ASTM D7328 Standard Test Method for Determination of Existent and Potential Inorganic Sulfate and Total Inorganic Chloride in Fuel Ethanol by Ion Chromatography Using Aqueous Sample Injection
13. Report
13.1 Existent Inorganic Sulfate and Total Chloride - Report the total chloride and existent inorganic sulfate content results to nearest 0.1 mg/kg for samples containing more than 3.0 mg/kg, to the nearest 0.01 mg/kg below 3.0 mg/kg. Specify that these results were obtained using Test Method D7328.
13.2 Potential Sulfate - Report the potential sulfate content results to nearest 0.1 mg/kg for samples containing more than 8.0 mg/kg, to the nearest 0.01 mg/kg below 8.0 mg/kg. Specify that these results were obtained using Test Method D7328.
14. Quality Control
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 the procedures in Section 11. These results are plotted in a control chart 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 Type II water according to Table 2 in a 1 L solution. The ion concentrations are calculated according to Eq 7(a) and Eq 7(b). Check samples generated from Table 2 are then analyzed by the procedures in Section 11. 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) (a)
chloride in standard (mg/L) = Vb x Cb x 10(-3) (b)
where:
Va = volume of sulfate stock solution (Table 2, Column 4), in mL,
Ca = concentration of sulfate stock (Eq 1), in mg/L,
Vb = volume ofchloride stock solution (Table 2, Column 3), in mL, and
Cb = concentration of chloride stock (Eq 2), in mg/L.
14.2 When QC/Quality Assurance (QA) protocols are already established in the testing facility, these can be used when they confirm the reliability of the test result.
14.3 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 as determined by the statistical evaluation of the interlaboratory test results is as follows:
15.1.1 Repeatability - The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method exceed the following values only in one case in twenty.
15.1.1.1 Total Chloride - The pooled limit of quantitation (PLOQ) is 0.75 mg/kg. Repeatability r between 0.75 mg/kg and 50 mg/kg total chloride measured is calculated as follows:
r = 0.02078 (X + 10.0709)
15.1.1.2 Existent Inorganic Sulfate - The pooled limit of quantitation (PLOQ) is 0.55 mg/kg. Repeatability r between 0.55 mg/kg and 20 mg/kg existent inorganic sulfate measured is calculated as follows:
r = 0.2319 (X + 1.000E - 04)(0.5000)
15.1.1.3 Potential Sulfate - The pooled limit of quantitation (PLOQ) is 4.0 mg/kg. Repeatability r between 4.0 mg/kg and 50 mg/kg potential sulfate measured is calculated as follows:
r = 0.1763 (X(0.4000))
where:
X = analyte concentration in mg/kg.
15.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of the test method exceed the following values only in one case in twenty.
15.1.2.1 Total Chloride - Reproducibility R between 0.75 mg/kg and 50 mg/kg total chloride measured is calculated as follows:
R = 0.1173 (X + 10.0709)
15.1.2.2 Existent Inorganic Sulfate - Reproducibility R between 0.55 mg/kg and 20 mg/kg existent inorganic sulfate measured is calculated as follows:
R = 1.0963 (X + 1.000E - 4)(0.5000)
15.1.2.3 Potential Sulfate - Reproducibility R between 4.0 mg/kg and 20 mg/kg potential sulfate measured is calculated as follows:
R = 1.0505 (X(0.4000))
where:
X = analyte concentration in mg/kg.
15.2 Bias - Since there was no generally accepted reference material available at the time of the interlaboratory testing, no statement of bias can be made at this time.
15.3 Table 3 shows precision values calculated from Eq 8-13.
16. Keywords
16.1 aqueous injection; denatured ethanol; ethanol; existent inorganic sulfate; fuel ethanol; ion chromatography; potential sulfate; total chloride
