deactivated 1% with water). The extract in 2 ml of hexane is transferred to the column. The column is then eluted with 50 ml of pentane (f1), and 200 ml of 1:1 CH2Cl2:pentane (f2). This recovers the aliphatic (f1) and aromatic hydrocarbon/chlorinated hydrocarbon (f2) fractions. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 018 TBT The concentration of butyltins including tetrabutyltin, tributyltin, dibutyltin, and monobutyltin were determined as described by Wade et al. (1990) for sediments and Garcia-Romero et al. (1993) for tissues. Sediments are freeze-dried and a 10-15 gram aliquots of dry sediments are placed into a 50 ml centrifuge tube. Tripropyltin (TPT), is added as surrogate. The sample is extracted with 40 ml of 0.2% tropolone in methylene chloride by vigorously shaking the capped tube with a wrist action shaker. The tube is centrifuged and the supernatant collected. This procedure is repeated two more times. The extract is then concentrated on a rotary evaporator to approx. 20 ml. The samples are transferred into a 50 ml centrifuge tubes and the methylene chloride is replaced with hexane. Tissue samples are homogenized, an aliquot (2-10g) wet is weighed into a centrifuge tube and surrogate (TPT, approximately 300 ng as Sn) added. The sample is extracted using a Tissumizer after addition of 100 ml of 0.2% tropolone in methylene chloride and sodium sulfate as a drying agent. The sample and reagents are tissumized for 3 min. The tube is centrifuged and the solvent removed. The extraction is repeated two more times after adding 100 ml of 0.2% tropolone in methylene chloride. The extracts are combined and concentrated on a rotary evaporator to approx. 20 ml. The samples are transferred into a 50 ml centrifuge tubes and the methylene chloride is replaced with hexane. Sediment or tissue samples are hexylated in the centrifuge tubes by adding 2 ml of hexylmagnesium bromide under a nitrogen atmosphere and heating at 60 C in a water bath for six hours. The excess hexylmagnesium bromide is neutralized by adding 5 ml of 6 M hydrochloric acid. The organic fraction is removed and saved and the aqueous phase is extracted three more times with 10 ml of pentane each time. Sodium sulfate is added to the combined extracts to remove water. The samples are then concentrated to 2 ml, which is transferred to a silica (13.5 g)/alumina (17.0g) column and eluted with 50 ml of pentane. Samples are concentrated to 0.5 ml and tetrapropyltin (4PT), approximately 300 ng as Sn, is added as a recovery standard. Samples are quantitatively analyzed by gas chromatography using a flame photometric detector equipped with a 610 nm filter. The sample concentrations are reported as ng of Sn per gram of dry or wet sediment or tissue. REFERENCE: Wade, Terry L., Bernardo Garcia-Romero, and James M. Brooks (1990) Butyltins in Sediments and Bivalves from U.S. Coastal Areas. Chemosphere, Vol. 20, No. Garcia-Romero, B., Terry L. Wade, Gregory G. Salata, and James M. Brooks (1993) Butyltin Concentration in Oysters From The Gulf of Mexico From 1989 to 1991. Environmental Pollution, Vol. 81, pp. 103- Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 019 Percent Total Volatile Solids Samples are dried in the same manner as for percent moisture (method code 3) except that the procedure is done using high temperature quartz or Vycor crucibles. After the percent moisture has been determined, the dried samples are heated in an electric muffle furnace at 550 degrees centigrade for 4 hours. Samples are cooled in a desiccator and reweighed. The percent total volatile solids (TVS) are then calculated as follows: Percent TVS = (A-C) * 100/A A = Weight of dry solids prior to muffle furnace heating REFERENCE APHA, AWWA and WPCF. 1976. Standard Methods for the examination of water and wastewater. Method 208 G. pp. 96-98. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 020 Trace Method Total Sediment BOMB Digest Sediments are digested in heavy-walled, screw-cap Teflon Bombs with concentrated nitric acid, concentrated hydrofluoric acid and 4.5% boric acid added sequentially with separate 6-12 hour oven heating (120 deg. C) after each addition. This procedure results in a total digestion with all trace elements present in the sediment sample being solubilized. Most metals in the digestate are determined by graphite furnace AAS, in which electrical heating is used to produce an atomic cloud. Some elements are typically in high enough concentration (e.g. Mn, Zn) to be determined by flame AAS. Mercury is determined by cold vapor atomic absorption spectrometry (AAS), in which Sn2+ is used to reduce Hg0. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 021 Trace Metal Total Tissue BOMB Digest Tissues are digested in heavy-walled, screw-cap Teflon Bombs with concentrated high purity nitric acid. Bombs are heated (for 2-8 hours) and opened three times to release CO2 build-up. Oven temperature is 129 deg. C. This procedure results in a total digestion with all trace elements present in the tissue samples being solubilized. Most metals in the digestate are determined by graphite furnace AAS, in which electrical heating is used to produce an atomic cloud. Some elements are typically in high enough concentration (e.g. Zn) to be determined by flame AAS. Mercury is determined by cold vapor atomic absorption spectrometry (AAS), in which Sn2+ is used to reduce Hg0. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 022 Total Cyanide (sediment, Tissues or Water) Total cyanide was determined according to EPA method for water and waste (Method # 335.2). Sediment samples are h REFERENCES Bark, L.S. and Higson, H.G. (1964) Investigation of Reagents for the Colorimetric Determination of Small Amounts of Cyanide. Talanta, 2:471-479. Elly, C.T. (1968) Recovery of Cyanides by Modified Serfass Distillation. Journal Water Pollution Control Federation, 40:848-856. Annual Book of ASTM Standards, Part 31 (1976) Water. Standard D2036- 75, Method A, p. 503. Standard Methods for the Examination of Water and Wastewater (1975) 14th Edition, p. 367 and 370, Method 413B and D. Egekeze, J.O. and Ochne, F.W. (1979) Direct Potentiometric Determination of Cyanide in Biological Materials. J. Analytical Toxicology, Vol. 3, p. 119, May/June. Casey, J.P., Bright, J.W. and Helms, B.D. Nitrosation Interference in Distillation Tests for Cyanide. Gulf Coast Waste Disposal Authority, Houston, Texas. EPA, Methods for Chemical Analyses of Water and Wastes (1983). U.S. Environmental Monitoring and Support Lab-Cincinnati, Ohio. pp. 302-310. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 023 Sediment Trace Metals by INAA This method determines the total concentration of antimony (Sb), arsenic (As), barium (Ba), cerium (Ce), cesium (Cs), cobalt (Co), chromium (Cr), europium (Eu), iron (Fe), hafnium (Hf), manganese (Mn), neodymium (Nd), rubidium (Rb), scandium (Sc), selenium (Se), tantalum (Ta), titanium (Ti), thorium (Th) and vanadium (V) in sediment. Sediment samples are freeze-dried and mechanically powdered with a mortar and pestle prior to loading. Approximately 0.50g of dry powdered sediment is weighed into 2/5 dra m polyethylene polyvials and heat sealed. Samples are arranged in groups of 13 including 2 certified reference materials (CRM as comparator standards), 1 quality control CRM, 8 samples (1 in duplicate) and 1 procedural blank. Other quality control samples are included within the 9 sample slots per can as needed including matrix spikes and blank spikes. Each group of samples is placed in an aluminum can and up to 6 aluminum cans (72 samples and 6 blanks) are irradiated at one time. Samples are irradiated for 14 hours at the TAMU NSC TRIGA reactor using a continuously rotating, long-tube rotisserie device. The nominal thermal neutron fluence for the irradiation is 1xE14 neutron s/cm2. Irradiated samples are allowed to decay for 10 days and then analyzed using gamma-ray spectroscopy. Gamma-ray spectra are acquired for each sample using high resolution pure germanium detectors linked to multi-channel analyzers used in the pulse height analysis mode. Detector efficiencies are typically 20-25% with an observed resolution of 1.8-1.9 KEV full-width half-max at 1332.5 KEV. Analog to digital convertor (instrumental) dead time is kept at 10%. Peak extraction and NAA calculations are accomplished using Nuclear Data proprietary PEAK and NAA programs. Analytical determinations are made by direct comparison with comparator standards (CRM's) having known concentrations of the desired elements. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 024 Tissue Trace Metals by INAA This method determines the total concentration of antimony (Sb), arsenic (As), barium (Ba), cerium (Ce), cesium (Cs), cobalt (Co), chromium (Cr), europium (Eu), iron (Fe), hafnium (Hf), manganese (Mn), neodymium (Nd), rubidium (Rb), scandium (Sc), selenium (Se), silver (Ag), tantalum (Ta), titanium (Ti), thorium (Th), vanadium (V) and zinc (Zn) in tissue. Tissue samples are freeze-dried and mechanically powdered with metal-free equipment prior to loading. Approximately 0.30g of dry powdered tissue is weighed into 2/5 dram polyethylene polyvials and heat sealed. Samples are arranged in groups of 13 including 2 certified reference materials (CRM as comparator standards), 1 quality control CRM, 8 samples (1 in duplicate) and 1 procedural blank. Other quality control samples are included within the 9 sample slots per can as needed including matrix spikes and blank spikes. Each group of samples is placed in an aluminum can and up to 6 aluminum cans (72 samples and 6 blanks) are irradiated at one time. Samples are irradiated for 14 hours at the TAMU NSC TRIGA reactor using a continuously rotating, long-tube rotisserie device. The nominal thermal neutron fluence for the irradiation is 1xE14 neutrons/cm2. Irradiated samples are allowed to decay for 10 days and then analyzed using gamma-ray spectroscopy. Gamma-ray spectra are acquired for each sample using high resolution pure germanium detectors linked to multi-channel analyzers used in the pulse height analysis mode. Detector efficiencies are typically 20-25% with an observed resolution of 1.8-1.9 KEV full-width half-max at 1332.5 KEV. Analog to digital convertor (instrumental) dead time is kept at 10%. Peak extraction and NAA calculations are accomplished using Nuclear Data proprietary PEAK and NAA programs. Analytical determinations are made by direct comparison with comparator standards (CRM's) having known concentrations of the desired elements. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 025 Tissue Organics The tissue samples were extracted by the NOAA Status and Trends Method (MacLeod et al., 1985) with minor revisions (Brooks et al., 1989; Wade et al., 1988). Briefly, the tissue samples were homogenized with a Teckmar Tissumizer. A 1 to 10-gram sample (wet weight) was extracted with the Teckmar Tissumizer by adding surrogate standards, Na2SO4, and methylene chloride in a centrifuge tube. The tissue extracts were purified by silica/alumina column chromatography to isolate the aliphatic and PAH/pesticide/PCB fractions. The PAH/pesticide/PCB fraction was further purified by HPLC in order to remove interfering lipids. The quantitative analyses were performed by capillary gas chromatography (CGC) with a flame ionization detector for aliphatic hydrocarbons, CGC with electron capture detector for pesticides and PCB's, and a mass spectrometer detector in the SIM mode for aromatic hydrocarbons (Wade et al., 1988). The pesticides and PCBs are initially analyzed on a DB-5 capillary column. The analyte identity and concentrations are confirmed on a DB-17 capillary column. REFERENCES Brooks, J.M., T.L. Wade, E.L. Atlas, M.C. Kennicutt II, B.J. Presley, R.R. Fay, E.N. Powell, and G. Wolff (1989) Analysis of Bivalves and Sediments for Organic Chemicals and Trace Elements. Third Annual Report for NOAA's National Status and Trends Program, Contract 50-DGNC-5-00262. MacLeod, W.D., D.W. Brown, A.J. Friedman, D.G. Burrow, O. Mayes, R.W. Pearce, C.A. Wigren, and R.G. Bogar (1985) Standard Analytical Procedures of the NOAA National Analytical Facility 1985-1986. Extractable Toxic Organic Com Wade, T.L., E.L. Atlas, J.M. Brooks, M.C. Kennicutt II, R.G. Fox, J. Sericano, B. Garcia, and D. DeFreitas (1988) NOAA Gulf of Mexico Status and Trends Program: Trace Organic Contaminant Distribution in Sediments and Oysters. Estuaries 11:171-179. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 026 Dioxin/Furan Analysis The procedure uses matrix specific extraction, analyte specific cleanup, and HRGC/HRMS analysis techniques. If interferences are encountered, the method provides selected cleanup procedures to aid in their elimination. A specified amount of the sample matrix is spiked with a solution containing each of fifteen isotopically (13C12) labeled PCDDs/PCDFs. The sample is then extracted according to a matrix specific extraction procedure. Aqueous samples that are judged to contain 1% or more solids, and solid samples that show an aqueous phase, are filtered, the solid phase and the aqueous phase extracted separately, and the extracts combined before cleanup. Following a solvent exchange step, the extracts are cleaned up by column chromatography on alumina, silica gel, and AX-21 activated carbon on silica. The preparation of the final extract for HRGA/HRMS analysis is accomplished by adding two isotopically (13C12) labeled recovery standards. Two uL of the concentrated extracts are injected into an HRGC/HRMS system capable of performing selected ion monitoring at resolving powers of at least 10,000 (10% valley definition). The identification of the sixteen 2378-substituted isomers for which a 13C-labeled standard is available is based on their elution at their exact retention time and the simultaneous detection of the two most abundant ions in the molecular ion region. The identification of OCDF is based on its retention time relative to 13C-OCDD. Confirmation is based on a comparison of the ratios of the integrated ion abundance of the molecular ion species to their theoretical abundance ratios. Quantitation of the individual congeners is achieved in conjunction with the establishment of a multipoint calibration curve for each homologue, during which each calibration solution is analyzed once. REFERENCES Tondeur, Yves, "Method 8290: Analytical Procedures and Quality Assurance for Multimedia Analysis of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans by High-Resolution Gas Chromatography/High-Resolution Mass Spectrometry", USEPA EMSL, Las Vegas, Nevada, June 1987. (Revision 0, November 1990.) USEPA Office of Water Regulation and Standards, Industrial Technology Division, "Method 1613: Tetra- through Octa- Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS", Revision A, April 1990. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 027 Analysis of Tetra Ethyl Lead Tetra ethyl lead was analyzed by graphite furnace atomic absorption spectrometry (GFAAS, SW-846 7421) following extraction with toluene (ASTM D 3341-80). The methods were performed as follows: Extraction: Liquids (FWS samples 001, 002) - 25 ml sample were extracted with 50 ml of an iodine monochloride reagent and 25 ml of petroleum either. Solids (FWS samples 003, 004) - 10 g samples were extracted with 30 ml toluene for 1 hour, and then filtered. A 20 ml aliquot of the extract was then put through the above extraction with iodine monochloride and petroleum ether. The extract from both liquid and solid samples was then digested with nitric acid and brought to a volume of 100 ml for analysis. Analysis: Digested extracts, in an aqueous/dilute nitric acid matrix, were analyzed for lead by GFAAS. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 028 Total Petroleum Hydrocarbons The sediment samples were freeze-dried and extracted in a Soxhlet extraction apparatus. The freeze-dried sediment samples were homogenized and a 15-gram sample was weighed into the extraction thimble. Surrogate standards and methylene chloride were added and the samples extracted for 12 hrs. The extracts were treated with copper to remove sulfur. Extract is rotovaped to 5 mL and then brought to dryness under a clean nitrogen stream. GC internal standards are added and the extract is run on gas chromatograph with flame ionization detector. TPH is determined by summing the total unresolved complex mixture (UCM) and the total resolved (all peaks in the chromatogram). The concentration is based on an average of the response factors for alkanes from n-C10 through n-C34. Chromatograms are also provided. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 029 Organophosphate Pesticides - Tissues The tissue samples were extracted by EPA SW-846 method 3540 using a Soxhlet extraction apparatus. The tissue samples were homogenized and aliquots sample weighed, ground with 30 grams of anhydrous sodium sulfate and transferred into the extraction thimbles. Surrogate standards and methylene chloride were added and the samples extracted for 16-24 hrs. Lipids were removed from the extracts using gel permeation chromatography. The quantitative analyses were performed using EPA SW-846 method 8141 by capillary gas chromatography (CGC) with a flame photometric detector for organophosphate pesticides. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 030 Organophosphate Pesticides - Sediments The sediment samples were extracted by EPA SW-846 method 3550 extracted using sonication. The sediment samples were homogenized and an aliquot weighed and ground with anhydrous sodium sulfate. Surrogate standards are added to the sample and the sample was extracted three times with 1:1 methylene chloride/acetone by sonication. Lipids were removed from the extracts using gel permeation chromatography. The quantitative analyses were performed using EPA SW-846 method 8141 by capillary gas chromatography (CGC) with a flame photometric detector for organophosphate pesticides. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 031 EPA Method for Semivolatiles The sediment samples are dried with sodium sulfate, surrogate standards are added and the sediment sample extracted with methylene chloride in a Accelarated Solvent Extraction (ASE) apparatus. Copper is added to remove elemental sulfur. The tissue samples are extracted by the NOAA Status and Trends Method (Qian et al., 1998). Briefly, the tissue samples were homogenized with a Teckmar Tissumizer. A 1 to 10-gram sample (wet weight) was extracted with the Teckmar Tissumizer by adding surrogate standards, Na2SO4, and methylene chloride in a centrifuge tube. The extracts were purified by gel permeation chromatography as outlined by the EPA methods. The quantitative analyses were performed by capillary gas chromatography (GC) with a mass spectrometer detector in the SCAN mode for semivolatile hydrocarbons (EPA) Contract Laboratory for Organic Analyses OLM04.2 and EPA 8270). The compound list is based on the EPA CLP protocol but analytes from SW846 Method 8270 have been added. References: Qian, Y., J. L. Sericano and T. L. Wade. (1998) Extraction Tissues for Trace Organic Analysis. In Sampling and Analytical Methods of the National Status and Trends Program Mussel Watch Project: 1993-1996 Update (G. G. Lauenstein and A. Y. Cantillo, eds). NOAA Technical memorandum NOS ORCA 130. Pages 98 to 101. U.S. Environmental Protection Agency. USEPA. Contract Laboratory Program Statement of Work for Organic Analysis. OLM04.2 Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 032 EPA Method for Volatiles A 5.0 milliliter water sample, 5.0 gram sediment sample or 2.0 gram tissue sample are placed in the extraction tubes of a OI Corporation Purge and Trap system. System monitoring and surrogate standards are added to the tubes. The samples are purged with purified helium at a flow of 40 ml/min for 11 min at a temperature of 75 degrees C. The purged analytes are trapped on a 0.31 x 25cm stainless steel column packed with 8 cm each of Tenax-GC, Silica gel, and Charcoal. The trap is held at ambient temperatures (25 degrees C). After purging is completed the analytes are backflushed for two minutes from the trap to the head of the analytical capillary column and the analytes are analyzed by GC/MS. The quantitative analyses were performed by capillary gas chromatography (GC) with a mass spectrometer detector in the SCAN mode for semivolatile hydrocarbons (EPA Contract Laboratory for Organic Analyses OLM04.2 and EPA 8270). The compound list is based on the EPA CLP protocol but analytes from SW846 Method 8270 have been added. REFERENCES U.S. Environmental Protection Agency. 1999. USEPA Contract Laboratory Program Statement of Work for Organic Analysis. OLM04.2 Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 035 Simultaneously Extracted Metals (SEM) -- Sediment Simultaneously extracted metals (SEM) are those metals released during the analysis for acid volatile sulfides Metals in the digestate are determined by 3 techniques, depending upon concentration and element. Arsenic, selenium, cadmium, and lead are determined by graphite furnace AAS, in which electrical heating is used to produce an atomic cloud. Remaining elements (and Cd or Pb when in high concentration) are determined by atomic emission using an argon plasma. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 036 Methyl Mercury in Tissue Tissue samples for methyl-mercury analysis are extracted by the method of Uthe et al. (1972) and Wagemann et al. (1997) and analyzed by gas chromatography with electron capture detector (GC/ECD). Briefly, wet (ca. 1 g) or dry tissue (0.2-0.5 g) samples are acidified with 4 ml of HBr (2.5N) and 8 ml of CuSO4 (0.1N) solutions. The aqueous solutions are extracted with 5-7 ml of toluene three times. The combined toluene extract are washed twice with 7 ml of Na2S2O3 (0.005N) aqueous solution. About 4 ml of HBr (2.5N) and 0.5 ml of NaBr (3N) are added to the combined Na2S2O3 aquous solution. The aqueous solution is extracted with 4 ml of toluene twice. The toluene extract is dried with anhydrous sodium sulfate. An aliquot of the final toluene extract is taken and a GC external standard (tetra-chlorinated m-xylene, TCMX) is added. Methyl mercury in the toluene extract is analyzed by a GC/ECD equipped with a 30m x 0.25 mm (i.d.) DB-17 capillary column. The GC/ECD is programed to run from 100oC to 300oC in 20 minutes. GC/ECD calibration standards are made from methyl mercury chloride and are converted to methyl mecury bromide. Methyl mercury concentrations are reported as ppm of mercury. References: Uthe, J.F., Solomon, J. and Grift, B. (1972) Rapid semimicro method for the determination of methyl mecury in fish tissue. J. AOAC., 55: 583-589. Wagemann, R., Trebacz, E., Hunt, R. and Boila, G. (1997) Percent methylmercury and organic mercury in tissue of marine mammals and fish using different experimental and calculation methods. Environ. Toxicol. Chem., 16:1859-1866. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 037 Chlorophylls and other Plant Pigments Sample Preservation and Storage Upon arrival at the laboratory samples are inspected, logged in, and unique laboratory identification numbers are assigned. Chain-of-custody protocols are followed. Instrument Analysis After extraction with acetone and adding international standard, twenty (20) l of the sample extract is injected onto the HPLC system using an autosampler. Instrument settings are: Column Oven Temperature ambient Solvents: Gradient Elution Sample Analysis Once optimal HPLC operating parameters have been established and the instrument is functioning according to specifications (see above), 20 l of each sample/standard are injected directly onto the HPLC system consisting of a tertiary gradient pump and a Spherisorb C18 column using an autosampler. The response of the UV/Visible absorbance detector is recorded with at 436 nm. Calculations Peak identification was based on the comparison of retention times with that of authentic standards. Compound quantitation was based on response factors determined from standard compounds relative to international standard, amount of internal standard added to each sample, peak areas of the internal standard and each peak, and the sample amount. Standards Individual pigment standard was obtained from US EPA, Sigma-Aldrich, and Hoffman-LaRoche. Canthaxanthin was used as internal standard and added to each sample prior to extraction. Two hundred (200) ng of canthaxanthin was generally added to each sample. All the sample preparation, extraction, and analysis were conducted under reduced light conditions to minimize the exposure to light and the light induced decompositions. REFERENCES Wright, S.W., Jeffrey, S.W., Mantoura, R.F.C., Llewellyn, C.A., Bjornland, T., Repeta, D., Welschmeyer, N., 1991. Improved HPLC method for the analysis of chlorophylls and carotenoids from marine phytoplankton. Marine Ecology Progress Series 77, 183-196. Qian, Y., Jochens, A.E., Kennicutt II, M.C., Biggs, D.C., 2003. Spatial and temporal variability of phytoplankton biomass and community structure over the continental margin of the northeast Gulf of Mexico based on pigment analysis. Continental Shelf Research, 23, 1-17. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 038 Biomass Determination Total Wet Weight Samples which are taken in the field from a known area or volume of habitat are shipped to the lab. On receipt, Dry weight and ash weight determination One aliquot of the wet sample was weighed and placed in a preweighed aluminium foil boat. This aliquot was dried in an oven at 70oC for a minimum of 24 hours. The dried samples were weighed on an analytical balances after cooling to room temperature. The samples were returned to the oven for another 2 hours and the reweighed after cooling. If the weight difference between the two weighings after drying is less than 0.02 g, the last weight was used to calculated the percent solid of the sample. If the weight difference is larger than 0.02 g, the sample was returned to the oven and dried until constant weight was achieved. The dry aliquot is placed in a preweighed, precombusted cruciable. The samples along with the cruciables were combusted at 550oC for 24 h. Upon cooling, the samples along with the cruciables were weighed on an analytical balances. The samples were returned to the oven for additional 12 hours before the second weighing. If the weight difference between the two weighings after combustion was less than 0.01 g, the last weight was used to calculate the ashfree dry weight of the sample. If the weight difference was larger than 0.01 g, the sample was returned to the oven and combusted until constant weight was achieved. The residue is the ash weight. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 039 Hydrazine Analysis in Sediments Sample Preservation and Storage Upon arrival at the laboratory samples are inspected, logged in, and unique laboratory identification numbers are assigned. Chain-of-custody protocols are followed. Samples were stored at -20oC. Extraction: Samples were extracted with 3 ml of 0.1N sulfuric acid and 1 ml of acetone twice. Extraction was performed with sonication. After centrifuge, the supernatant was transferred into a vial. The volume of the combined extracted was measured and 1 ml aliquot of the extract was transferred into a 2 ml vial. 0.5 ml of pentafluorobenzaldehyde solution (1 ml in 100 ml methanol) was added to each vial and heated at 70oC for 40 min to derivatize hydrazine. Instrument Analysis After cooling, twenty (20) æl of the derivatized sample extract is injected onto the HPLC system using an autosampler. Hydrazine and 1,1'-dimethylhydrazine were analyzed on a 25 cm x 4.6 mm Spherisorb C18 column with methanol/water (80/20, v/v) as the mobile phase. Target analytes were detected at 313 nm. Calculations Peak identification was based on the comparison of retention times with that of authentic standards. Compound quantitation was based on response factors determined from standard compounds, peak areas of each peak, and the sample amount. Standards Hydrazine and 1,1'-dimethylhydrazine standards were obtained from Aldrich. A working solution of 1 ug/ml was prepared by dissolving appropriate amount of the standards into 0.1N sulfuric acid solution. Calibration standards were prepared by derivatizing with pentafluorobenzaldehyde solution. Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 040 Determination of Pesticides and PCBs by GC/MS The tissue samples were extracted by the NOAA Status and Trends Method (MacLeod et al., 1985) with minor revisions (Brooks et al., 1989; Wadeet al., 1988). Briefly, the tissue samples were homogenized with a Teckmar Tissumizer. A 1 to 10-gram sample (wet weight) was extracted with the Teckmar Tissumizer by adding surrogate standards, Na2SO4, and methylene chloride in a centrifuge tube. The tissue extracts were purified by silica/alumina column chromatography to isolate the aliphatic and PAH/pesticide/PCB fractions. The PAH/pesticide/PCB fraction was further purified by HPLC in order to remove interfering lipids. The sediment samples were dried with sodium sulfate and extracted using a DIONEX accelarated solvent extraction (ASE) system. The freeze-dried sediment samples were homogenized and a 10-gram sample was weighed into the extraction thimble. Surrogate standards and methylene chloride were added and the samples extracted. The extracts were treated with copper to remove sulfur and were purified by silica/alumina column chromatography (MacLeod et al., 1985; Brooks et al., 1989) to isolate the aliphatic and aromatic/pesticide/PCB fractions. The quantitative analyses were performed by capillary gas chromatography (CGC) with a mass spectrometer detector in the SIM mode for pesticides or PCBs. Quantification is based on the primary ion and two additional masses for each analyte are also monitored for verification of the peak identification. The masses are based on EPA protocols such as EPA 680 for PCBs and 8270c for pesticides. All 209 PCB congeeners have been identified with many co-elutions. Total homologs and Arclors can also be determined. Brooks, J.M., T. L. Wade, E. L. Atlas, M. C. Kennicutt II, B. J. Presley, R. R. Fay, E. N. Powell, and G. Wolff (1989) Analysis of Bivalves and Sediments for Organic Chemicals and Trace Elements. Third Annual Report for NOAA's National Status and Trends Program, Contract 50-DGNC-5-00262. MacLeod, W.D., D. W. Brown, A. J. Friedman, D.G. Burrow, O. Mayes, R.W. Pearce, C.A. Wigren, and R. G. Bogar (1985) Standard Analytical Procedures of the NOAA National Analytical Facility 1985-1986. Extractable Toxic Organic Compounds. 2nd Ed. U.S. Department of Commerce, NOAA/NMFS. NOAA Tech. Memo. NMFS F/NWC-92. Wade, T.L., E. L. Atlas, J. M. Brooks, M. C. Kennicutt II, R. G. Fox, J. Sericano, B. Garcia, and D. DeFreitas (1988) NOAA Gulf of Mexico Status and Trends Program: Trace Organic Contaminant Distribution in Sediments and Oysters. Estuaries, 11, 171-179.Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 041 Determination of PBDE’s by GC/MS The tissue samples were extracted by the NOAA Status and Trends Method (MacLeod et al., 1985) with minor revisions (Brooks et al., 1989; Wade et al., 1988). Briefly, the tissue samples were homogenized with a Teckmar Tissumizer. A 1 to 10-gram sample (wet weight) was extracted with the Teckmar Tissumizer by adding surrogate standards, Na2SO4, and methylene chloride in a centrifuge tube. The tissue extracts were purified by silica/alumina column chromatography and finally by HPLC in order to remove interfering lipids. The sediment samples were dried with sodium sulfate and extracted using a DIONEX accelarated solvent extraction (ASE) system. The freeze-dried sediment samples were homogenized and a 10-gram sample was weighed into the extraction thimble. Surrogate standards and methylene chloride were added and the samples extracted. The extracts were treated with copper to remove sulfur and were purified by silica/alumina column chromatography (MacLeod et al., 1985; Brooks et al., 1989). The quantitative analyses were performed by capillary gas chromatography (CGC) with a mass spectrometer detector in the SIM mode for polybrominated diphenyl ethers (PBDEs). Quantification is based on the primary ion and two additional masses for each analyte are also monitored for verification of the peak identification. The masses are based on EPA protocols such as EPA 1614 for PBDEs. Brooks, J.M., T. L. Wade, E. L. Atlas, M. C. Kennicutt II, B. J. Presley, R. R. Fay, E. N. Powell, and G. Wolff (1989) Analysis of Bivalves and Sediments for Organic Chemicals and Trace Elements. Third Annual Report for NOAA's National Status and Trends Program, Contract 50-DGNC-5-00262. MacLeod, W.D., D. W. Brown, A. J. Friedman, D.G. Burrow, O. Mayes, R.W. Pearce, C.A. Wigren, and R. G. Bogar (1985) Standard Analytical Procedures of the NOAA National Analytical Facility 1985-1986. Extractable Toxic Organic Compounds. 2nd Ed. U.S. Department of Commerce, NOAA/NMFS. NOAA Tech. Memo. NMFS F/NWC-92. Wade, T.L., E. L. Atlas, J. M. Brooks, M. C. Kennicutt II, R. G. Fox, J. Sericano, B. Garcia, and D. DeFreitas (1988) NOAA Gulf of Mexico Status and Trends Program: Trace Organic Contaminant Distribution in Sediments and Oysters. Estuaries, 11, 171-179.
Lab Name: Geochemical & Environmental Research Group, Texas A&M Method Code 042 Determination of Triazines by GC/MS The tissue samples were extracted by the NOAA Status and Trends Method (MacLeod et al., 1985) with minor revisions (Brooks et al., 1989; Wade et al., 1988). Briefly, the tissue samples were homogenized with a Teckmar Tissumizer. A 1 to 10-gram sample (wet weight) was extracted with the Teckmar Tissumizer by adding surrogate standards, Na2SO4, and methylene chloride in a centrifuge tube. The tissue extracts were purified by silica/alumina column chromatography and finally by HPLC in order to remove interfering lipids.
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