Лако-красочные материалы — производство

To answer the enquiry about the fragrance of muguet (lily of the valley), it would be most appropriate to use headspace analysis. Some natural materials, especially flowers and fruits, are often not available in sufficient quantity for even a laboratory extraction, while others yield an extract that does not reflect the fragrance of the flower. It is for these flowers that headspace analysis has great advantages. Using the non­destructive headspace trapping technique and light, portable sampling equipment, the fragrance of any flower, fruit or other natural source can

be collected from the field (or greenhouse) and returned to the labora­tory for analysis without disturbing the flower or plant (Figure 12.1).

Muguet is a popular garden flower, so finding plants could be as easy as visiting a garden centre or asking friends. Once some suitable flowers have been found, the headspace equipment is taken to the garden, the special glass bell jar carefully set up over the flowers and the headspace collected on several different types of traps. First, about four small thermal desorption traps are used, in which enough sample can be collected in a few minutes, then some larger-capacity solvent desorp­tion traps are left in place for about 8 hours each. This ensures that a representative sample of the odour is collected and provides appro­priate samples for the different analytical techniques to be used.

Back in the laboratory, the thermal desorption traps are analysed by GC-MS and GC-FID (flame ionization detector), by which means the major components can be quantified and identified. This reveals that the major components of the headspace of muguet are benzyl alcohol, citronellol and citronellyl acetate, and that the minor components with important odours are myrcene, /nmy-ocimene, trans-rose oxide, and 6- methylhept-5-en-2-one. Usually, many compounds in the sample cannot be identified definitively by GC-MS. Therefore, the larger traps are desorbed with diethyl ether or a similar solvent, and the resulting solution analysed by GC-sniffmg to determine which compo­nents had a muguet odour. The solution is also concentrated and analysed by GC-MS to investigate the trace components. The use of nitrogen — and sulfur-specific detectors facilitates the identification of nitrogen — or sulfur-containing compounds, such as indole (1) and benzyl cyanide (2), which have, indeed, been found in muguet.

The results passed on to the perfumer would include the name of the compound, its relative proportion in the headspace sample and an indication of the odour intensity of the material. The perfumer can then select the important odour materials and combine them in an accord to re-create the scent of the flower.

To complete an analysis of fresh, tropical fruit, we took advantage of the Quest office in Indonesia and asked an employee who was travelling to Indonesia to take the equipment, since it is easily portable. With the help of the local perfumers the equipment was set up to capture the fragrance of the best smelling fruit in a local market. The traps containing the samples were sent back to the laboratory, where the analysis revealed exactly which compounds contributed to the real freshness of the fruit. The GC-MS and GC-sniffing results showed that methyl 3-methylbutanoate, methyl 3-methylpentanoate, methyl 3- methylpent-2-enoate, and methyl rrans-hex-2-enoate are found in these fruits and contribute significantly to their odour. By providing the results of these analyses to the perfumers, we are able to help them understand the construction of the natural fragrances and re-create the original odour more closely.

Modern natural product analysis reveals both the chemical composi­tion of new oils or flower scents and the identity of novel fragrant molecules that may become new perfumery ingredients in the future. It is chemical detective work to solve the mysteries of nature’s fragrances that have evolved over the millennia.