FTIR Analysis of Kidney Stone Using IRSpirit-TX

Significance of the Topic

This report highlights the critical role of Fourier Transform Infrared (FTIR) spectroscopy in nephrology, specifically for analyzing kidney stones. Accurate determination of stone composition can guide clinical management, reveal metabolic disorders or dietary influences, and support the development of prevention strategies. The use of attenuated total reflection (ATR) FTIR enables rapid and minimally invasive analysis, preserving valuable sample material for complementary techniques such as SEM–EDS or thermal analysis.

Objectives and Overview

The primary objective is to demonstrate a streamlined workflow for kidney stone characterization using the IRSpirit-TX FTIR spectrophotometer with QATR-S ATR accessory. The study outlines sample preparation, spectral acquisition, and automated composition identification through the IR Kidney Stones Library. Emphasis is placed on ease of operation, reproducibility, and speed of analysis.

Methodology

• Sample Preparation: Kidney stone fragments obtained from a medical center were pulverized with an agate mortar and pestle to fine powder, eliminating moisture and homogeneity issues encountered with KBr pellet techniques.
• ATR Measurement: A small spatula of powdered stone was pressed against a ZnSe ATR prism to collect spectra without extensive sample manipulation.
• Analysis Conditions: Spectra were acquired on IRSpirit-TX at 4 cm⁻¹ resolution over 4000–500 cm⁻¹, with 45 scans accumulated and SqrTriangle apodization. A DLATGS detector was used to maximize signal-to-noise performance.
• Data Processing: ATR correction was applied to match transmission-based library spectra. Automated library search was performed using LabSolutions IR software against the NICODOM IR Kidney Stones Library.

Used Instrumentation

• IRSpirit-TX FTIR Spectrophotometer (Shimadzu): Compact bench-top system with DLATGS detector for high sensitivity (S/N 37 000:1).
• QATR-S Single-Reflection ATR Accessory: ZnSe prism (1.8 mm diameter) with torque-limited clamp for secure sample contact.
• LabSolutions IR Software: Library search tool coupled with the NICODOM IR Kidney Stones Library (1 668 spectra covering oxalates, phosphates, urates, cystine, and organic components).

Main Results and Discussion

ATR-corrected spectra of the kidney stone sample exhibited characteristic absorption bands matching a mixture of carbonate apatite and struvite. The library search yielded a high match score, confirming the dual composition. Key spectral features included phosphate stretching modes near 1040 cm⁻¹ and carbonate bands around 1410 cm⁻¹, alongside ammonium-phosphate vibrations indicative of struvite.

Benefits and Practical Applications

Utilizing ATR-FTIR with minimal sample preparation accelerates the identification of kidney stone composition, supporting rapid clinical decision-making. The small required sample size preserves material for further microscopy or thermal analysis. The automated library search eliminates subjective interpretation, ensuring consistent results in QA/QC and research settings.

Future Trends and Potential Applications

• Expansion of spectral libraries to include rare stone types and pathological variations.
• Integration with hyphenated techniques (e.g., GC-FTIR) for complex organic components.
• Development of in situ ATR probes for endoscopic or surgical applications.
• High-throughput automation and cloud-based spectral matching for clinical laboratories.
• Machine learning algorithms to predict stone formation risk factors from spectral data.

Conclusion

This study demonstrates that ATR-FTIR analysis with the IRSpirit-TX and QATR-S accessory provides a rapid, reliable, and minimally demanding approach to kidney stone characterization. Automated library searching ensures accurate composition identification, supporting both clinical and research laboratories in advancing nephrolithiasis diagnostics.

References

1. Placzyńska M., Milart J., Lubas A., Samotyjek J., Jurkiewicz B., Kalicki B., Jobs K. Association between the metabolic profile of urolithiasis in children with idiopathic hypercalciuria and the composition of the stone assessed by infrared spectroscopy. Pediatr Pol. 2023;98(4):271–277.