Trace elements analysis in biological samples by radioisotopic x-ray fluorescence.

Area of Science:

• Analytical Chemistry
• Biophysics
• Medical Diagnostics

Background:

• X-ray fluorescence (XRF) is a powerful analytical technique.
• Radioisotope-induced XRF offers a simplified approach for elemental analysis.
• Biological samples present unique challenges for trace element quantification.

Purpose of the Study:

• To evaluate the efficacy of radioisotope-induced X-ray fluorescence for simultaneous trace element analysis in biological samples.
• To determine the sensitivity and applicability of XRF for quantifying elements in blood, serum, and platelets.
• To explore the use of XRF for biological tracer studies, such as measuring platelet lifespan.

Main Methods:

• Biological samples (blood, serum, platelets) were prepared as thin specimens on filter paper.
• Analysis was performed using radioisotope-induced X-ray fluorescence with either a gas proportional counter or an X-ray semiconductor detector.
• Stable tracers like Selenocystine were used to label blood components for concentration detection.

Main Results:

• The thin specimen approximation allowed for linear quantification of elements and minimized interelement effects.
• Detection limits for elements (atomic number 20-92) ranged from parts per million (ppm) to tens of ppm with short measurement times, and down to sub-ppm levels with longer times.
• The technique successfully quantified Cl, K, Ca, Fe, Cu, Zn, and Br in blood and serum samples.
• Platelet lifespan was measured after labeling with stable Selenocystine.
• Sensitivity was enhanced by three orders of magnitude using pre-enrichment with ion-exchange resins for large liquid volumes (≥500 ml), enabling urine analysis and trace copper detection in serum.

Conclusions:

• Radioisotope-induced XRF is a simple, sensitive, and versatile method for simultaneous trace element analysis in various biological matrices.
• The technique is suitable for routine analysis of elements in blood and serum, as well as for specialized applications like biological tracer studies.
• Further sensitivity enhancements are achievable through pre-enrichment strategies, broadening the scope of XRF in biological and environmental sample analysis.