Objective.Microscopic two-dimensional (2D) elemental distributions of tissues can be probed by synchrotron-based 2D x-ray fluorescence (XRF) scanning. Converting 2D XRF data into elemental concentration maps (ECMs) enhances the scientific value of such studies by facilitating comparisons within the increasingly larger pool of published data. This study developed and tested a computationally fast method able to perform such conversions.Approach.A semicircular cortical bone slice, 0.38-mm-thick and ∼150 mm2in area, transversally sectioned from a lamb tibia was analyzed at the VESPERS beamline of the Canadian Light Source synchrotron. The 2D XRF scan consisted of short sequential microbeam irradiations in 10µm steps. The scan was repeated at four incident photon energies and probed two rectangular areas (0.24 mm2) at the sample's opposite edges. K-shell XRF peaks of seven elements (P, Ca, Fe, Ni, Cu, Zn, and Sr) were identified in the acquired x-ray spectra. Using physical and geometrical assumptions of the fundamental parameter method (FPM), the developed computer code generated ECMs of the investigated microscopic areas.Main Results.Generated ECMs indicated relatively uniform distributions of the seven chemical elements, with localized peaks near the sample edges. The average elemental concentrations at the four photon energies agreed with each other and compared well with literature data.Significance.A fast FPM-based computer code for converting 2D XRF data into ECMs was developed and tested. The code can be applied to investigations of other biological tissues extending the applicability of existing quantitative XRF methods.

As a biomarker of past uptake of zinc, hair presents an interesting option since its growth can provide a stored record over time. This study investigates the distribution of zinc in hairs gathered from a series of grizzly bears (Ursus arctos horribilis). A relatively new approach to measuring zinc along the length of a hair, portable X-ray fluorescence (pXRF), was applied with 10 different bears each with a single strand of hair, and one bear chosen as a duplicate. Results obtained from pXRF were compared with zinc concentrations, using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) obtained from the same hair strands. Mercury was also measured by LA-ICP-MS to assess seasonal changes in diet associated with salmon consumption by some bears. Measurements started near the root end of the hair and, for the pXRF readings, progressed in 2 mm steps along the length of each hair. Energy spectrum analysis of the pXRF results provided a ratio of zinc to sulfur signal, which scaled with zinc concentration reported by LA-ICP-MS. Comparison of pXRF results with LA-ICP-MS zinc concentrations showed general agreement from individual hairs in both concentration levels and spatial trends. Nonetheless, some hairs revealed discrepancies between the pXRF and LA-ICP-MS outcomes. While it was assumed mercury and zinc would be correlated, and associated with salmon consumption in the fall, this was only the case for two bears, while the other bears had either negative relationships between the metals or no relationship at all. While mercury was consistently associated with salmon consumption in the fall, zinc was not. It appears that pXRF is a viable means of tracking zinc along the length of a single hair. This measurement technique has potential to be a rapid, non-invasive approach to monitoring zinc in animal or human populations.

To date, there are few studies concerning determination of minerals in infant formulae intended to survey compliance of manufacturer claims and compliance with regulations. In this study, we collected infant formulae from the Las Vegas market to investigate the levels of Na, Mg, K, Mn, Fe, and Zn using inductively coupled plasma mass spectrometry (ICP-MS) following hot block-assisted digestion. Within analytical uncertainty, infant formula samples met label claims for Na, Mg, K, Fe, and Zn and were within the United States Food and Drug Administration (FDA) regulations. Estimated daily intakes (EDIs) of analyzed minerals from consumption of different types of infant formulae were: (158-316) mg d-1 for Na, (42.5-63.8) mg d-1 for Mg, (618-1025) mg d-1 for K, (0.006-0.345) mg d-1 for Mn, (4.79-16.6) mg d-1 for Fe and (4.11-8.88) mg d-1 for Zn. Except for Zn, the levels of other elements conform to currently recommended dietary reference values. In this study we also evaluated the accuracy of portable X-Ray Fluorescence (pXRF) for measuring Zn and Fe in infant formula. Bland-Altman analysis indicates that pXRF can be applied as a reliable technique for determination of Zn and Fe in infant formula.

INTRODUCTION:Recent advances in portable X-ray fluorescence (XRF) have opened up the possibility of a rapid and cost-effective method for measuring elemental content in nail clippings. Two elements of particular interest for intake assessment through nail clipping measurement are zinc and selenium. The New Zealand-based Mother and Infant Nutrition Investigation (MINI) provides an ideal testing ground for the application of portable XRF in the measurement of zinc and selenium. Two aspects requiring further study with portable XRF are the optimal time of measurement and the optimal approach to energy spectrum analysis. METHODS:A subset of nail clippings from 20 mother-infant pairings were initially selected for analysis over three separate MINI study visits. This paper considers measurements from visit 3 (12 months postpartum). For portable XRF, a mono-energetic X-ray beam was used to excite characteristic X-rays from zinc and selenium. Individual XRF measurements were made for 60 s (real time). In each case, analysis of the elemental signal was performed in four different ways: (1) automated system output concentration; (2) element signal to total signal ratio; (3) element signal to Compton scatter signal; (4) element signal to coherent scatter signal. XRF results were compared against zinc and selenium concentrations obtained from a "gold standard" method of inductively coupled plasma mass spectrometry (ICP-MS). RESULTS:ICP-MS results from the visit 3 nail clippings determined a mean zinc concentration of 104 µg/g and a mean selenium concentration of 0.606 µg/g. Analysis of XRF energy spectra from 60 s measurements showed that zinc was clearly detected in all cases. The selenium signal was more challenging, but was also detected from all spectra. For both zinc and selenium, correlations between XRF results and ICP-MS concentrations were highly significant (p < 0.01) in all cases, with the zinc results more strongly correlated than selenium. Of the four approaches to XRF signal analysis, the three approaches involving an external software package provided superior results relative to the automated system output. Correlations of XRF results with ICP-MS concentrations were similar between these three approaches. CONCLUSION:ICP-MS concentrations for both zinc and selenium were found to be lower from visit 3 relative to results from visit 1 and visit 2. This may indicate overall dietary changes postpartum. Correlations of XRF results with ICP-MS concentrations suggest that a relatively short 60 s measurement time is adequate for a reliable zinc assessment, but not for selenium. Although correlations of XRF results with ICP-MS concentrations were similar between three different methods of spectra analysis, practical considerations may favor use of the element signal to total signal approach.

Zinc and selenium are essential minerals for human nutrition. Reliable biomarkers of zinc status and selenium status in humans are therefore important. This work investigates a novel portable X-ray fluorescence (XRF) method with the ability to rapidly assess zinc and selenium in nail clippings. This approach used a mono-energetic X-ray beam to excite characteristic X-rays from the clippings. Nail clippings were obtained from the Mother and Infant Nutrition Investigation (MINI), a study designed to assess nutrition in a population of women and their breastfed children in New Zealand. Twenty mother-infant pairings were selected to provide nail clippings at two time points (visit 1 at 3 months postpartum; visit 2 at 6 months postpartum). Nail clippings from each mother-infant pairing were divided into three groupings of clippings prior to analysis: those obtained from a big toe of the mother, those from the other toes of the mother, and those from the toes and fingers of the infant. Clippings were prepared and mounted prior to XRF measurement, providing four distinct fragments from each clipping grouping. These fragments were assessed by XRF using a measurement time of either 300 s (visit 1) or 180 s (visit 2). XRF results were determined through both an automated system output and an analysis of the X-ray energy spectrum. Following this assessment of zinc and selenium with the non-destructive XRF method, clippings were measured for zinc and selenium concentration using a “gold standard” technique of inductively coupled plasma mass spectrometry (ICP-MS). Mean ICP-MS concentrations ranged from 122 μg/g to 127 μg/g for zinc, and from 0.646 μg/g to 0.659 μg/g for selenium. Precision, assessed by a relative standard deviation of measurement, was superior for ICP-MS relative to XRF. For both zinc and selenium, XRF results were compared with ICP-MS concentrations. Linear equations of best fit were determined for each comparison between XRF and ICP-MS results. Coefficients of determination (r2) were stronger for zinc (from 0.74 to 0.95) than selenium (from 0.53 to 0.70). A decrease in XRF measurement time from 300 s to 180 s did not appear to adversely affect the correlation between XRF and ICP-MS results. Using the mono-energetic portable XRF method, the correlation of XRF zinc results with ICP-MS zinc concentrations was improved over previous findings, and selenium measurement was reported for the first time. The method may prove useful for future applications to trace element analysis using nail clippings as a biomarker.

Background: Novel and emerging biomarkers of zinc status are being developed to help study and address zinc deficiency around the world. Two potential biomarkers, nail and hair, involve the measurement of zinc from easily accessible keratin-based components of the body. Portable X-ray fluorescence (XRF) is a relatively new approach to the assessment of zinc in nail or hair, and has a number of compelling advantages compared with other techniques. The aim of the current study was to test the ability of XRF to measure zinc in keratinized reference materials (RMs) designed to simulate nail and hair.Methods: Four Keratin Matrix RMs were prepared and characterized for numerous trace elements by the New York State Department of Health's Wadsworth Center. The Keratin Matrix RMs consisted of powdered samples of caprine (goat) horns pooled from several animals. Concentrations of zinc, as assessed by inductively coupled plasma mass spectrometry (ICP-MS), were similar to what would be expected from human nail or hair tissues. Repeat measurements of the RMs were made using a portable XRF system. The XRF zinc results were compared with the ICP-MS zinc concentrations. Three different approaches to quantifying the zinc content by XRF were performed: (1) zinc signal to total signal ratio, (2) zinc signal to sulfur signal ratio, and (3) system output zinc concentration.Results: The portable XRF results from a given RM were found to be consistent across repeat trials under all three approaches to XRF quantitation. Precision, calculated as the relative standard deviation of repeat measurements ranged from an average result of 0.8 % (using the system output zinc concentration method) to 6.1 % (using the zinc signal to sulfur signal ratio method). Measurement of the RMs provided XRF zinc results which scaled well with ICP-MS zinc concentration, particularly when using the XRF zinc to total and system zinc concentration methods. A Bland-Altman plot showed that the XRF system zinc concentration output exceeded the ICP-MS zinc concentration by, on average, 10.2 % +/- 1.2 %.Conclusion: Overall, both accuracy and precision of measurement were found to be promising for portable XRF, provided appropriate conversions to concentration are introduced. The results of this study indicate that portable XRF is an effective and dependable method of assessing zinc concentration in keratinized tissue RMs. This will have implications for the future use of portable XRF to monitor zinc status in humans through measurements of nail and hair.

The aim of this study was to determine whether X-ray fluorescence spectrometry (XRF) could be used to detect changes in hair zinc concentration in response to a modest daily increase in zinc from the consumption of zinc biofortified wheat flour. This study was conducted as part of an effectiveness trial (BiZiFED2) exploring the potential for zinc biofortified wheat to alleviate zinc deficiency in adolescent girls aged 10–16 years in Pakistan (trial registration ID ISRCTN17107812). A randomized controlled design was used. Participants received either control flour or zinc biofortified flour for 6 months. Consumption of biofortified flour resulted in an average daily increase in dietary zinc intake of 1.5 mg per day above that of the control flour. At baseline and at the end of the intervention, individual hair samples (control: n = 59, intervention: n = 64) were analyzed for zinc and sulfur content by XRF. Data were analyzed using linear mixed effects models to contrast between trial groups the changes from baseline to end point and also to compare baseline and end point values within each trial group. Increases from baseline to endpoint in both sulfur and zinc were significantly greater in the intervention group compared to control (sulfur counts. Control: baseline = 119.87 ± 20.33 and endpoint = 121.58 ± 23.58/intervention: baseline = 122.67 ± 24.19 and endpoint = 131.60 ± 21.34); (Zinc counts. Control: baseline = 50.88 ± 14.33 and endpoint = 54.82 ± 14.61/intervention: baseline = 49.61 ± 10.77 and endpoint = 58.79 ± 12.20). For these parameters, there were also significant increases from baseline to endpoint in the intervention group but not in control. Furthermore, for Zn:S count ratio there were no differences in terms of the magnitude of the change from baseline to endpoint in the control group, although significant increases from baseline to endpoint were evident in the intervention group (Zn:S count ratio. Control: baseline = 0.42 ± 0.10 and endpoint = 0.45 ± 0.08/intervention: baseline = 0.41 ± 0.08 and endpoint = 0.45 ± 0.08). A modest increase in dietary zinc over 6 months resulted in a detectable increase in both sulfur and zinc counts in individual hairs measured using XRF. This offers a sensitive, non-invasive method to monitor changes within subjects in response to dietary zinc interventions.

Development of portable X-ray fluorescence devices has made it easier to quickly assess trace elements such as zinc in human tissue. A TOPAS Monte Carlo code was used to investigate the use of a portable X-ray fluorescence system for detecting zinc in nail clippings. The obtained energy spectra from different nail thicknesses were analyzed and three different normalization techniques (coherent, Compton, and entire spectrum) were introduced. The simulation results suggested that coherent normalization can be a particularly robust normalization procedure.

Micronutrient deficiency remains an enormous problem in refugee settings. Transforming refugees’ food systems through the scaling up of kitchen gardening and fortifying relief food crops with minor food components including nutrient-dense spices can help improve the quality of staple foods. Globally, spices are indispensable in the daily diet and play an important role in the socio-cultural setting of different communities. Forty turmeric and curry powder samples were collected from different market establishments and geographic locations in East Africa. The samples were analyzed for selected elements using Portable X-Ray Fluorescence (PXRF). The contents of potassium (K), calcium (Ca), zinc (Zn) and strontium (Sr) in turmeric powder were statistically different among geographic origins (Ethiopia, Kenya and Uganda). We also aimed to determine if a small portion of spices (turmeric (5 g) and curry (4 g)) would contribute to an adequate intake (AI) or recommended dietary allowance (RDA) for selected minerals, for refugee men and women aged between 19 and 50 years as defined by the Food and Nutrition Board of the Institute of Medicine (IOM). For the reference groups, the contributions of turmeric and curry powder to AI/RDA for K, Ca and Zn varied between 0.48 to 4.13%. On the other hand, turmeric was identified to contribute > 20% AI/RDA for refugee men and women aged between 19 and 50 years for two micro minerals: manganese (Mn) and iron (Fe). Considering turmeric and curry powder of East African origins are good sources of minerals and present acceptable toxic metal(loid)s loads coupled with low cost, these spices particularly turmeric should be more widely popularized and recommended for food-to-spice fortification among the refugee population located in East Africa.

Arsenic is a toxic metalloid which has been associated with a wide range of health effects in humans including skin abnormalities and an elevated risk of skin, bladder, kidney, and lung cancer, diabetes, and cardiovascular disease. The measurement of arsenic concentration in nail clippings is often used in population studies as an indicator of arsenic exposure. Portable X-ray fluorescence (XRF) is an emerging technique for measuring arsenic in nail clippings. In the current study, single toenail clippings from 60 Atlantic Canadian participants were assessed for arsenic using a new portable XRF approach. A mono-energetic portable XRF system using doubly curved crystal optics was used to measure each clipping for a total of 900 s. Energy spectra from each clipping were analyzed for arsenic characteristic X-rays to provide a normalized arsenic signal. The same clippings were then analyzed for arsenic concentration using a "gold standard" method of inductively coupled plasma mass spectrometry (ICP-MS). Nail clipping arsenic concentrations measured by ICP-MS ranged from 0.030 μg/g to 2.57 μg/g, with a median result of 0.14 μg/g. Portable XRF results for arsenic were compared against ICP-MS arsenic concentrations, with a linear equation of best fit determined between the two variables. A correlation coefficient of r = 0.77 was found from the 59 nail clippings returning an ICP-MS arsenic concentration above the limit of quantitation. When the comparison was limited to the 20 clippings having an XRF normalized signal at least twice as large as the associated uncertainty of measurement, the correlation coefficient was r = 0.89. With the selection of an arsenic concentration of 0.1 μg/g as a cut-off value between "exposed" and "non-exposed" individuals, the XRF method provided a test sensitivity of 76% and a specificity of 81%. The corresponding positive predictive value was 88% and the negative predictive value was 65%. The portable XRF technique used in this study shows promise as a means of assessing arsenic concentration in toenail clippings.

Kitchen gardening is considered a way to reconnect with agriculture and complement the cereal-based relief food offered to refugees in East Africa. This work aimed at profiling mineral content of okra in four refugee camps and settlements located in Ethiopia and Uganda and its contribution to adequate intake (AIs) or recommended dietary allowances (RDAs) for young children and pregnant and lactating women (PLW). The study also evaluated the applicability of portable X-ray fluorescence (PXRF) as compared with inductively coupled plasma mass spectrometry (ICP-MS) for mineral profiling of okra powder samples. The contents of minerals (mg kg −1 ) from the ICP-MS readings were in the following ranges: K (14,385–33,294), Ca (2610–14,090), P (3178–13,248), Mg (3896–7986), Cu (3.81–19.3), Fe (75.7–1243), Zn (33–141) and Mn (23.1–261). Regardless of geographic origin, at low-end consumption probability (17 g day −1 for young children and 68 g day −1 for PLW), okra could contribute ˂ 15% (2.7–12.9%) AI for macro-minerals (K and Ca). In addition, the contributions to RDA values for Fe and Zn, elements of known public health interest, ranged from 4.5 to 34.7% for young children. Interestingly, regression lines revealed strong agreement between ICP-MS and PXRF readings for Mn and Zn, with R 2 values > 0.91. This information is useful in support of nutrition-sensitive kitchen gardening programs through scaling culturally important crops in refugee settings.

A variety of biomarkers are available for the assessment of human exposure to, and absorption of, trace elements. The measurement of trace elements in nail or nail clippings offers some benefits relative to other body sites. Typically, concentrations of elements are assessed in clippings, using high precision methods such as inductively coupled plasma mass spectrometry or instrumental neutron activation analysis. Over the last decade, portable X‐ray fluorescence (pXRF) has emerged as a novel method with potential advantages for the measurement of trace elements in nail and nail clippings. This review paper examines early developments and recent work in the use of pXRF to measure elements such as As, Se, Mn, Zn, Cr, Pb, and Hg in nails and nail clippings. While initial pXRF studies were limited to the use of nail phantoms and nail clipping phantoms, more recent work has applied the pXRF method with real nail clippings and nails. Results have been promising, but a number of issues have emerged requiring additional attention. These relate to the analysis of X‐ray spectra, selection of X‐ray beam for excitation, method validation and normalization, and practical aspects of study design. With consideration of these issues, pXRF offers significant potential to provide a straightforward, economical, and rapid measurement approach to help improve our understanding of trace element exposure and related health outcomes.

Zinc is an essential trace element in humans. Zinc deficiency can result in a range of serious medical conditions which include effects on growth and development, the immune system, the central nervous system, and the gastrointestinal system. Diagnosis of zinc deficiency is often precluded by the lack of a noninvasive and reliable biomarker. Zinc concentration in nail is considered an emerging biomarker of zinc status in humans. Whether zinc in nail accurately reflects zinc status is beyond the scope of the current study, but is an important research question. The development of a portable method to quickly assess zinc concentration from a single nail clipping could be a useful advance. In this study, single toenail clippings from 60 individuals living in Atlantic Canada were measured for zinc using a portable X-ray fluorescence (XRF) technique. These samples were obtained from the Atlantic PATH cohort, part of the largest chronic disease study ever performed in Canada. Each toenail clipping was measured using three 300 s trials with a mono-energetic portable XRF system. Results were then assessed using two different approaches to the XRF analysis: (1) factory-calibrated zinc concentrations were output from each trial, and (2) energy spectra were analyzed for the characteristic X-rays resulting from zinc. Following the measurement of zinc using the non-destructive portable XRF method, the same clippings were measured for zinc concentration using the "gold standard" technique of inductively coupled plasma-mass spectrometry (ICP-MS). A linear equation of best fit was determined for the relationship between average XRF output zinc concentration and ICP-MS zinc concentration, with a correlation coefficient r = 0.60. Similarly, a linear equation of best fit was found for the relationship between a normalized XRF energy spectrum zinc signal and ICP-MS zinc concentration, with a correlation coefficient r = 0.68. Individual ICP-MS zinc concentrations ranged from 32 μg/g to 140 μg/g, with a population average of 85 μg/g. The results of this study indicate that portable XRF is a sensitive method for the measurement of zinc in a single nail clipping, and provides a reasonable estimation of zinc concentration. Further method development is required before portable XRF be considered a routine alternative to ICP-MS for the assessment of zinc in nail clippings.

The traditional Ethiopian flat bread, injera, is a regular component of daily diets in Ethiopia and Eritrea. This bread is also popular among urban refugees particularly Eritreans in Addis Ababa. The levels of metal(loid)s in 40 composite (120 sub-samples) injera samples, representing 4 types of market establishments in Addis Ababa, were determined using inductively coupled plasma-mass spectrometry (ICP-MS) and portable X-ray fluorescence (PXRF). For ICP-MS analysis, the accuracy of the method was evaluated by the analysis of a certified reference material and recovery experiments. It was found that the correlations between the mean levels of Al and Fe and between Al and Mn in injera were highly significant (p < 0.001). It was also found that 1.5 fresh injeras would cover 48–75% of recommended dietary allowance (RDA) for Mg, 17–21% of RDA for K, 19–23% of RDA for Ca, and 60–72% of RDA for P for an adult group aged between 19 and 50. Daily intakes of Al, Fe, and Mn were found to be above the provisional tolerable daily intake (PTDI)/maximum tolerable daily intake (MTDI) values. The mean target hazard quotient (THQ) values for Fe and Mn were greater than 1. The total THQ values varied from 6.52 to 8.53 among market establishments. Estimating carcinogenic risk due to exposure to As, Cr, and Pb indicated that perennial injera consumers might remain at cancer risk. This would further escalate if other staple food items and spices are considered. Hence, there is a need for home-based strategies to reduce extrinsic soil-Al-Fe-Mn in injera/tef batter.

For the past several decades, synchrotron radiation has been extensively used to measure the spatial distribution and chemical affinity of elements found in trace concentrations (<few µg/g) in animal and human tissues. Intense and highly focused (lateral size of several micrometers) X-ray beams combined with small steps of photon energy tuning (2–3 eV) of synchrotron radiation allowed X-ray fluorescence (XRF) and X-ray absorption spectroscopy (XAS) techniques to nondestructively and simultaneously detect trace elements as well as identify their chemical affinity and speciation in situ, respectively. Although limited by measurement time and radiation damage to the tissue, these techniques are commonly used to obtain two-dimensional and three-dimensional maps of several elements at synchrotron facilities around the world. The spatial distribution and chemistry of the trace elements obtained is then correlated to the targeted anatomical structures and to the biological functions (normal or pathological). For example, synchrotron-based in vitro studies of various human tissues showed significant differences between the normal and pathological distributions of metallic trace elements such as iron, zinc, copper, and lead in relation to human diseases ranging from Parkinson’s disease and cancer to osteoporosis and osteoarthritis. Current research effort is aimed at not only measuring the abnormal elemental distributions associated with various diseases, but also indicate or discover possible biological mechanisms that could explain such observations. While a number of studies confirmed and strengthened previous knowledge, others revealed or suggested new possible roles of trace elements or provided a more accurate spatial distribution in relation to the underlying histology. This area of research is at the intersection of several current fundamental and applied scientific inquiries such as metabolomics, medicine, biochemistry, toxicology, food science, health physics, and environmental and public health.

A mono-energetic X-ray beam from a portable X-ray fluorescence device was used to excite characteristic X-rays from zinc in a series of nail clipping phantoms. Twenty nail clipping phantoms having equal zinc concentrations of ~40 µg/g, but with different physical characteristics, were measured individually for 300 s using a small diameter (~1 mm) X-ray beam. Energy spectra obtained from the measurements were analyzed using PyMca software. Zinc signal size varied widely between the different clippings, with a relative standard deviation of 41% observed in the combined signal from zinc Kα and Kβ characteristic X-rays. Three different normalization approaches were introduced to account for variation in the amounts of sample interrogated by the X-ray beam. All three approaches produced similar results, and successfully reduced the relative standard deviation to between 12% and 13%. A clear trend was still observed, however, between the normalized zinc signal and the thickness of clipping measured. To account for this effect, normalized signals were adjusted to calculate “thickness-corrected” values. The relative standard deviation of these thickness-corrected values was 6.2%. Reproducibility of measurement from individual clippings was excellent, with relative standard deviations on the order of 1%, with or without normalization. Overall, this new method of measuring zinc in nail shows promise for the assessment of zinc status in humans using a portable device. The method is sensitive, rapid, and requires only a single nail clipping.

When analyzing characteristic peaks in X-ray fluorescence (XRF) spectra, the peak area is the value most often used to quantify peak size. However, some studies have reported the amplitude of the peak instead of the area. When the width of the peak is allowed to vary from trial to trial in order to provide the best possible fit to the data, these two alternative methods can yield slightly different results. In the current study, these two approaches to peak analysis are compared for data obtained from bone reference materials having certified lead concentrations of 1.09 ± 0.03 μg/g, 16.1 ± 0.3 μg/g, 13.2 ± 0.3 μg/g, and 31.5 ± 0.7 μg/g. Measurements were made with an Olympus Innov-X Delta Premium portable XRF system. Using both the area and amplitude methods, lines of best fit were constructed for the lead Lα and lead Lβ signals as a function of lead concentration. Additionally, coefficients of variation were calculated for each reference material and condition of analysis. To assess possible variations over time, the procedure was performed at two points separated by about one year. The amplitude and area methods were found to produce results which were consistent and proportional. Using either method, lead XRF signal plotted as a function of known lead concentration produced adjusted r2 values of ∼0.99. The amplitude method provided slightly higher adjusted r2 values overall. Coefficients of variation were generally very similar between the two methods, although more pronounced differences emerged from measurements of the lowest concentration reference material.

A variety of adverse health effects have been identified as resulting from zinc deficiency. Zinc supplementation may therefore be indicated for certain individuals or populations. A rapid and straightforward means of assessing zinc status in humans would be of considerable medical benefit. In this study, the feasibility of measuring zinc levels in human fingernails or toenails using a portable x-ray fluorescence technique was assessed. Whole nail models (or phantoms) were constructed from resin, and dosed with various concentrations of zinc. These different concentration "nails" were cut into small slices of 4.4 ± 0.2 mm width. The combination of these various slices into different arrangements allowed the modeling of different time-dependent zinc exposure scenarios. A portable x-ray fluorescence device was tested using an "open beam" configuration having a beam diameter of ∼9 mm, and using a "weld mask" configuration with the beam width reduced to 2.9 mm. Minimum detection limits were determined to be 0.15 ± 0.01 ppm for the open beam, and 1.13 ± 0.08 ppm when using the weld mask. By scanning across the length of the model nails, it was demonstrated that differences in zinc levels deposited over time could be detected, and that the weld mask configuration was better suited to resolving spatial changes. The x-ray fluorescence approach was found to be highly sensitive for detecting zinc in nail, and capable of differentiating patterns of zinc uptake over time.