Steam distillation essential oils apparatus

Different plants including spearmint (Mentha spicata L ), rosemary (Rosmarinus officinalis L.), dill (Anethum graveolens L.), clary sage (Salvia sclarea L.) and chamomile (Matricaria chamomilla L.) were extracted with CO2 in a high pressure apparatus with 5 L extractor vessel volume. Fractionation of extracts was carried out by releasing the separation pressure at two stages. The extracts were separated into essential oil rich oil and fatty/waxy products. The extracts were collected as separate samples successively in time. The extraction with carbon dioxide was compared to conventional steam distillation (essential oils) and to Soxhlet extraction with hexane (fatty oils). 

The quality of caraway fruits used in pharmaceutical and food industry is given one of the main criteria - the essential oil content and D-carvone content, respectively. The amount of caraway processed in the pharmaceutical industry reaches 10 - 15 % of total caraway production (Sedlakova et al., 2001). The minimal limit of the essential oil (30 ml.kg"1 of dried drug) and D-carvone content in the essential oils required by the Czech Pharmacopoeia is 50 % (2006). Also, according to European Pharmacopoeia (6th Ed) caraway fruits contain not less than 30 ml.kg 1 of essential oil in dried drug. The specification in the application for designation of origin (PDO) for Czech caraway requires also minimum of 50 % of D-carvone. The steam distillation at Clavenger apparatus and GC methods are required for the assessment by the several standards. Table 6 describes the essential oil content of Czech caraway varieties. 

Steam distillation is the standard method used for the determination of volatile oil. In British Pharmacopoeia, the dimension of the essential oil apparatus was specified, since all parts of the apparatus affect the yield of the volatile oil and avoid any controversy in the quality of the herbs. This method is usually employed to determine high volatile oil content herbs. Aromdee et al steam distilled various species of curcumas. Curcuma aromatica, C. aeruginosa by the method described in BP using xylene as an organic entraptor. They found the volatile oils in C. aromatica was 0.88-0.96% v/wet wt (Aromdee, 2010), where as C. aeruginosa was 0.55-0.42% v/wet wt (Aromdee, 2007). The content of volatile oil in other species of curcuma. 

Steam distillation. Chamomile essential oil was isolated by steam distillation. Hydro distillation lasted for 2 h into n-hexane, sample weights were 2 g of dry drag matter. The modified distillation apparatus by Coocking and Middleton was used [6]. 

Production. Essential oils are obtained from plant materials by distillation with water or steam. After condensation of the vapor phase, the oil separates from the aqueous phase and is removed. The yield of essential oil, based on the starting plant material, generally ranges from a few tenths of 1 % to a few percent. The apparatus used in the production of natural fragrance concentrates is described in [223]. 

The methods of steam distillation have been summarized by Bernhauer [13] and Thormann [14]. A detailed discussion of practical and theoretical aspects of steam distillation as illustrated by the distillation of essential oils is given by von Weber [15], Rigamonti [16] developed a nomogram which can be used to calculate the steam requirements for various enrichments. Prenosil [16a] compared theoretical and experimental steam distillation data for multicomponent mixtures. He modified the calculating method by introducing a value for evaporation efficiency. Steam distillation can also be carried out in thin-film apparatus. Berkes etal. [16 b] give a description of the material transfer conditions of a steam distillation performed in such apparatus in terms of the balance equations. 

This method, specimens and water are heated in a steam distillation apparatus, once the water is boiled, volatile constituents will be carried along with the water vapour and then condensed in to a trap containing water and an immiscible solvent. Water and the solvent will separate into two phases. The volatile oils is dissolved in the solvent. A standard method described in British Pharmacopoeia (BP) 2010, Essential oil in Herbal Drugs, is very useful in determining the total content of volatile oils in herbs. The volatile distillate thus obtained can be used for determination of the constituents either qualitatively or quantitatively. 

The roots of distillation methods are attributed to Arabian Alchemists centuries with Avicenna (980-1037) describing the process of steam distillation, who is credited with inventing a coiled cooling pipe to prepare essential oils and aromatic waters. The rst description of distilling essen tial oils is generally attributed to the Spanish physician Arnaldus de Villa Nova (1235-1311) in the thirteenth century. However, in 1975, a perfectly preserved terracotta apparatus was found in the Indus Valley, which is dated to about 3000 BC and which is now displayed in a museum in Taxila, Pakistan. It looks like a primitive still and was presumable used to prepare aromatic waters. Further ndings indicate that distillation has also been practiced in ancient Turkey, Persia, and India as far back as 3000 BC. 

The following is a controversial method for essential oil extraction by comparison with classical hydrodistillation methods. In this method, the steam enters the distillation chamber from the top passes through the biomass in the still pot (e.g., the distillation chamber) and percolates into the condenser located below it. Separation of the oil from the aqueous phase occurs in a battery of Florentine asks. It is claimed that this method is very gentle and thus suitable for the treatment of sensitive plants. The biomass is held in the still chamber (e.g., still pot) on a grid that allows easy disposal of the spent plant matter at the completion of the distillation. The whole apparatus is relatively small, distillation times are reduced, and there is less chance of the oil being overheated. It appears that this method is fairly costly and thus likely to be used only for very-high-priced biomass. 

The simultaneous combination of steam distillation and solvent extraction, usually implemented by a Likens-Nickerson apparatus or its analogues, has also been widely used for the isolation of essential oil. The chemical composition of such essential oils will be analysed by GC-MS [40]. 

This brown residue was then subjected to distillation in a current of steam. In a suitable rectifying apparatus the essential oil alone is carried over, free from any waxy matters. The water condensed in the course of this operation is exhausted with ether, after saturation with common salt, and the evaporation of the ether leaves a residue which is termed the soluble essential oU. The portion which floats on the surface of the condensed water and which is isolated by simple decantation is termed the direct essential oil the name of total essential oil is given to that which is obtained by mixing the two former oils in proportion to their yields. 

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