ASTM D3524 Diesel Fuel Diluent in Used Diesel Engine Oils
ASTM D3524 Standard Test Method for Diesel Fuel Diluent in Used Diesel Engine Oils by Gas Chromatography
7. Preparation of Apparatus
7.1 Column Preparation - Any satisfactory method used in the practice of the gas chromatography that will produce a column meeting the requirements of 5.3 may be used. The column must be conditioned at the maximum operating temperature until baseline shift due to column bleeding has been reduced to a minimum.
7.1.1 The column can be conditioned very rapidly and effectively by the following procedure:
7.1.1.1 Disconnect the column from the detector.
7.1.1.2 Purge the column thoroughly at ambient temperature with carrier gas.
7.1.1.3 Turn off the carrier gas and allow the column to depressurize completely.
7.1.1.4 Raise the column temperature to the maximum operating temperature and hold at this temperature for at least 1 h with no flow through the column.
7.1.1.5 Cool the column to at least 100°C before turning on carrier gas again.
7.1.1.6 Program the column temperature up to the maximum several times with normal carrier gas flow. The column then should be ready for use.
7.1.2 An alternative method of column conditioning, which has been found effective for columns with an initial loading of 10 % liquid phase, consists of purging the column with carrier gas at the normal flow rate while holding the column at maximum operating temperature for 12 to 16 h.
7.1.3 Column Resolution - To test column resolution use Fig. 1 and calculate the resolution, R, from the distance between the C16 and C 18 n-paraffin peaks at the peak maxima, d, and the width of the peaks at the baseline, Y1 and Y2, as follows:
R = [2(d1 - d2)]/Y1 + Y 2
Resolution, R, using the above equation, must be at least 3 and not more than 5.
7.2 Chromatograph - Place in service in accordance with the manufacturer's instructions. Typical operating conditions are shown in Table 1.
7.2.1 If a flame ionization detector is used, the deposits formed in the detector from combustion of the silicone rubber decomposition products must be removed regularly, since they change the response characteristics of the detector.
7.2.2 If the sample inlet system is heated above 300°C, a blank run must be made after new septums are installed, to check for extraneous peaks produced by septum bleed. At the sensitivity levels commonly employed in this method, conditioning of the septum at the operating temperature of the sample inlet system for several hours will minimize this problem. Recommended practice is to change septums at the end of the day's operation rather than at the beginning.
8. Preparation of Sample
8.1 Weigh 1.0 +/- 0.01 g of decane ( Warning - see Note 6) into a 15-mL vial. Shake the sample in the delivered bottle and add 10.00 +/- 0.01 g of sample to the vial (Warning - see Note 5). Cap and mix well.
9. Calibration
9.1 Run each of the calibration mixtures (6.4) by the procedure described in Sections 8 and 10, injecting approximately the same volume as chosen for the sample. Record the total areas due to decane and to the fuel portion in each mixture.
9.1.1 There can be an overlap between the diesel fuel and lube oil peaks. Using a chromatogram of one of the calibration mixtures, select the retention time of the minimum overlap. Use this retention time as the end of the area due to the diesel fuel for all subsequent analyses. See Fig. 2 for a typical chromatogram.
9.2 Determine the ratio, R, for each standard as follows:
R = A/B
where:
A = total area due to diesel fuel peaks, and
B = area due to n-decane.
9.3 Plot a calibration curve relating R to the weight percent of diesel fuel.
