ANALYSIS OF BROMIDE USED AS A NON-PARTITIONING TRACER

1.0 PURPOSE

The purpose of this SOP is to ensure reliable and reproducible analytical results of bromide in water samples for laboratory-based or on-site (field-based) GC-FID analyses, and to permit trace-ability 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 bromide used as a non-partitioning tracer, in both laboratory and field studies, to estimate the amount and distribution of residual non-aqueous phase liquids (NAPLs) present in the saturated zone. This SOP may not be specifically applicable to the activities of other organizations.

This SOP was written by Eberhard Roeder and Cindy Lee at Clemson University.

The method involves ion chromatography (IC) techniques for estimation of concentrations of bromide in water samples. The method has been found to provide reliable and reproducible quantitation of bromide for concentrations > mg/ml; this value is then considered to be the Method Detection Level (MDL). The standards calibration curve was found to be linear up to 1,000 mg/ml for the bromide, and it may be linear even beyond this value, but was not tested. (In laboratory and field experiments, the output concentrations of the bromide will not exceed this upper limit.)

Samples selected for IC analysis may be chosen on the basis of preliminary screening to determine approximate concentration ranges, and select appropriate IC 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-samples into 2-ml vials for analysis.

3.0 RESPONSIBILITIES

All NAPL project staff, faculty, and students are responsible for knowing the procedures outlined below for analysis of alcohol tracers used in the Clemson test.

4.0 PROCEDURES

4.1 Sample Containers, Collection, Transportation and Storage

Sample Containers. Water samples collected in the field are contained in 4-ml glass sample vials (Fisher Catalog #03-393G or equivalent) or 20 ml glass sample vials (Fisher # 03-339-14C) with open caps and Teflon-faced septa. Water samples collected in the laboratory are contained in 2 ml vials with open caps and Teflon-faced septa (Baxter catalog # C4901-230 and # C4901-238 or equivalent). The glass vials or the caps are not reused.

Sample Collection. Each sample vial is completely filled with aqueous samples, such that no head space 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 analysis, and/or shipped back to CU laboratories; samples are packed in coolers and shipped via overnight air express (e.g., FedEx). The samples are stored in a refrigerator at 4C, until they are ready for 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

For laboratory analysis, samples were removed directly from the sampling vials.

A sample dilution is prepared if response for any peak in the sample exceeds the calibration range. 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 are diluted if screening analyses indicate that the bromide tracer concentrations exceeds 200 mg/ml.

4.3 Apparatus and Materials

Glassware. Disposable micro-pipettes (10, 100 ml; Fisher Catalog # 21-175B; 21-175F) and Class A volumetric pipettes (1 or 2 ml) are required for sample dilution. Drummond Dialamatic micro-dispensers (Fisher Catalog # 21-170-15A and # 21-170-15D or equivalent) may be used with the disposable micropipettes. Vials (2 ml) with Teflon-faced caps (Baxter Catalog # C4901-230 and # C4901-238 or equivalent) are required for analysis. Hamilton syringes (10 to 250 ml, Baxter Catalog # S9661-2, # S9661-6 or equivalent) are required for addition of internal standard.

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

The IC system used at CU is a Dionex QIC Analyzer with conductivity detector. The QIC Analyzer is interfaced with a IBM-compatible PC loaded with Labtech (ver 9.02) software.

• Column: The column is an IonPac® Anion Exchange AS14 (4 x 250 mm) column (Dionex # 46124) and a AS14 (4 x 50 mm) guard column (Dionex # 46134).



• Gases: Dry-grade air is used to operate the injection valve.

Reagents. Reagent water is defined here as the water in which an interferant is not observed at the MDL of the parameters of interest. Laboratory reagent water is distilled, deionized tap water in the laboratory studies and reagent grade water (Baxter Catalog # C4531 or equivalent) in the field studies.

Eluent. The eluent is 3.5 mM Na₂CO₃/ 1.0 mM NaHCO₃ prepared in the following manner. Add 1.484 g of Na₂CO₃ and 0.336 g of NaHCO₃ to 4 L of filtered, distilled, deionized tap water and mix well.

Standard Solutions. Analytical standard solutions are prepared from pure materials in the laboratory. Stock standard solutions, at approximately 1000 mg/ml of each alcohol, are prepared in reagent water and kept in 12 ml glass vials (Baxter Catalog # C4802-12 or equivalent) with Teflon-lined caps; minimal head space ensures no volatile losses. These stock solutions are stored at 4C.

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 reagent water.

Calibration Check Standards: Calibration check standards are prepared by diluting stock standard solution in reagent water.

4.4 Calibration

Calibration Standards for Laboratory Studies. Six calibration standards are prepared as follows: from a stock standard solution at a concentration of approximately 1,000 mg/ml, appropriate dilutions are prepared in reagent grade water using Class A volumetric pipettes or Hamilton glass syringes. Target concentration values for the calibration curve are 1, 10, 20, 100, and 200 mg/ml.

Since working calibration standards are prepared by dilution of a stock standard solution, pre-cautions must be taken to ensure the accuracy of the stock mixture. Two stock solutions are prepared from primary weights and dilution using separate analytical balances. Target concentrations of the stock standard solutions are 1000 mg/ml. Dilution from each are used to prepare a single set of calibration standards. Using this technique, systematic errors may be detected and corrective actions taken to ensure the preparation of accurate working standards.

Internal Standard. Isopentanol is used as the internal standard for the analysis of the alcohol tracers. A stock solution of isopentanol is prepared at 8,000 mg/ml for laboratory analysis and at 1600 mg/ml for field analysis. Ten ml of the stock solution is added to each 1 ml (200 ml in the case of field analysis) aqueous sample before analysis.

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 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 (reagent water) should be run every 20 to 25 samples.

4.6 Instrument Procedures

Ion Chromatography Condition. Recommended operating conditions are as follows:

Pressure in the regenerant bottle should be set at between 10 and 15 psi. Regenerant flow should be above 10 ml/min. Eluent flow should be between 1.2 to 1.4 ml/min.

4.7 Sample Preparation

Draw 5 ml of filtered, distilled, deionized tap water into filtering syringe. Eject water through filter into sample injection syringe. Rinse injection syringe. Draw about 1 ml of sample into filtering syringe without filter. Draw an additional 2 ml of air. Use 1 ml of air to eject water from filter apparatus. Filter sample into injection syringe. Use remaining 1 ml of air to empty filter apparatus. Draw about 2 ml of sample into filtering syringe without filter and repeat.

4.8 Sample Analysis

Analysis. The samples are allowed to reach ambient temperature prior to IC analysis. Screw injection syringe onto injection port. Switch the injector selector to LOAD. Inject 0.5 ml into sampling port. If repeat injections are necessary, 0.3 ml is adequate.

Analyte Identification. Analyte identification is based on absolute retention time. The bromide peak appears at 5.5 min.

Analyte Quantitation. When an analyte has been identified, the concentration is determined by an internal standard calibration technique 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.

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 filtered, distilled, deionized tap water between analyses.



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

4.9 Safety

High-pressure compressed-gas cylinders must be secured to a firm mounting point, whether they are located internally or externally. Always store or move gas cylinders with the safety cap in position. Store or move gas cylinders in a vertical position only. Use only approved regulators and tubing connections.

Turn off the QIC Analyzer power and unplug the line before removing the protective panel on the back of the instrument. Periodically check for leaks and clean up any spills. Ensure that air lines cannot become kinked, punctured or otherwise damaged. Refer to the Materials Safety Data Sheets (MSDS) for additional information on environmental toxicity data and for safety information, procedures and regulations.