Method 8326 (0.006 to mg/l Al 3+ ) Powder Pillows

Transcription

1 , 8326 Eriochrome Cyanine R Method 1 Scope and Application: For water 1 Adapted from Standard Methods for the Examination of Water and Wastewater. DOC Method 8326 (0.006 to mg/l Al 3+ ) Powder Pillows Test preparation How to use instrument-specific information The Instrument-specific information table displays requirements that may vary between instruments. To use this table, select an instrument then read across to find the corresponding information required to perform this test. Table 40 Instrument-specific information Instrument Sample cell Cell orientation DR Fill line faces right DR Fill line faces user DR Fill line faces user DR 3800, DR 2800, DR Fill line faces right Before starting the test: Clean all glassware with 6.0 N HCl and deionized water before use to remove contaminants from the glass. Check the sample temperature. It must be between C (68 77 F) for accurate results. 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. Collect the following items: Description Quantity ECR Reagent Powder Pillow 1 ECR Masking Reagent Solution 1 drop Hexamethylene-tetramine Buffer Reagent Powder Pillow 1 25-mL graduated mixing cylinder with glass stopper 1 Sample cells (see Instrument-specific information) 2 See Consumables and replacement items for reorder information. Page 1 of 8

2 Eriochrome Cyanine R method with powder pillows Programs 9 ECR Start 1. Select the test. Insert an adapter if required (see Instrumentspecific information). Refer to the user manual for orientation. 2. Fill the 25-mL mixing cylinder to the 20-mL mark with sample. Add one ECR Reagent Powder Pillow for 20-mL sample size. 3. Insert the stopper. Invert several times to completely dissolve powder. Undissolved reagent will cause inconsistent results. 4. Start the instrument timer. A 30-second reaction period will begin. 5. After the timer expires, add one Hexamethylenetetramine Buffer Reagent powder pillow. 6. Insert the stopper. Invert several times to dissolve powder. A red-orange color will develop if aluminum is present. 7. Blank Preparation: Put one drop of ECR Masking Reagent Solution into a clean square sample cell. 8. Pour 10 ml from the mixing cylinder into the blank cell. Swirl to mix. The solution will begin to turn yellow. Zero 9. Prepared Sample: Fill a second square sample cell to the 10-mL mark with the remaining solution in the cylinder. 10. Start the instrument timer. A 5-minute reaction period will begin. 11. Within five minutes after the timer expires, wipe the blank then insert it into the cell holder. 12. ZERO the instrument. The display will show: mg/l Al 3+ This test uses a non-zero intercept for the calibration curve on some instrument platforms. Page 2 of 8

3 Eriochrome Cyanine R method with powder pillows (continued) Read 13. Immediately wipe and dry the prepared sample then insert it into the cell holder. 14. Read the results in mg/l Al 3+. See the user manual for instructions to change to alternate form Al 2 O 3. If fluoride is present, measure the fluoride concentration and refer to the Fluoride Concentration (mg/l) table. Interferences Table 41 Interfering substances Interfering substance Interference level and treatments Acidity Greater than 62 mg/l as CaCO 3 Alkalinity Greater than 750 mg/l as CaCO 3 Ca 2+ Greater than 1000 mg/l as CaCO 3 Cl Greater than 1000 mg/l as Cl Cr mg/l (error is 5% of reading) Cu 2+ 2 mg/l (error is 5% of reading) Fe 2+ Greater than 4 mg/l (error is positive and equals mg/l Fe 2+ x ) Fe 3+ Greater than 4 mg/l (error is positive and equals mg/l Fe 2+ x ) F See the Fluoride Concentration (mg/l) table. Hexameta phosphate 0.1 mg/l as PO 3 4 (error is 5% of reading) Mg 2+ Greater than 1000 mg/l as CaCO 3 Mn 2+ Greater than 10 mg/l NO 2 Greater than 5 mg/l NO 3 Greater than 20 mg/l ph PO 4 3 (ortho) or A sample ph between about 4.9 and 7.5 causes dissolved aluminum to partially convert to colloidal and insoluble forms. This method measures much of that hardto-detect aluminum without any ph adjusting pretreatment as is necessary in some other methods. 4 mg/l (error is 5% of reading) Page 3 of 8

4 Interfering substance Polyphosphate SO 2 4 Zn 2+ Table 41 Interfering substances (continued) Interference level and treatments See procedure below. Greater than 1000 mg/l Greater than 10 mg/l Polyphosphate interference can be reduced by converting polyphosphate to orthophosphate by the following steps: 1. Rinse a 50-mL graduated mixing cylinder and a 125-mL Erlenmeyer flask containing a magnetic stir bar with 6 N hydrochloric acid. Rinse again with deionized water. This will remove any aluminum present. Note: Rinse two Erlenmeyer flasks if a reagent blank is used; see step Measure 50 ml deionized water into the 125-mL Erlenmeyer flask using the graduated cylinder. This is the reagent blank. Because of the test sensitivity, this step must be done only when any of the reagents used in the following pretreatment are replaced even if the new reagent has a matching lot number. When the pretreated sample has been analyzed, correct for the aluminum concentration of the reagent blank. Refer to the instrument user manual. 3. Measure 50 ml sample into the 125-mL Erlenmeyer flask using the graduated cylinder. Use a small amount of deionized water to rinse the cylinder contents into the flask. 4. Add 4.0 ml of 5.25 N Sulfuric Acid Standard Solution *. 5. Use a combination hot plate/stirrer to boil and stir the sample for at least 30 minutes. Add deionized water as needed to maintain a sample volume of ml. Do not boil dry. 6. Cool the solution to near room temperature. 7. Add 2 drops of Bromphenol Blue Indicator Solution*. 8. Add 1.5 ml of 12.0 N Potassium Hydroxide Standard Solution* using the calibrated, plastic dropper provided. Swirl to mix. The solution color should be yellow or green but not purple. If the color is purple, begin with step 1 again using an additional 1 ml Sulfuric Acid Standard Solution in step While swirling the flask, add 1.0 N Potassium Hydroxide Solution*, a drop at a time, until the solution turns a dirty green color. 10. Pour the solution into the graduated cylinder. Rinse the flask contents into the graduated cylinder with deionized water to bring the total volume to 50 ml. 11. Use this solution in step 2. of the ECR method. Note: Fluoride interference can be corrected by using the Fluoride Concentration (mg/l) table. Example: If the fluoride concentration is known to be 1.00 mg/l F and the ECR method gives a reading of mg/l aluminum, what is the true mg/l aluminum concentration? Intermediate values can be found by interpolation. Do not use correction graphs or charts found in other publications. Answer: mg/l * See Optional reagents and apparatus for reorder information Page 4 of 8

5 Sample collection, preservation and storage Accuracy check Table 42 Fluoride Concentration (mg/l) (mg/l) True Concentration (mg/l) Al Collect samples in clean glass or plastic containers. Preserve samples by adjusting the ph to 2 or less with concentrated nitric acid (about 1.5 ml per liter). Preserved samples can be stored up to six months at room temperature. Before analysis, adjust the ph to with 12.0 N Potassium Hydroxide Standard Solution* and/or 1 N Potassium Hydroxide Solution *. Correct the test result for volume additions. Required for accuracy check: Class A glassware (pipettes and volumetric flasks) Standard Solution, 100 mg/l OR Voluette Ampule Standard Solution, 50-mg/L Deionized water Standard solution method Prepare a mg/l aluminum standard solution as follows: 1. Using Class A glassware, pipet 1.00 ml of Standard Solution 100 mg/l as Al 3+, into a 1000-mL volumetric flask. 2. Dilute to the mark with deionized water. * See Optional reagents and apparatus for reorder information. Page 5 of 8

6 3. Prepare this solution daily. Do the Eriochrome Cyanine R method with powder pillows. Go to step 4. OR Method performance 1. Add 2.0 ml of solution from an Voluette Ampule Standard Solution (50-mg/L as Al) into a 1000-mL volumetric flask. 2. Dilute to volume with deionized water. Prepare this solution daily. 3. Do the Eriochrome Cyanine R method with powder pillows test procedure. 4. Select Options>More>Standard additions from the instrument menu. 5. Accept the shown concentration. If an alternate concentration is used, enter the actual concentration. Program Standard Summary of method Eriochrome Cyanine R combines with aluminum in a sample to produce an orange-red color. The intensity of color is proportional to the aluminum concentration. Test results are measured at 535 nm. Consumables and replacement items Precision 95% Confidence Limits of Distribution Sensitivity Concentration change per Abs change mg/l Al mg/l Al mg/l Al 3+ Required reagents Description Quantity/Test Unit Catalog number Reagent Set (100 Tests), includes: ECR Reagent Powder Pillows 1 100/pkg Hexamethylenetetramine Buffer Reagent Powder Pillows 1 100/pkg ECR Masking Reagent Solution 1 drop 25 ml SCDB Required apparatus Description Quantity Unit Catalog number Cylinder, graduated mixing, 25-mL, with glass stopper 1 each Sample cell, 10 ml square, matched pair 2 2/pkg Thermometer, 10 to 110 C each Recommended standards Description Unit Catalog number Standard Solution, 100-mg/L as Al ml Page 6 of 8

7 Recommended standards Description Unit Catalog number Standard Solution, 10-mg/L as Al ml Standard Solution, 10-mL Voluette Ampule, 50-mg/L as Al 16/pkg Water, deionized 4 L Optional reagents and apparatus Description Unit Catalog number Ampule breaker for Voluette Standards each Bromphenol Blue Indicator Solution 100 ml Cylinder, graduated mixing, 50-mL, Class A each Deionized Water 500 ml Erlenmeyer Flask, 125-mL each Hot Plate with Stirrer, 7 x 7 inches, 115 VAC each Hydrochloric Acid, 6.0 N 500 ml Nitric Acid 1:1 500 ml ph Paper, 0 14 ph range 100/pkg Pipet, TenSette, ml each Pipet Tips for /pkg Potassium Hydroxide Standard Solution, 12.0 N 100 ml Potassium Hydroxide Solution, 1.0 N 50 ml Sodium Hydroxide Standard Solution, 5.0 N 50 ml Stir Bar, magnetic, octagonal, 22.2 x 7.9 mm each Sulfuric Acid Standard Solution, 5.25 N 100 ml Volumetric Flask, Class A, 1000-mL each Page 7 of 8

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