CONFERENCE ON INDUSTRY MILESTONES, SHARING SUCCESSES AND DEMYSTIFYING MARKET REQUIREMENTS 25 - 26 July 2019 PRETORIA SA Pharmacopoeial Standards and Analysis of Essential oils with respect to South African Essential Oils Prof. Dr. K. Hüsnü Can Başer Near East University Faculty of Pharmacy Department of Pharmacognosy Lefkosa (Nicosia), N. Cyprus [email protected] www.khcbaser.com Quality control • Due to volatile nature of their active ingredients, quality control of essential oils is extremely important. • In order to safeguard their quality, standards and specifications exist in national and international Standard monographs as well as pharmacopoeias and codices. European Pharmacopoeia Essential oils TESTS General Tests The essential oil complies with the prescribed limits for the following tests Relative density, refractive index, optical rotation, fatty oils and resinified essential oils, Supplementary Tests If necessary, the essential oil complies with the prescribed limits for the following tests Freezing point, acid value, peroxide value, foreign esters, residue on evaporation, solubility in alcohol, water in essential oils. Water in Essential oils • EP6-2.8.5 Mix 10 drops of the essential oil with 1 ml of carbon disulphide R. The solution remains clear on standing. Foreign Esters in Essential oils • EP6-2.8.6 Heat 1 ml of the essential oil for 2 min on a waterbath with 3.0 ml of a freshly prepared 100 g/l solution of potassium hydroxide R in alcohol R. No crystals are formed within 30 min even after cooling. Fatty oils and resinified essential oils in Essential oils • EP6-2.8.7 Allow 1 drop of the essential oil to fall onto filter paper. The drop evaporates completely within 24 h without leaving any translucent or greasy spot. Odour and Taste of Essential oils • EP6-2.8.8 Mix 3 drops of the essential oil with 5 ml of 90 per cent V/V alcohol R and stir in 10 g of powdered sucrose R. The odour and taste are similar to that of the plant or parts of the plant from which the essential oil has been obtained. Residue on evaporation of Essential oils • EP6-2.8.9 The residue on evaporation of an essential oil is the percentage by mass of the oil which remains after evaporation on a water bath under the conditions specified below. Apparatus: The apparatus consists of: - Waterbath with a cover having holes of 70 mm diameter, - Evaporating dish of heat-resistant glass which is inert to the contents, - Desiccator Residue on evaporation of Essential oils Residue on evaporation of Essential oils • Method: Weigh the evaporating dish after having heated it on the water-bath for 1 h and cooled it in the desiccator. Weigh into the evaporating dish 5.00 g of the essential oil, unless otherwise prescribed. Heat the oil on the vigourously boiling water-bath in a draught-free atmosphere for the prescribed time. Allow to cool in the desiccator and wait. During the test, the level of water in the bath is maintained about 50 mm beneath the level of the cover. Solubility in Alcohol of Essential Oils All essential oils are soluble in absolute alcohol and many are soluble in dilute alcohol. It is, therefore, possible to determine the number of volumes of dilute alcohol required for the complete solubility of one volume of oil. Sometimes, however, the solutions obtained are not clear, then, they are defined as “opalescent”. Solubility in Alcohol of Essential Oils EP6 - 2.8.10 • 1.0 ml of the essential oil in a 25 ml or 30 ml glass-stoppered cylinder. Place in a constant temperature device, maintained at a temperature of 20 ± 0.2 oC . Using a burette of at least 20 ml capacity, add the alcohol of the strength prescribed in the monograph by increments of 0.1 ml until solution is complete and then continue adding by increments of 0.5 ml to a total of 20 ml, shaking frequently and vigorously. Record the volume of alcohol added when a clear solution has been obtained and, if the solution becomes cloudy or opalescent before 20 ml of alcohol has been added, record the volume added when the cloudiness or opalescence appears and, where applicable, the volume added when the cloudiness and oplescence disappears. Solubility in Alcohol of Essential Oils • If a clear solution has not been obtained when 20 ml of alcohol of the prescribed strength has been added, repeat the test using the next highest concentration of alcohol. An essential oil is said to be “soluble in n volumes and more of alcohol of given strength l” when the clear solution in n volumes remains clear when compared with the undiluted oil after further addition of alcohol of the same strength up to a total of 20 volumes of alcohol. An essential oil is said to be “soluble in n volumes and more of alcohol of given strength l becoming cloudy when diluted” when the clear solution in n volumes becomes cloudy in n1 volumes (n1 less than 20 ) and stays so after further gradual addition of alcohol of the same strength up to a total of 20 volumes of alcohol. Solubility in Alcohol of Essential Oils • An essential oil is said to be “soluble in n volumes and more of alcohol of given strength l with cloudiness between n1 and n2 volumes” when the clear solution in n volumes becomes cloudy in n1 volumes (n1 less than 20 ) and stays so after further gradual addition of alcohol of the same strength up to a total of n2 volumes of alcohol and then becomes clear (n2 less than 20). • An essential oil is said to be “soluble with opalescence” when the alcoholic solution shows a bluish tinge similar to that of a standard of opalescence freshly prepared as follows: mix 0.5 ml of silver nitrate solution R2 and 0.05 ml of nitric acid R; add 50 ml of a 12 mg/l solution of sodium chloride R; mix and allow to stand protected from light for 5 min. Relative density • The specific gravity of an oil is the weight of a given volume of the oil at a specific temperature compared with the weight of an equal volume of water at the same temperature, all weighings being taken in air. A pycnometer is used for this determination. Optical rotation • The optical rotation ( ) of an oil is the angle through which the plane of polarization is rotated when polarized light passes through it. Results are expressed as dextrorotatory (+) or levorotatory (-) according to whether the plane of polarization is rotated chlockwise or anticlockwise, respectively, as determined by viewing towards the light source. Unless otherwise specified, the optical rotation is measured at a wavelength of the sodium D line (589.3 nm) at a temperature of 19.5 oC to 20.5 oC in a layer 1 dm thick. Polarimeters are used for the determination of optical activity. This technique provides useful data on the optical purity of the oil. Refractive index • The refractive index ( ) of an oil with reference to air is the ratio of the sine of the angle of incidence to the sine of the angle of refraction of a beam of light passing from air into the oil. It varies with the wavelength of the light used in its measurement. Abbe type refractometers are widely used for the determination of the refractive index. Freezing point • The freezing point is the highest temperature observed during the solidification of a supercooled liquid. Chemical tests Sensory evaluations • Sensory evaluations can be carried out only by expert noses. Such an ability can be gained after years-long tedious but systematic olfactive training. To an experienced nose, the evaporation pattern of an essential oil smeared on a smelling strip, over a period of time, gives information about its source, age, main components and even its authenticity. Smelling must be carried out at intervals immediately after dipping to 1,2 and 6 hours, and after standing overnight over a period not less than 18 hours. Comparison with an authentic sample of acceptable quality will help the assessor to make a correct judgement. As obvious, sensory evaluations are subjective and may vary from person to person. Therefore, such assesments are, in general, realized by a panel of experts and in all cases their assesments should be verified and documented by experimental proof. Quality control • Gas chromatography (GC) is the most important technique for the separation of essential oil constituents and their quantitation. • Gas chromatography/mass spectrometry (GC/MS) may only be necessary to identify constituents which appear unexpectedly in a known essential oil of for the analysis of new essential oils. KHC Baser, Analysis and quality assessment of essential oils. In: A Manual on the Essential Oil Industry, KT de Silva (Ed), UNIDO, Vienna (1995). Conformity to specifications • Essential oils are complex mixtures and their quality assessment requires multifarious analyses. The first and the simplest analysis is carried out by sensory organs, that is the smell, colour and viscosity means a lot to an experienced perfumer. Instrumental techniques developed in recent decades have revolutionized the advancements in the science and trade of essential oils for detecting adulteration, and for elucidating the structures of many hitherto unknown aroma chemicals occurring in essential oils. Such compounds have also been a model for new families of flavour and fragrance chemicals. It has also made quantification of even less than part per billion (ppb) amounts of essential oil constituents possible. With such a degree of sophistication, it is now a reality to assure the quality of an essential oil in almost absolute terms. Conformity to specifications • For known essential oils of commerce, specifications have been drawn and published by authoritative organizations, the most important for essential oils being TC54 Committee of the International Standards Organization (ISO).