Elemental Composition Analysis of Sheep Tears Using Particle-Induced X-Ray Emission

Objective: To identify the elemental composition of ovine tears using particle-induced X-ray emission (PIXE). Animals Studied: Ten physically healthy female sheep. Procedures: Tear samples were collected using Schirmer tear test strips. Tear samples were collected once daily over five consecutive days to assess reproducibility. Elemental analysis was performed with PIXE. Data were processed with GUPIX software. Median values of the elements identified were calculated and statistically analyzed with Kruskal–Wallis and post hoc Dunn's tests. Results: The analysis demonstrated consistent elemental concentrations over the 5-day sampling period. Among the elements detected, chloride (Cl) and sodium (Na) exhibited the highest concentrations. Conclusions: This study establishes PIXE as a valuable technique for detecting and analyzing the elemental composition of the tear film in sheep. By providing a precise method for elemental analysis in small biological samples, this approach lays the groundwork for future research exploring its reliability and sensitivity in tear analysis and potential as a biomarker for ocular and systemic health. The impact of variables including age, diet, and environmental exposure on tear film constituents should be studied, potentially extending the methodology to other species.