STANDARD OPERATING PROCEDURE

ANALYSIS OF AQUIFER CORE EXTRACTS

FOR BENZENE AND AlKYLBENZENES

(INCLUDING XYLENE ISOMERS)

USING THE HEWLETT PACKARD 5971A MSD SYSTEM

Disclaimer:

This Standard Operating Procedure has been prepared for the use of the Robert S. Kerr Environmental Research Laboratory of the U.S. EPA and may not be specifically applicable to the activities of other organizations.

1. Purpose: (Scope and Application)

This method was developed specifically for the Hewlett Packard (HP) 5971A MSD DOS based system to perform mass ion quantification of petroleum aromatics found in aquifer core samples from the Park City, Kansas petroleum decontamination project site. The method may be applied to other applications with appropriate modifications. Methylene Chloride extracts of contaminated cores containing Benzene, Toluene, Ethylbenzene, p-Xylene, m-Xylene, o-Xylene and Pseudocumene are quantified between 0.02 mg/ml and 500 mg/ml (0.02 to 500 nanograms injected into injector port). While the procedure described here has not been devised or tested for maximum sensitivity, gas chromatographic and detector parameter values were chosen in an attempt to provide a high level of sensitivity. The procedure attempts to make good use of the automation capabilities designed into the HP GC/MSD system including vial sampling and injection, data processing, and use of a custom spreadsheet to speed the reporting of a large quantity of data. It should be noted that this is the first RSKERL SOP written to describe an HP 5971A MSD system application. It is assumed that as the physical limits of the detector are explored and more data processing capabilities of the software are learned important modifications will be added to this procedure.

This method is restricted to use by or under the supervision of analysts experienced in the use of gas chromatography, the HP DOS based 5971A ChemStation and the interpretation of data such as described in this procedure.

2. Summary of Method:

Samples are methylene chloride extracts of aquifer core samples contaminated with petroleum (eg., AVGAS or JP-4). Water is removed from the extracts by using a narrow column of sodium sulfate. 0.45 ml of sample or check standard is mixed with 50 ml of 100 mg/ml fluorobenzene (internal standard) in an HP GC autosampler vial to give an internal standard concentration of 10 mg/ml. 1 ml of sample is obtained and injected into a HP 5890 Series II GC injector port using a HP 7673A autosampler. A septumless "JADE" injection valve is used to eliminate the need for changing septa and to improve precision in long, automated runs. A fused silica capillary column with bonded "Carbowax" PEG stationary phase is used to separate the Xylene isomers. Initial column temperature is 32 ºC and no cryogenic cooling is required. An HP 5971 mass analyzer with the accompanying DOS based Chemstation software is used to quantify selected ions of Benzene, Toluene, Ethylbenzene, Xylenes and Pseudocumene and the internal standard Fluorobenzene. Following acquisition, the data is processed, quantified using a standard calibration curve and results automatically added to a custom EXCEL summary spreadsheet. The chromatographic run time for each analysis is 20.0 minutes and the total time for an analysis is approximately 35 minutes.

3. References

3.1 HP 5890 Series II Operating Manual, Edition 5, March 1991

3.2 HP 5890 Series II Reference Manual, Edition 4; October 1990

3.3 HP 5890 Series II Gas Chromatography Tutorial Guide, Edition 1, June 1989

3.4 HPGlO34B Software for MS ChemStation (DOS Series)-Workbook, November 1990

3.5 HPGlO34B Software for MS ChemStation (DOS Series)Handbook, November 1990

3.6 HP 5971A Mass Selective Detector Hardware Manual, February 1990

3.7 Cleaning the HP5971A Ion Source, Videotape, Hewlett Packard #P-787