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SIDE BY SIDE COMPARISON TABLE FOR THE DETERMINATION OF CYANIDE BY UV DIGESTION AND AMPEROMETRIC DETECTION FIA METHOD - 10-204-00-5-D (ASTM D7511-09 e ) TOPIC Method ASTM D7511-09e LACHAT METHOD NUMBER 10-204-00-5-D Rev 1, 21 March 2011 SCOPE AND APPLICATION Approximately 3-500 g CN/L 2-500 g CN/L SUMMARY OF METHOD Samples are treated to remove potential interferences, according to the method. The treated sample is introduced into a segmented flow injection analysis (SFA) system, where it is treated with UV light to break down cyanide complexes, and acidified to produce hydrogen cyanide (HCN) The hydrogen cyanide gas diffuses through a hydrophobic gas diffusion membrane, from the acidic donor stream into an alkaline receptor stream. The captured cyanide is sent to an amperometric flow-cell detector with a sliver working electrode. In the presence of cyanide, silver in the working electrode is oxidized at the applied potential. The anodic current measured is proportional to the concentration of cyanide in the standard or sample injected. Liquid samples are first mixed with acid reagents and then introduced into an in-line digestion unit. In this unit, the samples are passed over a 312nm UV lamp to cleave metal- CN complexes. The CN- released by the acidic reagents and UV light is mixed with acid to form HCN (g), which passes through a hydrophobic membrane in a distillation block and is trapped in a sodium hydroxide solution. The addition of hydrochloric acid converts cyanide ions to hydrogen cyanide (HCN (g) ) that passes through a gas diffusion membrane into an alkaline receiving solution where it is converted back to cyanide ion. The cyanide ion is monitored amperometrically with a silver working electrode, silver/silver chloride reference electrode, and platinum/stainless steel counter electrode, at an applied potential of zero volts. The current generated is proportional to the cyanide concentration present in the original sample. Calibrations and data are processed with the instruments data-acquisition software. INTERFERENCES High levels of carbonate can release CO 2 into the acceptor stream and cause an interference with the amperometric detector, that results in a slight masking effect (15 percent negative bias with 20 ppb cyanide in 1500 ppm carbonate). Sulfide will diffuse through the gas diffusion membrane and can be detected in the amperometric flow cell. Oxidized products of sulfide can also rapidly convert CN - to SCN - at a high ph. Refer to Section 6.1 of Test Method D7511-09e for additional information Calibrations and data are processed with the instruments data-acquisition software. High levels of carbonate can release CO 2 into the acceptor stream and cause an interference with the amperometric detector, that results in a slight masking effect (15 percent negative bias with 20 ppb cyanide in 1500 ppm carbonate). Sulfide will diffuse through the gas diffusion membrane and can be detected in the amperometric flow cell. Oxidized products of sulfide can also rapidly convert CN - to SCN - at a high ph. Refer to Section 4 of the method for additional information on interferences. 2
EQUIPMENT AND SUPPLIES REAGENTS AND STANDARDS regarding interferences for the analysis of cyanide, and Section 11 of Test Method D7511-09e for elimination of interferences. Instrument, equipped with a precise sample introduction system, a gas diffusion manifold with hydrophobic membrane, and an amperometric detection system to include a silver working electrode, an Ag/AgCl reference electrode and a Pt or stainless counter electrode. An auto sampler is recommended but not required. Use computer hardware supplied by the Instrument manufacturer. Pump tubing and membrane should also be those specified by the manufacturer Sodium hydroxide solution, 1M: 40 g NaOH/L Acceptor /diluent Solution A: (0.1M NaOH). Dissolve 4 g of NaOH in 1L of water. Acceptor reagent B (0.025M sodium hydroxide) Dilute 25 ml of sodium hydroxide to 1L Lachat QuikChem Flow Injection Analyzer with auto sampler, injection valve, peristaltic pump, in-line digestion module with 8W, 312nm lamp, gas diffusion manifold, and amperometric detector. The Amperometric Detection system has a silver working electrode, Ag/AgCl reference electrode, Pt stainless steel counter electrode, with applied potential of 0.0 volts. Stock Sodium hydroxide solution, 1N: 40 g NaOH/L Carrier/Acceptor (0.025M NaOH) Sodium Hydroxide: 1.0 g/l (0.025M) or 25 ml of 1M stock solution per liter. Stock Cyanide solution: 1000 mg CN - /L. In a 1L volumetric flask containing 2 g of NaOH, dissolve 2.51g of KCN (Potassium cyanide). TA1 (Total Acid Reagent 1): 55 ml of sulfuric acid is added carefully to about 800 ml of DI water. When cool (room temp), 20 ml of hypophosphoric acid is added. Dilute to volume. TA2( Total Acid reagent 2: 1 g of bismuth nitrate pentahydrate is weighed into a flask containing 55 ml of water. 55 ml of sulfuric acid is added, and the flask is swirled until the bismuth nitrate pentahydrate is dissolved. 800 ml of DI water is added. When the solution has cooled to room temperature, 20 ml of hypophosphorus acid is added, and the solution diluted to volume. Stock Cyanide Solution: Same. TA1 (Total Acid Reagent 1): Same TA2( Total Acid reagent 2: Same 3
Standards (mg CN/L) 3 to 500 g CN/L in 0.025M NaOH Standards (mg CN/L) 2 to 500 g CN/L in 0.025M NaOH Sodium Chloride (NaCl) solution, 3 M Reference Electrode Storage Solution 43.88 g of NaCl/250 ml SAMPLE COLLECTION PRESERVATION AND STORAGE Unless otherwise noted, samples must be stabilized with NaOH at the time of collection, to a ph of 12-12.5. (See ASTM Practices D3370 and D3856 Same, see method. CALIBRATION AND Standards ( g CN/L) Standards ( g CN/L) STANDARDIZATION 400 to 2.0 500, 250, 100, 50, 25, 10, 5, 2, 0 PROCEDURE See Method Same, see method. SAFETY The following chemicals have the Same, see method. potential to be highly toxic or hazardous, for detailed explanation, consult the MSDS. Hydrogen cyanide gas Potassium cyanide Hypohosphorous Acid Bismuth Nitrate pentahydrate Sodium hydroxide Hydrochloric acid Lead acetate Mercury (II) cyanide Potassium nickel cyanide DATA ANALYSIS AND CALCULATIONS METHOD PERFORMANCE/VALIDATION DATA Calibration: 2 nd order quadratic Calibration range: 400 to 2.0 g CN/L Sample Throughput 14-40 samples per hour Precision/ Accuracy: See Method Calibration: 2 nd order with 1/x weighting Conc = 9.88e4 *Area 2 + 2.01* Area 1.31 R = 1.0000 Calibration Range: 2 to 500 g CN/L Sample Throughput: 12 samples/hour Precision, Single Lab: x = 100.12 g CN - /L known conc. =100.0 g CN - /L %RSD = 0.49% x=243.2 g CN - /L known conc. =250.0 g CN - /L %RSD = 0.17% 4
Method Detection Limit 1.0 g CN-/L Method Detection Limit, Single Lab: 0.21 g CN - /L Recovery of Potassium, Ferrocyanide, Ferricyanide, and Nickle cyanide Recoveries in tap water. Potassium, Nickel, and Mercury cyanide are recovered at levels greater than 93%. Recoveries in wastewater. Potassium, Nickel, Mercury and iron cyanides are recovered at levels greater than 95%. Compound Amount in Sample Average Value Obtained % Recovery * Zinc cyanide 100.0 μg CN-/L 95.95 μg CN - /L 95.95 Ferro cyanide 100.0 μg CN-/L 99.5 μg CN - /L 99.5 Ferri cyanide 100.0 μg CN-/L 102 μg CN - /L 102.0 Silver cyanide 100.0 μg CN-/L 102.5 μg CN - /L 102.5 Nickel cyanide 100.0 μg CN-/L 102 μg CN - /L 102.0 *(determined/known) * 100 FINAL REAGENT RATIOS Carrier: 100% - amperometric reaction. Sample: 200 L Carrier: 100% - amperometric reaction. Sample: 52 L References: 1. Standard Test Methods for Cyanide in Waters, Annual Book of ASTM Standards, Vol. 11.02, Revised 1994, D 2036-91, pp, 79-113. 2. ASTM Designation:D7511-09 e2. Standard Test Method for Total Cyanide by Segmented Flow Injection Analysis, In-Line Ultraviolet Digestion and Amperometric Detection. 3. Lachat QuikChem Method number 10-204-00-5-A. 4. ISO method number 17380. 5. U.S. Environmental Protection Agency, Methods for the Chemical Analysis of Water and Wastes, EPA-600/4-79-020, Revised March 1983, Method 335.4. 6. Guideline and Format for EMSL-Cincinnati Methods. EPA-600/8-83-020, August 1983. 7. Standard Methods, For the Examination of Water and Waste Water, 20th ed. Revised 1998, Method 4500-CN - Cyanide. 8. ASTM committee, Test method under the jurisdiction of D-19 on water, Test group #. 19.06.01.33, Draft #3, March 15, 2000. 9. U.S. Environmental Protection Agency, Guideline Establishing Test Procedures for the Analysis of Pollutants; Available Cyanide, Proposed Rule, 40 CFA part 136, July 7, 1998. 5
10. Emil B Milosavljevic, and Ljiljana Solujic, Rapid Distillationless Free Cyanide Determination by a Flow Injection Ligand Exchange Method, Environ Sci. Technol. 1995, 29, 426-430.. 6