IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 59, NO. 8, AUGUST 2010 2243 Distillation of Essential Oil From Leaves of Eucalyptus camaldulensis by Using Microwave Power Source Mahit Gunes and Mehmet Hakkı Alma Abstract—The essential oil from the leaves of Eucalyptus camaldulensis Dehnh was distilled by microwave-applied hydrodistillation (MWHD), and the properties obtained were compared with hydrodistillation (HD) techniques. The chemical composition of essential oil obtained by the microwave method was analyzed by gas chromatography (GC) and GC mass spectrometry (GC-MS). Index Terms—Essential oil distillation, Eucalyptus camaldulensis, microwave irradiation. I. I NTRODUCTION Essential oil is concentrated hydrophobic liquid containing volatile aroma compounds from plants. It is also known as volatile or ethereal oil, or simply as the “oil of” the plant material from which they were extracted, such as oil of clove. Oil is “essential” in the sense that it carries a distinctive scent, or essence, of the plant [1]. Essential oils are generally extracted by distillation. Other processes include expression or solvent extraction. They are used in perfumes, cosmetics, and bath products, for flavoring food and drink, and for scenting incense, household cleaning products, and as medicine for various treatments ranging from skin treatments to remedies for cancer [2]. Several techniques are currently available for the extraction of essential oils from plants, including supercritical fluid extraction, pressurized liquid extraction, pressurized hot-water extraction, hy- drothermal extraction, water-vapor extraction, solvent extraction, membrane-assisted solvent extraction, solid-phase microextraction, stir-bar sorptive extraction, and ultrasounds. Recently, microwave- assisted extraction methods have appeared to be particularly attractive due to fast heating of aqueous samples [3]–[5]. Microwave heating has many advantages (such as a noncontact heat source, more effective heating, faster energy transfer, reduced thermal gradients, selective heating, reduced equipment size, and faster response to process heating control) over conventional heating, including more even distribution of heat and better control over the heating process. Microwave energy, with a frequency of 2.45 GHz, is well known to be used in production and several characterization and purposes [3]–[6]. In the literature, there are a few studies on the distillation of essential oil from Eucalyptus species by using hydrodistillation (HD). However, to our knowledge, there is no study on the distillation of essential oil by using microwave irradiation power. Therefore, in this paper, we intended to investigate whether the microwave applied in situ distillation method is feasible to extract the essential oil from E. camaldulensis. Manuscript received February 2, 2010; revised March 10, 2010; accepted March 11, 2010. Date of publication May 10, 2010; date of current version July 14, 2010. The Associate Editor coordinating the review process for this paper was Dr. Devendra Misra. M. Gunes is with the Department of Computer and Instructional Technology, K.S.Ü. University, Kahramanmaras 46200, Turkey (e-mail: mgunes@ksu.edu.tr). M. H. Alma is with the Department of Industrial Engineering of Forestry, K.S.Ü. University, Kahramanmaras 46200,Turkey (e-mail: alma@ksu.edu.tr). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIM.2010.2047988 Fig. 1. Experimental setup. II. MATERIALS AND METHODS In this paper, the leaves of E. camaldulensis were collected from Turkish State Forest in Hatay with an altitude of 150 m. The plant was authenticated by Dr. Ahmet Ilcim, University of KSU, Turkey. Fifty grams of leaves of E. camaldulensis was submitted to HD with a Clevenger-type apparatus and extracted with 300 ml of water for 3 h. The essential oil was collected, dried under anhydrous sodium sulfate, and stored at −8 ◦ C until used. Fig. 1 schematically shows the experimental setup that is used to obtain the essential oil by means of microwave heating from 50 g of leaves mixed with 100 ml of water. A 2455-MHz magnetron has been used to supply microwave power at three different levels to the leaf–water mixture. A conventional Clevenger apparatus was linked to a round bottom glass placed in the microwave oven. The excess water was refluxed to the extraction vessel to restore water to the plant material. The essential oil from E. camaldulensis was collected at three different powers, e.g., 300, 600, and 900 W, for a certain time (20 min), dried under anhydrous sodium sulfate, and stored at −8 ◦ C until used. The essential oil (11.5 mg) was diluted with diethyl ether (Et 2 O; 1 ml) and analyzed on a mass spectrometer coupled with a gas chromatograph (GC). An SE-54 fused silica capillary column (30 m × 0.25 mm i.d.; 0.25-μm film thickness) and carrier gas He (at 1.15 ml/ min) were used. One microliter of the diluted oil was injected into the column (split 1 : 10). The GC oven temperature was kept at 60 ◦ C for 5 min and programmed to 260 ◦ C at a rate of 2 ◦ C/ min and then kept at 260 ◦ C. The injector temperature was 250 ◦ C. Mass spectra were taken at 70 eV (EI mode). Identification of components in the oil was based on logarithmic retention indexes relative to n-alkanes and mass spectra compared with own data collections based on authentic reference substances, the National Institute of Standards and Technology library, as well as by comparison with data reported in the literature. Quantification of the essential oil was conducted by GC with flame ionization detector. The oil (1 μl) was injected into the same column under the same GC conditions as described for the GC mass spectrometry (GC-MS) study. However, the split ratio was 1 : 14. 0018-9456/$26.00 © 2010 IEEE