ANALYSIS OF SELECTED TARGET COMPOUNDS

(OU1-LNAPL) IN CO-SOLVENT MATRIX

1.0 PURPOSE

The purpose of this SOP is to ensure reliable and reproducible analytical results of specific compounds selected as target analytes in OU1-LNAPL in the cosolvents selected by the Clemson University NAPL group for laboratory-based or on-site (field-based) GC-FID analyses, and to permit traceability of possible causes of error in analytical results.

2.0 SCOPE

This SOP describes the analytical procedures used by Clemson University (CU) for analysis of target analytes, in both laboratory and field studies, which were selected as surrogates for the OU1-LNAPL, a complex mixture of weathered JP-4 fuel and other unidentified and unquantified organic compounds. The matrices of interest include aqueous solutions of thirty, sixty and ninety-five percent tert-butanol and an 80:15:5 percent solution of tert-butanol, hexanol and water. This SOP may not be specifically applicable to the activities of other organizations.

This SOP was written by John Coates, Patrick Haskell, and Cindy Lee at Clemson University.

The target analytes selected for use in the CU laboratory and field studies are o-xylene, 1,2-dichlorobenzene, naphthalene, decane, undecane, and tetradecane.

The method involves gas chromatography (GC) techniques for determination of concentrations of target analytes in the cosolvent matrix; a flame-ionization detector (FID) is used to quantify the analyte concentrations in the sample. The method has been found to provide reliable and reproducible quantitation of target compounds for concentrations >10 g/ml; this value is then considered to be the Method Detection Level (MDL). The standards calibration curve for FID response was found to be linear up to 500 g/ml for all target compounds, and it may be linear even beyond this value, but was not tested.

Samples selected for GC-FID analysis may be chosen on the basis of preliminary screening to determine approximate concentration ranges, and select appropriate GC parameters (e.g., sample injection volumes; concentration range for standard curves, etc.) However, strategies for sample screening themselves are outside the scope of this SOP.

Water samples from laboratory and field experiments may be sub-sampled into 2-ml GC vials for analysis.

3.0 RESPONSIBILITIES

All NAPL project staff, faculty, and students are responsible for knowing the procedures outlined below for analysis of target analytes selected for the Clemson test.

4.0 PROCEDURES

4.1 Sample Containers, Collection, Transportation and Storage

Sample Containers. Samples are contained in 4-ml glass sample vials (Fisher Catalog # 03-393G or equivalent) with open caps and Teflon-faced septa. The glass vials or the caps are not reused.

Sample Collection. Each sample vial is completely filled with samples, such that no headspace of air exists, and capped. The vials are not opened until the time of sub-sampling or analysis.

Transportation and Storage. For field studies, the samples are stored in coolers containing "blue ice," and later stored in refrigerators in a trailer located on the site. Samples may be subjected to on-site GC analysis, and/or shipped back to CU laboratories; samples are packed in coolers with blue ice and shipped via overnight air express (e.g., FedEx). The samples are stored in a refrigerator at 4°C, until they are ready for GC analysis. After sub-sampling, the samples are returned to cold storage. For laboratory studies, the samples are stored in a refrigerator if the period prior to analysis is expected to exceed eight hours.

4.2 Sub-Sampling and Dilution

Disposable, Pasteur glass pipettes (Baxter Catalog # 13-678-20B or equivalent) are used to transfer samples from 4-ml sample vials to the 2-ml GC vials. Samples may need to be diluted with cosolvent prior to GC analysis. The dilution (usually 10x to 100x) necessary is determined from preliminary screening analysis.

4.3 Apparatus and Materials

Glassware. Disposable micro-pipettes (10, 100 l; Fisher Catalog # 21-175B; 21-175F) and Class A volumetric pipettes (1 or 2 ml) are required for sample dilution. Drummond Dialamatic microdispensers (Fisher Catalog # 21-170-15A and # 21-170-15D or equivalent) may be used with the disposable micropipetter. Disposable Pasteur glass pipettes (Baxter Catalog # 13-678-20B or equivalent) are required for sub-sampling. GC vials (2 ml) with Teflon-faced caps (Baxter catalog # C4901-230 and # C4901-238 or equivalent) are required for GC analysis. Class A volumetric pipettes (0.5, 1, 2, 5, 10 ml) are required for the calibration standards.

Gas Chromatograph System. An analytical GC system is required, complete with a temperature-programmable oven, and either an integrator or a PC-based data aquistion/analysis software. Also required are other accessories, including analytical columns and the gases required for GC-FID operation.

The GC systems used at CU are a Hewlett Packard (HP) 5880 equipped with a FID, a HP 5890 series II+ with an autosampler and FID, a HP 5890A with FID, and a HP 6890 with an autosampler and FID. The HP 5880 is interfaced with a HP 5880A Level Four GC Terminal integrator; the HP 5890A is interfaced with an ??? integrator; and the HP 5890 series II+ and the HP 6890 are interfaced with a IBM-compatiable PC loaded with HP ChemStation software.

· Column: The capillary column is a J & W Scientific DB-5 (30-m long, 0.25-mm i.d.) with a 1-m film thickness (Baxter catalog # C4587-89 or equivalent).

· Gases: Zero-grade air and ultra-high purity (UHP) hydrogen are used for the FID, and UHP helium is used as the carrier gas.

Reagents. All solvents and reagents used in standard preparation are of maximum purity and show no interference with other analytes at the lowest practical quantitation limit for any analyte. Field solvents have no guaranteed purity and are checked for interference with each target analyte and appropriate practical quantitation limits are thereby developed. Laboratory reagent water is distilled, deionized tap water which shows no interference with the target analytes.

Standard Solutions. Analytical standard solutions are prepared from pure materials in the laboratory. At CU, the following reagents are used in the preparation of standard solutions:

Reagent Minimum Purity Manufacturer

o-xylene 95 % Burdick & Jackson

1,2-dichlorobenzene 98 % Mallinkrodt

undecane 99 % Aldrich

naphthalene 98 % Aldrich

d8-naphthalene 98 % Aldrich

tetradecane 99 % Aldrich

TBA 99 % J. T. Baker

n-hexanol 98 % Aldrich

isopropyl alcohol 99. 5 % Mallinkrodt

tetrahydrofuran 99 % Mallinkrodt

The primary stock standard is prepared in isopropyl alcohol (IPA). A Class A volumetric flask is filled to the neck with IPA, placed on an analytical balance accurate to 0.1 mg, and appropriate masses of pure compounds are added to bring their approximate concentration to 5000 mg/L. Analytes are added in reverse order of their volatility; naphthalene, tetradecane, undecane, 1,2-dichlorobenzene and o-xylene. Secondary stock solutions are prepared by diluting the primary stock to concentrations of 200, 100, 50, 25, 10, and 5 mg/L by adding 400, 200, 100, 50, 20 and 10 mL each of the primary standard to 10 mL class A volumetric flasks containing either 95 % TBA and water or 81 % TBA, 15 % hexanol and water. Secondary standards at 2 mg/L and 1 mg/L are prepared by adding 10 and 5 mL respectively of the primary standard to 25 mL class A volumetric flasks containing either the TBA or TBA/hexanol solution. Microliter quantities are measured with microliter syringes such that each volume measured equals at least 40 % of the total volume of the syringe.

Secondary stock solutions are prepared in both the TBA and TBA/hexanol solutions in order to account for matrix effects exhibited by the presence of the semi-volatile solvent, n-hexanol, in certain samples. Primary and secondary stock solutions are stored at 4°C when not in use and are allowed to warm to room temperature prior to subsampling in order to allow the solvent density to return to where it was at the time of standard solution preparation.

Stock standard solutions, at 1,000 g/ml of each analyte, are prepared in the appropriate mixture of cosolvents and kept in 12 ml glass vials (Baxter catalog # 4802-12) with Teflon-lined caps; zero headspace minimizes volatile losses. These stock solutions are stored at 4°C.

Old stock solutions are discarded and a fresh batch prepared every month. Any time a comparison with the check standards indicates a problem, a new batch of standards must be prepared.

· Working Calibration Standards (Secondary Dilution Standards): Working calibration standards are prepared by diluting stock standard solutions in the appropriate mixture of cosolvents.

· Calibration Check Standards: Calibration check standards are prepared by diluting stock standard solution in the appropriate mixture of cosolvents.

4.4 Calibration

Calibration Standards. Prepare five calibration levels as follows: All standards are prepared by dilution of a stock solution (e.g., 200 g/ml). As an example, add 0.1, 1, 2, 10, and 20 ml of the stock standard solution (200 g/ml) solution and dilute to 20 ml with reagent water. This gives five calibration levels (g/ml) as follows:

4.5 Quality Control

Quality control procedures that will be followed are:

· GC injector septa must be changed every 30 to 40 injections or sooner if any related problems occur.

· Injector liners must be cleaned or changed daily or sooner if any related problems occur.

· An acceptable method blank analysis must be performed once for each 12-hour time period.

· Standard calibration must be verified every time the flame is started.

· Check standard and blank (appropriate cosolvent) should be run every 10 to 12 samples.

4.6 Instrument Procedures

Gas Chromatography Condition. Recommended operating conditions are as follows:

The initial oven temperature is 50°C which is held for 3 min before increasing at 10°C/min to 160°C which is held for 0 min. The second ramp increases at 30°C/min to 300°C and held for 5 min. The injector temperature is 250°C and the detector is at 320°C. The injection volume is 1 l. For the HP 5880, the carrier gas is set at 1.5 ml/min. The linear velocity is 35 cm/s. The N₂ make-up gas is at 20 ml/min, the H₂ is at 30 ml/min, and the air at 440 ml/min. For the HP 6890, the carrier gas is set at 2 ml/min. The N₂ make-up gas is at 48.5 ml/min, the H₂ is at 40 ml/min, and the air at 450 ml/min. For the HP 5890 series II+ (with electronic pressure control) the H₂ is set at 30 ml/min and the air at 400 ml/min with the combined flow at 31 ml/min.

A typical chromatogram for standards of the target analytes in the cosolvent matrix analyzed using the HP 5890 series II+ GC system is attached here as Figure 1.

4.7 Sample Preparation

Sub-sampling. Samples are transferred from sample vials to GC vials and capped with open-top, Teflon-lined septa caps.

Dilution. Prepare a sample dilution if responses for any peaks in the sample exceed the calibration ranges. The dilution should allow the analyst to obtain the greatest response within the analytical range, or refer to screen results to determine if initial dilution is required. For on-site analyses, samples were diluted if screening analyses indicated that the target analyte concentrations exceeded 200 g/ml.

4.8 Sample Analysis

Analysis. The samples are allowed to reach ambient temperature prior to GC analysis. From the GC vials with sub-sampled (and diluted, if necessary) samples, 1 l is withdrawn with a glass syringe and manually injected in the HP 5880 injector. For the HP 6890 and 5890 series II+ GC system, the GC vials are loaded onto the autosampler and 1 l injections are made.

Analyte Identification. Analyte identification is not based on absolute retention time. A relative retention time for each analyte of interest is established by comparison to a specific reference peak (e.g., the solvent peak, a major component peak, a spiked internal standard or reference). The analyte of interest must elute at the same relative retention time as the standard; small changes in the absolute retention times are expected due to variations in flow rate, column temperature or other operational parameters. The primary criterion is that the relative retention time of the sample component must be within ±0.1 min of the standard.

Analyte Quantitation. When an analyte has been identified, the concentration is determined by either of two techniques. One uses an internal standard calibration technique where

or

where RRF is the relative retention factor, Area(A) is the area of the analyte peak, Mass(A) is the mass of the analyte, Mass (IS) is the mass of the internal standard, and Area (IS) is the area of the internal standard peak. The second technique is the concentration is determined based on the peak area which is converted to concentration using a linear standard calibration curve.

Interferences. Contamination by carryover can occur whenever high-level and low-level samples are sequentially analyzed.

· To reduce carryover, the injector syringe should be rinsed with reagent water between analyses.

· Whenever a sample with an unusually high concentration is encountered, it should be followed by an analysis of a blank to check for cross-contamination.

4.9 Safety

The main safety issue concerning the use of the GC at a field site relates to the compressed gases in use. The FID gases (hydrogen and air) form explosive mixtures. It is important to keep this in mind at all times and be aware of the hazard potential in the event of an undetected hydrogen leak. All gas connections must be properly tested at installation.

High-pressure compressed-gas cylinders must be secured to a firm mounting point, whether they are located internally or externally. Gas cylinders should preferably be located outside the trailer on a flat, level base, and the gas lines run inside through a duct or window opening. If the gases are located outside, then some form of weatherproofing for the gauges will be necessary. As a temporary measure, heavy-duty polyethylene bags, secured with tie-wraps, have been used successfully; this may not be very elegant but it is very effective for short-term use of the GC. A more permanent protective housing must be built if the GC is located at the trailer for an extended time period. If it is not possible to arrange external siting easily, the gas cylinders should be secured to a wall inside the trailer.

The main operating drawback to locating the gas cylinders externally is that it is not easy to monitor the cylinder contents from the instruments; the gas which could be used up most quickly is air for the FID, particularly if two instruments are hooked up to the same supply and they are running continuously. It may be worth having a reserve cylinder of air, just in case.

Miscellaneous Safety Issues. It is good laboratory practice to make sure the flame is attended at all times. When it is necessary to change the injection liner on the GC, the detector gases should be shut off. The column must be connected to the detector before igniting the flame. The trailer should be kept well ventilated when using the GC. Refer to the Materials Safety Data Sheets (MSDS) for additional information on environmental toxicity data and for safety information, procedures, and regulations.