## 1 Introduction  
_Lavandula angustifolia_ Mill. (also named _Lavandula officinalis_ Chaix)--the true laverander--is a essential oil-bearing plant known worldwide, which history of usage starts in Greek and Roman times and last up to this day. The entire genus belongs to the large _Lamiace_ family, which is mostly native to the Mediterranean region, however true laverander is a commonly growing plant in England, Europe, North America and Australia. The most valuable part of the plant are flowers due to their much higher essential oil content than leaves, and a favorable linalool to linalyl acetate to camphor ratio [1].  
Nowadays due to the well-recognizable aroma laverander plants or their derivatives find applications in numerous ways, like in perfumery, cosmetics and household products, antimicrobial agents, food fragrance and flavor improvement or as food preservatives [1; 2; 3]. Furthermore, the essential oil obtained from laverander is an interesting object for trials considering biological activity and even in medicinal trials. Some studies and overviews from recent years mention the anti-aging, analgesic, neuroprotective, sedative or anticancer activities of laverander essential oil [2; 3; 4; 5; 6; 7; 8; 9].  
These various laverned essential oil applications are due to their unique chemical composition, rich in monoterepenes, sesquiterpenes, sesquiterpenoids, aliphatic compounds and especially an abundance of monoterepenoids [10], with linalool and linaly acetate highlighted as main flower components [11; 12; 1]. In the case of the leaves the main essential oil constituents are eucalypt (1,8-cineole), camphor and borneol [13; 14; 15].  
As the main factors affecting the quality of the essential oils obtained from essential oils-bearing plants, plant chemotype, growing conditions and location, fertilizers used, time of harvesting and post-harvest treatment (including preservation method) are mentioned [2; 11]. Among those factors, the preservation method has the most significant influence, where the most common one for plants rich in essential oils is drying [16; 17; 18]. Drying of essential oil-bearing plants allows one to obtain sustainable products with guaranteed quality, although it may cause also considerable losses of valuable constituents--mainly affecting the volatile constituents [17]. Furthermore, the color of the raw material may be strongly influenced by drying [16].  
The traditional and natural method of drying uses solar radiation, however nowadays convective drying (CD), which uses flows of the hot air [17; 18], is the most common drying method used in natural products treatment. Nevertheless other techniques like freeze-drying, infrared drying, vacuum-microwave drying (VMD), spray drying or a combination of convective pre-drying with vacuum-microwave finishing drying (CPD-VMFD) are lately the objects of numerous investigations regarding natural products drying [18]. Unfortunately in case of drying the true laverned leaves only single factors were investigated. Interest in this topic is due to the necessity to find an optimal drying method for specific raw materials. In addition, not only a specific technique, but also its parameters, like drying time, temperature or pressure have a significant influence on the quality of the obtained products [19; 20; 21; 22]. Overall the most important are air velocity and temperature--for plants the most suitable temperature is one between 50 \({}^{\circ}\)C and 60 \({}^{\circ}\)C [16].  
The objective of this study was to determine the volatile profile composition and compound quantity of true laverned leaves and the influence of three drying methods (CD, VMD, CPD-VMFD) applied with various parameters. The study was done by a solid-phase microextraction (SPME) coupled with gas chromatography mass spectrometry technique (GC-MS). Also the total essential oil content was validated by using a hydrodistillation extraction technique.