8. Sampling
8.1 Collect the sample in a scrupulously clean glass or polyethylene bottle in accordance with Test Method D1176. Collect at least 100 mL of sample.
9. Calibration and Standardization
9.1 Analyze each standard solution separately to determine the analyte's retention time.
9.2 Set the chromatograph up in accordance with the conditions specified in Table 2 and Fig. 2. The use of other equipment, eluants, or flows requires calculation of suitable dilution factors and instrument settings that permit the analyst to obtain the resolution and detection limits given in Fig. 1 and Table 1, respectively.
9.3 Prepare concentrations of chloride at 0.08, 0.4, 0.8, and 4.0 mg/L from the stock solution. All final solutions should be made with eluant as described in 5.2. Calibrate the ion chromatograph with at least five levels of the analyte, starting near but above the minimum detection limit (MDL) and further defining the working range in samples subsequent to dilution. These chloride analyte examples reflect a dilution of 99 + 1 (v/v) with eluant. Ifit is desirable to calibrate for another anion species, these may be combined in the preceding five calibration standards once the retention times have been established individually. Concentrations of these other anions in the calibration solutions must bracket the expected range for these species and include a level near the MDL for each species.
NOTE 1 - Ion chromatography equipment other than that described in this test method may require that standards be prepared at higher or lower levels.
9.4 Analyze a blank containing only the eluant as described in Section 10.
9.5 A mid-range standard must be used to verify the resolution of anions, regardless of a desire to quantitate all of them.
9.6 Analytical curves must be established at only one detector scale setting in order to prevent a change of slope affecting the analytical curve.
9.7 The analytical calibration curve and an eluant blank shall be verified daily prior to the analysis of samples to verify the system resolution, calibration, and sensitivity.
9.8 The analytical calibration curve, analyte retention times and resolution, and an eluant blank shall be verified subsequent to a change of the system eluant.
9.9 Conditions:
NOTE 2 - If a gradient pump is available, refer to Fig. 2 for an example of a step gradient that has proven successful for cleaning the column of strongly retained species such as polyphosphates and molybdate, which would otherwise elute in subsequent runs.
NOTE 3 - The sample loop volume will vary based on the column capacity, sensitivity, and other factors. Refer to ion chromatography equipment manuals and column information for machine-specific details.