Identification of perfumery residues contained in glass objects from Parthian to early Islamic period with gas-chromatography coupled with mass spectroscopy

Abstract

It has been a long time since aromatic plants and aromatic materials have been used in perfumery.Therefore, production of perfume flask had become noticeable among craftsmen and artists. The use of plants and other aromatic substances in perfumery has been possible by obtaining their essential oils. The production of perfumes are mainly derived from plants such as roses, cloves and saffron, incense and sandalwood and plant gums. Amber, musk and Azfar were also taken from some animals such as Gazelle and Amber fish. Perfume flasks are little containers made by a variety of different materials that have been shaped or embellished by standard technology and ornaments of their historical period. Glass has been one of the most favorite materials to make a perfume flask through the time. \nThis research gives a brief overview of the history of perfumery, from the Achaemenid era to the first centuries of the Islamic era. Then it analyzes remained materials inside the five glass containers, which are considered to be perfume bottles, from the Parthian period to the first centuries of the Islamic era. These glass perfume bottles are kept in the Glassware and Ceramic Museum of Iran currently. \nThis analysis has been done by Coupled gas chromatography with mass spectrometer in the gas chromatography laboratory of Research Institute of Medicinal Plants and Drugs, Shahid Beheshti University. The main composition which has been detected and identified are waxes, cholesterol, and natural fatty acids. Due to its sensitivity, speed, versatility, and ability to identify traces of compounds in a mixture, the GC-MS technique s application is a brilliant method for archaeological organic chemistry and can be applied to analyse any substance containing volatile organic compounds expected. In two samples of our collection, residual perfumes were extracted. \nFor this test, the containers were first washed with n-hexane solvent and the solution was transferred into the sampling dishes for transfer to the laboratory. On the day of sampling, the objects were selected from the samples which were photographed. Then, through a Pasteur pipette, about 2 ml of n-hexane was placed in the dishes and the material was washed by rotating and the extract transferred into the pipette and prepared for the analysis by evaporating of hexane. It should be noted that n-hexane solvent has no destructive effect on the objects and because of its high volatility, immediately it will be disappeared completely and there is no trace of it in the container. \nGas chromatography coupled with mass spectrometry (GC-MS) is a powerful tool for separation and identification of natural and chemical materials. In this method, after the initial preparation, the components of a mixture are injected into the device through a special syringe in the amount of half a microliter of the tested solution. The materials are separated based on the difference between the boiling point and interaction with the chromatographic column, will be entered into the Ionization Mass Spectrometry source, because of generating powerful electric and magnetic fields, the mixture’s components will be identified quantitatively and qualitatively based on their electrical charge to mass ratio (m/z). \nFor this analysis, 1 to 3 mg of the sample was taken and 1 ml of KOH hydroalcoholic solution (potash alcohol) was added and then subjected to alkaline hydrolysis at 60 ° C for 3 hours. After hydrolysis, the neutral organic components were extracted with n-hexane. Then, according to the internal standard, injection of the solution was analyzed in GC-MS. It was then interpreted based on comparisons of components and reference materials with library items and mass spectrum. In order to identify the type of fatty acid compositions, GC-MS equipped with a DB-5 column with a length of 30 m and an inner diameter of 0.25 mm and a thin layer thickness of 0.25 μm was used. The oven temperature was increased from 60 °C to 250 °C at velocity of 5 °C/min and was kept at 250 °C for 10 minutes. Helium carrier gas with a flow rate of 1.1 ml/min was used and 70-eV electrons was used for ionization and a mass range was from 43 to 456 amu. \nIn order to analyze the essential oil using gas chromatography coupled with mass spectrometry, the components were identified. The components and compounds were identified by the use of various parameters such as retention time (RT) and retention index (RI), study of mass spectrum and comparing the spectrum with standard compounds and basic data in the GC-MS database by Xcalibur Software. The relative percentage of each components of the essential oil was obtained according to the area under the curve in the GC \nBased on the chromatogram table, the following results were obtained: \nSample 1 (Table 1, Figure 1), the perfume flasks from the Arsacid era: the most important compounds identified in container No. 1 including the paraffin compounds, cholesterol (animal-based oils), vegetable oils, and fatty acids and waxes. Also, an important substance in the solution obtained from washing was flavonoid. It is a polyphenolic substance which is found in the extract obtained from the petals and pollen of plants. \nSample 2 (Table 2, Figure 2), a semi-thin blue glass container, probably from the Arsacid era: the most important components identified include an essential oil, wax and fatty acid. \nSample 3 (Table 3, Figure 3), a thin glass container probably from the Sassanid era: the most important compounds identified include fatty acids such as palmitic acid, stearic acid and linoleic acid. Such materials indicate that this container has been in contact with vegetable-base oils and 80% of the substances identified in this container are fatty acids. \nSample 4 (Table 4, Figure 4), a semi-thin glass container from the first centuries of the Islamic period: there are only paraffin materials such as wax and beeswax and do not contain any fatty acids. The most important substance in this sample is natural linalool, which is classified as a perfume. \nExample 5 (Table 5, Figure 5), the perfume flask with base from the first centuries of the Islamic period: the most important compounds identified are plant-based fatty acids, paraffin compounds or waxes, and phthalate compounds. \nAccording to the tests performed in two case studies (samples No. 2 and 4), aromatic substances and essential oils are present in the identified compounds. It shows that natural perfumes and essential oils can actually stay in the glass and the adsorption of glass is very high for keep of such materials. Except for sample No. 4, other samples contain a variety of fatty acids and proved that such glasses were used as preservative objects. Wax can be seen in all samples. Fats have been identified in various forms such as cholesterol (animal base oil), palmitic acids (plant base fats) and paraffinic substances.