Comparing dried and liquid blood serum samples of depressed patients: An analysis by Raman and infrared spectroscopy methods

In this study differences between dried and liquid blood serum samples of healthy and depressed individuals measured by Raman (range 0-3000 cm−1) and FTIR (Fourier Transform Infrared) (range 900-3000 cm−1) spectroscopy were evaluated. The resulting spectra and accurate analysis led to the conclusion that an appropriate measurement of the background and the elimination of peaks from water had the greatest impact on the reliability of the results. Furthermore, after detailed studies of FTIR and Raman spectra of dried and liquid blood serum samples, including a complete analysis of peaks after Kramers-Kröning (KK) transformation, it was found that the sample preparation did not affect the results obtained by Raman spectroscopy. In FTIR measurements only a minimal effect on peak intensity was observed.