ASTM D4768 for 2,6-Ditertiary-Butyl Para-Cresol and 2,6-Ditertiary-Butyl Phenol
ASTM D4768 Standard Test Method for Analysis of 2,6-Ditertiary-Butyl Para-Cresol and 2,6-Ditertiary-Butyl Phenol in Insulating Liquids by Gas Chromatography
9. Procedure
9.1 Test Specimen Preparation:
9.1.1 Accurately weigh a cleanup column to 0.001 g. Pipet 0.25 mL of the test specimen onto the top of the cleanup column. Weigh the cleanup column to 0.001 g. Record the difference as Wx.
9.1.1.1 Due to variances between different batches of alumina, care must be taken to prepare both the working standards and test specimens by using the same batch of cleanup columns. The same "batch" should be interpreted to mean the same lot number of alumina, preparation date, and conditioning time.
9.1.2 To remove nonpolar interferences, wash the test specimen with approximately 5 mL of hexane or heptane, collecting the eluate in a waste container. Remove as much of the solvent as possible by using pipet bulb pressure, but do not allow the column to dry out.
9.1.3 Elute the inhibitor(s) from the column with three washes consisting of 1 mL of methanol each, collecting the eluate in a clean 5-mL volumetric container. Dilute to 5 mL volume with methanol and mix well.
9.2 Test Specimen Chromatography - Inject a volume of test specimen into the chromatograph under the same chromatographic conditions used to analyze the working standard(s).
10. Calculation
10.1 Identify the type(s) of inhibitors present by comparing the retention time obtained from the test specimens to those obtained for the working standards.
10.2 Using the results of the regression analyses (7.5.1), determine the uncorrected weight percent (Cu) of the inhibitor in the test specimens. Calculate the inhibitor content(s) as follows:
C = Cu x Wx
where:
C = weight of inhibitor in test specimen, %,
Cu = weight normalized, obtained from regression analyses of working standards, %, and
Wx = mass of 0.25 mL test specimen as recorded in 9.1.1.