ASTM D4291 standard test method for trace ethylene glycol in used engine oil
10. Procedure
10.1 Set the operating conditions of the chromatograph as described in 7.4. Inject exactly 5 µL of water extract directly on the column. Record the peaks at a sensitivity that allows the maximum peak size compatible with the method of measurement.
NOTE 8 - A typical chromatogram is shown in Fig. 1.
10.2 After each sample analysis is completed, inject 5 µL of water and allow to elute.
NOTE 9 - Small amounts of ethylene glycol are retained by the chromatographic column when higher concentrations of the glycol are injected. Therefore, when analyzing for very low concentrations of ethylene glycol, make repeated injections of water until no peak is found at the ethylene glycol retention time.
11. Calculations
11.1 The concentration of ethylene glycol in the original oil sample is calculated as follows:
Ethylene glycol, mass ppm = F x A x Ww/Ws
where:
F = response factor for ethylene glycol as calculated in 8.3,
A = peak area for ethylene glycol,
Ww = weight of the water as determined in 9.1, and
Ws = weight of the oil sample as determined in 9.1.
12. Precision and Bias
12.1 The precision of this test method as obtained by statistical examination of interlaboratory test results is as follows:
12.1.1 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 test method, exceed the following values only in one case in twenty.
Repeatability, n = 0.212X
where:
X = ethylene glycol content, mass ppm.
12.1.2 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.
Reproducibility, R = 0.528X
where:
X = ethylene glycol content, mass ppm.
12.2 Bias - Bias cannot be determined because there is no acceptable reference material suitable for determining the bias for the procedure in this test method.
13. Keywords
13.1 antifreeze; ethylene glycol; gas chromatography; used engine oil
