GC-MS Analysis of A _Helichrysum italicum_ Hydrosol: Sensitivity, Repeatability and Reliability of Solvent Extraction versus Direct Hydrosol Analysis  
[PERSON]  
1  
[PERSON]  
Faculty of Pharmacy, University of Ljubljana, 1000 Ljubljana, Slovenia 1  
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Hydroosols are a coproduct in the production of essential oils by distillation. Their composition of volatile compounds is to some extent similar to essential oils, yet they contain more hydrophilic compounds. However, their analysis is complex, as the concentrations of volatiles are low [18]. The most common method of hydrosol analysis is gas chromatography coupled with mass spectrometry (GC-MS), which also allows researchers to identify the detected compounds.  
Analytical methods can be carried out in different ways. Extraction of volatiles with an organic volatile solvent is most commonly performed [1; 19; 20; 21; 22]. After extraction, the concentration of volatile compounds in the analyzed sample is increased. The main disadvantage of organic solvent extraction is that the ratios between the detected compounds typically change in comparison to the original composition of a hydrosol due to the different partition coefficients between water and an organic solvent for each compound present in the hydrosol. A solid-phase microextraction (SPME) method can also be used to analyze the volatile compounds present in the gas phase above the hydrosol [23; 24]. The disadvantages of the method are a low concentration of compounds in the volatile phase and different compositions of volatile and aqueous phases due to the different volatilities of the compounds present in a hydrosol. Direct hydrosol analysis is most rarely used. The reasons for this are poor compatibility of aqueous samples with GC columns and a low concentration of compounds in the hydrosol.  
_Helichrysum italicum_ is an up to 70 cm tall medicinal plant that belongs to the Asteraceae family. It is also called \"everlasting\" or \"immortelle\" because its inflorescences remain bright yellow after drying or the \"curry plant\" because of its characteristic, curry-like smell. _H. italicum_ is traditionally widely used in European countries, particularly Italy, Spain, Portugal and Bosnia and Herzegovina. In these countries, the flowers and leaves of the plant are most commonly used in the treatment of health disorders such as allergies, colds, cough, skin, liver and gallbladder disorders, inflammation, infections and sleeplessness [25; 26]. Increased interest in _H. italicum_ has been noted recently, which is reflected in the growing body of evidence for the science-based medicinal use of the plant's preparations [27; 28; 29; 30; 31; 32; 33; 34; 35].  
While the composition and effects of _H. italicum_ essential oil are well studied, showing antimicrobial [25; 36; 37; 38; 39], anti-inflammatory [25; 40], antioxidant [41] and anti-collagenase and anti-elastase activities [42], significantly less research has been done with _H. italicum_ hydrosols. The most common compounds were shown to be alpha-terpineol, 3,5-dimethyloctane-4,6-dione, 2,4-dimethyl-heptane-3,5-dione, italidione I and II, linalool and nerol [43]. On the other hand, to the best of our knowledge, the biological effects of the hydrosol have not yet been investigated.  
The purpose of our work is to identify the advantages and disadvantages of different methods of _H. italicum_ hydrosol analysis with GC-MS. Emphasis is placed on qualitative analysis, repeatability, reliability and the presence of impurities due to sample handling. Conclusions can generally be applied to hydrosols of other plant sources since they have similar physicochemical properties.