## 2 Materials and Methods
From the spectroscopic parameters of the detected absorption lines (central frequencies, estimated absorption coefficients) substances present in the studied gas mixture were identified using electronic catalogs [17; 18]. A comparative analysis of the chemical composition of vapors and thermal decomposition products was then carried \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**No.** & **Age** & **Diagnosis** & **TNM** & **Gleason** & **ISUP Grade** & **PSA** & **UAm Test** \\  & & & **Classification** & **Score (GS)** & **Groups** & **PSA** & **UAm Test** \\ \hline
3 & 66 & Prostate cancer & pT3 aN0M0 & \(3+4=7\) & 2 & 6.1 & Normal \\
4 & 70 & Prostate cancer & pT3 bN1M0 & \(3+4=7\) & 2 & 27 & Normal \\
7 & 60 & Prostate cancer & pT2 cN0M0 & \(3+4=7\) & 2 & 8.9 & Normal \\
8 & 58 & Prostate cancer & pT3 aN1M0 & \(4+4=8\) & 4 & 15 & Normal \\
9 & 76 & Prostate cancer & pT2 cN0M0 & \(3+3=6\) & 1 & 26 & Glucose—6 mmol/L \\
13 & 62 & Prostate cancer & pT3 bN0M0 & \(3+4=7\) & 2 & 47.3 & Normal \\
14 & 73 & Prostate cancer & pT2 aN0M0 & \(3+3=6\) & 1 & 6.5 & RBC—100 cells/\(\mu\)L \\
15 & 58 & Prostate cancer & pT3 bN0M0 & \(3+4=7\) & 2 & 28 & Normal \\
16 & 58 & Prostate cancer & pT2 cN0M0 & \(3+4=7\) & 2 & 19 & Normal \\
17 & 55 & Prostate cancer & pT2 cN0M0 & \(4+4=8\) & 4 & 10.9 & HGB—25 g/L \\
18 & 74 & Prostate cancer & pT2 cN0M0 & \(3+3=6\) & 1 & 9 & WBC—16 cells/\(\mu\)L \\  & & & & & & & RBC—12 cells/\(\mu\)L \\
19 & 62 & Prostate cancer & pT3 aN0M0 & \(4+3=7\) & 3 & 18 & Normal \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Information about patients. Figure 1: Block diagram of the experiment measuring spectra of urine thermal decomposition products using the fast frequency sweep spectrometer. The example of spectra presented here includes the red (sample of prostate cancer patient) with absorption lines of formic acid (HCOOH) and carbonyl sulfide (OCS) and blue (sample of conditionally healthy volunteer) curves with an absorption line of carbonyl sulfide (OCS). out to identify differences in the urine samples from prostate cancer patients and healthy volunteers. Each chemical substance has its own unique spectrum. The spectroscopic characteristics of the absorption lines of a substance are determined by the geometry of the molecule, masses of its constituent atoms, and the total dipole moment. Therefore, the absorption lines are unambiguous signs of the presence of a given substance in the studied multicomponent gas mixture. For qualitative analysis of changes in the composition of different samples, it is possible to count the number of lines recorded in the measured spectrum for each individual substance in the mixture of thermal decomposition products of urine. It is important to take measurements under the same conditions (the same amount of liquid sample in the flask before dehydration, the operating pressure in the cell maintained at a certain level, the same stage of dehydrated sample heating). With a higher relative concentration of a specific substance in the mixture, the number of its absorption lines will increase due to the increase in the concentration of the substance. The amplitude of the detector signal of the stronger lines will also increase. This is true for the case when both strong and weak lines of the substance lie in this range. Consequently, an increase or a decrease in the number of absorption lines enables a qualitative conclusion that the concentration of a given substance increases or decreases from sample to sample. Some substances are always present in the thermal decomposition products of urine, regardless of the volunteer's health condition.