# Searching for Potential Markers of Glomerulopathy in Urine by HS-SPME-GC\(\times\)GC TOFMS
## 3 Discussion  
On urine sample chromatograms, varying numbers of particular chromatographic signals were observed from 100 to 250 peaks coming from different substances present in the samples. Moreover, we observed variations in the number of samples in which certain compounds were detected. This phenomenon occurred regardless of which group the samples were collected, from the patients or healthy control. Such a large number of varied compounds posed a significant difficulty in classifying the substances and selecting potential biomarkers. This may result from a large number of factors influencing biosynthesis of volatile metabolites (metabolic pathways, genetic differences, consumed food, age, sex, physiological state, addictions, etc.). Substances present in urine can be divided into characteristic chemical groups such as ketones, aldehydes, hydrocarbons, volatile sulfur compounds, heterocycles, alcohols, phenols and terpenes. The substances  
Figure 4: Principal component analyses (PCA) used to display variation between statistically significant determined VOCs, where: 1. cyclohexanone; 2. 3-ethylcyclopentanone; 3. 3-hexanone; 4. 3-heptanone; 5. methyl hexadecanoate; 6. 9-hexadecen-1-ol; 7. 3-methyl-2-pentanone; 8. 6,10-dimethyl-5,9-undecadien-2-one; 9. 2-pentanone; 10. acetophenone; 11. 2-methoxy-4-vinylphenol; 12. 1-decanol; 13. N-acetylpyrrole; 14. 6-methylhept-5-en-2-one; 15. dimethyl sulfone; 15. dimethyl sulfone; 16. 1-tetradecanol, 17. 4-heptanone; 18. benzaldehyde; 19. 2-nonanone; 20. 5-methyl-3-hexanone; 21. dimethyl trisulfide; 22. 2-aminobenzaldehyde; 23. 3-methylcyclopentanone; 24. hexanal; 25. 1-octanol; 26. benzeneacetaldehyde; 27. 2,5-dimethylpyrazine; 28. nonanal; 29. 9-octadec-1-ol; 30. indole; 31. theaspirane; 32. benzonitrile; 33. 2-heptanone; 34. 4-methylphenol; 35. phenol; 36. decanal; 37. 1-methyl-4-(1-methylethenyl)-benzene; 38. N-phenylformamide, 39. ethyl acetate; 40. octanal. most numerously represented were ketones. They amounted to almost 46% of all volatile substances identified in the samples from healthy volunteers and 49% of those found in samples from ill persons. Ketones are the products of metabolism and result from oxidation of secondary alcohols and fatty acids. Part of ketones can be also of dietary origin [6]. The most frequently observed ketones included acetone, acetophenone, 3-ethylcyclopentanone, 5-methylohexan-3-one, benzophenone, 2-pentanone, 2-heptanone, 2-butanone, 3-hexanone, 4-heptanone, 3-methylcyclopentanone, cyclohexanone and 1-octen-3-one. The next groups were aldehydes and alcohols, ca. 10 and 12% of all the chemical compounds respectively. We observed the presence of a series of aliphatic aldehydes from acetaldehyde to decanal, including also unsaturated and methylated compounds (i.e., 2-methylbutanal, 2-methyl-2-butenal). This is similar to the observations of [PERSON] and [PERSON] [6; 7]. Nonanal was identified in the majority of samples. We also found aldehydes containing a benzene ring, i.e., benzaldehyde, 2,4-dimethylbenzaldehyde, 2-hydroxybenzaldehyde, 4-methylbenzaldehyde, 4-(1-methylethyl)-benzaldehyde and alpha-methylbenzeneacetaldehyde. As for the presence of alcohols in the samples, the most frequently observed were 1-dodecanol, 1-octanol, 1-tetradecanol, benzyl alcohol, 1-hexanol, 1-nonanol, 1-octen-3-ol and 1-butanol. Many terpen were identified among the detected substances. The substances most frequently present in the samples included limonene,pinene, menthalienes, mentol, mentone, valencene, geraniol, linalool, thujene, myrcene, sabinene hydrate, \(\beta\)-caryophyllene, linalool oxides, etc. Considering that terpen are produced by plant organisms and not the human body, we assumed that the source of terpen and their metabolites in urine is food. This assumption is supported also by the works of other [6; 7]. Due to this fact, we excluded this group of substances from the set of potential disease markers.