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Anleitung Zusammenfassung
Any iron(III) ions present in the water sample are reduced to iron(II) ions by ascorbic acid before the complex is formed. This method complies with regulations in many countries and therefore can often be used for reporting purposes. Contact your local Hach distributor to determine if this method can be used for regulatory reporting purposes in your country. SHELF LIFE OF TEST REAGENT The test reagents are stable at room temperature for 30 months as indicated by the expiration date on the package. SAMPLE COLLECTION, PRESERVATION AND STORAGE Collect samples in acid-cleaned glass or plastic containers. No acid addition is necessary if analyzing the samples immediately. To preserve samples, adjust the pH to 2 or less with concentrated nitric acid (about 2.00 ml per liter). Preserved samples may be stored up to six months at room temperature. If reporting only dissolved free iron, filter sample immediately after collection and before adding nitric acid. Before analysis, adjust the pH to between 3 and 5 with 5.0 N sodium hydroxide standard solution. Do not exceed pH 5 as iron may precipitate. Correct the test results for volume additions. INTERFERENCES The ions listed in the table have been individually checked up to the given concentrations. Cumulative effects and the influence of other ions have not been evaluated. There is no interference from: 1000 mg/L: Cl 500 mg/L: Ca2+ 100 mg/L: Ag+ 70 mg/L: Cd2+ 2+2+2+2-2+3+6+ 50 mg/L: Co, Zn, Pb, CO3 , Hg, Cr, Cr 25 mg/L: Ni2+ 10 mg/L: Cu2+ 5 mg/L: Sn2+ Higher amounts of copper, nickel, and tin cause high-bias results. Total iron including undissolved iron and complexed iron can only be determined after digesting with the Metal Prep Set HCT 200. (Total iron measuring range 0.12 – 6.00 mg/L). ACCURACY CHECK Standard Solution Method Prepare a 3.00 mg/L Fe standard solution by pipetting 0.30 ml of 1000 mg/L Fe into a 100 ml volumetric flask. Dilute to the mark with deionized water. Stopper and invert to mix. Prepare this solution daily. Perform the iron procedure as described. Standard Addition Method (a) Measure 100 ml of sample into three mixing cylinders. (b) Using a pipette add 0.10, 0.20 and 0.30 ml of 1000 mg/L Fe standard solution to the three samples. Mix well. (c) Analyze each sample using the procedure. The Fe concentration should increase 1.00 mg/L for each 0.10 ml of standard added. METHOD PERFORMANCE Precision In a single laboratory, using a standard solution of 3.00 mg/L Fe and two representative lots of reagent, a single operator obtained a standard deviation of +/- 0.15 mg/L on a total of 14 samples. TIPS AND TECHNIQUES 1. Adjust pH of preserved samples to between pH 3 – 5 before analysis. Water samples with pH < 2 affects the reagent. 2. The outside of the vial must be clean before placing it in the instrument. Wipe it down with a damp towel, followed by a dry one. 3. For a proof of accuracy, use the standard solution or standard addition method. (See Accuracy Check). 4. See your Instrument’s Procedure Manual for instructions on adjusting the calibration curve if needed. 5.The temperature of the water sample and the sample vial should be between 15 – 25°C (59 – 77F). SAFETY Good safety habits and laboratory techniques should be used throughout the procedure. Consult the Material Safety Data Sheet for information specific to the reagents used. HCPE 159 B / Druckfarbe schwarz / 1 PROCEDURE for Free Iron HCT 159 HCT 159 DR/4000—Rev 2.39 HCT 159 MEASURING RANGE: applies to DR/4000, DR/2500 DR/2010 and DR/800 0.10 - 5.00 mg/L Free-Fe / 0.12 - 6.00 mg/L Tot-Fe 1 1. Enter program number and set up the instrument as explained for each instrument type. ZERO 5 3 4.0ml Sample 2 4 15min 2.Pipet 4.0 ml sample into the sample vial. 3. Close sample vial and invert a few times, until the freeze-dried contents are completely dissolved. 4. Start the instrument timer. A 15-minute reaction period will beginn. 5. Zero the instrument using the zero vial (white cap) provided and read the sample. PROCEDURE for Total Iron: After digestion with the Metal Prep Set HCT 200, follow the procedure steps 1 – 5. Note If this is the first time you have run this revision of the test on your DR/4000, you must contact your local Hach distributor for an upgrade of your software (Cat.No. 49544-00). Software Version number 2.39 contains the factory UniCell™ programs. INSTRUMENT SET-UP 1. Press the soft key under HACH PROGRAM (or USER PROGRAM if the method was entered as a USER PROGRAM). Enter program number 2130 (or 159 if the method was entered as a USER PROGRAM). Press ENTER. 2. The display will show: HACH PROGRAM: 2130 Iron, HCT 159 The wavelength (.), 485 nm, is automatically selected. 3. Insert the Test N’Tube adapter into the cell holder by sliding it under the thumb screw and into the alignment grooves. Fasten in place by tightening the thumb screw. 4. Follow the procedure steps. (Note: If measuring Total Iron and performed the sample digestion using the HCT 200 Metal Prep Set, select th...