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FlanaginIntroduction : Introduction Chemical spot tests are accepted screening evaluations for specific metals in soil, dust, and water samples. A reliable spot test for testing soils at and around contaminated sites containing lead is a useful site characterization tool. The following field lead detection methodology is not adequate for quantitation of lead or appropriate for legal interpretations. Purpose: Purpose Students learn to use spot test to test for lead in their environment: Soil sample testing Paint chip testing Tap water testingSafety: Safety Lead nitrate - Pb(NO3)2 - Toxic if taken internally (i.e., by mouth). Do not eat or drink while performing field test. ToxNet information attached or MSDS sheet attached. Citrate Buffer (pH 3.0) (0.1M) is an organic acid, should not be taken internally, splashed into eyes, or come in contact with skin. Wear protective gloves when handling and do not eat of drink while performing tests. ToxNet information attached or MSDS sheet attached. Rhodizonate - toxicity unknown. Will discolor skin. Avoid contact with skin of eyes. Safety: Safety Sample and control soils may contain fungi, bacteria or small nematodes or insects. Do not allow prolonged contact with skin, do not eat or drink while performing sampling or analyses. Proper hygiene, sanitation and ventilation procedures should be observed. Respiratory protection is not mandatory. Chemicals & Standards: Chemicals & Standards Deionized Water (DI) Citrate Buffer (pH 3.0) (0.1M) Rhodizonate Color Indicator (0.2%, w/v) MW214, 50 mg/25ml Lead (Pb) Standard - Pb(NO3)2, 64 ppm Negative Control Soil Positive Control SoilEquipment: Equipment Straws (spatulas) Small-scale pipettes Lab top Absorbent paper towel wedges Paper towels Pen or pencil Report sheetProcedure : Procedure Preparation of Reagents & other Materials For 100 ml of Citrate Buffer pH ~ 3.0: Add 7.4 ml of 0.2M NaH2PO4 to 92.6 ml of 0.1M Citric Acid (1M Sodium Phosphate NaH2PO4 = 119 g/L, 0.2 M = 23.8 g/L or 0.595 g / 25 ml) (1M Citric Acid C6H8O7 = 192 g/L, 0.1 M = 19.2 g/L or 1.92 g / 100 ml)Procedure : Procedure For 25 ml of 0.2 % Rhodizonate Indicator: 50 mg / 25 ml DI water 0.2% = 0.2g / 100 ml = 200 mg / 100 ml = 50 mg / 25 ml **** Rhodizonate is light sensitive; must use within 24 hours after mixing, MW = 214. For 25 ml of 64 ppm Lead Nitrate Standard - Pb(NO3)2 : 64 ppm = 64 mg / L = 1.6 mg / 25 ml Soil Test: Soil Test Designate moderately spaced areas on Lab top for the following: DI Water Citrate Buffer Lead Nitrate Standard (positive control) Negative Control Soil Soil. Sample(s) Positive Control Soil Soil Test: Soil Test . Place three (3) drops of the liquids above and approximately one pinch (small amount from SSC straw spatula) of soil (do your best to keep soil amounts consistent) in their designated Lab top areas. Add three (3) drops of Citrate Buffer directly onto each individual sample (liquids, soil controls and all samples). Soil Test: Soil Test Add three (3) drops of Rhodizonate Color Indicator directly onto each individual sample and all samples. Immediately after this is done, RECORD ALL COLOR CHANGES with and without magnifying glass. Place one end of a paper towel strip onto each of the mixtures using one strip per mixture. NOTE COLOR AND INTENSITY OF EACH. Results /Discussion: Results /Discussion DI water, citrate buffer, and negative control soils will appear as either colorless or slightly yellow. Lead nitrate standard and soils with lead contamination will appear red. Rhodizonate will react with other metals (see Feigl, p. 284, “Sodium Rhodizonate, at pH~3, also forms colored compounds with Tl+, Ag+, Cd+2, Ba+2, and Sn+2. the sensitivity of some of these reactions is less than that with Pb+2.” 4 Laboratory analyses with chromium nitrate, zinc metal, iron (ferric nitrate), copper sulfate, and potassium iodide controls did not result in a red color change using 0.2% Rhodizonate with the pH 3 citrate buffer (Carney and Parras. U.S. EPA9 ).Waste Disposal: Waste Disposal Clean the Lab Top with paper towels. Place paper towels and all other paper or plastic waste into a plastic bag and carry the refuse off site. The Small Scale Chemistry (SSC) procedure will produce very little chemical or paper waste. The waste can be deposited in the municipal trash.References: References Thompson, Stephen, 1989. Chemtrek: Small-Scale Experiments for General Chemistry, Prentice-Hall, Inc., Englewood Cliffs, New Jersey, ISBN 0-205-11913-1 Waterman, Edward L., Thompson, S., 1993. Small-Scale Chemistry Laboratory Manual, Addison-Wesley Publishing Company, Inc., New York, New York, ISBN 0-201-25006-3References: References Texas Education Agency, January 2000. Texas Safety Standards – Kindergarten through Grade 12, A Guide To Laws, Rules, Regulations, and Safety Procedures For Classroom Laboratory and Field Investigations, Funded by: Texas Education Agency’s National Science Foundation Cooperative Agreement #ESR-9712001, the Charles A. Dana Center, and The University of Texas at Austin. Feigl, Fritz, 1972. Spot Tests in Inorganic Analysis, 6th Edition, Lead - (2) test with Sodium Rhodizonate. p. 282 - 287. Elsevier publishing company Amsterdam, Amsterdam and New York, New York, ISBN No. 0-444-40929-7. References: References Marano, Ross, January 2002. Chemicals and Supplies for Small-Scale Chemistry Workshops, email communication to Dr. Pete Test of the Fort Worth Public School System. U.S. EPA/G.Carney. U.S. EPA, March 1995. Residential Sampling for Lead: Protocols for Dust and Soil Sampling: Final Report, Pollution Prevention and Toxics (7404), EPA 747-R-95-001, March 1995, U.S. Environmental Protection Agency, Washington, D.C. References: References U.S. EPA, September 1993. Standard Operating Procedures for the Field Analysis of Lead in Paint, Bulk Dust, and Soil by Ultrasonic, Acid Digestion and Colorimetric Measurements, PB94-121738, Atmospheric Research and Exposure Assessment Laboratory, Research Triangle Park, NC 27711. U.S. EPA, May 1995. A Field Test of Lead-Based Paint Testing Technologies: Summary Report, Office of Prevention, Pesticides, and Toxic Substances 7101, EPA 747-R-95-002a, U.S. Environmental Protection Agency, Washington, D.C.References: References Carney, Gerald and Bryan Parras. 2002Spot test analyses using lead, cadmium, zinc, iron, and nickel nitrate standards. Part of a small scale chemistry training workshop at Southwest High School, Ft. Worth, TX. February 1, 2002. U.S. Environmental Protection Agency, Region 6, Dallas, TX. You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.