| | | 1. Select sample amount from tables following these steps. Digest the sample according to the procedure in Section 3. Note: If sample cannot be analyzed immediately after collection, see Sampling and Storage following these steps. Note: Rinse glassware with 1:1 hydrochloric acid and deionized water before use to avoid errors due to iron deposits on the glass. | | 2. Use the analysis volume in the same table. Pipet the sample analysis volume into a 25-mL mixing cylinder. If the aliquot is more than 0.5 mL, adjust the pH according to the instruction following the digestion method. Dilute to the 25-ml mark with deionized water. | | 3. Fill a second 25-mL graduated mixing cylinder with deionized water (the blank). Note: For proof of accuracy, a 0.4 mg/L iron standard solution (preparation given in the Accuracy Check) can be used in place of the sample. | | 4. Add the contents of one FerroZine Iron Reagent Solution Pillow to each cylinder. Swirl to mix. Note: 0.5 mL of FerroZine Iron Reagent Solution can be used in place of the solution pillow if preferred. Note: If the sample contains rust, see Interferences following these steps. | | |