Environmental Sampling and Analysis for Metals - Chapter 18 ppt

269 Selected Methods for Determination of Metals in Environmental Samples 18.1 METHODOLOGY Methods are developed to analyze diverse media for specific parameters. Each method is approved by the Environmental Protection Agency (EPA), which specifies the procedures, instrument calibra- tion, sample preparation, analytical procedures, and quality control requirements for the analytical work. EPA methods are differentiated according to the media (matrix) of the sample analyzed. Each laboratory has a written guidebook that contains specific procedures used, known as standard oper- ating procedures (SOPs). SOPs should be constantly revised to include new methodologies and pro- cedural changes. The SOPs are an important tool for the quality assurance/quality control (QA/QC) operation of the laboratory. 18.1.1 EPA-APPROVED METHODS AND REFERENCES FOR ANALYZING WATER SAMPLES 18.1.1.1 Methods and References for Analyzing Drinking Water Methods for Chemical Analysis of Water and Wastes (EPA 600/4–79–020, revised March 1983) Methods for Determining Organic Compounds in Drinking Water (EPA 600/4–88–039, December 1988) Standard Methods for the Examination of Water and Wastewater (APHA-AWWA-WPCF, 19th ed., 1998) (an updated edition is issued every 5 years) Manual for Certification of Laboratories Analyzing Drinking Water (EPA 570/9–90/008, April 1990) CFR Part 141, Subpart C and Subpart E (monitoring and analytical requirements) EPA 500 series (should be used for organic analyses of drinking waters and raw source waters) 18.1.1.2 Methods and References for Analyzing Surface Waters and Wastewater Effluents Methods for Chemical Analysis of Water and Wastes (EPA 600–4–79–020, revised in March 1983) Test Methods for Evaluating Solid Waste (EPA SW-846, 3rd ed., 1986; rev. ed., December 1987) 40 CFR, Part 136 (Tables IA, IB, IC, ID, and IE, July 1989) 18 © 2002 by CRC Press LLC 270 Environmental Sampling and Analysis for Metals 18.1.1.3 Methods and References for Analyzing Water Sources (Surface and Groundwater) Pursuant to 40 CFR Part 261 (RCRA) Test Methods for Evaluating Solid Waste (EPA SW-846, 3rd ed., 1986; rev. ed., December 1987) 40 CFR, Part 261 (Methods, Appendix III, 1989) USEPA Contract Laboratory Program Statement of Work for Inorganic Analyses (EPA SOW ILMO3.0, March 1990) USEPA Contract Laboratory Program Statement of Work for Organic Analyses (EPA SOW OLMO3.1, August 1994) 18.1.1.4 Methods and References for Microbiological and Biological Tests of Water Samples Microbiological Methods for Monitoring the Environment (EPA 600/8–78–017, 1987) 40 CFR, Part 141 (Subpart C, monitoring and analytical requirements, July 1989) 40 CFR, Part 136 (Table IA, July 1989) Methods for Measuring the Acute Toxicity of Effluent to Freshwater and Marine Organisms (EPA 600/4–85–013, 3rd ed., 1985) Short-Term Methods for Estimating the Chronic Toxicity of Effluent and Receiving Waters to Freshwater Organisms (EPA 600/4–89–1990) Short-Term Methods for Estimating the Chronic Toxicity of Effluent and Receiving Waters to Marine and Estuarine Organisms (EPA 600/4–87–028, 1988) 18.1.2 EPA-APPROVED METHODS AND REFERENCES FOR ANALYZING SEDIMENTS AND RESIDUALS 18.1.2.1 Methods and References for Analyzing Soils, Sediments, Domestic and Industrial Sludges, Solid and Hazardous Wastes Test Methods for Evaluating Solid Waste (EPA SW-846, 3rd ed., 1986; rev. ed., December 1987) 40 CFR, Part 261 (Appendix III, July 1989) Procedures for Handling and Chemical Analysis of Sediments and Water Samples (EPA/Corps of Engineers, CE-81–1, 1981) USEPA Contract Laboratory Program Statement of Work for Inorganic Analysis (EPA SOW ILMO3.0, March 1990) USEPA Contract Laboratory Program Statement of Work for Organic Analysis (EPA SOW OLMO3.1, August1994) POTW Sludge Sampling and Analysis Guidance Document (EPA Permits Division, August 1989) 18.1.3 APPROVED MODIFICATION OF EPA METHODS 18.1.3.1 EPA Method 300.0 This method may be used for the analysis of specified ions in ground water and surface water, except for fluoride. It is currently approved for drinking water analysis. © 2002 by CRC Press LLC Selected Methods for Determination of Metals in Environmental Samples 271 18.1.3.2 EPA Methods 601, 602, 624, and 625 Capillary columns may be used instead of the specified packed columns if the laboratory meets the pertinent accuracy and precision criteria and detection limit with this modification. 18.1.3.3 EPA Methods 601 and 602 The photoionization detector and electrolytic conductivity detector may be used in a series if the lab- oratory can meet the performance criteria. 18.1.3.4 EPA Methods 602, 8020, 8021 These methods may include analysis of xylene and methyl-tert-butyl-ether (MTBT). 18.1.3.5 EPA Methods 610, 625, 8100, 8310, 8250, 8270 These methods may include analysis of methylnaphthalenes. 18.1.3.6 EPA Method 5030/8010 This method must be modified to analyze EDB in soils. An electron-capture detector instead of an electrolytic conductivity detector must be used. 18.1.4 EPA CONTRACT LABORATORY PROTOCOL (CLP) This protocol was developed for the Superfund program. CLP specifies a set of methods based on the existing methodology for organic and inorganic parameters, but which are modified to incorporate certain quality control, calibration, and deliverable requirements. The data package includes a full reporting of quality control procedures and data, making it particularly useful if litigation is a possi- bility. The results of the analyses are provided in many different formats, ranging from a sample re- port only to a full-documentation data package. The CLP, as stated in the EPA statement of work (SOW), has a high level of quality assurance re- quirements. The deliverable requirements include quality control summaries (method blank, initial calibration verification, duplicate analysis, and matrix spike/matrix spike duplicates) and quality control data, as well as data on a diskette. Consequently, CLP has become a commonly requested methodology and has the effect of separating larger laboratories — which have the equipment, cer- tifications, and trained personnel capable of producing data according to this protocol — from the thousands of smaller environmental laboratories which do not. Because EPA methods, as now written, are not interchangeable, it is very difficult for an analyt- ical laboratory to accommodate all quality control criteria for all methods. Thus, the EPA’s current intent is to create a unified method to minimize the requirement differences. 18.1.5 DETERMINATION OF SELECTED METALS IN ENVIRONMENTAL SAMPLES Table 18.1 summarizes the methods, method numbers, and references used for determination of met- als in environmental samples. 18.2 ALUMINUM Aluminum (Al) is the third most abundant element of the Earth’s crust, occurring in mineral rocks and clays. Soluble, insoluble, and colloidal aluminum may appear in treated water or wastewater as © 2002 by CRC Press LLC 272 Environmental Sampling and Analysis for Metals a residual of coagulation with aluminum-containing material. Filtered water from a modern, rapid- sand filtration plant should have an aluminum concentration less than 50 µg/l. Selection of method: The FAAS, GrAAS, and ICP methods are preferred. For discussion of in- strumentation and analysis procedures, see Chapters 8, 9, and 12, respectively. 18.2.1 FLAME ATOMIC ABSORPTION SPECTROSCOPY (FAAS) Aluminum may be as much as 15% ionized in a nitrous oxide/acetylene flame. Use an ionization sup- pressor of 1000 µg/ml K as KCl (dissolve 95 g of KCl and dilute to 1000 ml). The calibration stan- dards should contain the same type of acid in the same concentration as in the sample (usually 5 ml of acid per 100 ml), and 2 ml/100 ml of KCl solution as suppressor (see above). Parameter FL GR Other Method No. Ref. Method No. Ref. Aluminum + + — 202.1&2 R-1 7020 R-3 Antimony + + — 204.1&2 R-1 7040 R-3 Arsenic – + — 206.2 R-1 7060 R-3 Barium + + — 208.1&2 R-1 7080 R-3 Beryllium + + — 210.1&2 R-1 7090 R-3 Boron –– Curcumin 4500-BB R-2 — — Boron –– Carmine 4500-BC R-2 — — Cadmium + + — 213.1&2 R-1 7130 R-3 Calcium + –— 215.1 R-1 7140 R-3 Calcium ––EDTA titrimetric 215.2 R-1 — — Chromium + + — 218.1&2 R-1 7190 R-3 Chromium 6+ –– Colorimetric 3500CrD R-2 7196 R-3 Cobalt + + — 219.1&2 R-1 7200 R-3 Copper + + — 220.1&2 R-1 7210 R-3 Iron + + — 236.1&2 R-1 7380 R-3 Lead + + — 239.1&2 R-1 7420 R-3 Magnesium + + — 242.1&2 R-1 7450 R-3 Manganese + + — 243.1&2 R-1 7460 R-3 Mercury –– Cold vapor 245.1. R-1 7470, 7471 R-3 Molybdenum + + — 246.1&2 R-1 7480 R-3 Nickel + + — 249.1&2 R-1 7520 R-3 Potassium + –— 258.1 R-1 7610 R-3 Selenium – + — 270.2 R-1 7740 R-3 Silver + + — 272.1&2 R-1 7760 R-3 Sodium + –— 273.1 R-1 7770 R-3 Thallium + + — 279.1&2 R-1 7840 R-3 Tin + + — 282.1&2 R-1 7870 R-3 Titanium + + — 283.1&2 R-1 — — Vanadium + + — 286.1&2 R-1 7910 R-3 Zinc + + — 289.1&2 R-1 7950 R-3 Note: Metals analysis by inductively coupled plasma (ICP) method is widely used according to method 6010, with reference to R-3. Fl = flame atomic absorption technique; Gr = graphite furnace atomic absorption technique; R-1 = methods for Chemical Analysis of Water and Wastes (EPA-600/4-79-020, Revised March 1983); R-2 = Standard Methods for the Examination of Water and Wastewater (AWWA, 18th ed., 1992); R-3 = Test Methods for Evaluating Solid Wastes (EPA SW- 846 EPA SW-846, 3rd ed., 1986). TABLE 18.1 Methods for Determination of Metals © 2002 by CRC Press LLC Selected Methods for Determination of Metals in Environmental Samples 273 18.2.1.1 Instrument Parameters • Instrument: Aluminum hollow cathode lamp • Fuel: Acetylene • Oxidant: Nitrous oxide • Type of flame: Rich fuel • Background correction: Not required 18.2.1.2 Performance Characteristics • Optimum concentration range: 5 to 50 mg/l • Detection limit: 0.1 mg/l • Sensitivity: 1 mg/l • Wavelength: 309.3 nm 18.2.2 GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY (GRAAS) Background correction may be required if the sample contains highly dissolved solids. Chloride ion and nitrogen used as a purge gas reportedly suppress the aluminum signal; therefore, the use of halide acids and nitrogen as a purge gas should be avoided. 18.2.2.1 Instrument Parameters • Drying time and temperature: 30 sec at 125°C • Ashing time and temperature: 30 sec at 1300°C • Atomizing time and temperature: 10 sec at 2700°C • Purge gas: Argon • Wavelength: 309.3 nm Other operating parameters should be set as specified by the instrument manufacturer. 18.2.2.2 Performance Characteristics • Optimum concentration range: 20 to 200 mg/l • Detection limit: 3 mg//l 18.3 ANTIMONY The level of antimony (Sb) present in natural waters is usually less than 10 µg/l and may be present in higher concentrations in hot springs or waters draining mineralized areas. Antimony is a regulated contaminant under various federal and state programs. Selection of method: The GrAAS method (Chapter 8) is the method of choice because of its sen- sitivity. Alternatively, use the FAAS method (Chapter 9) or the ICP method (Chapter 12) when high sensitivity is not required. 18.3.1 FLAME ATOMIC ABSORPTION SPECTROSCOPY (FAAS) In the presence of lead (1000 mg/l), spectral interference may occur at the 217.6-nm resonance line. In this case, the 231.1-nm antimony line should be used. © 2002 by CRC Press LLC 274 Environmental Sampling and Analysis for Metals 18.3.1.1 Instrument Parameters • Instrument: Antimony hollow cathode lamp • Wavelength: 217.6 nm • Fuel: Acetylene • Oxidant: Air • Type of flame: Lean fuel 18.3.1.2 Performance Characteristics • Optimum concentration range: 1 to 40 mg/l • Sensitivity: 0.5 mg/l • Detection limit: 0.2 mg/l 18.3.2 GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY (GRAAS) High Pb concentration may cause a measurable spectral interference on the 217.6 nm-line. In this case, a secondary wavelength or Zeeman background correction should be used. See Chapter 9 for general discussion of the furnace technique. A soft-digestion procedure is the only recommended one for Sb, as discussed in Sections 15.2.2 and 15.8. The addition of HCl to the digestate prevents fur- nace analysis of many metals. 18.3.2.1 Instrument Parameters • Drying time and temperature: 30 sec at 125°C • Ashing time and temperature: 30 sec at 800°C • Atomizing time and temperature: 10 sec at 2700°C • Purge gas: Argon or nitrogen • Wavelength: 217.6 nm (primary); 231.1 nm (alternate) • Background correction: Required Other operating parameters should be set as specified by the instrument manufacturer. 18.3.2.2 Performance Characteristics • Optimum concentration range: 20 to 300 mg/l • Detection limit: 3 mg/l The above concentration values and instrument conditions are based on the use of a 20- µl injection, continuous-flow purge gas and nonpyrolytic graphite. See instrument manufacturer’s operations manual for information. 18.4 ARSENIC Severe poisoning can arise from the ingestion of arsenic trioxide (As 3 O 2 ) in amounts as small as 100 mg; chronic effects may result of the accumulation of arsenic compounds in the body at low intake levels. Carcinogenic properties are also known. The toxicity of arsenic depends on its chemical form. The As concentration in potable waters is usually less than 10 µg/l, but values as high as 100 µg/l have been reported. Aqueous arsenic may result from mineral dissolution, industrial discharges, or the ap- plication of herbicides. Selection of methods: The hydride-generation atomic absorption method (Chapter 11) is the method of choice, although the GrAAS (Chapter 9) is simpler. © 2002 by CRC Press LLC Selected Methods for Determination of Metals in Environmental Samples 275 18.4.1 GASEOUS HYDRIDE ATOMIC ABSORPTION METHOD This method is applicable for sample matrices that do not contain high concentrations of Cr, Cu, Hg, Ni, Ag, Co, and Mo. Instrumentation and analytical procedures are discussed in Chapter 11. The typ- ical detection limit for this method is 0.002 mg/l. 18.4.2 GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY (GRAAS) Following the appropriate dissolution (acid digestion) of the sample, a representative aliquot of the digestate is spiked with nickel nitrate solution and is placed manually or by means of an automatic sampler into a graphite furnace. See Chapter 9 for details of the GrAAS technique. 18.4.2.1 Instrument Parameters • Drying time and temperature: 30 sec at 125°C • Ashing time and temperature: 30 sec at 1100°C • Atomizing time and temperature: 10 sec at 2700°C • Purge gas: Argon • Wavelength: 193.7 nm Other operating parameters should be set as specified by the instrument manufacturer. 18.4.2.2 Performance Characteristics • Optimum concentration range: 5 to 100 mg/l • Detection limit: 1 mg/l 18.4.2.3 Interferences Elemental As and many of its compounds are volatile; therefore, samples may be subject to losses of As during sample preparation. Spike samples and standard reference materials should be processed to determine if the chosen dissolution method is appropriate. Caution must be employed during the selection of temperature and times for the dry and char cy- cles. A nickel nitrate solution must be added to all digestates prior to analysis to minimize volatiliza- tion losses during drying and ashing. Arsenic analysis may be subject to severe nonspecific absorption and light scattering caused by matrix components during atomization. Aluminum is a severe positive interferant in the analysis of arsenic. Zeeman background correction is very useful in this situation. If the analyte is not completely volatilized and removed from the furnace during atomization, memory effects will occur. If this situation is detected by means of blank burns, the tube should be cleaned by operating the furnace at full power at regular intervals during the analysis. 18.4.2.4 Reagents • Concentrated HNO 3 • Hydrogen peroxide, H 2 O 2 (30%) • As stock solution, 1000 mg/l (commercially available or prepared according to recipe in Appendix H) • Nickel nitrate, 5% (dissolve 24.780 g of Ni(NO 3 ) 2 .6H 2 O in reagent-grade water and dilute to 100 ml) • Nickel nitrate, 1% (dilute 20 ml of the 5% nickel nitrate solution to 100 ml with reagent- grade water) © 2002 by CRC Press LLC 276 Environmental Sampling and Analysis for Metals 18.4.2.5 Procedure 1. Prepare samples for the analysis as described in Sections 15.6.2 and 15.6.3. 2. Pipet 5 ml of digested solution into a 10-ml volumetric flask, add 1 ml of the 1% nickel nitrate solution, and dilute to 10 ml with reagent-grade water. The sample is ready for in- jection into the furnace. 3. The 193.7-nm wavelength line is recommended. 4. A background correction system is required. For other spectrophotometric parameters, follow the manufacturer’s instructions. 5. Furnace parameters suggested by the manufacturer should be employed as guidelines. Because temperature-sensing mechanisms and temperature controllers can vary among in- struments or with time, the validity of the furnace parameters must be periodically con- firmed by systematically altering the furnace parameters while analyzing a standard. In this manner, losses of analyte due to overly high temperature settings or losses in sensi- tivity due to less-than-optimum settings can be maintained. Similar verification of furnace parameters may be required for complex sample matrices. 6. Calibration curves must be composed of a minimum of a blank and three standards. A cal- ibration curve should be made for every hour of continuous sample analysis. 7. Inject a measured microliter aliquot of sample into the furnace and atomize. If the con- centration found is greater than the highest standard, the sample should be diluted in the same acid matrix and reanalyzed. The use of multiple injections can improve accuracy and help detect furnace pipeting errors. 8. Run a check standard after every ten injections of samples. Standards are run in part to monitor the life and performance of the graphite tube. Lack of reproducibility or sig- nificant change in the signal for the standard indicates that the graphite tube should be replaced. 9. Employ a minimum of one blank with a sample batch to verify any contamination. 10. The standard addition method (Section 7.7.1.1.1) should be employed for the analysis of all EPTOX extracts. 11. QC requirements are listed in Chapter 13. 18.5 BARIUM Barium (Ba) stimulates the heart muscle. However, a barium dose of 550 to 600 mg is considered fatal to human beings. Despite its relative abundance in nature (16th in order of rank), barium occurs only in trace amounts in water (0.7 to 900 µg/l, with a mean of 49 µg/l). Higher concentrations in drinking water often signal undesirable industrial waste pollution. Selection of method: Preferably, analyze via the FAAS (Chapter 8), GrAAS (Chapter 9), or ICP (Chapter 12) method. 18.5.1 FLAME ATOMIC ABSORPTION SPECTROSCOPY (FAAS) The FAAS technique is described in Chapter 8. A high, hollow, cathode-current setting and a narrow spectral band pass must be used, because both barium and calcium emit strongly at barium’s analyt- ical wavelength. Barium undergoes significant ionization in the nitrous oxide/acetylene flame, re- sulting in a significant decrease in sensitivity. All samples and standards must contain 2 ml of potas- sium chloride (KCl) ionization suppressant per 100 ml of sample. (Dissolve 95 g of KCl in reagent- grade water and dilute to 1 liter.) © 2002 by CRC Press LLC Selected Methods for Determination of Metals in Environmental Samples 277 Prepare calibration standards via dilutions of the stock solution at the time of analysis. The cali- bration standards should be prepared to contain the same type and concentration of acid as the sam- ples to be analyzed after digesting. All calibration standards should contain 2 ml of the KCl (ioniza- tion suppressant) solution. 18.5.1.1 Instrument Parameters • Instrument: Barium hollow cathode lamp • Wavelength: 553.6 nm • Fuel: Acetylene • Oxidant: Nitrous oxide • Type of flame: Rich fuel • Background correction: Not required 18.5.1.2 Performance Characteristics • Optimum concentration range: 1 to 20 mg/l • Sensitivity: 0.4 mg/l • Detection limit: 0.1 mg/l 18.5.2 GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY (GRAAS) The use of halide acid should be avoided. Because of possible chemical interaction, nitrogen should not be used as a purge gas. 18.5.2.1 Instrument Parameters • Drying time and temperature: 30 sec at 125°C • Ashing time and temperature: 30 sec at 1200°C • Atomizing time and temperature: 10 sec at 2800°C • Purge gas: Argon • Wavelength: 553.6 nm Other operating parameters should be set as specified by the instrument manufacturer. 18.5.2.2 Performance Characteristics • Optimum concentration range: 10 to 200 mg/l • Detection limit: 2 mg/l 18.6 BERYLLIUM Beryllium (Be) and its compounds are very poisonous and in high concentrations can cause death. Inhalation of beryllium dust can cause a serious disease called berylliosis. Beryllium disease also can cause dermatitis, conjunctivitis, acute pneumonitis, and chronic pulmonary berylliosis. Beryllium is used in atomic reactors, aircraft, rockets, and missile fuels. Entry into water can result from the dis- charges of these industries. The usual range of beryllium in drinking waters is 0.01 to 0.7 µg/l. Selection of methods: FAAS, GrAAS, and ICP methods may be used (see Chapters 8, 9, and 12, respectively). © 2002 by CRC Press LLC 278 Environmental Sampling and Analysis for Metals 18.6.1 FLAME ATOMIC ABSORPTION SPECTROSCOPY (FAAS) Background correction may be required. Concentration of aluminum greater than 500 ppm may sup- press beryllium absorbance. The addition of 0.1% fluoride has been found effective in eliminating this interference. High concentrations of magnesium and silicon cause similar problems and require the use of the standard additions method. 18.6.1.1 Instrument Parameters • Instrument: Beryllium hollow cathode lamp • Wavelength: 234.9 nm • Fuel: Acetylene • Oxidant: Nitrous oxide • Type of flame: Rich fuel • Background correction: Required 18.6.1.2 Performance Characteristics • Optimum concentration range: 0.05 to 2 mg/l • Sensitivity: 0.025 mg/l • Detection limit: 0.005 mg/l For concentrations below 0.02 mg/l, the furnace procedure is recommended. 18.6.2 GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY (GRAAS) Long residence time and high concentrations of the atomized sample in the optical path of the graphite furnace can result in severe physical and chemical interference. Furnace parameters must be optimized to minimize these effects. In addition to the normal interferences experienced during graphite furnace analysis, beryllium analysis is subject to severe nonspecific absorption and light scattering during atomization. Simultaneous background correction is required to avoid erroneous high results. 18.6.2.1 Instrument Parameters • Drying time and temperature: 30 sec at 125°C • Ashing time and temperature: 30 sec at 1000°C • Atomizing time and temperature: 10 sec at 2800°C • Purge gas: Argon • Wavelength: 234.9 nm • Background correction: Required Other operating parameters should be set as specified by the instrument manufacturer. The above concentration values and instrument conditions are for a Perkin Elmer HGA-2100, based on the use of a 20- µl injection, continuous-flow purge gas, and nonpyrolytic graphite. Smaller sizes of furnace devices or those employing faster rates of atomization can be operated using lower atomization temperatures for shorter time periods than the recommended settings above. 18.6.2.2 Performance Characteristics • Optimum concentration range: 1 to 30 mg/l • Detection limit: 0.2 mg/l © 2002 by CRC Press LLC [...]... the standards and sample Then add 2.0 ml of 0.12M H2SO4 in excess At this point, pH should be 2.4 6 Add 5.0 ml of APDC solution (Section 18. 11.1.1.1) and mix The pH should then be approximately 2.8 © 2002 by CRC Press LLC 288 Environmental Sampling and Analysis for Metals 7 Add 10.0 ml of MIBK (Section 18. 11.1.1.6) and shake vigorously for 3 min 8 Allow the layers to separate and add reagent-grade... procedure in Section 18. 11.1 18. 12 COBALT Cobalt (Co) normally occurs at levels of less than 10 µg/l in natural waters Wastewaters may contain higher concentrations Selection of method: Use the FAAS (Chapter 8), GrAAS (Chapter 9), or ICP (Chapter 12) method © 2002 by CRC Press LLC 290 Environmental Sampling and Analysis for Metals 18. 12.1 GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY (GRAAS) 18. 12.1.1 Instrument... standards should be prepared at the time of analysis To each of the 100-ml standards and the sample, add 2.0 ml of 40% ammonium phosphate solution (40 g (NH4)2HPO4 per 100 ml of reagent-grade water) The calibration standards should be prepared to contain 0.5% (v/v) HNO3 Many plastic pipet tips (yellow) contain cadmium Use “cadmium-free” tips © 2002 by CRC Press LLC 280 Environmental Sampling and Analysis. .. Press LLC 282 Environmental Sampling and Analysis for Metals The buffer solution can be used for about 1 month Discard the buffer when 1 or 2 ml are added to the sample and it fails to produce a pH of 10.0 at the titration endpoint 18. 9.2.2.2 Eriochrom Black T Indicator Weigh 0.5 g of indicator and 100 g of NaCl into a porcelain mortar, and mix well Alternatively, a coffee grinder may be used for complete... avoided 18. 24.2.1 Instrument Parameters • • • • • Drying time and temperature: 30 sec at 125°C Ashing time and temperature: 30 sec at 400°C Atomizing time and temperature: 10 sec at 2700°C Purge gas: Argon Wavelength: 328.1 nm © 2002 by CRC Press LLC 300 Environmental Sampling and Analysis for Metals Other operating parameters should be set as specified by the instrument manufacturer 18. 24.2.2 Performance... mixing 18. 9.2.2.3 0.02N EDTA Titrant Dissolve 3.723 g of EDTA disodium salt in about 700 ml of DI water in a 1-liter volumetric flask and dilute to the mark with DI water Standardize against standard 0.02N CaCO3 solution 18. 9.2.2.4 Calcium Carbonate Standard Solution Weigh 1.0000 g of anhydrous CaCO3 (primary standard) and transfer to a 500-ml Erlenmeyer flask Place a funnel in the flask neck and add... by CRC Press LLC 286 Environmental Sampling and Analysis for Metals 18. 10.1.2 Performance Characteristics • Optimum concentration range: 0.5 to 10 mg/l • Sensitivity: 0.25 mg/l • Detection limit: 0.05 mg/l For concentration of chromium below 0.2 mg/l, the furnace procedure is recommended 18. 10.2 GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY (GRAAS) Low concentrations of calcium and/ or phosphate may... potassium chromium standard I (Section 18. 11.1.1.3) to 1 liter with reagent-grade water 1 ml = 10 µg Cr 18. 11.1.1.5 Potassium Dichromate Standard Solution III Dilute 10 ml of potassium dichromate standard II (Section 18. 11.1.1.4) to 1 liter with reagent-grade water 1 ml = 0.10 µg Cr 18. 11.1.1.6 Methyl Isobutyl Ketone (MIBK) Avoid material that comes into contact with metal or metal-lined caps 18. 11.1.1.7 Sodium... LLC Selected Methods for Determination of Metals in Environmental Samples 303 For concentrations of vanadium below 0.5 mg/l, the furnace technique is recommended 18. 28.2 GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY (GRAAS) Vanadium is refractory and prone to form carbides Consequently, memory effects are common, and care should be taken to clean the furnace before and after analysis Nitrogen should... preparing a color-comparison © 2002 by CRC Press LLC Selected Methods for Determination of Metals in Environmental Samples 285 blank containing 2 ml of 1N NaOH and a scoopful of indicator powder and sufficient EDTA titrant (0.05 to 0.10 ml) to produce an unchanging color 18. 9.3.4 Calculation Calcium as CaCO3 = (ml × N × 50 × 1000)/ml sample (18. 2) where ml = ml of ETA standard used for titration N = . technique; R-1 = methods for Chemical Analysis of Water and Wastes (EPA-600/ 4-7 9-0 20, Revised March 1983); R-2 = Standard Methods for the Examination of Water and Wastewater (AWWA, 18th ed., 1992); R-3. 270.2 R-1 7740 R-3 Silver + + — 272.1&2 R-1 7760 R-3 Sodium + –— 273.1 R-1 7770 R-3 Thallium + + — 279.1&2 R-1 7840 R-3 Tin + + — 282.1&2 R-1 7870 R-3 Titanium + + — 283.1&2 R-1 —. 206.2 R-1 7060 R-3 Barium + + — 208.1&2 R-1 7080 R-3 Beryllium + + — 210.1&2 R-1 7090 R-3 Boron –– Curcumin 4500-BB R-2 — — Boron –– Carmine 4500-BC R-2 — — Cadmium + + — 213.1&2 R-1