Organic Carbon, Total

Transcription

1 Method Direct Method 1 Scope and Application: For water, drinking water, and wastewater 1 U.S. Patent 6,368,870 LR (0.3 to 20.0 mg/l C) Test Preparation Before starting the test: A reagent blank is required for each series of samples. Collect the following items: Quantity Total Organic Carbon Direct Method Low Range Test N Tube Reagent Set 1 Cylinder, graduated, 10-mL 1 DRB200 Reactor 1 ph Paper 1 Flask, Erlenmeyer, 50-mL 1 Magnetic Stirrer 1 Pipet, TenSette, 0.1 to 1.0 ml plus tips 1 Pipet, TenSette, 1.0 to 10.0 ml plus tips 1 Stir Bar, magnetic 1 Test Tube Rack 1 3 Water, organic-free 3.0 ml Wipes, disposable, Kimwipes 1 Note: Reorder information for consumables and replacement items is on page 6. Direct Method Method HRS MIN SEC 1. Turn on the DRB 200 reactor. Select the TOC program. 2. Use a graduated cylinder to add 10 ml of sample to a 50-mL Erlenmeyer flask that contains a stir bar. 3. Add 0.4 ml of Buffer Solution, ph 2.0. Use ph paper to make sure the sample ph is Place the flask on a stir plate and stir at a moderate speed for 10 minutes. OrganicCarbonTotal_10129_LR.fm Page 1 of 6

2 5. Label two Low Range Acid Digestion vials sample and reagent blank. 6. Use a funnel to add the contents of one TOC Persulfate Powder Pillow to each Acid Digestion vial (colorless liquid). 7. Use a TenSette Pipet to add 3.0 ml of organic-free water to the reagent blank vial and 3.0 ml of prepared sample to the sample vial. Swirl to mix. 8. Rinse two blue Low Range Indicator Ampules with deionized water and wipe them with a soft, lint-free wipe. Do not touch the ampules sides after wiping. Pick them up by the top. 9. Lower one unopened ampule into each Acid Digestion vial. When the score mark on the ampule is level with the top of the Acid Digestion vial, snap the top off the ampule and allow it to drop into the Acid Digestion vial. Do not invert or tilt the vial after inserting the ampule. 10. Cap the vial assemblies tightly and insert them in the COD reactor for 2 hours at C. 11. Carefully remove the vial assemblies from the reactor. Place them in a test tube rack. Allow the vials to cool for one hour for accurate results. The liquid in the reagent blank vial should be dark blue. 12. Select the test. Page 2 of 6 OrganicCarbonTotal_10129_LR.fm

3 13. Wipe the reagent blank with a damp towel, followed by a dry one, to remove fingerprints or other marks. 14. Insert the reagent blank vial assembly in the 16-mm round cell holder. 15. Press ZERO. The display will show: 0.0 mg/l C. 16. Wipe the sample vial assembly with a damp towel, followed by a dry one, to remove fingerprints or other marks. 17. Insert the sample vial assembly in the 16-mm round cell holder. 18. Press READ. Results are in mg/l C. Interferences The following have been tested for interference and found not to interfere up to the indicated levels: Table 1 Interfering Substances and Levels Substance Aluminum Ammonia Nitrogen ASTM Wastewater Bromide Maximum Level Tested 1000 mg/l as N No effect 500 mg/l Br Bromine 25 mg/l Br 2 Calcium 2000 mg/l as CaCO 3 Chloride 500 mg/l Chlorine Cl 2 Chlorine Dioxide 6 mg/l ClO 2 Copper Cyanide Iodide CN 50 mg/l OrganicCarbonTotal_10129_LR.fm Page 3 of 6

4 Table 1 Interfering Substances and Levels (continued) Substance Iron (II) Iron (III) Maximum Level Tested Magnesium 2000 mg/l as CaCO 3 Manganese (VII) 1 mg/l Monochloramine 14 mg/l NH 2 Cl as Cl 2 Nitrite 500 mg/l NO 2 Ozone 2 mg/l O 3 Phosphate 3390 mg/l PO 3 4 Silica 100 mg/l SiO 2 Sulfate 5000 mg/l SO 2 4 Sulfide 20 mg/l S 2 Sulfite 50 mg/l SO 3 2 Zinc 5 mg/l Sampling and Storage Accuracy Check If the sample contains greater than 600 mg/l CaCO 3 alkalinity, lower the sample ph to less than 7 before testing by adding Sulfuric Acid Solution. Most sample turbidity is either dissolved during the digestion stage or settled during the cooling period. Sample turbidities up to 50 NTU have been tested without interference. Collect samples in clean glass bottles. Rinse the sample bottle several times with the sample to be collected. Fill the bottle completely full before capping. Test samples as soon as possible. Acid preservation is not recommended. Homogenize samples containing solids to assure representative samples. Standard Additions Method (Sample Spike) 1. After reading test results, leave the sample cell (unspiked sample) in the instrument. 2. Press OPTIONS>MORE. Press STANDARD ADDITIONS. A summary of the standard additions procedure will appear. 3. Press OK to accept the default values for standard concentration, sample volume, and spike volumes. Press EDIT to change these values. After values are accepted, the unspiked sample reading will appear in the top row. See the user manual for more information. 4. Prepare a 150-g/L C standard by transferring 15.00mL of 1000-mg/L C stock solution to a 100-mL Class A volumetric flask. Dilute to volume with organic-free water. Mix. 5. Use the TenSette Pipet to add 0.1, 0.2, and 0.3 ml of the 150-mg/L C standard to each of three Acid Digestion Vials. 6. Add the contents of one TOC Persulfate Powder Pillow to each vial. Page 4 of 6 OrganicCarbonTotal_10129_LR.fm

5 Method Performance 7. Add 3.0 ml of sample to each vial. Swirl to mix. Continue the test starting at step 8 on page 2 of this procedure. 8. Analyze each sample spike as described in the procedure above, starting with the 0.1 ml sample spike. Accept each standard additions reading by pressing READ. Each addition should reflect approximately 100% recovery. 9. After completing the sequence, press GRAPH to view the best-fit line through the standard additions data points, accounting for the matrix interferences. Press IDEAL LINE to view the relationship between the sample spikes and the Ideal Line of 100% recovery. Standard Solutions Method 1. Prepare a 1000-mg/L organic carbon stock standard by dissolving g dry primary standard Potassium Acid Phthalate in Organic-free Reagent Water and dilute to 1000 ml. This stock standard is stable for about 1 month at room temperature. Alternatively, open one ampule of TOC Standard Solution, 1000 mg/l C. Perform the TOC procedure as described above. 2. Prepare a 10.0-mg/L C standard by transferring ml of the stock standard to a 1000-mL Class A volumetric flask. Dilute to volume using Organic-Free Reagent Water. Stopper and mix thoroughly. Prepare this standard fresh daily. 3. To adjust the calibration curve using the reading obtained with the standard solution, press OPTIONS>MORE on the current program menu. Press STANDARD ADJUST. 4. Press ON. Press ADJUST to accept the displayed concentration. If an alternate concentration is used, press the number in the box to enter the actual concentration, then press OK. Press ADJUST. Precision Standard: 10.0 mg/l C Program 95% Confidence Limits of Distribution mg/l C Sensitivity Portion of Curve Abs Concentration Mid-range mg/l C Summary of Method Note: To test for higher ranges of TOC use Method or Method The total organic carbon (TOC) is determined by first sparging the sample under slightly acidic conditions to remove the inorganic carbon. In the outside vial, organic carbon in the sample is digested by persulfate and acid to form carbon dioxide. During digestion, the carbon dioxide diffuses into a ph indicator reagent in the inner ampule. The adsorption of carbon dioxide into the indicator forms carbonic acid. Carbonic acid changes the ph of the indicator solution which, in turn, changes the color. The amount of color change is related to the original amount of carbon present in the sample. Test results are measured at 598 and 430 nm. OrganicCarbonTotal_10129_LR.fm Page 5 of 6

6 Consumables and Replacement Items Required Reagents Description Quantity/Test Unit Cat. No. Reagent Set, Total Organic Carbon Direct Method Low Range Test N Tube, includes: 50 vials Acid Digestion Solution Vials, High Range TOC /pkg Buffer Solution, Sulfate 0.4 ml 25 ml Funnel, micro 1 each Indicator Ampule, Low Range TOC /pkg TOC Persulfate Powder Pillows /pkg ph Paper 1 5/pkg Water, Organic-free 3.0 ml 500 ml Not sold separately. Required Apparatus Description Quantity/Test Unit Cat. No. Cylinder, graduated, 10-mL 1 each DRB200 Reactor, 110 V, 15 x 16 mm 1 each LTV DRB200 Reactor, 220 V, 15 x 16 mm 1 each LTV Flask, Erlenmeyer, 50-mL 1 each Magnetic Stirrer 1 each Pipet, TenSette, 0.1 to 1.0 ml 1 each Pipet Tips, for TenSette Pipet /pkg Pipet, TenSette, 1.0 to 10.0 ml 1 each Pipet Tips, for TenSette Pipet /pkg Stir Bar, magnetic 1 each Test Tube Rack 1 3 each Wipes, Disposable, Kimwipes 1 280/pkg Recommended Standards Description Unit Cat. No. Potassium Acid Phthalate 500 g TOC Standard Solution (KHP Standard, 1000-mg/L C) 5/pkg Optional Reagents Description Cat. No. Sulfuric Acid Solution FOR TECHNICAL ASSISTANCE, PRICE INFORMATION AND ORDERING: In the U.S.A. Call toll-free Outside the U.S.A. Contact the HACH office or distributor serving you. On the Worldwide Web techhelp@hach.com HACH COMPANY WORLD HEADQUARTERS Telephone: (970) FAX: (970) Hach Company, All rights reserved. Printed in Germany. Updated April 05 Edition 1