ASTM D7058 Standard Test Method for Determination of the Red Dye Concentration and Estimation of Saybolt Color of Aviation Turbine Fuels and Kerosine Using a Portable Visible Spectrophotometer
12. Report
12.1 Report the dye concentration below 0.026 mg/L as No Dye Present.
12.2 Report the red dye concentration at or above 0.026 mg/L to the nearest 0.001 mg/L as Solvent Red 26 equivalent dye.
12.3 Report the color value as units of estimated Saybolt color.
13. Precision and Bias
13.1 Interlaboratory tests of the procedure were carried out using 18 samples covering the red dye concentration range equivalent from 0.000 to 0.374 mg/L of Solvent Red 26 equivalents and covering the range of Saybolt color from -13 to +30. Seven laboratories participated in the interlaboratory tests. The precision of this procedure, as determined by the statistical examination of the interlaboratory test results, is as follows:
13.1.1 Repeatability - The difference between successive results, obtained with the same apparatus under constant operating conditions on identical samples, would in the long run, in normal and correct operation of the test method, exceed the following value in only one case in twenty:
13.1.1.1 for Solvent Red 26 equivalent dye concentrations between 0 to 0.750 mg/L:
r = 0.006 mg/L
13.1.1.2 for samples in the Saybolt color range of -16 to +30:
r = 1.1 Saybolt color units
13.1.2 Reproducibility - The difference between two single and independent results obtained from different instruments on identical samples, would in the long run, in normal and correct operation of the test method, exceed the following value in only one case in twenty:
13.1.2.1 for Solvent Red 26 dye concentrations between 0 to 0.750 mg/L:
R = 0.026 mg/L
13.1.2.2 for samples in the Saybolt color range of -16 to +30:
R = 4.6 Saybolt color units
13.2 Bias - Since there is no accepted reference material suitable for determining the bias for the procedure in this test method, bias has not been determined.
13.3 Relative Bias (Dye Concentration) - Among certain samples, some bias proportional to the dye concentration was observed when the dye concentration results were compared to the expected concentrations. The observed bias does not appear to be of a systematic nature and is not known to be related to the accuracy of this test method, since the activity levels of the dye in sample preparation have not been determined, only estimated.
13.4 Relative Bias (Saybolt Color) - Some bias was observed when the color results were compared to the Test Method D156 results, however, this bias was observed only for samples that had high concentration of the dye (>0.180 mg/L). The bias for the base fuels was within the standard error of Test Method D156.
13.5 The precision statements in 13.1 were derived from the 1997 interlaboratory test program. Participants analyzed seven sets of undyed base fuels and 13 sets of dyed base fuel/color combinations in duplicate in the Saybolt color range of -16 to +30 and dye concentration from 0 to 0.374 mg/L, seven laboratories participated with the automatic apparatus and five laboratories participated with the manual Test Method D156 apparatus.
14. Keywords
14.1 aviation turbine fuel; kerosine; red dye concentration; Saybolt color; visible spectrometry
