Quantitative determinations and imaging in different structures of buried human bones from the XVIII-XIXth centuries by energy dispersive X-ray fluorescence – Postmortem evaluation

Elemental analysis using portable X-ray fluorescence: Guidelines for the study of dry human bone

OBJECTIVE

X-ray fluorescence (XRF) is a non-destructive technique that measures the elemental concentration of different materials, including human bone. Recently, it began to be applied to paleopathological studies due to the development of portable devices and their relative ease of use. However, the lack of uniform procedures hampers comparability and reproducibility. This paper aims to provide guidelines for an efficient and standardized evaluation of bone elemental composition with a portable XRF (pXRF) device.

MATERIALS

This technical note is based on the application of the Thermo Scientific Niton XL3t 900 GOLDD+.

METHODS

This work includes suggestions for the choice and preparation of human bone samples, both from archaeological context and documented collections, and methodological procedures in pXRF setup, such as choice of calibration, assessment of accuracy, and analysis run time. Additionally, recommendations for data validation and statistical analysis are also included.

CONCLUSIONS

This technique has great potential in paleopathology since bone chemical variations may be associated with different pathological conditions, environmental contamination (e.g., lead), and/or administered treatments, such as mercury. Following an expected increase in the number of studies, it is essential to establish good practices that allow results from different researchers to be comparable.

SIGNIFICANCE

X-ray fluorescence is a non-destructive technique that measures small concentrations (ppm) of elements from magnesium (12Mg) through bismuth (83Bi).

LIMITATIONS

pXRF does not detect elements lighter than Mg, and its lower energy excitation penetrates less than other techniques.

SUGGESTIONS FOR FURTHER RESEARCH

Other research groups should test these guidelines and comment on their usefulness and replicability.

Rapid direct determination of tin in beverages using energy dispersive X-ray fluorescence

This article presents a new method for the simpler and faster determination of tin in beverages using EDXRF. Absorption coefficients for aqueous calibration samples were calculated and shown to be nearly identical to those of the beverage samples, thus permitting the use of aqueous standard solutions for external calibration. Beverage samples could then be measured directly using the external calibration. Determination of tin using this method takes 4 min. The LOD and LOQ were 4 mg L^-1 and 15 mg L^-1 respectively, and the precision was 3.89%. Different canned beverages (cold coffee, various fruit juices) were measured and the results compared to the concentrations obtained using ICP-OES after digestion. The two methods showed good compatibility, thus establishing the newly developed method as a rapid, simple, and accurate method for the determination of tin in beverages.

μXRF and LA-ICP-TQMS for quantitative bioimaging of iron in organ samples of a hemochromatosis model

Hereditary hemochromatosis is the most common autosomal recessive genetic disorder of the iron metabolism. Iron accumulation in various organs, especially in liver and pancreas leads to diseases and may cause organ failure. In this study, methods for elemental bioimaging by means of quantitative micro X-ray fluorescence analysis (μXRF) and laser ablation-inductively coupled plasma-triple quadrupole mass spectrometry (LA-ICP-TQMS) were developed and applied to investigate the pathophysiological development of iron accumulation in murine tissue based on animals with an iron-overload phenotype caused by a hepatocyte-specific genetic mutation. The use of an external calibration with matrix-matched gelatin standards enables the quantification of iron by means of μXRF without the typically used fundamental parameters method or Monte Carlo simulation, which becomes more imprecise when analyzing thin tissue sections. A fast, non-destructive screening of the iron concentration and distribution with a spatial resolution of 25 μm in liver samples of iron-overload mice was developed. For improved limits of detection and higher spatial resolution down to 4 μm, LA-ICP-TQMS was used with oxygen as reaction gas. By monitoring the mass shift of ⁵⁶Fe to ⁵⁶Fe¹⁶O, a limit of detection of 0.5 μg/g was obtained. With this method, liver and pancreas samples of iron-overload mice as well as control mice were successfully analyzed. The high spatial resolution enabled the analysis of the iron distribution in different liver lobules. Compared to the established Prussian blue staining, both developed methods proved to be superior due to the possibility of direct iron quantification in the tissues.

Characterization of Arsenic in dried baby shrimp (Acetes sp.) using synchrotron-based X-Ray Spectrometry and LC coupled to ICP-MS/MS

The arsenic content of dried baby shrimp (Acetes sp.) was investigated as part of an independent field study of human exposure to toxic metals/metalloids among the ethnic Chinese community located in Upstate New York. The dried baby shrimp were analyzed in a home environment using a portable X-ray Fluorescence (XRF) instrument based on monochromatic excitation. Study participants had obtained their dried baby shrimp either from a local Chinese market or prepared them at home. The shrimp are typically between 10-20 mm in size and are consumed whole, without separating the tail from the head. Elevated levels of As were detected using portable XRF, ranging between 5-30 μg/g. Shrimp samples were taken to the Cornell High Energy Synchrotron Source (CHESS) for Synchrotron Radiation μXRF (SR-μXRF) elemental mapping using a 384-pixel Maia detector system. The Maia detector provided high resolution trace element images for As, Ca, and Br, (among others) and showed localized accumulation of As within the shrimp's cephalothorax (head), and various abdominal segments. As quantification by SR-μXRF was performed using a Lobster hepatopancreas reference material pellet (NRC-CNRC TORT-2), with results in good agreement with both portable XRF and ICP-MS. Additional As characterization using μX-ray Absorption Near Edge Spectroscopy (μXANES) with the Maia XRF detector at CHESS identified arsenobetaine and/or arsenocholine as the possible As species present. Further arsenic speciation analysis by LC-ICP-MS/MS confirmed that the majority of As (>95%) is present as the largely non-toxic arsenobetaine species with trace amounts of arsenocholine, methylated As and inorganic As species detected.

Asbestos containing materials detection and classification by the use of hyperspectral imaging

In this work, hyperspectral imaging in the short wave infrared range (SWIR: 1000-2500nm) coupled with chemometric techniques was evaluated as an analytical tool to detect and classify different asbestos minerals, such as amosite ((Fe²⁺)₂(Fe²⁺,Mg)₅Si₈O₂₂(OH)₂)), crocidolite (Na₂(Mg,Fe)₆Si₈O₂₂(OH)₂) and chrysotile (Mg₃(Si₂O₅)(OH)₄), contained in cement matrices. Principal Component Analysis (PCA) was used for data exploration and Soft Independent Modeling of Class Analogies (SIMCA) for sample classification. The classification model was built using spectral characteristics of reference asbestos samples and then applied to the asbestos containing materials. Results showed that identification and classification of amosite, crocidolite and chrysotile was obtained based on their different spectral signatures, mainly related to absorptions detected in the hydroxyl combination bands, such as Mg-OH (2300nm) and Fe-OH (from 2280 to 2343nm). The developed SIMCA model showed very good specificity and sensitivity values (from 0.89 to 1.00). The correctness of classification results was confirmed by stereomicroscopic investigations, based on different color, morphological and morphometrical characteristics of asbestos minerals, and by micro X-ray fluorescence maps, through iron (Fe) and magnesium (Mg) distribution assessment on asbestos fibers. The developed innovative approach could represent an important step forward to detect asbestos in building materials and demolition waste.