X-ray Fluorescence Microanalysis Research Articles

Quantitative X-ray fluorescence micro-analysis of wood samples and visualization of tree rings

The following paper describes the quantitative analysis of wood samples of black pine (Pinus nigra) using a benchtop Micro X-ray Fluorescence (μXRF) device for elemental analysis and surface scanning. Calibration of the device for quantitative elemental analysis and local density measurements of wood was performed by utilizing characteristic X-ray line intensities and backscattered radiation intensities. The influence of a variable wood density and matrix composition on X-ray spectra were studied with Monte Carlo calculations. The Monte Carlo model was validated with a set of reference materials possessing known compositions and densities. It has been demonstrated that Monte Carlo simulations with the MCNP code, along with, only one reference material are required for the quantitative XRF analysis. The backscattered radiation in the XRF spectra can be used for simple recognition of individual tree rings and their corresponding shapes.

Does climate change alter the nutrient trends of Cedrela fissilis Vell. trees in the southern Brazilian Amazon?

BackgroundThe increase in the frequency and intensity of droughts is pointed out as one of the main factors altering biogeochemical cycles in the Amazon basin. An eco-nutritional approach using X-ray fluorescence micro-analysis (µXRF) is proposed to verify the long- and short-term effects of droughts on the growth and xylem nutrient concentrations of Cedrela fissilis Vell.MethodsFourteen radii were selected from a tree-ring width chronology and X-rayed by Itrax Multiscanner. Profiles of ring width, wood density, and concentrations of aluminum (Al), phosphorus (P), sulfur (S), calcium (Ca), potassium (K), manganese (Mn), iron (Fe) and strontium (Sr) together with Al/Ca, Ca/Mn, K/Ca, Sr/Ca and Mn/S ratios were constructed and correlated with precipitation, temperature, the difference between precipitation and potential evapotranspiration (P-PET) and standardized precipitation–evapotranspiration index (SPEI).ResultsDuring dry years, C. fissilis showed narrower, less dense rings, lower Al, P, S and Ca, and higher K and Fe concentrations (the opposite was found in wet years). Ring width decreased (together with Al, P, S, K, Ca, Mn, Fe, Sr, Al/Ca, K/Ca and Sr/Ca) and wood density increased (together with Ca/Mn and Mn/S), which was associated with an increase in evapotranspiration and temperature over time, mainly since 1990. Cedrela fissilis showed a tendency to increase its capacity for resistance, and a recovery and resilience in growth over time associated with responses in Al, Ca, P and S. However, it showed a risk in the capacity for recovery of the pre-drought density values, associated with unsatisfactory responses in Al, Ca, K, Fe and P.ConclusionsThis study is the first attempt to analyze tree-ring nutritional evidences of C. fissilis trees to climate sensitivity and resilience to drought, based on long-term data from seasonal moist tropical forests of the Amazon. Our data suggested that C. fissilis is undergoing alterations in the concentration, use and redistribution of nutrients associated with increasing wood density and decreasing growth over time, due to the increase of drought frequency in the southern Amazon.

Uncertainty of Quantitative X-ray Fluorescence Micro-Analysis of Metallic Artifacts Caused by Their Curved Shapes.

This paper summarizes the effects of irregular shape on the results of a quantitative X-ray fluorescence (XRF) micro-analysis. These effects become relevant when an XRF analysis is performed directly on an investigated material. A typical example is XRF analyses of valuable and historical objects whose measurements should be performed non-destructively and non-invasively, without taking samples. Several measurements and computer simulations were performed for selected metallic materials and shapes to evaluate the accuracy and precision of XRF. The described experiments and the corresponding Monte Carlo simulations were related to the XRF device designed and utilized at the Czech Technical University. It was found that the relative uncertainty was typically about 5-10% or even higher in quantitative analyses of minor elements due to irregular shapes of surfaces. This must be considered in cases of the interpretation of XRF results, especially in the cultural heritage sciences. The conclusions also contain several recommendations on how to measure objects under hard-to-define geometric conditions with respect to reduction in the surface effect in quantitative or semi-quantitative XRF analyses.

Особенности термолиза ароматических карбоксилатов Cr (III)

The article discusses the main methods for obtaining carbon composite nanomaterials and highlights the thermolysis method as one of the main methods. To understand the essence of thermal decomposition processes as a method for synthesis of carbon nanomaterials, chromium (III) aromatic carboxylates have been considered. These are chromium (III) 8-hydroxyquinolinate, benzoate, salicylate, phthalate, and p-aminobenzoate. The article thoroughly discusses the procedure for the synthesis of these chromium (III) carboxylates from the most common inorganic chromium (III) salts under simple conditions. The thermal decomposition process was carried out in two environments (in oxidizing air and neutral argon), the obtained products were compared. For a detailed study of the processes of decomposition of chromium (III) carboxylates, thermal analysis methods (TG and DSC) were used on a Netzsch 449 Jupiter synchronous thermal analyzer. To study the morphology and composition of the products, the methods of X-ray phase analysis, optical and scanning electron microscopy, and X-ray fluorescence microanalysis were used. We used a Rigaku Ultima IV X-ray diffractometer and a scanning electron microscope with a Jeol JSM-7001F elemental microanalysis attachment. On the basis of the obtained results, the estimated formulas of the initial chromium (III) carboxylates were calculated. The mechanisms of the processes occurring during the thermal decomposition of chromium (III) aromatic carboxylates were also proposed. For a more accurate determination of the composition of the synthesized chromium (III) carboxylates and a more accurate description of the processes of thermal decomposition of these salts, the corresponding aromatic carboxylic acids were also subjected to thermal decomposition. The appendix to the article contains all the obtained data for a more accurate interpretation of the results and a more detailed description of the thermal decomposition processes.

Kinetics of Macro and Micronutrients during Germination of Habanero Pepper Seeds in Response to Imbibition

The aim of this study was to evaluate the concentration and distribution of a number of macro- and micronutrients in response to imbibition in habanero pepper seeds extracted from fruits with different stages of maturity and postharvest storage times, as well as in their seedlings. Fruits were harvested unripe, half-ripe, and ripe, and were subjected to storage for 0 (control), 7, and 14 days postharvest prior to seed extraction. An X-ray microfluorescence analysis was carried out on seeds pre- and post-imbibition, as well as on seedlings at 10 and 14 days after sowing. K, Ca, Fe, P, Mg, and Mn were detected by elemental analysis. The results indicated that the elements had a higher concentration and distribution in seeds extracted from half-ripe fruits and ripe unstored fruits, as well as in seeds extracted from fruits stored for 7 and 14 days postharvest. K and Ca were the elements with the highest distributions and concentrations in seeds and seedlings pre- and post-imbibition compared to the other elements. At all maturity stages, postharvest storage increased the concentration and distribution of mineral nutrients in seeds and seedlings before and after imbibition. Storage translocated mineral elements to the radicle before germination, increased meristem growth in emerged seedlings, decreased electrical conductivity, and increased germination. Fourteen days of postharvest storage increased the distribution of macro- and micronutrients in immature seeds, decreasing electrical conductivity, potentiating germination, and improving mineral element distribution in seedlings.

Interface heterogeneity of periodic multilayer mirrors investigated by X-ray fluorescence, scattering spectroscopy, and mathematical methods of statistics

Multilayer interference structures (X-ray mirrors) based on the alternating layers of Mo/Si and W/Si were investigated using laboratory X-ray micro-fluorescence analysis (micro-XFA) and statistical analysis. The physics of interaction processes of primary X-ray radiation scattered on the surface of multilayer periodic structures have been studied. Using the X-ray spectroscopy together with the mathematical methods of statistics made it possible to evaluate a degree of homogeneity and to compare the chemical compositions of different samples of the multilayer mirrors. A correlation between the statistical characteristics of bimodal frequency distribution and the reflectivity properties of X-ray mirrors for the scattered radiation has been revealed. The frequency distributions of mathematical statistics for experimentally collected intensities of the scattered Rh Kα radiation indicate the depth heterogeneity of the studied samples. Used in this work approach gives a new strategy for testing to improve of efficiency of X-ray mirrors based on the multilayer nanoscale structures.

Micro- and Nanostructure of Layered Si\Sn\Si Films, Formed by Vapor Deposition

The peculiarities of surface relief of the Si-Sn-Si layered films, used to produce the silicon nanocrystals with properties of quantum dots, were studied by the methods of electron and atomic force microscopy with the involvement of X-ray fluorescent microanalysis. It was shown that the quasispherical structuring of the relief at the scale 20-20000 nm is typical for the surface of silicon-tin layered films. The role of layer thicknesses is experimentally analyzed under formation of the surface relief (roughness, shapes, and lateral dimensions) during their vacuum deposition from a vapor-gas phase. The peculiarities of the relief of amorphous silicon films deposited on the surface of molten tin are shown. The fractal-like type nanostructuring of amorphous silicon films deposited on the surface of liquid tin was discovered.

Confocal XRF imaging for determination of arsenic distribution in a sample of historic plaster

This paper describes the use of X-ray fluorescence (XRF) scanning, XRF microanalysis, and confocal XRF for identification of toxic elements, especially arsenic, in a sample taken from a historic wall of the rectory building in Potštát (Přerov district, Czech Republic). We focused our attention mainly on the confocal XRF imaging, which can visualize non-destructively a cross-section of a selected part of the sample. Since the images of X-ray intensities are disturbed by the X-ray absorption in a sample, a method reducing this effect was proposed and applied for the determination of the arsenic depth distribution. This method comprises an experimental determination of attenuation coefficients for the excitation beam and the arsenic characteristic X-rays as well. These coefficients are derived from the exponential decrease of scattered radiation intensities in energy regions corresponding to the excitation X-ray energies and energies of scattered X-rays close to the arsenic Kα line, respectively. This correction improved the image showing the depth distribution of arsenic in the sample.

Screening Forage Grasses with Atomic Absorption Spectrometry, X-ray Fluorescence and X-ray Microanalysis

Breeding cool-season (C3) grasses with higher magnesium (Mg) content is a promising attempt for reducing grass tetany hazard in ruminants. Faster methods for plant mineral analyses could increase the number of individual plants screened for higher Mg content (High-Mg). This study evaluates the effectiveness of energy dispersive X-ray microanalysis (EDX) as well as energy reflectance X-ray spectrometry (XRF) for screening high-Mg grass genotypes. The approach was verified by using two tall fescue cultivars having known differences in magnesium (Mg) content, viz. HiMag (high-Mg cultivar) and Ky-31 (control cultivar). We assumed that cultivars with known variation in Mg concentrations could provide a test for the applicability of the new methodology in finding naturally occurring high and low Mg containing grass genotypes. Plants samples included a population of 8 plants consisting of four harvests for three years and were analyzed for Mg, calcium (Ca), and potassium (K) by EDX and ERF, and data were verified with atomic absorption spectrometry wet (AAS). While observing the frequency distribution for different nutrient concentrations, HiMag tall fescue showed higher Mg and lower K concentrations than that of Ky-31. There was positive linear relationship between AAS and EDX estimated Mg, Ca and K (r = 0.88, 0.62 and 0.89, respectively), indicating close agreement between AAS and EDX estimation. Also, there was a positive linear relationship between AAS and XRF, as the r values were 0.87, 0.65 and 0.88 for Mg, Ca, and K, respectively. The tetany ration was established for EDX and XRF and the results were dependable with wet chemistry. SAARC J. Agric., 19(2): 245-256 (2021)

Forms of Uranium Presence in Soil on the Territory of the Sublimate Shop at AEKhK AO

Integrated study of the physicochemical state of uranium in radioactively contaminated soils of the sublimate shop of Angara electrolysis chemical combine AO (SS AEKhK AO). According to the X-ray absorption spectroscopy, the predominant form of uranium is (UVIO2)2+ in all the soil samples studied. The scanning electron microscopy combined with X-ray fluorescence microanalysis was used to characterize the composition and morphology of uranium-containing particles with sizes of fractions to several tens of micrometers everywhere occurring in the soils. It was shown that the predominant fractions of accessible uranium in the soils are the “carbonate” fraction (40–60%) and that associated with Fe/Mn oxides. A considerable part of uranium is bound to clayey minerals. Data on the forms of uranium were used to develop a technology for purification of the radioactively contaminated soil by the method of hydroseparation with reagent processing of the isolated target fraction.

Phosphorus speciation by P-XANES in an Oxisol under long-term no-till cultivation

In highly weathered soils with low phosphorus (P) content and high P fixing capacity, long-term application of P fertilizers may influence P speciation. The combined use of macro- and microscopic techniques can provide information on P distribution and reactivity in soils, which is an important key to determine its loss potential into the environment. In this study, we aimed to evaluate the effects of rates of P on solid-state P speciation in an Oxisol under no-till (NT) for 26 years in Brazil. Soil samples were collected from experimental plots that received 0 to 50 kg ha−1P annually. X-ray Fluorescence microanalysis (µ-XRF), X-ray Absorption Near-Edge Structure (XANES), and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies were used along with soil mineralogical and conventional chemical analyses. Phosphorus availability increased with the applied P rates. Based on the µ-XRF analysis, high Pearson correlation coefficients (r) were obtained for P vs Al, Si and Fe contents (r = 0.97, 0.81 and 0.84, respectively, with P < 0.0001); and partial correlation showed co-localized effects mainly for Al and Si. The Fe-EXAFS results hinted to the presence of non-crystalline iron (Fe) minerals being favored in the cultivated soils, likely as a consequence of the higher rates of P applied and utilization by the crops. P-XANES data revealed that after the fertilization, the proportion of P sorbed to goethite did not vary, but the proportion of P sorbed to hematite decreased, while P sorbed to kaolinite increased. The long-term continuous application of P fertilizers beyond plant uptake capacity favored P build-up in soils, resulting not only in poor P use efficiency but also in exacerbated risk of P loss to the environment.

Zinc concentrations in the expressed prostatic fluid of patients with bladder cancer

Introduction: In our previous studies it was concluded that the zinc (Zn) level in in human expressed prostatic fluid (EPF) is a first candidate with the role of offering a new, simple, fast, reliable, and non-invasive diagnostic tool for prostate cancer (PCa) screening. However it was unclear how other non-prostatic diseases inherent of the old persons, including heart diseases, atherosclerosis, diabetes, asymptomatic cancer of different localization and some others, impact on a chemical element composition of expressed prostatic fluid. Thus, the purpose of this study was to evaluate whether significant changes in the levels of Zn in EPF exist in patients with bladder cancer (BC). Methods: Prostatic fluid levels of Zn were prospectively evaluated in 17 patients with BC and 51 healthy male inhabitants (control group). Measurements were performed using 109Cd radionuclide-induced energy dispersive X-ray fluorescent microanalysis developed by us. Results: Mean value  standard deviation of mean (MSD) for concentration of Zn in the EPF of healthy males and patients with BC was 573202 mg/L and 625±108 mg/L, respectively. Using both parametric Student’s t-test and non-parametric Wilcoxon-Mann-Whitney U-test it was shown that the Zn concentration in the EPF of patients with BC did not differ from that in healthy subjects. Conclusion: Such serious illness as BC did not impact on the Zn concentration in the EPF.

A Case of Surgical Extraction of the Lower Third Molars in a Cranial Series from the Pucará de Tilcara Fortress (Jujuy Province, Argentina)

This study analyzes the earliest known case of surgical extraction of the lower third molars, observed in a cranial series from Pucará de Tilcara fortress (15th–16th centuries AD), northwestern Argentina, excavated in 1908–1910. Crania were transported to the Kunstkamera in 1910 under an exchange project. Traces of dental surgery were registered in the mandible of a male aged ~40. Both third molars had been extracted after the removal of soft tissues and parts of the alveoli. Teeth were extracted by scraping alveolar walls with semicircular movements. The results of scanning electron microscopy, X-ray fluorescence, and X-ray microanalysis suggest that a stone tool was used. The results of macroscopic and CT analysis suggest that the surgery was motivated by the exacerbation of chronic periodontal disease and probably by caries. The left third molar was extracted without complications 2–3 months before the individual’s death. On the right side, the pathological process continued, culminating in osteomyelitis and its complications. The surgeon’s skill notwithstanding, the extraction of the right third molar did not cure the patient, who died, apparently following the destructive stage of acute osteomyelitis complicated by orofacial phlegmon. Our findings suggest that the level of dental surgery practiced in the Inca Empire was ahead of the diagnostic expertise.

RNAi-Mediated Silencing of ITPK Gene Reduces Phytic Acid Content, Alters Transcripts of Phytic Acid Biosynthetic Genes, and Modulates Mineral Distribution in Rice Seeds

Phytic acid is the principal storage form of phosphorus in plant seeds and an essential signalling molecule in several regulatory processes of plant development. However, it is known as an anti-nutrient compound owing to its potent chelating property. Thus, reducing the phytic acid content in crops is desirable. Studies involving regulation of MIPS and IPK1 genes to generate low phytate rice have been reported earlier. However, the functional significance of OsITPK and the effect of its down-regulation on phytic acid content and the associated pleiotropic effects on rice have not yet been investigated. In this study, tissue specific RNA interference (RNAi)-mediated down-regulation of a major ITPK homolog (OsITP5/6K-1) resulted in 46.2% decrease in phytic acid content of T2 transgenic seeds with a subsequent 3-fold enhancement in the inorganic phosphorus content. Silencing of OsITP5/6K-1 altered the transcript levels of essential phytic acid pathway genes, without significantly affecting the transcript levels of other OsITPK homologs. Furthermore, the mapping of elements through X-ray microfluorescence analysis revealed significant changes in the spatial distribution pattern and translocation of elements in low phytate seeds. Additionally, low phytate polished seeds exhibited 1.3-fold and 1.6-fold enhancement in iron and zinc content in the grain endosperm, respectively. Silencing of OsITP5/6K-1 also altered the amino acid and myo-inositol content of the transgenic seeds. Our results successfully established that RNAi-mediated silencing of OsITP5/6K-1 gene significantly reduced the phytate levels in seeds without hampering the germination potential of seeds and plant growth. The present study provided an insight into the mechanism of phytic acid biosynthesis pathway.

Persistent Calyxes in Postbloom Fruit Drop: A Microscopy and Microanalysis Perspective.

Citrus postbloom fruit drop, caused by Colletotrichum spp., is an important disease in the Americas. The pathogen infects citrus flowers, produces orange-brown lesions on petals, and may cause the abscission of young fruit. In diseased flowers, the calyxes remain attached to the peduncle after the young fruit drop. No anatomical and microanalysis studies have been conducted to determine whether calyx tissues can be infected by Colletotrichum spp. and why calyxes remain attached to the peduncle. Based on light microscopy, we demonstrate that the ovary abscission zone exhibits a separation region composed of layers of thickened lignified walled cells, indicating that abscission involves the disruption of cell walls. The first layers of the protective zone (PZ) are composed of densely packed cells with suberized walls produced by the wound meristem. Beneath the PZ, there is a compact mass of small cells that accumulate starch grains. X-ray fluorescence microanalysis (µ-XRF) confirmed the increased accumulation of calcium in the receptacle of the persistent calyxes compared to non-inoculated citrus flowers. Moreover, the peduncle pith and the receptacle exhibit hypertrophied cells with thick walls that may be related to calyx retention. Fungal structures are not observed inside the persistent calyx tissues.

Selenium toxicity in upland field-grown rice: Seed physiology responses and nutrient distribution using the μ-XRF technique.

Selenium (Se) is an essential element for human and animal, although considered beneficial to higher plants. Selenium application at high concentration to plants can cause toxicity decreasing the physiological quality of seeds. This study aimed to characterize the Se toxicity on upland rice yield, seed physiology and the localization of Se in seeds using X-ray fluorescence microanalysis (μ-XRF). In the flowering stage, foliar application of Se (0, 250, 500, 1000, 1500, 2000 g ha-1) as sodium selenate was performed. A decrease in rice yield and an increase in seed Se concentrations were observed from 250g Se ha-1. The storage proteins in the seeds showed different responses with Se application (decrease in albumin, increase in prolamin and glutelin). There was a reduction in the concentrations of total sugars and sucrose with the application of 250 and 500g Se ha-1. The highest intensities Kα counts of Se were detected mainly in the endosperm and aleurone/pericarp. μ-XRF revealed the spatial distribution of sulfur, calcium, and potassium in the seed embryos. The seed germination decreased, and the electrical conductivity increased in response to high Se application rates showing clearly an abrupt decrease of physiological quality of rice seeds. This study provides information for a better understanding of the effects of Se toxicity on rice, revealing that in addition to the negative effects on yield, there are changes in the physiological and biochemical quality of seeds.

Using Prostatic Fluid Levels of Some Trace Elements and Their Combinations in Non-Invasive and Highly Accurate Screening for Prostate Cancer

Objective: Prostate specific antigen (PSA) does not provide the high reliability and precision that is required for an accurate screening for prostate cancer (PCa). The aim of our study was to search for a simple, rapid, direct, preferably non-invasive, and highly accurate biomarker and procedure for the screening for PCa. Method: The levels of trace elements (TE) Br, Fe, Rb, Sr, and Zn were prospectively evaluated in expressed prostatic fluid (EPF). Also Zn/Br, Zn/Fe, Zn/Rb, Zn/Sr concentration ratios as well as ZnRb and (ZnRb)/Fe concentration combinations were calculated for EPF samples, obtained from 38 apparently healthy males and from 33, 51, and 24 patients with chronic prostatitis, benign prostatic hyperplasia, and PCa, respectively. Measurements were performed using an energy dispersive X-ray fluorescent (EDXRF) microanalysis. Results: It was found that in the EPF of cancerous prostates the levels of Rb, Zn, Zn/Br, Zn/Fe, Zn/Sr, ZnRb, and (ZnRb)/Fe were significantly lower in comparison with those in the EPF of normal, inflamed, and hyperplastic prostates. For example, in comparison hyperplastic with cancerous prostates p values obtained using Student’s t-test and Wilcoxon-Mann-Whitney U-test were Conclusions: The levels of TE and their combinations in EPF, obtained by EDXRF, is a fast, reliable, andnon-invasive diagnostic tool that can be successfully used by local, non- urologist physicians at the point-of-care to provide a highly effective PCa screening and as an additional confirmatory test before a prostate gland biopsy.

Using Prostatic Fluid Levels of Zinc to Bromine Concentration Ratio in Non-Invasive and Highly Accurate Screening for Prostate Cancer

Prostate specific antigen (PSA) does not provide the high reliability and precision that is required for an accurate screening for prostate cancer (PCa). The aim of our study was to search for a simple, rapid, direct, preferably non-invasive, and highly accurate biomarker and procedure for the screening for PCa. For this purpose the levels of bromine (Br) and zinc (Zn) were prospectively evaluated in expressed prostatic fluid (EPF). Also Zn/Br concentration ratio was calculated for EPF samples, obtained from 38 apparently healthy males and from 33, 51, and 24 patients with chronic prostatitis (CP), benign prostatic hyperplasia (BPH) and PCa, respectively. Measurements were performed using an application of energy dispersive X-ray fluorescent (EDXRF) microanalysis developed by us. It was found that in the EPF of cancerous prostates the levels of Zn and Zn/Br were significantly lower in comparison with those in the EPF of normal, inflamed, and hyperplastic prostates. It was shown that “Sensitivity”, “Specificity” and “Accuracy” of PCa identification using the Zn and Zn/Br levels in the EPF samples were all significantly higher than those resulting from of PSA tests in blood serum. It was concluded that the Zn and Zn/Br levels in EPF, obtained by EDXRF, is a fast, reliable, and non-invasive diagnostic tool that can be successfully used by local, non-urologist physicians at the point-of-care to provide a highly effective PCa screening and as an additional confirmatory test before a prostate gland biopsy.

Visible cellular distribution of cadmium and zinc in the hyperaccumulator Arabidopsis halleri ssp. gemmifera determined by 2-D X-ray fluorescence imaging using high-energy synchrotron radiation.

The striking sub-cellular distribution of cadmium (Cd) and zinc (Zn) in the Cd and Zn hyperaccumulator Arabidopsis halleri ssp. gemmifera was revealed by microbeam X-ray microfluorescence analysis (μ-XRF) using high-energy synchrotron radiation. Plants were grown in hydroponics with various Cd and Zn concentrations. The concentration of Cd in the aerial portions of the plants increased with increasing Zn exposure and the transportation efficiency of Cd from the root to the shoot was affected by both the Cd and Zn concentrations in the nutrient solution. The μ-XRF imaging clearly showed that Cd and Zn were preferentially accumulated in trichomes on the leaf, while the distribution of Cd in the leaf was changed by Zn treatment. It was observed that Cd treated with a higher Zn concentration (20 μM Cd + 100 μM Zn) was distributed in the mesophyll tissue at high concentrations. In addition, μ-XRF imaging clarified that the distribution of Zn inside the leaf was different from that of Cd at a cellular level. Zn was primarily distributed in the mesophyll tissue of the leaf blade. In contrast, Cd was localized in the vascular bundle of the main vein. That is, Zn was transported to mesophyll tissue from the vascular bundle more efficiently than Cd. As seen above, we were able to study the difference of the distribution of Cd and Zn, which are congeners and behave similarly, inside the plant body at the cellular level in detail by high-energy μ-XRF.

Simplifying Sample Preparation for Soil Fertility Analysis by X-ray Fluorescence Spectrometry.

Portable X-ray fluorescence (pXRF) sensors allow one to collect digital data in a practical and environmentally friendly way, as a complementary method to traditional laboratory analyses. This work aimed to assess the performance of a pXRF sensor to predict exchangeable nutrients in soil samples by using two contrasting strategies of sample preparation: pressed pellets and loose powder (<2 mm). Pellets were prepared using soil and a cellulose binder at 10% w w−1 followed by grinding for 20 min. Sample homogeneity was probed by X-ray fluorescence microanalysis. Exchangeable nutrients were assessed by pXRF furnished with a Rh X-ray tube and silicon drift detector. The calibration models were obtained using 58 soil samples and leave-one-out cross-validation. The predictive capabilities of the models were appropriate for both exchangeable K (ex-K) and Ca (ex-Ca) determinations with R2 ≥ 0.76 and RPIQ > 2.5. Although XRF analysis of pressed pellets allowed a slight gain in performance over loose powder samples for the prediction of ex-K and ex-Ca, satisfactory performances were also obtained with loose powders, which require minimal sample preparation. The prediction models with local samples showed promising results and encourage more detailed investigations for the application of pXRF in tropical soils.