Analysis of Inorganic Elements in Blood Using EDXRF

Importance of the topic

Accurate and rapid determination of inorganic elements in blood is critical for clinical diagnosis, toxicology and forensic investigations. Traditional techniques (ICP-AES, ICP-MS) provide trace-level sensitivity but require chemical pretreatment (dilution, deproteinization) and are limited to liquid sample workflows. Energy-dispersive X-ray fluorescence (EDXRF) offers non-destructive, minimal-preparation screening with short turnaround time, suitable for preliminary assessment of essential elements and heavy-metal exposure in whole blood.

Objectives and overview of the study

This application report evaluates the performance of the Shimadzu EDX-7200 EDXRF spectrometer for quantifying 15 inorganic elements in whole human blood. Two quantitation strategies were compared: conventional calibration-curve analysis using aqueous standards and a fundamental-parameter (FP) thin-film approach built into the instrument that does not require external standards. Key goals were to assess linearity, accuracy (recovery) after standard addition at 10 µg/mL, analysis speed, and practical sample handling requirements.

Methodology

• Selection of elements: Fifteen elements commonly involved in poisoning or clinical monitoring were targeted (V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sn, Hg, Tl, Pb).
• Calibration standards: Commercial ICP stock solutions (1000 µg/mL) were diluted to 0, 1, 5, 10, 25 and 50 µg/mL in ultrapure water. For calibration measurements 2.5 mL of each standard was placed into a sample cell sealed with a 5 µm polypropylene film.
• Sample preparation: Human whole blood was spiked to 10 µg/mL by adding 0.25 mL of a 100 µg/mL ICP standard to 2.25 mL blood, mixed and loaded (2.5 mL) into the same film-bottom sample cell. No deproteinization or chemical digestion was performed.
• Measurement strategy: Calibration-curve quantitation used a scattered X-ray internal standard method; the FP thin-film mode treated unmeasured organic and moisture components as a CH2O balance. Overlap-correction factors were applied for elements with spectral interferences (examples: Cr↔V, As↔Pb, etc.). Ni and Sn at 1 µg/mL were excluded from calibration because sensitivity was insufficient under the chosen integration times.

Used Instrumentation

• Instrument: Shimadzu EDX-7200 Energy Dispersive X-ray Fluorescence Spectrometer.
• Detector: Silicon drift detector (SDD).
• X-ray tube: Rhodium target.
• Tube voltage/current: Variable; examples used were 30 kV for V–Ni range and 50 kV for heavier elements. Calibration-mode used additional lower-voltage settings (e.g., 15 kV) for very light elements.
• Collimation/filters: 10 mm diameter collimator; a set of primary filters (#1–#5) selected per element group to optimize excitation and reduce background.
• Atmosphere: Air (measurements performed in air).
• Integration times: Calibration standards measured with 120 s per channel (longer integration); routine sample acquisition used 60 s × multiple channels. Dead time limited to a maximum of 30%.

Main results and discussion

• Linearity: Calibration curves showed excellent linearity across the prepared concentration range (0–50 µg/mL) with correlation coefficients (R) typically between ~0.9976 and 0.99999 for the reported elements.
• Qualitative background: The unspiked blood blank contained endogenous elements including P, S, Cl, K, Ca, Fe, Cu, Zn, Br and Rb.
• Quantitative accuracy: For the 10 µg/mL standard-addition tests, the calibration-curve method produced recoveries between 84% and 118% across elements. The FP thin-film method achieved recoveries between 84% and 103%, demonstrating that FP quantitation without external standards can provide sufficiently accurate results for screening.
• Precision: Reported 3σ uncertainties for quantified elements were generally on the order of 0.08–1.7 µg/mL depending on element and measurement conditions, indicating usable precision for µg/mL-level screening.
• Practical notes: Some heavier elements (e.g., Ni, Sn) exhibited limited sensitivity at the lowest calibrant level (1 µg/mL) under the experimental integration times. Overlap correction and appropriate filter/tube voltage selection were important to minimize spectral interferences.
• Throughput and sample handling: Typical analysis time per sample was on the order of 10 minutes, and no deproteinization or complex chemical pretreatment was required for whole blood.

Practical benefits and applications

• Rapid screening: The EDX-7200 enables fast, non-destructive screening of whole blood for essential and toxic elements at µg/mL concentrations without laborious sample cleanup.
• No standards required option: The FP thin-film approach allows qual-quantitative results without matrix-matched calibration standards, reducing preparative burden for routine screening or when standards are not readily available.
• Utility domains: Clinical research, emergency toxicology triage, forensic casework and occupational exposure monitoring where quick presumptive results are valuable prior to confirmatory ICP-MS/AES testing.

Future trends and opportunities

• Improved limits of detection: Longer integration times, optimized filters, improved detector technology and higher-excitation options could extend sensitivity toward sub-µg/mL levels for difficult elements.
• Matrix-matched calibrations and standard addition strategies: To further improve accuracy for complex biological matrices, development of matched blood-based standards or routine standard-addition workflows would reduce matrix-related biases.
• Hyphenation and complementary techniques: Combining EDXRF screening with targeted ICP-MS confirmation or chromatographic speciation workflows would provide a robust pipeline for both speed and definitive quantitation/speciation.
• Automation & informatics: Automated sample handling, integrated LIMS connectivity and automated overlap-correction algorithms will increase throughput and traceability for clinical/forensic labs.
• Portable/point-of-care potential: Advances in compact EDXRF hardware could support field triage in occupational or environmental exposure incidents, though sample containment and reproducibility must be addressed.

Conclusion

The study demonstrates that the Shimadzu EDX-7200 EDXRF spectrometer can deliver rapid, non-destructive quantitation of multiple inorganic elements in whole blood with µg/mL-level sensitivity suitable for screening. Both calibration-curve and FP thin-film approaches provided acceptable accuracy (calibration: 84–118%; FP: 84–103%) for standard-addition at 10 µg/mL. Minimal sample preparation and short analysis times (~10 minutes per sample) make EDXRF a practical frontline tool for clinical research, forensic screening and emergency toxicology, with confirmatory analyses recommended for cases requiring trace-level certainty.

References

• Shimadzu Corporation, Energy Dispersive X-ray Fluorescence Spectrometer EDX-7200 — Application News, First Edition Aug. 2026.