ASTM D7319 Standard Test Method for Determination of Existent and Potential Sulfate and Inorganic Chloride in Fuel Ethanol by Direct Injection Suppressed Ion Chromatography
13. Report
13.1 Report the chloride and sulfate content (either existent or potential, or both) results to nearest 0.1 mg/kg over the calibration range. Specify that these results were obtained using ASTM Test Method D7319.
14. Quality Control (QC)
14.1 Confirm the performance of the instrument or the test procedure by analyzing one or more quality check sample(s) after each calibration and on at least each day of use thereafter. For example, a good check sample could be a single representative ethanol sample (see X1.5) that is analyzed repetitively by procedures in 11.2-11.6. These results are plotted in control charts to check the system for statistical stability, as in X1.3.
14.1.1 Check samples can be prepared in water. Aqueous stock sulfate and chloride aliquots are added to water in accordance with Table 2 and the total volume of the resulting solution. The ion concentrations are calculated in accordance with Eq 8 and Eq 9. Check samples generated from Table 2 are then analyzed by the procedures in 11.2-11.6. These results are plotted in a control chart to check the system for statistical stability, as in X1.3.
Sulfate in Standard (mg/L) = Va x Ca x 10(-3)
Chloride in Standard (mg/L) = Vb x Cb x 10(-3)
where:
Va = volume of sulfate stock solution (9.1.1), in mL,
Ca = concentration of sulfate stock (Eq 1), in mg/L,
Vb = volume of chloride stock solution (9.1.2), in mL,
Cb = concentration of chloride stock (Eq 2), in mg/L.
14.1.2 When there is no QC/QA protocol established in the testing facility, Appendix X1 can be used as the QC/QA system.
15. Precision and Bias
15.1 Precision - The precision of this test method was determined by the statistical evaluation of the interlaboratory test results. For measuring total chloride, both methods of suppression provided a single precision statement. For existent and potential inorganic sulfate, the data indicated two distinct statistical populations, reflecting use of the packed bed trichamber suppressor regeneration approach and the continuous suppressor membrane regeneration approach. Repeatability and reproducibility statements for total chloride and existent and potential inorganic sulfate are provided with calculated values in Table 3.
15.1.1 Repeatability (r) - The difference between successive test results, obtained by the same operator using the same apparatus under constant operating conditions on identical test material, would in the long run, in the normal and correct operation of this test method provide the following repeatability values:
15.1.1.1 Total Chloride - The pooled limit of quantitation (PLOQ) is 0.75 mg/kg. Repeatability r between 0.75 and 50 mg/kg total chloride measured is calculated as follows:
r = 6.851E-02 x X(0.7000)
15.1.1.2 Existent Inorganic Sulfate - The pooled limit of quantitation (PLOQ) is 0.01 mg/kg. Repeatability r between 1.0 and 20 mg/kg existent inorganic sulfate measured is calculated as follows:
r = 0.09030 x (X + 1.000E-04)(0.6230)
15.1.1.3 Potential Sulfate - The pooled limit of quantitation (PLOQ) is 0.01 mg/kg. Repeatability r between 1.0 and 20 mg/kg potential sulfate measured is calculated as follows:
r = 0.09645 x (X + 0.59494)(0.8642)
15.1.2 Reproducibility (R) - The difference between two single and independent test results, obtained by different operators working in different laboratories on identical test material, would in the long run, in normal and correct operation of this test method provide the following reproducibility values:
15.1.2.1 Total Chloride - The Reproducibility R between 0.75 and 50 mg/kg total chloride measured is calculated as follows:
R = 0.4172 x X(0.7000)
15.1.2.2 Existent Inorganic Sulfate - Reproducibility R between 1.0 and 20 mg/kg existent inorganic sulfate measured is calculated as follows:
R = 1.2291 x (X + 1.000E-04)(0.6230)
15.1.2.3 Potential Sulfate - Reproducibility R between 1.0 and 20 mg/kg potential sulfate measured is calculated as follows:
R = 0.9408 x (X + 0.59494)(0.8642)
where:
X = analyte concentration in mg/kg.
15.2 Bias - Since no generally accepted standard reference materials with known values of sulfate and chloride in ethanol are available, bias of this test method cannot be determined.
15.3 Table 3 shows precision values calculated from Eq 10-Eq 15.
16. Keywords
16.1 anions; chloride; direct injection; ethanol; existent inorganic sulfate; inorganic chloride; potential sulfate; sulfate; suppressed ion chromatography; total chloride
