SLIDE XRF-1 XRF SLIDE XRF-2 Compatibility with the Triad Approach SLIDE XRF-3 Environmental Applications

X-Ray Fluorescence (XRF) MODULE AT A GLANCE Overview SLIDE XRF-1 XRF SLIDE XRF-2 Compatibility with the Triad Approach SLIDE XRF-3 Environmental Applications Operating Principles Advantages Limitations SLIDE XRF-4 Theory of Operation SLIDE XRF-5 Schematic Diagram of XRF Process SLIDE XRF-6 System Components Sources SLIDE XRF-7 Modes of Operation SLIDE XRF-8 Sampling Considerations SLIDE XRF-9 Quality Control SLIDE XRF-10 Advantages SLIDE XRF-11 Limitations SLIDE XRF-12 Potential Influences on Results Costing and Procurement Considerations SLIDE XRF-13 Costing and Procurement Considerations XRF i

Overview X-Ray Fluorescence (XRF) EPA XRF-1 XRF-1

Overview Compatibility with the Triad Approach Becoming more common as a means to increase the density of information that can be used to support project decision making Useful for most metals in soil when required sensitivities are in the low ppm range SW-846 method is available (Method 8200) Real-time results and high sample throughput can facilitate dynamic work plan strategies EPA XRF-2 Notes: XRF and several other field portable methods are becoming more commonly used throughout the hazardous waste industry. The data has been shown to be comparable to most fixed laboratory methods if the levels of sensitivity required by the project are sufficiently high (generally >10 parts per million [ppm]) as to allow for its use. The use of XRF allows for a much higher volume of data to be collected quickly and economically in support of many types of investigations and cleanups. EPA has spent substantial time and resources verifying the reliability of differing types of XRF units available on the market today. Many new units are appearing on the market making it necessary for users to team with providers when identifying the most appropriate analytical instrumentation and operating procedures. Manufacturers will provide customers with instrument-specific verification results upon request, but users are still encouraged to perform some type of project-specific demonstration of methods applicability before selecting any specific inorganic tool for use on a project. Near real-time project decision making requires that instrument reliability be verified before going into the field. Different strategies can require different instrument configurations and preparation methods as will be discussed in this module. Site-specific standards can improve performance as can drying, sieving or downsizing of sample grain size before analysis. The use of any or all of these types of sample preparation steps are mandated by the project-specific conditions and objectives for a particular site. XRF-2

Overview Environmental Applications Applicable to most site characterization efforts involving solids (soil, sediment, waste, inert metal objects) for:»site characterization»delineating hot-spots»cleanup design and optimization»verification of attainment of cleanup objectives EPA XRF-3 Notes: The use of XRF in the field is currently limited to solid media. The XRF can be used to analyze water samples, but seldom are the levels of sensitivity sufficient for most surface or groundwater related projects. Sites where metals are present at concentrations in the ppm range are best suited for the use of XRF. Mercury vapor analyzers on the other hand can provide sensitivities in the low parts per billion range and support decision making in the field for both solid and liquids. The XRF is uniquely suited for use in hot spot delineation and verification of the attainment of cleanup action levels. The XRF is particularly useful when used along with a dynamic work plan strategy designed to chase down contamination on a real-time basis. Raw data can be generated in the field on a real-time basis to ensure the long-term defensibility of the results obtained. By increasing the numbers of samples that can be collected the volume of waste needing removal or treatment can be minimized. Decision making at sites with metals contamination can be complicated because of the high degree of heterogeneity of contamination. Careful attention should be paid to considerations such as sample support or the size, shape, and orientation of the samples collected. For example, if a soil washing remedy is being entertained for use at a site and particular grain size fractions will be treated differently, it could be important to sieve a sample before analysis. At small arms firing ranges metals (primarily lead) in the course soil fractions greater than 40 mesh are often recycled. Between 40 and 200 mesh, fractions can sometimes be washed and the lead removed before the washed soil is relocated onsite. Finer sieve fractions greater than 200 mesh, generally contain most of the lead contamination and washing is ineffective. This can require that samples be characterized after sieving such that the varying waste streams can be treated appropriately and the proposed remedy costed. XRF-3

Operating Principles Theory of Operation Irradiate samples with X-rays Incident X-rays cause inner shell electrons to be ejected from atom Vacancies in inner shell are filled by outer shell electrons cascading toward nucleus Cascading electrons produce characteristic X-ray fluorescence EPA XRF-4 Notes: Samples are bombarded with X-rays (photons of energy) produced by radioisotopes such as iron-55 (Fe-55), cobalt-57 (Co-57), cadmium-109 (Cd-109), gadolinium-153 (Gd-153), americium-241 (Am-241), or X-ray tubes. When a sample is irradiated, the source X-rays may undergo scattering or absorption by sample atoms. If the X-ray source energy is greater than the absorption edge energy of the inner shell electron, inner shell electrons are ejected from the atom, creating vacancies. Electrons cascading toward the nucleus from outer shells fill the electron vacancies. Electrons in outer shells have higher energy states than inner shell electrons, and the outer shell electrons give off that energy in the form of X-rays as they move toward the nucleus. C The rearrangement of electrons results in emission of X-rays characteristic of the given atom. The emission of X-rays, in this manner, is termed X-ray fluorescence. A qualitative analysis is made by observing the energy of the characteristic X-rays. A quantitative analysis is made by measuring the X-ray intensity at characteristic wavelengths for a particular metal. XRF-4

Operating Principles Schematic Diagram of XRF Process X-ray adsorption and photoelectron ejection. e - X-ray fluorescence transitions. K β K α E > E Kabs E Kabs > E Labs E > E Labs K L E Kβ < E Kα K L L α E Lα < E Kα M M e - EPA XRF-5 Notes: The K, L, and M shells are the three electron shells generally involved in emission of X-rays during FPXRF analysis. The most commonly measured X-ray emissions are from the K and L shells. For light atoms like chromium, arsenic, and cadmium, a K-shell electron is ejected. For heavy atoms like lead, mercury, and uranium, an L-shell electron is ejected. Each characteristic X-ray line is defined with the letter K, L, or M, which signifies which shell had the original vacancy, and by a subscript alpha (") or beta ($), which indicates the higher shell from which electrons fell to fill the vacancy and produce the X-ray. The K " transition is on average 6 to 7 times more probable than the K $ transition; therefore, the K " line is approximately 7 times more intense than the K $ line for a given element, making the K " line the most logical choice for quantitation purposes because it optimizes the sensitivity of the method. The K lines for a given element are the most energetic lines and are the preferred lines for analysis. For a given atom, the X-rays emitted from L transitions are always less energetic than those emitted from K transitions. Unlike the K lines, the main L lines (L " and L $ ) for an element are of nearly equal intensity. The choice of one or the other depends on the interfering elements that might be present and the desired method sensitivity requirements. The L emission lines are useful for analyses involving elements of atomic numbers 58 (cerium) through 92 (uranium). XRF-5

Operating Principles System Components Sources Source energy must be greater than the absorption edge energy of the target analyte Matching radioactive sources with the identified potential contaminants can improve instrument sensitivity Multiple sources can be available with a single analyzer X-ray tubes generate sufficient energy to excite most metals EPA XRF-6 Notes: An X-ray source can excite characteristic X-rays from an element only if the source energy is greater than the absorption edge energy for the particular line of the element. FPXRF is more sensitive to an element with an absorption edge energy close to, but less than, the excitation energy of the source. For example, with the use of a Cd-109 source that produces a source of photons at 22.1 kiloelectron volts (kev), FPXRF would exhibit better sensitivity for zirconium, which has a K line energy of 15.7 kev than for chromium, which has a K line energy of 5.41 kev. Elements that are typically analyzed by the individual radioisotope sources include the following: Fe-55: Sulfur (S), potassium (K), calcium (Ca), titanium (Ti), and chromium (Cr) Cd-109: Vanadium (V), Cr, manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), strontium (Sr), zirconium (Zr), molybdenum (Mo), mercury (Hg), lead (Pb), rubidium (Rb), and uranium (U) Am-241: Cadmium (Cd), tin (Sn), antimony (Sb), barium (Ba), and silver (Ag) Co-57: Pb in paint (not as common because of radioactive safety concerns with Co-57) Gd-153: Pb in paint Cm-244: Fe, titanium (Ti), Cr, Ni, Cu, and Zn XRF-6

Operating Principles Using an X-ray tube, metals ranging in atomic number from titanium through uranium can be quantitated. FPXRF instruments can have more than one source. Typical arrangements include Cd-109 and Am-241 or Fe-55, Cd-109, and Am-241. Can an FPXRF instrument analyze for Cd using the Cd-109 source? Source Activity millicuries (mci) Half- Life (Year) Excitation Energy (kev) Elemental Analysis Range Radioisotope Sources Co-57 40 0.75 121.9 Cobalt to cerium Barium to lead K Lines L Lines Fe-55 20-50 2.7 5.9 Sulfur to chromium Molybdenum to barium K Lines L Lines Cd-109 5-30 1.3 22.1, 25.0, and 88.03 Calcium to rhodium Tantalum to lead Barium to uranium Gd-153 10 0.66 42 Iron to uranium (primarily for lead) Am-241 5-30 458 26.4 and 59.6 Copper to thulium Tungsten to uranium K Lines K Lines L Lines K Lines L Lines K Lines L Lines Curium (Cm)-244 60-100 17.8 14.2 Titanium to selenium Lanthanum to lead K Lines L Lines X-Ray Tube Sources X-ray tube N/A N/A 10-35 variable Titanium to Uranium ( * Additional elements may be added or substituted. A source selection table is provided at the end of this module. Please review this table and make sure you understand the basic principals for source selection. Often switching sources and spectral lines can be needed to meet project objectives, but selection of a different source or spectral line for an element can impact instrument performance. XRF-7

Operating Principles Modes of Operation In situ: Point-and-shoot mode Ex situ or intrusive: Sample collection and processing is used to improve the representativeness of results EPA XRF-7 Notes: For in situ operation, the window of the probe is placed in direct contact with the surface to be analyzed. The instrument is operated much like a gun in a point-and-shoot mode, and analyses are quick (usually 2 minutes). To minimize the effects of soil heterogeneity, three to four measurements can be taken in a small area and averaged to estimate a concentration. In this mode, the technology can analyze more than 100 samples per day (8 hours). Operation in the point-and-shoot mode requires the removal of nonrepresentative debris, such as rocks and leaves; a fairly smooth surface so the window makes good contact is also desirable. No standing water should be present when a measurement is made. For ex situ measurements, a sample is collected, prepared, and placed into a 31-millimeter (mm) or 40-mm polyethylene sample cup and covered with a transparent Mylar film. The sample cup is placed in a covered sample chamber for analysis. In this mode, the technology can analyze about 50 samples per day (8 hours). Sample preparation usually includes thorough homogenation, removal of nonrepresentative debris, sample drying, sometimes even grinding with a mortar and pestle, and passing the sample through a 40 or 60 mesh sieve. XRF-8

Operating Principles Identifying the need for ex situ analyses and the use of additional sample preparation steps is usually evaluated before going into the field or during early stages of a project. Sample results are usually taken in situ as well as ex situ from a typical area of a site. The samples are also generally split for analysis at a fixed laboratory. The resulting data is then plotted and the uncertainty as well as any systematic bias estimated relative to project decision criteria. The standard deviation of the results is generally used along with any indications for systematic bias to establish how many samples should be collected and what preparation steps will yield the most benefit. As mentioned previously, a project profile for the Ross Metals site is provided, which discusses how to determine when and if in-situ versus ex-situ readings are most appropriate. XRF-9

Operating Principles Sampling Considerations Site reuse Restoration alternatives Site heterogeneity (sampling frequency) Sample heterogeneity (sample size) Practical constraints Cost benefit EPA XRF-8 Notes: Before establishing what sample preparation steps should be considered it is important to keep in mind what potential reuse and restoration alternatives will be considered for a site. If the reuse calls for the first 2 feet of soil be removed, then perhaps soil samples for homogenization might be segmented into 6" cores that are then homogenized prior to analysis. If a remedial alternative includes soil washing and soil with a grain size of greater than 40 or 60 mesh sieve can be effectively remediated while soil with less than a 60 mesh sieve size cannot, than perhaps samples should be sieved using a 60 mesh sieve prior to performing the analysis. Careful consideration of site reuse and potential cleanup alternatives will assure that the appropriate samples are collected. There are numerous considerations that must be addressed before a field-based technology or any other analytical technology can be applied at a site. The site heterogeneity or uncertainty associated with an estimate of concentration over a particular area or exposure unit may need to be evaluated to meet project objects. It may also be desired to assure that no one particular hot spot has been overlooked. To meet either of these objectives, it is necessary to understand the characteristics of any sample population well enough to predict what size sample should be collected and how many samples are needed to provide a reasonable estimate of the parameters upon which project decisions will be made. XRF-10

Operating Principles In order to accomplish this task, historical data from a site or some preliminary data will need to be analyzed. The data analysis should include some descriptive statistical analysis to determine population characteristics such as normality, standard deviation, variance, etc. A complete discussion of the analyses required is beyond the scope of this module. The reader is referred to U.S. EPA G-9 (http://www.epa.gov/quality/qa_docs.html) and the Marino Scrap Yard statement of work, part 1, a preliminary conceptual site model (http://brownfieldstsc.org/completed_index.htm). Based upon an analysis of historical data or data from a demonstration of method applicability as described for the Bluffton, South Carolina site also found at the above mentioned web site, the project team can make a preliminary estimate of the numbers of samples and sample size that should be collected to assure the representativeness of the results. For example, if a population is normally distributed and relatively homogeneous, it may not be necessary to take a great number of samples, particularly if the grain size is relatively small and uniformed. Under these conditions, the need for a technology such as XRF may also not be advantageous. On the contrary, at most metals sites data is usually log normal or normal, however, grain size is erratic and so is the distribution of contaminants. Under these conditions classical statistical and sample uncertainty estimation theories may predict the need for the collection of many more samples of a much larger size than is economically feasible using a fixed laboratory sampling and analysis approach. The reader is referred to the use of Visual Sample Plan (www.hanford.gov/dqo/vsp_training/erc_vsp_course_install.html) to determine the number of samples required based on the standard deviation of a normal or log normally distributed data population. To evaluate the size of a sample or the area over which measurements may need to be collected (in situ only) it may be necessary to compare results from various sizes of samples. For in situ this might include a number of readings over a prescribed area, which are then compared statistically with each other to determine how many readings and over what duration (usually between 1 and 4 minutes) are sufficient. The comparability of these results to fixed laboratory results should then be established by graphing the results over a range that extends above and below the site action levels. This comparison will establish the presence or absence of any systematic bias. A field-based action level can be established by comparing any inherent bias with the area of acceptable uncertainty (known as the gray region) around the action level as determined using the standard deviation, if results are normally or lognormally distributed. Similarly, ex situ measurements using various sample sizes and or preparation steps may also need to be considered if in situ measurement variance produces unacceptable results. Initially differing sample sizes based on an understanding of grain size distributions and site variance should be collected, the samples analyzed using XRF and fixed laboratory methods and compared. Once again these results should be reviewed in cooperation with an experienced chemist to determine which series of preparations and/or homogenized sample sizes are the most appropriate for use. XRF-11

Operating Principles Practical and cost benefits must also be evaluated once the theoretical constraints on sample and site heterogeneity have been estimated. Visual Sampling Plan can be used to find a middle ground between what is economically feasible and practical and what is required to have sufficient confidence in a characterization effort. Based on the statistical data available, cost, and practical data, a project technical lead can balance the need for more sample analyses by sometimes considering the use of composites when the statistical data indicates that more samples are necessary than the budget will allow. XRF-12

Operating Principles Quality Control Energy calibration checks Blanks» Instrument» Method Calibration verification checks Precision Detection limits Reporting results EPA XRF-9 Notes: Energy calibration check samples consist of a pure element, such as iron (Fe), lead (Pb), or copper (Cu), that is analyzed to determine whether the characteristic X-ray lines are shifting, which would indicate drift within the instrument. This check also serves as a gain check in the event that ambient temperatures are fluctuating greatly (greater than 10 to 20 F). The energy calibration check should be run at a frequency consistent with the manufacturer s recommendations. Generally, this frequency would include the beginning of each working day, after the batteries are changed or the instrument is shut off, at the end of each working day, and at any other time when the instrument operator believes that drift is occurring during analysis. Two types of blanks may be used during FPXRF analysis. The first is an instrument blank. An instrument blank is used to verify that no contamination exists in the spectrometer or on the probe window. The instrument blank can be silicon dioxide, a Teflon block, a quartz block, clean sand, or lithium carbonate. The instrument blank should be analyzed at a minimum of once per day and preferably once every 20 samples. The instrument blank should not contain any target analytes above the method detection limit (MDL). The second type of blank is a method blank. The method blank is used to monitor for laboratory-induced contaminants or interferences. The method blank can be clean silica sand or lithium carbonate that undergoes the same sample preparation procedures as the other samples. The method blank should be analyzed at the same frequency as the instrument blank and should not contain any target analytes above the MDL. XRF-13

Operating Principles Calibration verification check samples are used to check the accuracy of the instrument and assess the stability and consistency of the analysis of the target analytes. The check sample can be an SSCS or a standard reference material (SRM) such as the National Institute of Standards and Technology (NIST) SRMs, which contain the target analytes, preferably at concentrations near any action levels for the site. Examples of NIST SRMs that can be used include SRMs 2709, 2710, and 2711. The check sample should be run at the beginning and end of each day. The percent difference (%D) between the true value and measured value should be less than 20 percent. Commercial performance evaluation (PE) samples that are prepared for ICP or AA methods are not recommended for an accuracy check. Precision or reproducibility of FPXRF measurements is monitored by analyzing a sample with low, medium, and high concentrations of target analytes. A minimum of one precision sample should be analyzed per day by conducting 7 to 10 replicate measurements on a sample. The precision is assessed by calculating a relative standard deviation (RSD) for the replicate measurements. The RSD values should be less than 20 percent for most analytes except Cr, which should be less than 30 percent. The precision is affected by the analyte concentrations. In general, as the concentration increases, the precision increases; therefore, it is especially important to know the precision of the instrument near action levels. The measurement time for each source also will affect precision. Shorter source measurement times (30 seconds) have less precision, and generally are used for initial screening or delineation of hot-spots. Longer measurement times (300-600 seconds) have greater precision and generally are used to meet more stringent requirements for precision and accuracy. The results for replicate measurements of a low-concentration sample can be used to generate an average site-specific MDL. The MDL is defined as three times the standard deviation (SD) of the results for a low concentration sample. With the exception of Cr, the MDLs for most analytes are in the range of 40 to 200 mg/kg. For chromium and several of the more common metals such as iron (Fe) and manganese (Mn), reporting limits are usually above 200 mg/kg. In FPXRF analysis, the SD from counting statistics is defined as the square root of the gross counts for the target analyte peak. On the data printout from most FPXRF instruments, the SD of the measurement will be given. Most manufacturers state that if the measured value is less than 3 times its counting statistics SD, the value should not be reported. It is possible for an analyte measurement to be above three times its SD, but below the MDL, calculated from the replicate measurements. In this case, it is advisable to qualify the data as estimated with a J. XRF-14

Advantages Advantages Portable Fast analysis Multi-element analytical technique No waste generated Easy to operate Limited sample preparation Nondestructive technique Suited to the Triad Approach EPA XRF-10 Notes: Most field-portable instruments weigh less than 10 pounds and can be operated with battery power for 8 to 10 hours. Transportable instruments are heavier and require a sheltered space and power outlets for operation. A sample can be analyzed in less than 5 minutes. A throughput of 50 to 100 samples in a day (8 hours) is easily achieved. As many as 35 elements can be analyzed in a single analysis using multiple radioisotope or X-ray tube sources. Because no solvents or acids are used for sample extraction, no waste is generated, which eliminates disposal costs. Most operators can be trained in 1 to 2 days. The software is menu-driven. No data manipulation is required. Instruments are marketed for use by general scientists. Limited or no sample preparation is required, which enhances sample throughput and saves time and money. Even when used in the ex situ mode, sample preparation is easier than for conventional fixed laboratory digestions. XRF-15

Advantages The sample is not destroyed during preparation or analysis; therefore, it is possible to perform replicate analyses on the same sample, and send the same sample for confirmatory analysis to perform comparability studies. The sample also may be archived for later use. Field-portable and transportable XRF units are uniquely suited to the Triad Approach, particularly the dynamic work plan. The use of these instruments in the field provides real-time or near-real-time measurements with little or no sample preparation. These real-time measurements can be used collaboratively with fixed laboratory analyses to provide field teams with the information needed to make informed project decisions quickly at the site. This use limits the number of mobilizations necessary to conduct site investigations, and allows excavation, confirmation sampling, characterization, and resource planning in near real-time. Use of these instruments for dynamic work plans will ultimately result in project time and cost savings. XRF-16

Limitations Limitations Relatively high method reporting limits Can be susceptible to interferences Radioactive sources can require licensing and have a limited life span Liquid nitrogen is needed for some models which can limit when and where they can be used XRF cannot generally be used for analyzing water samples EPA XRF-11 Notes: Detection limits for Cr are 200 mg/kg or greater. Action levels for some elements, such as As or Cd, may be below the detection limits of XRF. Increasing count times may lower detection limits for some analytes. FPXRF can also be used to identify hot-spots and focus more definitive off-site analyses. Elemental concentrations between different soil types or matrices may change, which can cause interferences such as those between As and Pb. Site-specific calibration standards can compensate for some of these effects. In some states, a specific license is required to operate some of the FPXRF instruments. The total cost to attend a radiation safety course, obtain the necessary paperwork, and pay the fee for the license can range from $500 to $1,000 per person. The Cd-109 source should be replaced or reshimmed every 2 to 4 years. The cost of replacement is approximately $2,000 to $5,000. Use of instruments with X-ray tube technology can negate many of the limitations associated with XRF instruments employing radioisotope sources. Some older models that have a Si(Li) detector will require liquid nitrogen and a dewar to hold the liquid nitrogen. This requirement adds time and cost to a project to (1) find a source of liquid nitrogen near the site, (2) purchase the liquid nitrogen, and (3) spend the time each day filling the internal dewar of the instrument and allowing the Si(Li) detector to cool down prior to analysis. While XRF can be used to analyze water samples method detection limits and system configurations are not available to facilitate its use. XRF-17

Limitations Potential Influences on Results Matrix effects»chemical matrix effects (absorption and enhancement phenomena)»spectral interferences (peak overlaps) High moisture content Inconsistent positioning of samples EPA XRF-12 Notes: Matrix effects result from variations in the physical character of the sample, such as particle size, uniformity, homogeneity, and surface conditions. Field studies have shown that the heterogeneity of a sample generally has the largest impact on comparability with confirmatory samples; therefore, the soil should be thoroughly homogenized before analysis. One way to reduce particle size effects is to grind and sieve soil samples to a uniform particle size. This practice will decrease the number of samples that can be analyzed in a day, but will generally result in greater precision and accuracy. Matrix effects can occur as a result of X-ray absorption and enhancement. For example, Fe tends to absorb Cu X-rays, while Cr will be enhanced in the presence of Fe. These effects can be corrected for mathematically using the software included with most FPXRF instruments. A general rule of thumb for interferences is that if the site-specific matrix has percentage levels of certain metals such as Fe or Cr (10,000 ppm) the potential for interferences with other metals may occur. Users are recommended to consult with instrument manufacturers when determining when and if matrix interferences could be impacting results. Manufacturers and vendors can prepare site-specific standards in some instances, which can reduce or help compensate for the influences of matrix interferences. Spectral interferences can occur when the energy difference between two peaks in evs is less than the resolution of the detector. In such cases, the detector will not be able to fully resolve the peaks. Examples include the overlap of the Fe K $ peak with the Cu K " peak, or the As K " XRF-18

Limitations peak with the Pb L " peak. In the case of As and Pb, Pb can be measured from the Pb L $ peak, and As can be measured from the As K " peak with the use of mathematical corrections that subtract out the Pb interference. Concentrations for As may be biased when samples have a Pb to As ratio of 10 to 1 or more. High moisture contents (above 20 percent) may tend to bias sample results low relative to results from a fixed laboratory which are reported on a dry weight basis. The effects of moisture content can be minimized by drying, preferably by using a convection oven or toaster at less than 100 C. Microwave drying can increase variability between FPXRF data and confirmatory data and can cause arcing when metal fragments are present in the sample. When moisture contents are generally low and in situ measurement is desirable, it may be possible to establish a field-based action level such that decisions can still be made on a real-time basis. Inconsistent positioning of samples in front of the instruments window is a potential source of error in the analysis. The strength of the X-ray signal decreases as the distance from the radioactive source increases. Results will vary when samples are placed in different positions in front of the instrument window. This error is minimized by maintaining the same distance between the window and the sample. For best results, the window of the instrument should be in direct contact with the sample or perhaps only separated by a thin layer of Mylar. The precision of FPXRF instruments is affected by the analyte concentration. In general, as the concentration of the analyte increases, the precision increases. However, this general rule may not work when concentrations are extremely high or low. Would it be prudent to dry soil samples if mercury was the target analyte? Approximately how deep do the X-rays penetrate into a soil sample? How can the depth of penetration potentially impact the reported results relative to fixed laboratory results and what can be done to compensate for this effect. XRF-19

Costing and Procurement Considerations Costing and Procurement Considerations Analytical instruments Accessories Rent, lease, procure as service EPA XRF-13 Notes: Analytical instruments vary in terms of their ability to analyze for different metals. In general, the broader the range of capabilities the higher the cost. Accessories such as auto samplers, data system components, dry ovens, etc. can also drive up the cost of analyses and should be carefully evaluated when deciding on whether to use a fieldbased measurement technology. Simple systems can be rented on a weekly basis, usually with a two-week minimum. Leases are available for more extended project applications. Most fixed laboratory operators now offer mobile laboratory services that can be used when more sophisticated sample preparation and documentation is required. Information presented in the table on the next page was collected from technology vendors on or before January 2003. XRF-20

Costing and Procurement Considerations XRF Field-Portable and Transportable Units Multi Element Analyzers Rental and Maintenance Costs Manufacturer Model Thermo Noran Spectrace License or State Registration Required to Operate TN 9000 Yes-License or State Registration Required to Operate Purchase Rent Purchase Price Maintenance Day Week Month $58,000 General maintenance $1,000/Year Common sources include Cd-109, which lasts about 1.5 years and costs $2,700 to replace; and Fe- 55, which lasts about 2.7 years and costs $1,600 to replace N/A 2 weeks $3,500 Minimum Rental Period Contact Information $6,000 2 weeks 800-736-0801 sales@thermomt.com Innov-X XT-260 X-ray tube No license requirements $32,500 General maintenance $1,000/year Tube replacement every 4-5 years cost $3,500* Metorex XMET-2000 Yes $30,000 General maintenance $1,000/year Common sources include Cd-109, which lasts about 2 years and costs $2,700 to replace, and Am-241, which has an infinite life Metorex XMET-3000T X-ray tube No license requirements Niton XL-700 Yes $29,000 (single-source unit) to $50,000 (tri-sourced unit) depending on configuration $30,000 General maintenance $1,000/year Tube replacement every 4-5 years cost $3,500* Common sources include Cd-109, which lasts about 1.5 years and costs $2,700 to replace; Fe-55, which lasts about 2.7 years and costs $1,600 to replace; and Am-241, which has a life of about 400 years and is essentially maintenance free $300 $1,400 $4,800 2 days 781-938-5005 info@innov-xsys.com N/A N/A $3,000 1 month 609-406-9000 http://www.metorex.com N/A N/A $3,000 1 month 609-406-9000 http://www.metorex.com N/A Duel source high resolution thin/bulk sample analyzer $2,780 Duel source high resolution thin/bulk sample analyzer $7,340 1 week 877-255-6943 http://www.niton.com/ XRF-21

Costing and Procurement Considerations Manufacturer Model License or State Registration Required to Operate Niton XLi Series Yes $29,000 (single-source unit) to $50,000 (tri-sourced unit) depending on configuration Niton XLt Series X-ray tube No license requirements Purchase Rent Purchase Price Maintenance Day Week Month $38,000 to $41,000 depending on configuration Common sources include Cd-109, which lasts about 1.5 years and costs $2,700 to replace; Fe-55, which lasts about 2.7 years and costs $1,600 to replace; and Am-241, which has a life of about 400 years and is essentially maintenance free General maintenance $1,000/year Tuber replacement every 2-5 years cost $5,000* N/A Not available for rental directly from Niton N/A Not available for rental directly from Niton N/A Not available for rental directly from Niton N/A Not available for rental directly from Niton N/A Not available for rental directly from Niton N/A Not available for rental directly from Niton Minimum Rental Period N/A Not available for rental directly from Niton N/A Not available for rental directly from Niton Contact Information 877-255-6943 http://www.niton.com/ 877-255-6943 http://www.niton.com/ EDAX Alloy Checker MK2 X-ray tube No license requirements Spectro 200T Yes $26,000 to $28,000 depending on configuration Spectro Titan X-ray tube No license requirements $35,000 This instrument is solely used for quality control of metals, metals identification, and/or alloy sorting. Not recommended as a remediation tool. $30,000 to $40,000 depending on configuration General maintenance $1,000/year Sample cups $110 per 100 General maintenance $1,000/year Tube replacement every 2-5 years cost $5,000* Sample cups $110 per 100 N/A N/A $4,500 1 month 201-529-6118 http://www.edax.com N/A N/A Lease to buy at 10% of unit cost per month N/A N/A Lease to buy at 10% of unit cost per month 1 month 3 month maximum 1 month 3 month maximum 740-965-2094 hsoisson@earthlink.net www.spectro-ai.com 740-965-2094 hsoisson@earthlink.net www.spectro-ai.com Notes: * X-ray tube technology for field portable and transportable XRF systems is relatively new so estimates of tube life are difficult. XRF-22

Supplemental Information Supplemental Information 1) Source selection from the Niton Corporation. This table provides sources for specific element analyses. 2) Manufacturer-specific method detection information where available. 3) EPA Method 6200 summary for field-portable XRF units. XRF-23

SOURCE SELECTION FROM THE NITON CORPORATION. THIS TABLE PROVIDES SOURCES FOR SPECIFIC ELEMENT ANALYSES.

MANUFACTURER-SPECIFIC METHOD DETECTION INFORMATION WHERE AVAILABLE

EPA METHOD 6200 SUMMARY FOR FIELD-PORTABLE XRF UNITS