Phosphorus, Reactive (Orthophosphate)

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1 Method 8048 DR/2400 * Adapted from Standard Methods for the Examination of Water and Wastewater ** Procedure is equivalent to USEPA method and Standard Method 4500-P-E for wastewater. Phosphorus, Reactive (Orthophosphate) PhosVer 3 (Ascorbic Acid) Method* Powder Pillows or AccuVac Ampuls (0.02 to 2.50 mg/l PO 4 ) Scope and Application: For water, wastewater, and seawater; USEPA Accepted for reporting for wastewater analyses** Tips and Techniques For more accurate results, determine a reagent blank value for each new lot of reagent. Follow the procedure using deionized water in place of the sample. Subtract the reagent blank value from the final results or perform a reagent blank adjust. See Section Reagent Blank on page 20 for more information. A blue color will develop if phosphorus is present. Wipe the outside of sample cells before each insertion into the instrument cell holder. Use a damp towel followed by a dry one to remove fingerprints or other marks. Powder Pillows Method 8048 Hach Programs 1. Touch Hach Programs. Select program 490 P React. PV. Touch Start. 2. Fill a sample cell with 10-mL of sample. 3. Add the contents of one PhosVer 3 phosphate Powder Pillow to the cell. Immediately cap and invert to mix (this is the prepared sample). 4. Touch the timer icon. Touch OK. A two-minute reaction period will begin. If the sample was digested using the Acid Persulfate digestion, a ten-minute reaction period is required. PhosphorusReac_AVPP_Other_PV3_Eng_Ody.fm Page 1 of 6

2 10 ml Zero 10 ml 5. Fill another sample cell with 10 ml of sample (this is the blank). 6. When the timer beeps, wipe the blank and place it into the cell holder. 7. Touch Zero. The display will show: 0.00 mg/l PO 4 8. Wipe the prepared sample and place it into the cell holder. Touch Read. Results will appear in mg/l PO 4. AccuVac Ampul Method 8048 Hach Programs 10 ml HRS MIN SEC 1. Touch Hach Programs. Select program 492 P React. PV AV. Touch Start. 2. Fill a sample cell with 10-mL of sample. (This is the blank.) Note: Collect at least 40 ml of sample in a 50-mL beaker. 3. Fill a PhosVer 3 Phosphate AccuVac Ampul with sample. Keep the tip immersed while the ampule fills completely. 4. Place an ampule cap securely over the tip of the ampule. Shake the ampule for approximately 30 seconds. Note: Accuracy is unaffected by undissolved powder. Page 2 of 6 PhosphorusReac_AVPP_Other_PV3_Eng_Ody.fm

3 10 ml Zero 5. Touch the timer icon. Touch OK. A two-minute reaction period will begin. If the sample was digested using the Acid Persulfate digestion, a ten-minute reaction period is required. 6. When the timer beeps, wipe the blank and place it into the cell holder. 7. Touch Zero. The display will show: 0.00 mg/l PO 4 8. Wipe the prepared sample and place it into the cell holder. Touch Read. Results will appear in mg/l PO 4. Interferences Interfering Substance Aluminum Arsenate Chromium Copper Hydrogen Sulfide Iron Nickel ph, excess buffering Silica Silicate Turbidity (large amounts) or color Zinc Greater than 200 mg/l Interferes at any level. Greater than 100 mg/l Greater than 10 mg/l Interferes at any level Greater than 100 mg/l Greater than 300 mg/l Interference Levels and Treatments Highly buffered samples or extreme sample ph may exceed the buffering capacity of the reagents and require sample pretreatment. ph 2 10 is recommended. Greater than 50 mg/l Greater than 10 mg/l May cause inconsistent results because the acid in the powder pillow may dissolve some of the suspended particles and because of variable desorption of orthophosphate from the particles. For highly turbid or colored samples, add the contents of one Phosphate Pretreatment Powder Pillow (Cat. No ) to 25 ml of sample. Mix well. Use this solution to zero the instrument. Greater than 80 mg/l Sample Collection, Storage, and Preservation Collect sample in plastic or glass bottles that have been cleaned with 1:1 Hydrochloric Acid Solution (Cat. No ) and rinsed with deionized water. Do not use commercial detergents containing phosphate for cleaning glassware used in phosphate analysis. PhosphorusReac_AVPP_Other_PV3_Eng_Ody.fm Page 3 of 6

4 Accuracy Check Analyze samples immediately for best results. If prompt analysis is not possible, preserve samples by filtering immediately and storing at 4 C (39 F) for up to 48 hours. The sample should be at room temperature before analysis. Standard Additions Method (Sample Spike) 1. After reading test results, leave the sample cell (unspiked sample) in the instrument. Verify the chemical form. 2. Touch Options. Touch Standard Additions. A summary of the standard additions procedure will appear. 3. Touch OK to accept the default values for standard concentration, sample volume, and spike volumes. Touch Edit to change these values. After values are accepted, the unspiked sample reading will appear in the top row. See Standard Additions in the instrument manual for more information. 4. Open a Phosphate 10-mL Ampule Standard, 50-mg/L PO Prepare a 0.1-mL sample spike by adding 0.1 ml of standard to the unspiked sample. Touch the timer icon. After the timer beeps, read the result. 6. Prepare a 0.2-mL sample spike by adding 0.1 ml of standard to the 0.1-mL sample spike. Touch the timer icon. After the timer beeps, read the result. 7. Prepare a 0.3-mL sample spike by adding 0.1 ml of standard to the 0.2-mL sample spike. Touch the timer icon. After the timer beeps, read the result. Each addition should reflect approximately 100% recovery. Note: For AccuVac ampules, fill three Mixing Cylinders (Cat. No ) with 50 ml of sample and spike with 0.2 ml, 0.4 ml, and 0.6 ml of standard. Transfer 40 ml from each of the three mixing cylinders to three 50-mL Beakers (Cat. No H). Analyze each standard addition sample as described in the procedure above. Accept each standard additions reading by touching Read. Each addition should reflect approximately 100% recovery. 8. After completing the sequence, touch Graph to view the best-fit line through the standard additions data points, accounting for matrix interferences. Touch View: Fit, then select Ideal Line and touch OK to view the relationship between the sample spikes and the Ideal Line of 100% recovery. See Section Standard Additions on page 32 for more information. Standard Solution Method 1. Use a 1.0-mg/L phosphate standard solution in place of the sample. Perform the procedure as describe above. 2. To adjust the calibration curve using the reading obtained with the 1.0-mg/L PO 4 Phosphate Standard Solution, touch Options on the current program menu. Touch Standard Adjust. 3. Touch On. Touch Adjust to accept the displayed concentration (the value depends on the selected chemical form). If an alternate concentration is used, touch the number in the box to enter the actual concentration, then touch OK. Touch Adjust. Page 4 of 6 PhosphorusReac_AVPP_Other_PV3_Eng_Ody.fm

5 Method Performance Summary of Method Precision Standard: 1.00 mg/l PO 4 Program See Section Precision on page 44 for more information, or if the standard concentration did not fall within the specified range. Sensitivity 95% Confidence Limits of Distribution mg/l PO mg/l PO 4 Portion of Curve Abs Program Concentration Entire range mg/l PO 4 Entire range mg/l PO 4 See Section Sensitivity on page 44 for more information. Orthophosphate reacts with molybdate in an acid medium to produce a mixed phosphate/molybdate complex. Ascorbic acid then reduces the complex, giving an intense molybdenum blue color. Test results are measured at 880 nm. Required Reagents Quantity Required Description Per Test Unit Cat. No. PhosVer 3 Phosphate Reagent Powder Pillows, 10-mL...1 pillow /pkg or PhosVer 3 Phosphate Reagent AccuVac Ampuls...1 ampule... 25/pkg Required Apparatus Beaker, 50-mL each H Sample Cells, 10-mL, w/cap /pkg Stopper for 18-mm tube /pkg Required Standards Phosphate Standard Solution, 10-mL Voluette Ampul, 50-mg/L as PO /pkg Phosphate Standard Solution, 50-mg/L as PO ml Phosphate Standard Solution, 1-mg/L as PO ml Water, deionized... 4 liters PhosphorusReac_AVPP_Other_PV3_Eng_Ody.fm Page 5 of 6

6 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 HACH COMPANY WORLD HEADQUARTERS Telephone: (970) FAX: (970) Hach Company, All rights reserved. Printed in the U.S.A. 9/04 1ed Page 6 of 6 PhosphorusReac_AVPP_Other_PV3_Eng_Ody.fm