TPTZ Method * (Powder Pillows or AccuVac Ampuls) Using Powder Pillows

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1 IRON, TOTAL (0 to 1.80 mg/l) TPTZ Method * (Powder Pillows or AccuVac Ampuls) Using Powder Pillows Method 8112 For water, wastewater, and seawater 1. Enter the stored program number for iron (Fe)- powder pillows. Press: PRGM The display will show: PRGM? Note: For most accurate results, perform a Reagent Blank Correction using deionized water (see Note: Adjust the ph of stored samples before analysis. 2. Press: 39 ENTER The display will show mg/l, Fe and the ZERO icon. Note: Total iron determination needs a prior digestion. Use any of the procedures in Digestion (Section 2). 3. Fill a sample cell with 10 ml of sample. Note: Sample ph is important in this test; see Interferences. Note: Rinse glassware with a 1:1 hydrochloric acid and deionized water before use to avoid errors due to iron deposits on the glass. 4. Add the contents of one TPTZ Iron Reagent Powder Pillow (the prepared sample). Cap and shake the cell for 30 seconds. Note: A blue color will develop if iron is present. * Adapted from G. Frederic Smith Chemical Co., The Iron Reagents, 3rd ed. (1980). 261

2 5. Press: TIMER ENTER A three-minute reaction period will begin. Note: Continue with Steps 6 to 8 while the timer is running. 6. Fill a second sample cell with 10 ml of sample (the blank). 7. Place the blank in the cell holder. Tightly cover the sample cell with the instrument cap. Note: Press EXIT to zero the instrument while the timer is running. Press: ZERO The cursor will move to the right, then the display will show: 0.00 mg/l Fe If Reagent Blank Correction is on, the display may flash limit. See Section After the timer beeps, place the prepared sample in the cell holder. Tightly cover the sample cell with the instrument cap. 9. Press: READ The cursor will move to the right, then the result in mg/l iron will be displayed. Note: Standard Adjust may be performed using a prepared standard (see 262

3 Using AccuVac Ampuls 1. Enter the stored program number for iron (Fe)- AccuVac Ampuls. Press: PRGM The display will show: PRGM? Note: For most accurate results, perform a Reagent Blank Correction using deionized water (see Note: Adjust the ph of stored samples before analysis. 2. Press: 39 ENTER The display will show mg/l, Fe and the ZERO icon. Note: Total iron determination needs a prior digestion. Use any of the three procedures in Digestion (Section 2). 3. Fill a sample cell with at least 10 ml of sample (the blank). Collect at least 40 ml of sample in a 50-mL beaker. Note: Sample ph is important in this test; see Interferences. Note: Rinse glassware with a 1:1 hydrochloric acid and deionized water before use to avoid errors due to iron deposits on the glass. 4. Fill a TPTZ Iron AccuVac Ampul with sample. Note: Keep the tip immersed while the ampul fills completely. 5. Invert the ampul (the prepared sample) repeatedly to mix. Wipe off any liquid or fingerprints. Note: A blue color will develop if iron is present. 6. Press: TIMER ENTER A three-minute reaction period will begin. 7. Place the blank into the cell holder. Tightly cover the sample cell with the instrument cap. 8. Press: ZERO The cursor will move to the right, then the display will show: 0.00 mg/l Fe Note: Press EXIT to zero the instrument while the timer is running. Note: If Reagent Blank Correction is on, the display may flash limit. See Section

4 9. When the timer beeps, place the prepared sample into the cell holder. Tightly cover the ampul with the instrument cap. 10. Press: READ The cursor will move to the right, then the result in mg/l iron will be displayed. Note: Standard Adjust may be performed using a prepared standard (see Sampling and Storage Collect samples in acid-washed glass or plastic bottles. Adjust the sample ph to 2 or less with nitric acid (about 2 ml per liter). Store samples preserved in this manner up to six months at room temperature. If reporting only dissolved iron, filter sample immediately after collection and before addition of nitric acid. Before testing, adjust the ph of the stored sample to between 3 and 4 with 5.0 N Sodium Hydroxide Standard Solution. Do not exceed ph 5 as iron may precipitate. Correct the test result for volume additions; see Correction for Volume Additions in Section 1. Accuracy Check Standard Additions Method (Powder Pillows) a) Snap the neck off a PourRite Iron Ampule Standard, 25 mg/l Fe. b) Use the TenSette Pipet to add 0.1 ml of standard to the prepared sample measured in Step 10. Swirl to mix. c) Measure the iron concentration as in Step 10. The measurement does not require the three-minute waiting period. 264

5 d) Add two additional 0.1-mL aliquots of standard, measuring the concentration after each addition. The iron concentration should increase by 0.25 mg/l for each 0.1- ml addition of standard. e) If these increases do not occur, see Standard Additions in Section 1 for more information. Standard Additions Method (AccuVac Ampuls) a) Use a graduated cylinder to measure 25.0 ml of sample into each of three 50-mL beakers. b) Snap the neck off an Iron Ampule Standard, 25 mg/l Fe. c) Using a TenSette Pipet, add 0.1, 0.2 and 0.3 ml of standard, respectively, to the 50-mL beakers. Swirl to mix. d) Fill a TPTZ AccuVac Ampul from each beaker. e) Measure the concentration of each ampul according to the procedure. The iron concentration should increase by 0.1 mg/l for each 0.1 ml addition of standard. f) If these increases do not occur, see Standard Additions in Section 1 for more information. Standard Solution Method Prepare a 0.4 mg/l iron working solution as follows: a) Using Class A glassware, pipet 1.00 ml of Iron Standard Solution, 100 mg/l Fe, into a 250-mL volumetric flask. b) Dilute to volume with deionized water. Stopper and invert repeatedly to mix. Prepare this solution daily. Method Performance Precision In a single laboratory using a standard solution of 1.00 mg/l Fe and two representative lots of reagent with the instrument, a single operator obtained a standard deviation of ±0.017 mg/l Fe. In a single laboratory using a standard solution of 1.00 mg/l Fe and one representative lot of AccuVac Ampuls with the instrument, a single operator obtained a standard deviation of ±0.022 mg/l Fe. 265

6 Estimated Detection Limit The estimated detection limit for program 39 is 0.04 mg/l Fe. For more information on the estimated detection limit, see Section 1. Interferences Interfering Substance Cadmium Chromium ( 3+ ) Chromium ( 6+ ) Cobalt Color or turbidity Copper Cyanide Manganese Mercury Molybdenum Nickel Nitrite Ion ph Interference Levels and Treatments Greater than 4.0 mg/l Greater than 0.25 mg/l Greater than 1.2 mg/l Greater than 0.05 mg/l If the sample is turbid, add one 0.1-g scoop of RoVer Rust Remover to the blank in Step 6 (Step 3 for AccuVac procedure). Swirl to mix. Greater than 0.6 mg/l Greater than 2.8 mg/l Greater than 50.0 mg/l Greater than 0.4 mg/l Greater than 4.0 mg/l Greater than 1.0 mg/l Greater than 0.8 mg/l A sample ph of < 3 or >4 after the addition of reagent may inhibit color formation, cause the developed color to fade quickly or result in turbidity. Adjust the sample ph to 3 5 before adding reagent using a ph meter or ph paper and adding (dropwise) an appropriate amount of iron-free acid or base (i.e., 1.0 N Sulfuric Acid Standard Solution or 1.0 N Sodium Hydroxide Standard Solution). Make a volume correction if significant volumes of acid or base are used. Summary of Method The TPTZ Iron Reagent forms a deep blue-purple color with ferrous iron. The indicator is combined with a reducing agent which converts precipitated or suspended iron, such as rust, to the ferrous state. The amount of ferric iron present can be determined as the difference between the results of a ferrous iron test and the concentration of total iron. 266

7 REQUIRED REAGENTS & APPARATUS (Using Powder Pillows) Quantity Required Description Per Test Unit Cat. No. TPTZ Iron Reagent Powder Pillows,... 1 pillow...100/pkg Sample Cell, ml, w/cap /pkg REQUIRED REAGENTS (Using AccuVac Ampuls) TPTZ Iron Reagent AccuVac Ampuls... 1 ampul...25/pkg REQUIRED APPARATUS (Using AccuVac Ampuls) Beaker, 50 ml each h Sample Cell, ml, w/cap /pkg OPTIONAL REAGENTS Drinking Water Standard, Metals, LR (Cu, Fe, Mn) ml Drinking Water Standard, Metals, HR (Cu, Fe, Mn) ml Hydrochloric Acid Solution, 1:1, 6.0 N ml Iron Standard Solution, 100 mg/l Fe ml Iron Standard Solution, Ampule, 25 mg/l Fe, 2 ml...20/pkg Nitric Acid, ACS ml Nitric Acid Solution, 1: ml RoVer Rust Remover g Sodium Hydroxide Standard Solution, 1.0 N ml MDB Sodium Hydroxide Standard Solution, 5.0 N ml MDB Sulfuric Acid Standard Solution ml MDB Water, deionized... 4 L OPTIONAL APPARATUS Description Unit Cat. No. AccuVac Snapper Kit...each Ampule Breaker, Ampules...each Cylinder, graduated, 25 ml...each Dropper, graduated, 0.5 and 1.0 ml marks...20/pkg Flask, volumetric, Class A, 250 ml...each ph Indicator Paper, 1 to 11 ph...5 rolls/pkg ph Meter, sension 1, portable, with electrode...each Pipet Filler, safety bulb...each Pipet, serological, 2 ml...each Pipet TenSette, 0.1 to 1.0 ml...each Pipet Tips, for TenSette Pipet...50/pkg Pipet, volumetric, Class A, 1.00 ml...each For Technical Assistance, Price and Ordering In the U.S.A. Call Outside the U.S.A. Contact the Hach office or distributor serving you. 267