Field Portable X-ray Fluorescence Research Articles

Evaluation and calibration of a Field Portable X-Ray Fluorescence spectrometer for quantitative analysis of siliciclastic soils and sediments

This paper documents the evaluation of a Field Portable X-Ray Fluorescence spectrometer (FP-XRF) as a bench top laboratory unit with regard to quantitative elemental analysis of siliciclastic soils and sediments. With the end-user in mind, we outline a calibration scheme that offers significant improvement in data quality over the manufacturer's calibration. Our calibration approach is based on Standard Reference Materials (SRMs) as calibration standards, the use of least-squares regression techniques that allow for uncertainty in both x and y data (i.e., type II linear regression), propagation of error with respect to predicted concentrations, and goodness of fit evaluation. Data presented include the repeated analysis of numerous standard reference sediments and soils, which are used to evaluate the instrument response to changes in concentration, signal stability over the course of ∼1 year, and calibration model suitability. We present Hudson River estuary sediment data along with independent confirmatory analyses as a demonstration. Our results for the estuarine sediments are in very good agreement with independent laboratory analyses, indicating that the FP-XRF is comparable to traditional laboratory instrument/analytical techniques, and capable of providing high quality data for numerous elements.

Analysis of Beverages for Hg, As, Pb, and Cd with a Field Portable X-Ray Fluorescence Analyzer

Analytical capabilities of a handheld X-ray tube analyzer for analysis of beverages were evaluated. Sets of standard solutions for the elements Hg, As, Pb, and Cd were prepared with mass fractions up to 5000 mg/kg. A thirst quencher beverage was spiked with these elements up to mass fractions of 2500 mg/kg. Portions of these solutions were placed in standard X-ray fluorescence (XRF) cells, as well as the original container, and analyzed by using a field portable Innov-X alpha-6000s XRF tube-type analyzer. Uncorrected analyzer output usually yielded qualitative or semiquantitative results for the spiked beverages in X-ray cells. Average correction factors applied to analyzer output yielded accurate (in terms of z-scores) quantitative results for As above 20 mg/kg and qualitative or semiquantitative results for the other elements. Weighted quadratic fit calibrations provided accurate quantitative or semiquantitative results for all elements at levels above 20 mg/kg. The instrument's preset X-ray overlap correction algorithm worked well for the beverage spiked with all four elements. Spiked beverages analyzed through the wall of the original polyethylene terephthalate container produced accurate results within measurement uncertainties after application of "container wall" correction factors.

<I>In situ</I> site assessment: a short overview and description of the field-portable XRF and its application

<I>In situ</I> site assessment: a short overview and description of the field-portable XRF and its application

Evaluation of Portable X-ray Fluorescence for Gypsum Quantification in Soils

The use of field portable X-ray fluorescence (XRF) spectrometry as a quantification tool for gypsum content in soils of West Texas and southern New Mexico, USA, was evaluated. Six sites were evaluated with gypsum contents ranging from less than 10% to greater than 90%. Samples collected from each site were scanned in the field using XRF and then transported to the laboratory for additional XRF scanning. Variables that might affect XRF scanning results, such as scanning time, particle size, moisture content, and so on, were evaluated. Both gypsum (CaSO4 • 2H2O) and calcite (CaCO3) were quantified using standard laboratory techniques. Three data sets were compared: (1) soil characterization data, obtained from the National Soil Survey Laboratory Research Database in Lincoln, NE; (2) quantitative X-ray diffraction; and (3) portable XRF (PXRF). The best correlation of gypsum XRF data (via Ca quantification minus calcite content) and laboratory data was between PXRF and quantitative X-ray diffraction (R = 0.96). On average, PXRF provided results within 6% of soil characterization data, the current laboratory standard for gypsum quantification. Field PXRF shows considerable promise as a rapid, quantifiable measure of gypsum in soils.

Laboratory Evaluation of a Field-Portable Sealed Source X-Ray Fluorescence Spectrometer for Determination of Metals in Air Filter Samples

Recent advances in field-portable X-ray fluorescence (FP XRF) spectrometer technology have made it a potentially valuable screening tool for the industrial hygienist to estimate worker exposures to airborne metals. Although recent studies have shown that FP XRF technology may be better suited for qualitative or semiquantitative analysis of airborne lead in the workplace, these studies have not extensively addressed its ability to measure other elements. This study involved a laboratory-based evaluation of a representative model FP XRF spectrometer to measure elements commonly encountered in workplace settings that may be collected on air sample filter media, including chromium, copper, iron, manganese, nickel, lead, and zinc. The evaluation included assessments of (1) response intensity with respect to location on the probe window, (2) limits of detection for five different filter media, (3) limits of detection as a function of analysis time, and (4) bias, precision, and accuracy estimates. Teflon, polyvinyl chloride, polypropylene, and mixed cellulose ester filter media all had similarly low limits of detection for the set of elements examined. Limits of detection, bias, and precision generally improved with increasing analysis time. Bias, precision, and accuracy estimates generally improved with increasing element concentration. Accuracy estimates met the National Institute for Occupational Safety and Health criterion for nearly all the element and concentration combinations. Based on these results, FP XRF spectrometry shows potential to be useful in the assessment of worker inhalation exposures to other metals in addition to lead.

Use of Field-Portable XRF Analyzers for Rapid Screening of Toxic Elements in FDA-Regulated Products

Analytical instrumentation continues its amazing evolution, especially in regard to generating ever more sensitive, faster, and reliable measurements. Perhaps the most difficult challenges are making these instruments small enough to use in the field, equipping them with well-designed software that facilitates and simplifies their use by nonexperts while preserving enough of their analytical capabilities to render them useful for a wide variety of applications. Perhaps the most impressive and underappreciated example of instruments that meet these criteria are field-portable X-ray fluorescence (XRF) analyzers. In the past, these analyzers have been routinely used for environmental applications (lead in paint and soil, metal particulates in air samples collected onto filters), geology studies (ore and soil analysis, precious metal identification), and recycling industries (alloy identification). However, their use in the analysis of toxic elements in food, food ingredients, dietary supplements, and medicinal and herbal products, especially within the FDA and regulatory environments, has been surprisingly limited to date. Although XRF will not replace atomic spectrometry techniques such as ICP-MS for sub-parts per million level analyses, it offers a number of significant advantages including minimal sample preparation, high sample throughputs, rapid and definitive identification of many toxic elements, and accurate quantitative results. As should be obvious from many recent news reports on elevated levels of toxic elements in children's lunchboxes, toys, and supplements, field-portable XRF analyzers can fill a very important niche and are becoming increasingly popular for a wide variety of elemental analysis applications. This perspective begins with a brief review of the theory of XRF to highlight the underlying principle, instrumentation, and spectra. It includes a discussion of various analytical figures of merit of XRF to illustrate its strengths and limitations compared to existing methods such as ICP-MS. It concludes with a discussion of a number of different FDA applications and case studies in which XRF has been used to screen, identify, and in some cases quantify toxic elements in various products. This work clearly demonstrates that XRF analyzers are an exceedingly valuable tool for routine and nonroutine elemental analysis investigations, both in the laboratory and in the field. In the future, it is hoped that both field-portable and laboratory-grade XRF analyzers will see more widespread use for investigational and forensic-type applications of food and other regulated consumer products.

Determination of Bromine in Regulated Foods with a Field-Portable X-Ray Fluorescence Analyzer

A field-portable X-ray fluorescence analyzer, factory-calibrated for soil analysis, was used to measure bromine (Br) mass fractions in reference materials, flour, bakery products, malted barley, selected U.S. Food and Drug Administration Total Diet Study foods, and other food products. By using a calibration based on instrumental neutron activation analysis results for Br in reference materials, accurate quantitative results, confirmed by z-scores, could be obtained for mass fractions of about 2-55 mg/kg. These results confirmed accuracy of results (with larger uncertainties) obtained by applying a simple correction factor to the analyzer's output value. Results showed that very short analysis times (<2 min) would be needed to screen foods for Br content at regulatory levels for brominated and enriched brominated flour (24 mg/kg Br) and whole wheat flour and bakery products (36 mg/kg Br). Feasibility for determination of Br in malted barley at the regulatory level (75 mg/kg Br) was demonstrated, but quantitative results at that level could not be assured because no reference material with a suitable mass fraction was available. Br mass fractions for all foods tested were well below regulatory levels.

Two and three-dimensional quantification of lead contamination in alluvial soils of a historic mining area using field portable X-ray fluorescence (FPXRF) analysis

Two- and three-dimensional element distributions in soils and sediments may be important for the identification of geomorphic processes and the reconstruction of landscape evolution. Field portable X-ray fluorescence (FPXRF) analysers provide new possibilities in the detection and quantification of these element distributions. Results from a research project studying the heavy metal contamination of alluvial soils in a historic mining area at the Vils River near Freihung (Eastern Bavaria, Germany) exemplify how FPXRF can be applied to quantify two- and three dimensional element distributions in a floodplain environment on different scales. The results show that two-dimensional lead distribution of topsoil bulk samples (0 to 20 cm depth) clearly depends on the geomorphology of the study area. Concentrations of more than 1000 mg kg − 1 lead are restricted to the river floodplain. On a fluvial terrace lead concentrations of the topsoils are consistently far below 500 mg kg − 1 . Within the floodplain environment the lead contamination is not homogeneously distributed but forms areas of higher and lower lead concentrations. Micro fluvial structures (channels, ridges) are polluted on different levels, depending on the composition of the sediments or the water contents. This demonstrates that accurate assessments of floodplain metal contamination can only be made if small scale spatial variability has been considered. Analysis of the three-dimensional lead distribution shows that concentrations of the in situ measurements range from 500–6000 mg kg − 1 subject to depth, geomorphology and distance from the Vils River. Although the absolute contents are higher, three-dimensional lead distribution derived from laboratory measurements is identical with the plotted results of the in situ investigations. By calculating a correction factor for further investigations, water content as one of the main causes for differing results between field and laboratory analyses can be diminished. In situ FPXRF analysis as a robust technique could be used to investigate metal contamination on floodplain soils at a range of spatial scales. It allows detailed sampling, which can yield important information on the geomorphological controls on metal contamination in such environments.

Applicability of hyperspectral technology for in situ phytoremediation

The characterization of heavy metal polluted abandoned mining sites is a complicated assignment due to the variable spatial distribution of the pollutants, therefore complex integrated method is required in order to assess precisely the amount and the distribution of the contaminants. The examined area is flotation sludge reservoir of abandoned Pb-Zn mining site with serious heavy metal contamination. located in Gyöngyösoroszi, Northern Hungary.The hyperspectral image of the flotation sludge is obtained by using a Digital Airborne Imaging Spectrometer DAIS 7915, in the frame of DLR HySens first Hungarian hyperspectral flight campaign (21/08/2002). Parallel to the flight campaign heavy metal content of soil samples were examined from the area of the flotation sludge. The analysis of hyperspectral data was verified by the examination of mine tailing samples by FPXRF (Field Portable X-ray Fluorescence spectrometry) (NITON XL-703).Determinations of heavy metal containing minerals are based on the spectral profiles of the pixels of the area with using USGIS standard spectral profiles of the examined materials (galena, pyrite, sphalerite, goethite and jarosit).&#x0D; Applying the Spectral Angle Mapper with BandMax classification the distribution of minerals (galena, pyrite, sphalerite, goethite, jarosit) in the area was defined. The mineral formation occurs especially at the levees and the barren places of the Szárazvölgyi flotation sludge reservoir. Based on the statistic results of the samples, principal component analysis and correlation coefficient between the different metal content of the samples were calculated. The highest correlations were found between Pb-Zn, Fe-Zn and between Fe-Pb. This prove the results of the principal component analysis, where usually Pb, Zn, Fe introduce the main component.&#x0D; Canopy analysis was also carried out with the hyperspectal image in order to classify the differences between vegetation types at the Szárazvölgy flotation sludge reservoir and analyse the applicability of it. Supervised classification methods were used to distinguish 8 vegetation types based on the spectral properties of the area. The results of the classifications were compared to a ground truth image, based on ortophoto, topographic map, and GPS based field data collection. According to results of the comparison, the paralellpiped classification method is proved to be appropriate method based on the overall accuracy of canopy classification, which was 54% due to heterogeneity of the vegetation. &#x0D; The results of hyperspectral data and FPXRF analysis suggest that Pb, Zn and Fe containing minerals have similar spatial distribution in the examined and barren area.&#x0D; Based on this study hyperspectral remote sensing is likely to be an effective tool for the characterization and modeling the distribution of Pb, Zn and Fe containing minerals at the examined heavy metal polluted sites. Further more, based on the vegetation analysis plant species for phytoremediation can be defined.

Lead in soil by field‐portable x‐ray fluorescence spectrometry—an examination of paired In Situ and laboratory ICP‐AES results

AbstractA major aspect of lead hazard control is the evaluation of soil lead hazards around housing coated with lead‐based paint. The use of field‐portable X‐ray fluorescence (FPXRF) to do detailed surveying, with limited laboratory confirmation, can provide lead measurements in soil (especially for planning abatement activities) in a far more cost‐efficient and timely manner than laboratory analysis. To date, one obstacle to the acceptance of FPXRF as an approved method of measuring lead in soil has been a lack of correspondence between field and laboratory results. In order to minimize the differences between field and laboratory results, RTI International (RTI) has developed a new protocol for field drying and sieving soil samples for field measurement by FPXRF. To evaluate this new protocol, composite samples were collected in the field following both U.S. Department of Housing and Urban Development (HUD) guidelines and ASTM International (ASTM) protocols, measured after drying by FPXRF, and returned to the laboratory for confirmatory inductively coupled plasma atomic emission spectroscopy (ICP‐AES) analysis. Evaluation of study data from several diverse sites revealed no statistical difference between paired FPXRF and ICP‐AES measurements using the new method. © 2008 Wiley Periodicals, Inc.

Use of Field‐Portable X‐Ray Fluorescence (FPXRF) Analyzer to Measure Airborne Lead Levels in Korean Workplaces

We evaluated the possibility of applying field-portable x-ray fluorescence (FPXRF) analysis as a rapid, on-site and near real-time method for evaluating airborne lead contamination in Korean workplaces. A total of 287 airborne lead filter samples were measured in 12 lead-using workplaces during routine industrial hygienic monitoring procedures as required by Korean government regulations. All filter samples were collected using the standard industrial hygiene sampling protocol described in NIOSH Method 7300 using closed-face 37-mm cassettes with preloaded cellulose ester membrane filters with a pore size of 0.8 microm. The samples were first analyzed using the non-destructive, FPXRF analytical method (NIOSH method 7702), and then subsequently analyzed using inductively coupled plasma atomic emission spectrophotometry (ICP) (NIOSH method 7300) as a reference analytical method. Pair-wise comparison of filter samples using the paired t-test revealed no statistically significant differences between the two methods over a wide range of airborne lead levels (0.018-0.201 microg/m(3)) either over the industries assessed or separately in the 12 lead-using workplaces. Linear regression of the data between the ICP and FPXRF methods produced a slope of 1.03, a y-intercept of 0.13 microg/sample, and a coefficient of determinant (r(2)) of 0.975 for all the data. For samples in the range from 0 to 100 microg, the corresponding values were 1.07, -1.20 microg/sample, and 0.925, respectively. There were no significant differences in the regression analyses of the three industry types (r(2)=0.964-0.982). Our data suggest that FPXRF data are highly correlated with those from the laboratory-based ICP method in terms of accuracy, precision, and bias. Therefore, FPXRF can be used for the rapid, on-site analysis of lead air-filter samples for values up to 26 microg/sample prior to laboratory confirmation by the ICP method.

F-21 Field Portable XRF Beyond Traditional Handheld Analyzers

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Sources, Sinks, and Exposure Pathways of Lead in Urban Garden Soil

The chemistry of Pb in urban soil must be understood in order to limit human exposure to Pb in soil and produce and to implement remediation schemes. In inner-city gardens where Pb contamination is prevalent and financial resources are limited, it is critical to identify the variables that control Pb bioavailability. Field-portable X-ray fluorescence was used to measure Pb in 103 urban gardens in Roxbury and Dorchester, MA, and 88% were found to contain Pb above the USEPA reportable limit of 400 mug g(-1). Phosphorus, iron, loss on ignition, and pH data were collected, Pb-bearing phases were identified by X-ray diffraction, and Pb isotopes were measured using inductively coupled plasma mass spectrometry. Four test crops were grown both in situ and in Roxbury soil in a greenhouse, and plant tissue was analyzed for Pb uptake by polarized energy-dispersive X-ray fluorescence. Variation at the neighborhood scale in soil mineralogical and chemical characteristics suggests that the bioavailable fraction of Pb in gardens is site specific. Based on Pb isotope analysis, two historical Pb sources appear to dominate the inventory of Pb in Roxbury gardens: leaded gasoline ((207) Pb/(206) Pb = 0.827) and Pb-based paint ((207)Pb/(206) Pb = 0.867). Nearly 70% of the samples analyzed can be isotopically described by mixing these two end members, with Pb-based paint contributing 40 to 80% of the mass balance. A simplified urban human exposure model suggests that the consumption of produce from urban gardens is equivalent to approximately 10 to 25% of children's daily exposure from tap water. Furthermore, analysis of over 60 samples of plant tissue from the four test species suggests that in these urban gardens unamended phytoremediation is an inadequate tool for decreasing soil Pb.

Health hazards by lead exposure: evaluation using ASV and XRF

Globally, of many toxic heavy metals, lead is the most widely used for various purposes, resulting in a variety of health hazards due to environmental contamination. Lead in the workplace enters the workers through inhalation of lead-contaminated air, by ingestion, and sometimes through dermal exposure. Furthermore, exposure outside the workplace can occur from inhalation of lead-contaminated air, ingestion of lead-contaminated dust and soil, consumption of lead polluted water, lead adulterated food and lead supplemented medicine. In the present study, an evaluation of blood lead was carried out with the aid of a 3010 B lead analyser, based on the principle of anodic stripping voltametry (ASV), and environmental lead in paint, soil and dust samples by a field portable X-ray fluorescence (XRF) analyser. This revealed a high incidence of lead toxicity in most of the lead-based industrial workers in the four facilities tested in India and high levels of lead in the environmental samples. Developed countries have complied with the global standards for regulating environmental lead poisoning in the workplace, eliminating to some degree excessive exposure to lead. A developing country, such as India, can tackle this problem by implementing national and international policies. The US Occupational Safety and Health Administration (OSHA) and Environmental Protection Agency (EPA) regulations, which are of prime importance, or similar regulations, can be adapted for use in India and implemented to minimize lead exposure and to reduce the resultant health hazards.

The effectiveness of low-cost soil treatments to reduce soil and dust lead hazards: The Boston lead safe yards low cost lead in soil treatment, demonstration and evaluation

The Boston lead safe yards low cost lead in soil treatment, demonstration, and evaluation was developed to explore the viability and effectiveness of low-cost soil interventions to reduce exposure to soil lead hazards. Buildings that had been abated for lead to Massachusetts's deleading standards in the previous 5 yrs and met other program requirements were recruited for the evaluation. Following individual property assessments, yards were treated with application of ground coverings and ground barriers in 2000–2001 and followed up at 1 yr. The treatment cost ranged from $1095 to $5643 with an average of $2798. Soil lead levels at the building dripline, measured with a field-portable X-ray fluorescence analyzer (Niton Model 702 Spectrum Analyzer), dropped from 2021 PPM at baseline to 206 PPM at 1-yr follow-up. Most of the barrier treatments continued to block access to the lead-contaminated soil at 1 yr. At the follow-up, few properties with grass treatment had areas that were completely bare, but 28% had more than a small amount of treated areas bare. Treatments were effective in reducing entryway dust lead in the rear of the building if the residents reported they had maintained the yard treatments. Each additional yard work activity reported was predicted to lower 1-yr floor dust lead loading at the rear common/main and dwelling unit entries by about 20%. Each additional 100 ft 2 of yard treated was predicted to lower 1-yr floor dust loading at the rear dwelling unit entry by 19%. Treatments did not show a dust lead effect at 1 yr in the front entryway of the building, but the investigators believe that this may be due to the effect of resident cleaning overshadowing the treatment effect.

A comparison of Cu, Pb, As, Cd, Zn, Fe, Ni and Mn determined by acid extraction/ICP–OES and ex situ field portable X-ray fluorescence analyses

Total concentrations of Cu, Pb, As, Cd, Zn, Fe, Ni and Mn were determined for 81 soil samples using two types of field portable X-ray fluorescence (FPXRF) system; dual isotope and X-ray tube. FPXRF metal concentrations were statistically compared with analytical results from aqua regia extractions followed by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP–OES) analysis. The ability of each FPXRF instrument to produce analytical results comparable to the reference method was assessed by linear regression. A high degree of linearity was found for Fe and Pb with the X-ray tube instrument and for Fe, Cu, Pb, Zn, Cd and Mn with the dual source instrument. FPXRF analyser performance improved with increased analysis time for Cu, Mn and Pb, whilst Fe, Zn, Cd, Ni and As showed no significant improvement. Particle size did not influence FPXRF analyser performance. Both the dual isotope and the X-ray tube FPXRF instruments are effective tools for rapid, quantitative assessment of soil metal contamination and for monitoring the efficacy of remediation strategies.

Using Field-Portable XRF to Assess Geochemical Variations Within and Between Dolerite Outcrops of Preseli, South Wales

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F67 Optimization of Quantification Schemes for Contemporary Field-Portable XRF Analyzers—Invited

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Triad case study: Former small arms training range

The U.S. Army Corps of Engineers (USACE) used the Triad approach to expedite site characterization of contaminated soil at the Former Small Arms Evergreen Infiltration Training Range in Fort Lewis, Washington. The characterization was designed to determine if surface soils contain significant concentrations of metals, with the focus on collecting sufficient data for determining appropriate future actions (i.e., risk analysis or soil remediation). A dynamic sampling and analytical strategy based on rapid field based analytical methods was created in order to streamline site activities and save resources while increasing confidence in remediation decisions. Concurrent analysis of soil samples during the Demonstration of Method Applicability (DMA) used both field portable X-ray Fluorescence (FPXRF) and laboratory methodologies to establish a correlation between FPXRF and laboratory data. Immediately following the DMA, contaminated soil from the impact berm was delineated by collecting both FPXRF data and fixed-laboratory confirmation samples. The combined data set provided analytical results that allowed for revisions to the conceptual site model for the range and directed additional sample collection activities to more clearly determine the extent and distribution of soil contamination.

Lead in Paint and Soil in Karnataka and Gujarat, India

Blood lead surveys in several areas of India have found very high percentages of children with elevated blood lead levels. Fifty-three percent of children under 12 years of age in a seven-city screening had blood lead levels equal to or greater than 10 μg/dL, the level currently considered elevated by the U.S. Centers for Disease Control and Prevention (CDC). A number of these surveys focused on populations near lead smelters or in areas with high lead levels from combustion of lead-containing gasoline. There is little information available, however, on the levels of lead in paint in India and in soil. Field portable X-ray fluorescence analyzers were used to determine environmental lead levels in paint, dust, air, soil, and other bulk samples near several lead-using industries and in the residential environments of children with very high blood lead levels, at least four times as high as the CDC limit. Soils near industrial operations, such as secondary lead smelters, and battery dismantling units contained levels up to 100,000 ppm of lead. Four of 29 currently available paints from five manufacturers measured 1.0 mg/cm 2 or above—the current U.S. definition of lead-based paint in housing—after the application of a single coat; four others measured at least 1.0 after three coats, and three others likely to have reached this level after the application of an additional one or two coats. In five of 10 homes of the elevated blood lead children, three or more locations in or around the home were found to have lead paint levels of 1.0 mg/cm 2 or higher. Soil exceeding the U.S. standard for residential areas (400 ppm) was found at only one of the houses. Other sources of lead exposure, including traditional ayurvedic medicine tablets, were also observed. Similar surveys would be useful elsewhere in India and in other developing countries.