ASTM D3525 Gasoline Diluent in Used Gasoline Engine Oils
ASTM D3525 Standard Test Method for Gasoline Diluent in Used Gasoline Engine Oils by Gas Chromatography
5. Apparatus
5.1 Gas Chromatograph - Any gas chromatograph may be used that has the following performance characteristics:
5.1.1 Detector - Only a flame detector can be used in this method. The detector must have sufficient sensitivity to detect 1.0 % n-tetradecane with a peak height of at least 40 % of full scale on the recorder under the conditions prescribed in this method, and without loss of resolution. The detector must be capable of operating continuously at a temperature equivalent to the maximum column temperature employed, and it must be connected to the column so as to avoid any cold spots. When operating at this sensitivity level, detector stability must be such that the baseline drift of not more than 1 % per hour is obtained.
5.1.2 Column Temperature Programmer - The chromatograph must be capable of temperature program operation over a range sufficient to establish a retention time of 0.25 min (15 s) for the initial peak and to elute the internal standard totally. For determination of fuel dilution the reproducibility of the programming rate is not significant, although a retention time repeatability of 0.3 min (18 s) should be available.
5.1.3 Sample Inlet System - The sample inlet system must be capable of operating continuously at a temperature equivalent to the maximum column temperature employed. The sample inlet system must be connected to the chromatograph column so as to avoid any cold spot.
5.2 Recorder - A recording potentiometer with a full-scale response time of 1 s or less can be used.
5.3 Column - Any column and conditions may be used, provided, under the conditions of the test, separations are in order of boiling points and the column resolution, R, is at least 3 and not more than 8. Since a stable baseline is an essential requirement of this method, electronic single column compensation is required to compensate for column bleed, which cannot be eliminated completely by conditioning alone.
5.4 Means must be provided for measuring the accumulated area under the chromatogram. This can be done by a computer or electronic integrator. The computer or integrator must have the capability of subtracting an area profile obtained in a blank run from the corresponding area profile obtained during a sample run.
NOTE 2 - Some commercially available gas chromatographs permit the storing of data as a baseline profile of a blank run (without sample injection). With such instruments, sample run data can be corrected for baseline drift through subtraction of the internally stored baseline profile data from the sample run profile data. With this feature, further baseline correction need not be required.
5.5 Flow Controllers - Control of baseline drift to not more than 1 % of full scale per hour as covered in 5.1.1 will require that the gas chromatograph be equipped with constant-flow controllers.
5.6 Sample Introduction Apparatus - The sample is introduced by use of a micro syringe, automatic sampling devices, or indium encapsulation; provided that the temperature is sufficiently high to vaporize completely hydrocarbons with an atmospheric boiling point of 315°C, and that the sampling system is connected to the chromatograph column so as to avoid any cold spots.
5.7 Syringes, 1-mL, graduated in 0.01 mL; 25-µL and 1-µL.
5.8 Vials, 1-dram (3.7-mL), septum-capped.
6. Reagents and Materials
6.1 Liquid Phase for Columns - Any nonpolar liquid phase suitable for column operation above 300°C may be used.
6.2 Solid Support - Usually crushed fire brick or diatomaceous earth, in the case of packed columns. Where solid support is used, sieve size and support loading should be such as will give optimum resolution and analysis time. In general, support loading of 3 to 10 % has been found most satisfactory.
6.3 Carrier Gas - Helium, nitrogen, or argon shall be used with the flame ionization detector.
NOTE 3 - Warning: Hydrogen, which is used with the flame ionization detector, is an extremely flammable gas under pressure.
NOTE 4 - Warning: Helium, nitrogen, and argon are compressed gases under pressure.
6.4 n-Tetradecane of 95 % minimum purity.
NOTE 5 - Warning: Combustible, vapor harmful.
6.5 n-Hexadecane of 95 % minimum purity.
NOTE 6 - Warning: Combustible, vapor harmful.
6.6 n-Octane of 95 % minimum purity.
NOTE 7 - Warning: Flammable, harmful if inhaled.
