EPA-NERL: 529: Explosives and Related Compounds in Water by SPE and Capillary Column GC/MS
|
Official Method Name
|
DETERMINATION OF EXPLOSIVES AND RELATED COMPOUNDS IN DRINKING WATER BY SOLID PHASE EXTRACTION AND CAPILLARY COLUMN GAS CHROMATOGRAPHY/MASS SPECTROMETRY (GC/MS) |
|---|---|
|
Current Revision
| Rev. 1.0, Sept. 2002 |
|
Media
|
WATER |
|
Instrumentation
|
Gas Chromatography with Mass Spectrometry Detection |
|
Method Subcategory
|
Organic |
|
Method Source
|
|
|
Citation
|
Munch, J.W., 2002, Determination of explosives and related compounds in drinking water by solid phase extraction and capillary column gas chromatography/mass spectrometry: U.S. Environmental Protection Agency Report EPA/600/R-05/052, Revision 1.0, 60 p. |
|
Brief Method Summary
|
Analytes and surrogates are extracted by passing a 1 L water sample through a solid phase extraction (SPE) cartridge containing 500 mg of a divinylbenzene/vinylpyrrolidone copolymer or a 47 mm disk containing a reverse phase sulfonated polystyrene divinylbenzene phase. The organic compounds are eluted from the solid phase with a small quantity of ethyl acetate. The sample components are separated, identified, and measured by injecting an aliquot of the concentrated extract into a high resolution fused silica capillary column of a GC/MS system with a programmed temperature vaporizing (PTV) injector. Compounds eluting from the GC column are identified by comparing their measured mass spectra and retention times to reference spectra and retention times in a data base. Analysis may be performed using either full scan or selected ion monitoring (SIM) mass spectrometry. Reference spectra and retention times for analytes are obtained by the measurement of calibration standards under the same conditions used for samples. The concentration of each identified component is measured by relating the MS response of the quantitation ion(s) produced by that compound to the MS response of the quantitation ion(s) produced by a compound that is used as an internal standard. Surrogate analytes, whose concentrations are known in every sample, are measured with the same internal standard calibration procedure.
The method provides instructions and demonstration data for both the SPE disk and cartridge extraction techniques and for three different GC/MS techniques: PTV splitless injection with full scan mass spectrometry, cold on-column injection with full scan mass spectrometry, and PTV splitless injection with SIM mass spectrometry. |
|
Scope and Application
|
This method provides procedures for the determination of explosives and related compounds in finished drinking water. The method may be applicable to untreated source waters and other types of water samples, but it has not been evaluated for these uses. The method is applicable to a variety of explosives that are efficiently partitioned from the water sample onto a solid phase extraction (SPE) sorbent, and sufficiently volatile and thermally stable for gas hromatography. |
|
Applicable Concentration Range
|
|
|
Interferences
|
1. During analysis, major contaminant sources are reagents and SPE devices. Analyses of laboratory reagent blanks provide information about the presence of contaminants. Solid phase extraction devices described in this method have two potential sources of contamination, both the solid phase sorbent and for cartridge extractions, the polypropylene cartridge that it is packed in. Manufacturers¿ brands and lot numbers of these devices should be monitored and tracked to ensure that contamination will not preclude analyte identification and quantitation.
2. Interfering contamination may occur when a sample containing low concentrations of compounds is analyzed immediately after a sample containing relatively high concentrations of compounds. Injection port liners must be replaced as needed (cleaning and deactivation by the analyst is not recommended). After analysis of a sample containing high concentrations of compounds, a laboratory reagent blank should be analyzed to ensure that accurate values are obtained for the next sample. In the case of automated analysis, the analyst may not be aware of high concentration samples until after an entire batch is analyzed. In this situation, the analyst should carefully review data from samples analyzed immediately after high concentration samples, and reanalyze them if necessary. |
|
Quality Control Requirements
|
See Chapter 9 |
|
Sample Handling
|
8.1 SAMPLE COLLECTION -- When sampling from a water tap, open the tap and allow the system to flush until the water temperature has stabilized (usually about 2 min). Adjust the flow to about 500 mL/min and collect samples from the flowing stream. The sample should nearly fill the 1 L or 1 qt bottle, but does not need to be headspace free. If preservatives have been added to the bottle prior to sampling, be careful not to rinse them out during sample collection. Keep samples sealed from collection time until analysis. When sampling from an open body of water, fill the sample container with water from a representative area. Sampling equipment, including automatic samplers, must be free of plastic tubing, gaskets, and other parts that may leach interfering analytes into the water sample.
8.2 SAMPLE DECHLORINATION AND PRESERVATION -- All samples must be dechlorinated and preserved with a microbial inhibitor at the time of collection. Jenkins, et al. (8) have clearly shown the need for microbial preservation of several of the method analytes. Copper sulfate pentahydrate is added as a microbial inhibitor at a concentration of 0.5 g/L of water (9). The Trizma Pre-Set Crystals pH7 buffer (Sect. 7.5) is added at a concentration of 5.0 g/L. The buffer acts to tie up free chlorine, and also keeps the copper in solution (9). The buffer should be added to all samples, even those that are unchlorinated. The copper sulfate and Trizma may be added to the sample bottles as dry salts prior to transporting the sample bottles to the sampling site. 8.2.1 As an alternative to the Trizma Pre-Set Crystals pH7 buffer, the following may be used : 0.3 g of tris(hydroxymethyl)aminomethane plus 4.7 g of tris(hydroxymethyl)aminomethane hydrochloride for each 1 L sample. 8.3 SAMPLE TRANSPORT AND STORAGE -- All samples should be iced during shipment and must not exceed 10o C during the first 48 hours. Samples should be confirmed to be at or below 10o C when they are received at the laboratory. Samples stored in the lab must be held at or below 6o C until extraction, but should not be frozen. Samples that are significantly above 10° C at the time of collection, may need to be iced or refrigerated for a period of time, in order to chill them prior to shipping. This will allow them to be shipped with sufficient ice to meet the above requirements. 8.4 HOLDING TIME -- Samples must be extracted within 14 days of collection. Sample extracts may be stored for up to 30 days after sample extraction, when stored in amber vials at 0° C or less. |
|
Maximum Holding Time
|
|
|
Relative Cost
|
|
|
Sample Preparation Methods
|
