ASTM D5580 for elements in finished gasoline by gas chromatography
ASTM D5580 Standard Test Method for Determination of Benzene, Toluene, Ethylbenzene, p/m-Xylene, o-Xylene, C9 and Heavier Aromatics, and Total Aromatics in Finished Gasoline by Gas Chromatography
13. Procedure
13.1 Preparation of Sample - Transfer 1 mL of internal standard (Ws) by a volumetric pipette into a tared and capped 10-mL volumetric flask or capped vial. Record the net mass of the internal standard added to the nearest 0.1 mg. Retare the capped flask or vial. Fill the volumetric flask or vial with 9 mL of chilled sample, cap, and record the net mass (Wg) of the sample added. Mix thoroughly. If using an automatic sampler then transfer an aliquot of the solution into a glass GC vial. Seal the GC vial with a TFE-fluorocarbon-lined cap. If the sample is not immediately analyzed, store at 0 to 5°C (32 to 40°F).
13.2 Chromatographic Analysis - Introduce an aliquot of the sample, containing internal standard, into the gas chromatograph using the same technique and sample size as used for the calibration analysis. An injection volume of 1 µL with a 11:1 split ratio has been used successfully. Chromatograph the sample twice using valve timing procedures in accordance with 10.5. Use times T1 and T3 for the first analysis to BACKFLUSH and RESET the valve. Use times T2 and T4 for the second analysis.
13.3 Interpretation of Chromatogram - Compare the retention times of sample components to those of the calibration analysis to determine the identities of the aromatics. Identify benzene, toluene, and the internal standard from the first analysis. Identify the internal standard, ethylbenzene, p/m-xylene, o-xylene, C9 and heavier aromatic composite from the second analysis. Refer to Fig. 4 and Fig. 5 for sample chromatograms.
NOTE 5 - Gasolines containing styrene will have an additional peak in the chromatogram. Styrene elutes just before o-xylene; the two peaks are partially, but not baseline, resolved. If quantitation of sytrene is desired, use the o-xylene calibration.
