- Direct-Push Technologies
- Fiber Optic Chemical Sensors
- Gas Chromatography
- Graphite Furnace Atomic Absorption Spectrometry
- High-Resolution Site Characterization (HRSC)
- Infrared Spectroscopy
- Laser-Induced Fluorescence
- Mass Flux
- Mass Spectrometry
- Open Path Technologies
- Passive (no purge) Samplers
- Test Kits
- X-Ray Fluorescence
Test kits are self-contained analytical kits that generally use a chemical reaction that produces color to identify contaminants, both qualitatively and quantitatively. Numerous different kits are used in the environmental field, in applications ranging from simple paper test strips used to assay various water quality parameters to sophisticated colorimetric reactions measured by UV fluorescence that give quantitative results for definitive site characterization. Test kits also can be used after an initial site characterization phase to monitor the operating conditions of a remediation system or to confirm that contaminated soils have been removed.
There are numerous advantages to using test kits in the field, including speed, portability, ease of use, low cost per sample, and the range of contaminants that can be analyzed. With supervision, a beginner can immediately begin to use some of the simpler tests, such as paper test strips, or colorimetric indicator tubes that typically do not involve the addition of reagents. While more sophisticated reagent kits, such as immunoassays, are designed specifically for easy operation, a background in environmental chemistry and familiarity with analytical techniques is an advantage for the operator. Although some field test kits are based on EPA methods used for reference and produce equivalent results, many kits are screening analytical methods, which means that the impact of potentially significant analytical interferences, imprecision, and bias need to be considered when interpreting kit responses, and comparing the results to results from other analytical procedures. For these reasons, the choice of kit, its application to project decision-making, and associated quality assurance and quality control (QA/QC) procedures should be overseen by properly trained and experienced personnel. Commercially available products are listed in this section solely as a means of disseminating useful information. The agency does not endorse specific technology vendors (view full disclaimer).
Many of the test kits that are employed in groundwater, and surface and waste water investigations are well known, and have been commercially available for many years. These kits may employ "microtitrations," where the titrant is added drop-wise to a small amount of sample collected in a vial containing an indicator that changes color in response to the presence of the analyte of concern. More usually, the kits employ colorimetric reactions where color is developed in response to the parameter of interest and compared to a color chart, or is measured using a photometer. Paper test strips are the simplest, most familiar and perhaps occasionally overlooked field test kits available for water investigations. These test strips are simply dipped into the sample, and the color developed on the strip is compared to a chart supplied by the manufacturer. Parameters that can be assessed using test strips include: free chlorine, pH, arsenic, copper, total dissolved iron, ammonia and nitrite/nitrate. More sophisticated test kits, termed "Water Quality Labs" by the manufacturer, are available and can analyze 20 water quality parameters, such as ammonia, chloride, acidity, alkalinity, hexavalent chromium, copper, iron, manganese, molybdenum, nitrite/nitrate, pH, sulfate, sulfide, and reactive phosphate. These kits are fully portable; reagents and meters and all the disposable supplies needed to run 100 tests for 19-20 parameters are packed into an attach� case. Specialized test kits are available for drinking water, wastewater, storm water and surface water investigations. Test kits can be customized by the manufacturer on request. As some of the tests included in these kits are based on EPA "wet chemistry" methods, the results from the test kit can be considered equivalent to those obtained from an off site laboratory. Single test kits are available for parameters such as zinc, iron, hexavalent chromium, ammonia, arsenic, and lead.
Test kits for air monitoring are also well known in the context of industrial hygiene, where Draeger Tubes™ may be used to monitor the concentrations of contaminants in ambient air to protect site workers. These tubes employ a colorimetric reaction to determine the presence of an airborne contaminant. However, their use can be expanded to aid site characterization. In addition to the traditional test kits used to determine water and ambient air quality, several innovative technologies are listed below that expand the range of the field test kit to the detection of organic analytes in soil, water, and oil matrices. Although not a comprehensive list, these examples of reagent kits, represent the diverse group of more recent products that are now commercially available:
- The Hanby Field Test Kit - petroleum products and PCBs in soil and water
- The Clor-N-Oil and Clor-N-Soil kits - polychlorinated biphenyls (PCBs) in soil and oil
- The Dexsil L2000DX analyzer - chlorinated organics in soil, water, dielectric fluids, and surface wipes.
- The PetroFLAG™- total petroleum hydrocarbons (TPH) in soil
- SiteLab® - aromatic compounds derived from petroleum based fuels in soil, sediment, and water.
- The SDI Quick - total Volatile Organic Halides (VOHs) in soil and water
- AQR Color-Tec® � total VOHs in soil and water
As previously noted, test kits have a wide variety of field applications. Water quality can be assessed and some metals determined in groundwater and surface water investigations. The ability to analyze VOHs in the field facilitates groundwater "plume chasing." Plumes of halogenated volatiles can be delineated using field data from direct push wells and field VOH analysis. The concentration of total iron in groundwater can be monitored in real-time using a field kit during the addition of ferrous iron to a groundwater system in the course of remedial action. The effectiveness of a remedial technology to remove arsenic, lead, or VOHs from groundwater can be monitored using a suitable field test kit.
The areal extent of soil contamination from many types of petroleum based fuel oils can be estimated using test kits. Similarly, the extent of soil contamination from polychlorinated biphenyls (PCBs) can be determined. Field test kits can be used to assess the need for the excavation of additional soil during a soil removal action, and to determine the point at which cleanup verification sampling can begin.
Although indicator tubes are used most frequently for indoor or outdoor health and safety monitoring to measure contamination in ambient air in the breathing zone of field personnel, they also can be used to directly characterize ambient air and soil gas on hazardous waste sites. The tubes can be placed in a tank, down a sewer, at the top of a monitoring well, or in many other locations to detect gases and vapors produced by solids and liquids, such as soils, sludges, and groundwater.
EPA has published colorimetric/turbidimetric methods for the following contaminants:
|Colorimetric Screening Procedure for RDX and HMX in Soil|
|Colorimetric Screening Method for Trinitrotoluene (TNT) in Soil|
|Screening Procedure for Total VOH in Water|
|Turbidimetric Screening Procedure for Total Recoverable Hydrocarbons in Soil|
|Test Methods for Total Chlorine in New and Used Petroleum Products (Field Test Kit Methods)|
|Screening Test Method for Polychlorinated Biphenyls in Soil|
|Screening Test Method for Polychlorinated Biphenyls in Transformer Oil|
Complete versions of the SW 846 methods listed above can be found on-line at:
EPA SW-846 On-line
However, when reviewing a method for use, the user should be aware that in some instances technologies may be offered by companies other than the entity noted by the method as being responsible for their development. In addition, technologies are traded between companies, and appear under new names, or may not be retained as product lines by the company that purchased them.
Nearly all the test kit technologies discussed in this document are dependent on colorimetric or turbidimetric reactions. Color or turbidity is developed in response to the presence of a contaminant, and the resulting color is matched to a color chart supplied by the kit manufacturer, or the intensity of the color/turbidity is measured using a photometer. Exceptions to the general statement include the SiteLab® system that uses the innate property of aromatic compounds to fluoresce in the presence of UV light, and the Dexsil LD2000DX analyzer that uses an ion selective electrode (ISE) to measure the analyte of interest.
The following paragraphs discuss the specific operational theories of several kits that cover a range of sample media.
Indicator tubes such as Draeger Tubes™ are designed to analyze air samples for airborne contaminants. Sealed glass tubes are filled with a reagent specifically sensitive to a target gas. If the target gas is present in an air sample drawn through the tube, a color change will occur in the tube�s reagent layer. The data obtained from indicator tubes are considered to be only qualitative or semi-quantitative.
Reagent kits also have been designed for analysis of water. Some reagent kits provide solvents that are used to extract analytes from soils and other solids into a liquid medium for analysis. Various reagent kits use chemical reactions specific to particular compounds that produce color in the visible spectrum. The change in color indicates the presence of the target compound, while the compounds are quantified if the intensity of the color produced can be compared with the color of standards of known concentrations. The level of certainty will vary depending on whether the intensity of the color is compared visually with a color chart or precise calibrated electronic detectors are used. Presented below is a brief discussion of the theory of operation of several of the more recent test kits.
The Hanby test specifically responds to aromatic compounds found in fuels and polychlorinated biphenyls (PCB). The test is based on the Friedel-Crafts reaction, in which aromatic substitution produces molecules with intense coloring. Comparisons of the intensity of color produced can be made either visually with a color chart or photometrical with a reflective photometer.
The Clor-N-Soil and Clor-N-Oil PCB kits use an indicator solution of mercuric nitrate and diphenylcarbazone. Alone, the two compounds form a complex to create a vivid purple color. Metallic sodium, which comes with the kit, is used to strip chloride ions from the PCBs (or other chlorinated molecules); the presence of free chloride ions binds up the mercuric ion and disrupts the colored complex. The endpoint is read as either "blue" (organic chlorine is not present above a set response level) or "not blue" (yellow or colorless when organic chlorine is present above a set response level).
The Dexsil L2000DX analyzer utilizes the same chemical reaction as the Clor-N-Soil and Clor-N-Oil kits to strip the chlorine out of chlorinated molecules, and convert it to inorganic chloride ions. Chloride ions are subsequently extracted into an aqueous buffer solution and are quantified using an ion selective electrode instead of a colorimetric reaction.
The PetroFlag™ kit uses a proprietary turbidimetric reaction to determine the TPH concentration of solvent extracted samples. The sample extract is added to a vial containing an aqueous emulsifier/development solution, and any TPH present is precipitated out, and remains in suspension. The resulting turbidity is measured using a turbidimeter, the PetroFlag ™ analyzer.
The Sitelab analytical system identifies categories of TPH, such as gasoline and diesel range organics, crude oil, and polyaromatic hydrocarbons in solvent extracts from soil, water, and sediment samples. This system employs the characteristic property of aromatic compounds derived from petroleum based fuels to fluoresce in the presence of UV light. Each group of compounds specific to one of the TPH categories will excite and emit UV energy at a specific wavelength that is measured by and quantitated against a curve stored in the UV photometer.
The SDI Quick uses a sample extract and color reagent to produce a reagent/analyte complex that is exposed to UV light. Color is developed proportional to the concentration of the analyte of interest and is used to quantitate total VOHs in soil and water. A small portable photometer called the Envirometer is used to expose the reagent/analyte complex to UV light and to measure the color intensity. The Envirometer uses a standard curve stored in the memory of the unit to quantify the concentration of the analyte.
The AQR Color-Tec® system employs the observation of a color change in a color tube in response to the presence of VOHs. VOHs are purged from either soil or water samples by a known volume of air , and the air is subsequently pulled through a color tube. A change in the color of the tube, yellow to purple, denotes the presence of VOHs. The length of the color change in the tube approximates the magnitude of the amount of VOHs, i.e., high, medium, or low.
The amount of equipment included with each test kit varies widely by the type and manufacturer of the kit. Some kits come with color wheels or color charts to be used for semi-quantitative analysis; electronic analyzers that detect and analyze the color change electronically also may be ordered with many kits. The complexity of the kit will depend on the type of test, the sample medium, and the level of data quality required.
The only equipment necessary to use indicator tubes are the tubes and a hand pump. To work properly, the tubes and pump must be obtained from the same manufacturer because the pumps are designed to deliver specific volumes of air to which the individual tubes tests are calibrated.
Most reagent kits on the market contain several basic pieces of equipment, including sample containers, reagents, and calibration standards. Some kits provide color charts to be used in estimating the degree of color intensity (sample concentration), while others use such instrumentation as spectrophotometers or proprietary analytical detectors to produce more precise results than can be obtained by using color charts. Common accessories include graduated cylinders, pipettes, balances, extraction apparatus, and timers.
The Hanby Field Test Kit comes in a carrying case that contains all the materials needed to perform an analysis. The Hanby Field Test Kit consists of glassware, an electronic balance, reagents for 15 tests, video and written instructions, and all other components necessary for the 15 analyses. Eleven calibration photographs of more common substances (fuels, solvents, transformer oils, used motor oil, and others) are included in the kit. Additional calibration photographs can be obtained from the vendor.
The Clor-N-Oil and Clor-N-Soil kits from Dexsil® consist of two plastic test tubes that contain ampoules of reagent and assorted accessories, such as the pipettes that are necessary for one analysis. A color chart also is included to illustrate examples of positive and negative results.
The PetroFLAG™ test system from Dexsil, which comes in a carrying case, consists of a hand-held digital analyzer, a portable electronic balance, a timer, two calibration standards (a blank and 1,000 parts per million), and enough reagents to perform 10 tests. The analyzer weighs less than a pound and will analyze as many as 18,000 samples before the 9-volt battery must be replaced. Minimal training is required to operate the menu-driven software.
The Dexsil L2000DX analyzer comes packed in a carrying case that in addition to the analyzer contains: an AC/DC transformer, a PC upload cable, a portable electronic balance, 5 ml pipettor, vial rack, timer, marking pen, 2 empty glass vials, data manager software CD, instruction manual, certificate of calibration, MSDSs, ion-specific electrode, polishing strips, and test tube rack. The test kit that contains all the tubes and reagents necessary for sample extraction and preparation for measurement is purchased separately.
SiteLab® test kit, packed in a field case, includes the UVF 3100A analyzer, optical emission filters, balance, adjustable pipette, solvent dispenser, tissues and markers, software, and user's manual.
The SDI Quick single-measurement system consist of the Envirometer instrument; a volumetric pipette, a small balance; and test kits, which are sold separately as disposable supplies. Each test kit contains premeasured calibration standards for conducting the initial calibration of the instrument and a calibration verification solution for making periodic checks of the calibration, extraction solvents, and colorimetric reagents for the analysis of five soil samples. The kits also contain an electronic balance for weighing soil samples, a filter medium for extracts, and other items needed for particular tests, such as a solid-phase extraction (SPE) cartridge for concentrating extracted TCE. The prepared sample is placed in a sample cuvette in a small portable photometer called the Envirometer. The Envirometer produces quantitative results of the analysis on the basis of the calibration curve stored in its memory.
The AQR Color-Tec® system's starter package includes a RAE® piston pump, pump stand, hotplate, stainless steel water bath, digital thermometer, heating rack, decontamination syringe, disposable supplies sufficient for 20 tests, and a QA/QC kit. The non-disposable items of hardware are packed in a carrying case.
Test kit operation can be very simple or rather complicated, depending on the particular method and the data quality level needed. Qualitative screening tests generally are simple to run. At the other extreme, some quantitative test kits involve numerous steps in sample preparation and analysis. The SW-846 Methods manual recommends that these methods be "restricted to use by or under the supervision of trained analysts," and "each analyst must demonstrate the ability to generate acceptable results." Non-technical personnel would require training in the use of the test kits. Because of the potential for interferences, interpretation of the data requires an understanding of analytical chemistry and the matrix being analyzed.
The operation of indicator tubes is straight forward. The tip of the indicator tube is broken and the tube is inserted into the pump. To collect a sample, a known volume of air is drawn through the tube by pumping the pump a specific number of times, as indicated in the manufacturer’s instructions for the specific test. A colored stain will be produced in the tube’s reagent layer if the target gas is present. The length of the color stain is proportional to the concentration of the gas; the concentration can be read by a scale printed on the tube. The analysis takes approximately one minute.
Use of a Hanby Field Test Kit to analyze a soil sample involves weighing five grams of soil sample, placing it into a beaker, adding an ampoule of solvent to the soil, and stirring the sample for approximately two minutes to extract the contaminant. The extract then is poured from the beaker into a marked test tube, and the catalyst is added to the test tube. The mixture is shaken for two minutes while the color change develops. The developed color of the precipitate is compared with a calibration photograph to obtain quantitative results. The water test is performed in the same manner, with the exception that a 500-milliliter (ml) water sample is extracted with solvent in a 500 ml separatory funnel, which is included in the water test kit. The procedure takes approximately 10-20 minutes.
The Dexsil Clor-N-Oil and Clor-N-Soil kits measure the total chlorine in PCB molecules. Several grams of soil sample are introduced into a vial that contains an ampoule of organic solvent, and the PCBs are extracted from the sample medium with the solvent. The extract is treated with metallic sodium to strip chlorine from the biphenyl compound as chloride ions. An acidic buffer is added to the extract to quench any unreacted sodium and to transfer the chloride ions into the aqueous phase. Finally, chloride ions are measured colorimetrically by an indicator solution that creates a purple or yellow color depending on the presence of chloride ions. The purple color indicates the absence of chloride, and therefore the absence of PCBs, in the sample. A yellow or clear color indicates the presence of chloride, and therefore the presence of PCBs, in the sample. The test takes approximately 10-15 minutes. The procedure for the analysis of oil samples is the same, except that no solvent extraction step is required.
Samples for analysis using the Dexsil L2000DX analyzer are prepared in a similar manner to those intended for Clor-N-Soil or Clor-N-Oil analysis. No extraction step is required for the preparation of oil samples before reaction with sodium, but all other matrices require extraction. Using soil as an example, a 10 gram (g) weight of soil is solvent extracted. The extract is dried and cleaned using a syringe mounted drying column, then reacted with metallic sodium and catalyst. The inorganic chloride generated by this reaction is extracted into an aqueous buffer that is filtered and then analyzed.
The PetroFLAG™ kit uses a two-point calibration–a blank and a 1,000 parts per million (ppm) standard. The analyzer's software package is used to adjust the calibration mathematically to quantify the particular petroleum fraction of interest. The PetroFLAG™ analysis involves weighing 10 grams of soil by an electronic balance, placing the soil sample in a test tube, adding extraction solvent to the tube, shaking the tube intermittently for four minutes, filtering the extract into a vial that contains development solution, and allowing the solution to react for 10 minutes. The filtration step is important because the analyzer measures the "turbidity" or "optical density" of the final solution. Approximately 25 samples can be analyzed per hour. The vial of developed solution is placed in the meter, and the instrument produces a quantitative reading that reveals the concentration of hydrocarbons in the soil sample.
The SiteLab® system for soil analysis requires a 5 g sample to be weighed into a jar, and extracted with 10 ml of methanol. The methanol extract is filtered using a syringe mounted filter, then diluted and poured into a cuvette for analysis.
The SDI Quick uses a photochemical reaction to produce a color proportional to the concentration of the analyte of interest. A small portable photometer called the Envirometer is used to measure the reaction. Three standards provided with each test kit are used to calibrate the Envirometer. The standard curve for the photochemical reaction is stored electronically in the unit. A calibration verification solution, also provided with each test kit, is used to verify the calibration curve. A soil sample is weighed, extracted with a solvent, and then filtered. The single analyte test system entails using an organic solvent to extract the analytes from soil and employs various combinations of solid phase extraction (SPE), liquid-liquid transfer and acid-base cleanup techniques to separate the analytes into an organic solvent. The extraction procedure used varies according to the specific test to be performed. Filtration helps to reduce interferences. The sample is placed in the Envirometer and the degree of absorbency of the sample is measured and converted into a concentration of total VOHs. The entire extraction and analysis procedure requires approximately 20-30 minutes.
The AQR Color-Tec® system relies on the color change in a "Gastec®" tube to detect VOHs. Water samples are placed in a 40 ml glass VOA vial for purging. Soil samples are also placed in a 40 ml VOA vial to be purged. Approximately 30 g of soil plus organic-free water are added to the vial. The sample is purged with a defined volume of air. The air is pushed through the vial's septum to the bottom of the vial it by the pump, via a hollow needle. Air containing the purged VOHs is extracted from the headspace above the sample, and passed through a colorimetric indicator, the Gastec® tube. Both the samples and colorimetric tubes require heating to 40�C in a water bath before purging and analysis to optimize the efficiency of both systems.
Test kits are available for almost all classes of environmental contaminants, as well as hundreds of individual compounds. Some kits analyze for general classes of compounds, while others analyze for specific contaminants. Several kits can be used to test for more than one analyte.
Indicator tubes are available commercially for almost 300 gases and vapors (both organic and inorganic), including common industrial gases and solvents.
Reagent kits have been developed for use in analyses for numerous analytes, as well. Typical organic analytes detectable by reagent kits include petroleum hydrocarbons, benzene, toluene, ethylbenzene, and xylenes (BTEX), PCBs, polynuclear aromatic hydrocarbons (PAH), trihalomethanes, and nitroaromatics (explosives such as trinitrolotoluene [TNT]). Some specific examples are:
- The Hanby test kits provide analytical results for petroleum fuels and constituents, such as gasoline, diesel fuel, jet fuel, crude oil, motor oil, BTEX, and PAHs, as well as PCBs in soil and water samples.
- The Clor-N-Oil and Clor-N-Soil kits are capable of detecting PCBs in oil, soil, or surface wipe samples.
- The PetroFLAG™ kit detects and provides quantitative results for gasoline, diesel fuel, jet fuel, fuel oil, motor oil, transformer oil, hydraulic oil, greases, and many other types of hydrocarbons in soil.
- The Dexsil L2000DX analyzer detects total chlorinated organics in soil, water, dielectric fluids, and surface wipes. However, if the species of chlorinated organics is known at a site, the analyzer can be programmed to convert and report quantitative results as the contaminant of interest. (Note this does not apply to known mixtures.)
- SiteLab® measures aromatic compounds derived from petroleum based fuels in soil and water.
- The SDI Quick quantitates total VOHs in soil and water.
- AQR Color-Tec® gives qualitative and semi-quantitative measurement of total VOHs in water and soil.
Performance specs include information on interferences, detection limits, calibration, quality control, and precision and accuracy.
Interferences can affect the detection and quantification of analytes in a sample. Some interferences can be inherent in the method of analysis. Other interferences may be inherent to the sample matrix and will vary according to the particular test and manufacturer. Manufacturers list specific interferences in their instructions. To produce useful data, it is important that the analyst understand the types of interferences and their effects on the results of analysis. Some of the effects are described below.
High relative humidity (higher than 90 percent) may interfere with the results of some tests by indicator tubes.
If more than one type of aromatic compound is present, interpretation of results obtained by the Hanby test kit may be inaccurate because of interference from other petroleum hydrocarbons. The Hanby test is not capable of distinguishing different hydrocarbon fractions in a complex mixture.
Clor-N-Oil and Clor-N-Soil kits may produce false positives for PCBs because of the presence of other chlorinated organics, since the two tests measure total concentrations of chlorine. It is important to know whether other chlorinated compounds are likely to be present before the test kits are used. Inorganic chloride salts present in road salt or seawater may produce false positive results in oils as no extraction is performed on these samples. The extraction process for soil samples leaves salts behind in the soil and only organochlorides are pulled into the solvent. A high sulfur content (>4%) will positively interfere with the Clor-N-Oil analysis.
The presence of organohalides, such as polybrominated or iodinated compounds, will bias results high for the Dexsil L2000DX analyzer.
The PetroFLAG™may produce false positive results if naturally occurring waxes and oils, such as vegetable oils, are present in the sample. PetroFLAG™ analyzes for total petroleum hydrocarbons with the results mathematically corrected to estimate the particular fraction present in the sample. Quantitation of individual petroleum products with PetroFLAG™ is possible only when the types of hydrocarbons to be analyzed for are known.
There is little evidence of chemical interference with the SiteLab® system, and soil moisture content probably has a very limited effect.
The SDI Quick is not liable to significant chemical interference, although 2,2,2-trichloroethanol has an interferent effect at a concentration of 2,000 micrograms per liter.
AQR Color-Tec® is subject to interferences present in the ambient air used as a purge. The presence of toluenes and xylenes give a negative interference to the development of color in the tube designed to detect VOHs. The presence of airborne toluenes/xylenes can be confirmed by the use of another Gastec® tube designed for the analysis of those compounds. Airborne VOHs will give a positive interference to VOH analysis by this method.
Most indicator tubes have detection limits in the range of ppms. A few can detect compounds in the range of hundreds of ppbs.
The Hanby test kit typically achieves detection limits of 1.0 milligram per kilogram (mg/kg) for soil and 0.10 milligram per liter (mg/L) for water. The typical range of the test is 1.0 to 1,000 mg/kg for soil and 0.10 to 20 mg/L for water.
Clor-N-Oil kits are available at concentrations of 20, 50, 100, or 500 ppm Aroclor 1242. Clor-N-Soil kits are available at a concentration of 50 ppm Aroclor 1242. The kits are prepared for those specific concentrations because those levels are common regulatory thresholds.
The Dexsil L2000DX analyzer has a range of 2 to 2000 ppm for chlorinated organic compounds in soil and 0.01 to 2,000 ppm in water.
The PetroFLAG™ test kit will detect hydrocarbons at concentrations in the range of 20 to 2,000 ppm. Higher concentrations can be measured by diluting the sample or using a sample of a smaller size. The PetroFLAG™ system exhibits a lower detection limit of about 20 ppm for heavier hydrocarbons, such as oil and grease. The detection limit for light fuels is higher—for example, 200 ppm for jet fuel and 400 ppm for weathered gasoline.
SiteLab® reports detection limits (in ppm) of 0.5 for gasoline range organics, 0.1 for diesel range organics, 0.025 – 0.05 for PAHs, 0.5 for TPH in the C10 to C40 carbon range, and 5.0 for crude oil.
The SDI Quick test kit for total VOHs has a method detection limit of 3-5 parts per billion in water, and 0.33 - 0.46 ppm in soil.
The AQR Color-Tec® system is semi-quantitative, but is sensitive, and can detect small quantities (approximately 2 micrograms per liter) of VOHs if a large volume (200 ml) of air is used for the purge. Although the method is semi-quantitative, it can give an indication of the amount of VOHs present, high, low, or medium. A conversion table is used to provide an estimated concentration for each tube reading.
There is no calibration involved in the use of colorimetric indicator tubes. The tubes are designed to produce an acceptable result if the appropriate volume of air is drawn through them, as required for each specific test.
The Clor-N-Soil and Clor-N-Oil kits are prepared carefully with premeasured solvents and reagents to produce results at a set threshold level. Kits can be purchased for several different "threshold" concentrations that trigger different regulatory requirements.
Calibration standards provided with the unit are used to perform a two-point calibration for the PetroFLAG™. A blank and a 1,000 ppm standard are run by the analyzer unit to create an internal calibration curve.
The Dexsil L2000DX analyzer is calibrated daily, before use. Calibration solution is provided by the manufacturer in the test kit that supplies the extraction solvents and other reagents. The results obtained from analysis of the calibration standard establish whether the electrode is working within an acceptable range of output and temperature.
SiteLab® UVF-3100A analyzer is calibrated using 5 calibration solutions to give a 5 point curve. The manufacturer provides calibration kits (each containing 5 standards) for gasoline range organics, diesel range organics, PAHs, and TPH -oil.
The SDI Quick uses three standards provided with each test kit to calibrate the Envirometer. A continuing calibration verification solution, also provided with each test kit, is used to verify the calibration curve.
AQR Color-Tec® system uses colorimetric tubes, and as such does not require calibration. However, the manufacturer recommends the use of spiked samples to monitor the efficiency of the analytical system.
Ensuring that the data generated is of a known quality is vital to ensuring the usefulness of those data. Quality control (QC) measures take several forms. They can be performed in the field, during sample analysis, or after sample data have been collected. The type and extent of QC necessary will vary according to the test to be performed and the data quality objectives of the project. A much higher level of QC is necessary to produce defensible data that will be used alone to support specific decisions than to produce screening data that will not be used alone to support decision-making. A fuller discussion of QC for field analytical systems is presented in "Using Dynamic Field Activities for On-Site Decision Making: A Guide for Project Managers" EPA/540/R-03/002 May 2003. In addition, this document contains a comprehensive list of the types of QC samples and the information they provide is available at: http://www.epa.gov/superfund/programs/dfa/download/guidance/40r03002.pdf.
Typical QC measures are discussed below and in the next section, which focuses on precision and accuracy.
Several of the reagent kits require that calibration standards be analyzed before analysis begins. When several standards of known concentration are analyzed, the test kit’s relative response at each concentration can be estimated. In that way, the concentrations in samples that fall anywhere within the range can be determined accurately.
Method blanks are "clean" samples of the same matrix as field samples that are taken through all the sample preparation and analysis steps through which the regular samples pass. Method blanks are used to monitor for contaminants inherent in any of the disposable supplies or reagents; for cross contamination; or for contamination caused by any other sources, such as poor decontamination procedures for reusable items. Method blanks can be prepared and run with all the test kits described here. Typically, one method blank should be analyzed for every 20 regular samples. The sample should not contain any target analytes at concentrations above the test kit’s detection limit. If such concentrations are above the detection limits, the technician should review the instructions supplied with the test kit to verify that all steps were followed properly, and ensure that reusable equipment and supplies used are properly decontaminated.
Duplicate analyses are two analyses performed on the same sample. Duplicates are used to monitor the precision or reproducibility of the analytical technique and should be analyzed at a frequency of one for every 20 regular samples. Care must be taken so that samples are homogeneous before splitting for duplicate analysis or else the duplicate comparison will be invalid. The variation between the results should be consistent with the QA/QC requirements of the project or with the recommendations of the manufacturer of the test kit.
Precision and Accuracy
Precision is a measure of the reproducibility of sample data between measurements and is affected by the homogeneity of the sample matrix, consistency of the test kit, and the analyst's technique. Accuracy is a measure of how close an analysis comes to the "true" concentration in a sample. There are several means of assessing the precision and accuracy of a test kit.
Control samples are used to assess the accuracy of the operator, the method, and kit being used. The samples are solutions of known concentrations often supplied by the manufacturer. They are analyzed with each set of calibration standards before analysis of the regular samples. The concentration in the control sample must fall within a specified range if the method is to be considered accurate. Third-party control samples having known concentrations of contaminants can be purchased for use with other reagent kits.
Confirmatory samples are collected from the same sample that is analyzed on site with the test kit but are sent to a laboratory off site for formal analysis. The results of the on-site analyses are compared with the results of the analyses by the off-site laboratory. The purpose of collecting confirmatory samples is to support proper interpretation of the results from the test kit and to judge the accuracy of the kit's data from the standpoint of making correct project decisions. The same caveat applies to confirmatory samples as to duplicate samples—if care is not taken to ensure that samples are homogeneous before splitting for off-site analysis, the comparison between the test kit result and the confirmatory result will be invalid because of sample variability. The rate of confirmatory samples should be sufficient to allow for management of analytical uncertainty so that the use of the kit's data can be defended as scientifically valid. The rate of confirmatory samples will therefore vary from project to project depending on the kit, the complexity of the matrix being examined, how the data are being used, and the likelihood that interferences could be causing erroneous results.
Confirmatory analysis should not be used as a substitute for proper QA/QC during test kit use. Many QC measures can be applied when using test kits, such as blanks, duplicate analyses, control samples, and carefully selected confirmatory analyses that build confidence that decisions at an action level are being made correctly.
Confirmatory soil and water samples should be collected if it is necessary to provide definitive determination of contaminant concentrations in a sample. Air samples may be collected in a summa canister or other appropriate container for formal analysis by an off-site laboratory.
The major advantage of test kits is their ease of use. Non-technical personnel can operate many kits with minimal training as long as clearly written operating procedures and sufficient supervision are provided. Test kit selection, sampling design, QA/QC protocol design, trouble-shooting of problems, and interpretation of results should be under the direct control of appropriately trained and experienced personnel who can use professional judgment to decide what is appropriate to meet project data needs.
Colorimetric indicator tubes and reagent kits are available for most common classes of contaminants. Colorimetric indicator tubes are available for air monitoring of several hundred compounds.
The portability of test kits is also a major advantage. Many do not require batteries or a power source, and others can run on disposable batteries.
Most test kits provide rapid results compared with off-site laboratory analysis, which may take days to weeks. Indicator tubes and semiquantitative test kits can provide results in just a few minutes. Other reagent kits that require sample extraction may take more time. The PetroFLAG™ kit can analyze approximately 25 samples per hour.
Another attractive feature of test kits is their price. The use of indicator tubes costs as little as $3 per sample, while a PetroFLAG™ analysis can be run for $16 per sample. The cost of purchasing an indicator tube pump is approximately $300 to $400, while the basic PetroFLAG™ kit can be purchased for only $730. Most of the non-disposable items, such as photometers and balances, usually can be rented from the vendor or a third party at reasonable rates.
Results obtained by indicator tubes are qualitative to semi-quantitative at best. The tubes are designed to test ambient air and gas samples and can detect volatile gases emanating from soil and water only indirectly. The tubes have temperature limitations of 0 to 40 degrees Celsius and relative humidity limits typically of 10 to 90 percent. Many detector tubes and reagent kits are subject to interferences, which are listed in the instruction sheets.
The limitations of the Hanby Field Test Kit may include inaccurate comparison of color if the sample is dark in color. Further, concentrations may be underestimated for highly refined petroleum fuels (those that are lacking in aromatic compounds). Interpretation of results may be inaccurate because of interference from other petroleum fractions.
The Dexsil Clor-N-Oil and Clor-N-Soil kits also can produce inaccurate color comparison if sample extracts are dark in color. In addition, interferences (false positive results) may occur because of the presence of other chlorinated compounds, such as pesticides or chlorinated solvents. It is important to know whether other chlorinated compounds are present before the test kits are used. Inorganic chloride salts present in road salt or seawater can produce false positive results in oil samples that do not undergo an extraction process. However, inorganic chlorides are eliminated in the extraction process for soils, waters, and swipes.
Results from the Dexsil L2000DX can be biased high by the presence of iodinated and brominated organic compounds in a sample.
For accurate quantitation with PetroFLAG™, the analyte to be tested for must be known, so that the instrument can be calibrated correctly. False positive results may occur if naturally occurring waxes and oils, such as vegetable oils, are present in the sample. The manufacturer recommends that the instrument be recalibrated if the ambient temperature varies by �10�C from the temperature at the time of initial calibration.
The use of the SiteLab® UVF-3100A analyzer is relatively simple , but on occasion , analytical experience is required to determine that a low reading sample may in fact be over-range. Guidance is given in the instruction manual that deals with "swamping" the detection system.
The SDI Quick uses reagents sensitive to UV light and testing should be performed away from direct sunlight, in a trailer, vehicle, or under a covering.
The AQR Color-Tec® analytical system requires a 120v AC electrical outlet to run the hotplate used for the heated purge, and warning the color indicator tubes. This requirement may limit the use of the system to an onsite trailer with electrical utilities, or may require taking a generator onsite.
Hand operated indicator tube pumps can be rented for approximately $50 per week or purchased for approximately $300 to $1,460 (automated pump). The indicator tubes, such as those manufactured by Draeger and Rae Systems, normally are sold in quantities of 10 per box at $55 to $200 per box.
Paper test strips range in cost from 50 tests for $12.50 (pH) to 100 for $120 (arsenic). Water Quality Laboratory test kits, for examples, those produced by Hach, range in price from $3,780 to $5, 652, depending on the complexity of the instrumentation included in the kit. These kits can analyze 100 samples for 19-20 parameters. Single parameter tests for metals in water, e.g., arsenic cost $120 for 100 tests.
The PetroFLAG™ system costs approximately $730, with replacement reagents costing from $16 per test.
Hanby test kits can be purchased from the vendor for approximately $900 for a water kit, or soil kit respectively. Refill test kits for additional samples cost $250 for 15 tests; a cost of approximately $17 per test.
The Dexsil L2000DX kit costs $3,675 from the vendor. Test kits containing extraction and analytical reagents are available at about $11 per sample, with a 20 sample minimum per kit.
The SiteLab® test kit containing the UVF 3100A analyzer and all the hardware needed for analysis can be rented from the manufacturer for $900 a week, or $2,500 a month. The purchase cost of the UVF-3100A was quoted as $13,750 by a third party vendor. Extraction kits containing all the disposable supplies necessary for soil, sediment, or water extractions cost $300.
The SDI Quick hardware kit with Envirometer, AC adapter, pipette, and scales costs $2,750, but can be rented at $400 per week, or $900 per month.
The AQR Color-Tec® starter package (hardware and supplies for 20 tests) may be purchased from the manufacturer for $1699. Replacement kits of disposable items sufficient for 20 further analyses can also be purchased from the manufacturer for approximately $496. The cost per sample is $20. QA/QC kits are available for $155.
Test kits costs vary significantly. Kit content, instrument design, accessories, and the quantity ordered will all affect test kit prices. Although the cost information provided in this section was correct at the time of writing (November 2007), the manufacturers should be contacted directly for current cost information as prices are subject to rapid change.
Verification of the performance of site characterization and field analytical technologies is conducted through a variety of programs. Evaluation and verification reports from EPA's Superfund Innovative Technologies Evaluation (SITE) Measuring and Monitoring Program, and EPA's Environmental Technology Verification Program (ETV) program are provided below.
Innovative Technologies Evaluation (SITE) Measuring and Monitoring Program
The SITE Demonstration Program encourages the development and implementation of innovative treatment technologies for (1) remediation of hazardous waste sites and (2) monitoring and measurement. In the SITE Demonstration Program, the technology is field-tested on hazardous waste materials. Engineering and cost data on the innovative technologies are gathered so that potential users can assess the technology's applicability to a particular site. Data collected during the field demonstration are used to assess the performance of the technology, the potential need for pre- and post-treatment processing of the waste, applicable types of wastes and waste matrices, potential operating problems, and approximate capital and operating costs. The following reports from the measuring and monitoring program are available for colorimetric:
- This innovative
technology evaluation report (ITER) presents the evaluation of the Clor-N-Soil
Test Kit designed to provide semi-quantitative results for PCBs in soil.
- This innovative technology verification report (ITVR) reports the evaluation of the Sitelab UVF-3100A system for TPH in soil.
Environmental Technology Verification (ETV) Program
EPA's Environmental Technology Verification (ETV) Program verifies the performance of innovative technologies. ETV was created to substantially accelerate the entrance of new environmental technologies into the domestic and international marketplaces. ETV verifies commercialized, private sector technologies. After the technology has been tested, the companies will receive a verification report that they can use in marketing their products. The results of the testing also are available on the Internet. Numerous ETV reports are presented for the detection of arsenic in water.
Other evaluations include
Dexsil L2000DX analyzer for PCBs