OPTIMIZING DRYING TIMES AND SAMPLE VOLUMES OF PLASMA AND URINE FOR MID-INFRARED SPECTROSCOPY ANALYSIS

Abstract

Purpose: The attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy is an analytical technique capable of discerning alterations in the molecular composition of plasma and urine derived from both healthy and non-healthy individuals. However, the lack of standardized protocols for drying time and sample volume hinders reproducibility and comparability of results. This study assesses the optimal drying duration and volume of plasma and urine for ATR-FTIR analytical procedures. Methods: Plasma and urine samples were evaluated at volumes of 5, 10, and 20 µL, deposited on the equipment crystal or in aluminum plates. Spectral data were recorded for 0 to 120 min on the equipment and 0 to 8 hours for the plates. The data were pre-processed with vector normalization and Rubberband baseline correction, and the area under the curve was calculated using means and standard deviations. Statistical analysis was performed using one-way and two-way ANOVA. Results: Plasma samples were dry after 15, 12, and 18 min for the 5, 10, and 20 µL respectively, whereas urine samples were dry after 12 min for the 5 µL and 10 µL, and after 40 min for the 20 µL. No significant differences were found between the drying processes on the equipment and aluminum plates. Conclusion: The results indicate that a volume of 10 µl is the most appropriate for analyzing plasma and urine, as samples achieved dryness within 12 min at this specific volume. We hope these results will contribute to improving clinical findings using ATR-FTIR for screening various diseases.