Fragrances Sampling and Analysis

Transcription

1 Fragrances Sampling and Analysis Picture: Roman Kaiser at field work Picture source: Givaudan Marco Stöckli, Eva Gleißner

2 called , How do we perceive odours? Marco Stöckli, Eva Gleißner

3 Problem: Menthone from Natural Menthol Marco Stöckli, Eva Gleißner

4 Problem: (-)-Menthone from Natural (-)-Menthol Natural Menthol as starting material delivers green, mossy off-note after oxidation Artificial: no off-note originates from nature! Marco Stöckli, Eva Gleißner

5 Problem: Menthone from Natural Menthol Menthone m/z 350 mostly sufficient Isomenthone How to determine the off-note? Marco Stöckli, Eva Gleißner

6 Odorants? Volatiles! called: , Marco Stöckli, Eva Gleißner

7 Mathematical background: vapour pressure Ideal liquid mixture: evaporation of molecules into vapour phase basically only dependent on its vapour pressure Diluted systems, e.g. an odourant in a solvent interaction with solvent molecules is strongly influencing the pressure Problem: only valid for closed systems with ideal behaviour Correction factors (activity, fugacity) Raoult s law p i - partial pressure of substance i in the air above the mixture p i 0 -vapor pressure in pure state x i -concentration in the liquid mixture in terms of mole fraction Henry s law K- air/liquid partition coefficient (constant at fixed T for a given system C s K Cs- concentration in C g sample; p p i i p Cg- concentration in gas phase o i K x i x i Marco Stöckli, Eva Gleißner

8 Mathematical background: Odour value Odour value (OV): measurement of odour strength Example: OV vapour pressure[ng/l] threshold concentration [ng/l] Vanillin : OV= vs Ethyl Vanillin: OV= Ethyl Vanillin smells 2x as strong as Vanillin! Marco Stöckli, Eva Gleißner

9 Odour Threshold Lowest by human nose detectable concentration of an odorant Strongly varying between substances Example: 2,4,6-Trichloranisole: 2 ng/m 3 5 µg in olympic swimming pool (50m*25m*2m) are sufficient to be detected by your nose! Menthol: mg/m 3 Measurement: empirical Marco Stöckli, Eva Gleißner

10 Odour Threshold Lowest by human nose detectable concentration of an odorant Strongly varying between substances Example: 2,4,6-Trichloranisole: 2 ng/m 3 5 µg in olympic swimming pool (50m*25m*2m) are sufficient to be detected by your nose! Menthol: mg/m 3 Measurement: empirical Marco Stöckli, Eva Gleißner

11 Exemplary Threshold concentration test Pool: 50 people; measured: lowest personal detection level X: concentration in ppb at which odorant was perceived Y: # of people who were able to detect odorant at that concentration Day 1 Day Marco Stöckli, Eva Gleißner

12 Odourants? Volatiles! Method of choice: Gas chromatography coupled to mass spectrometry (e.g. QqQ-MS; m/z 350) Apolar column; most fragrances are hydrocarbons Two detector possibilities: FID (flame ionisation detector) Olfactometric (nose) called , Marco Stöckli, Eva Gleißner

13 Isolation Extraction Organic solvent (hexane, Et 2 O): submerge plants and agitate with solvent concrete, absolute (wax, essential oils..) Supercritical fluid (CO 2 as solvent) absolute, CO 2 extracts Distillation Steam (passed through raw material to drive out volatiles condensate is separated from aequous hydrosol) Dry/ destructive distillation (direct heating, no carrier solvent) Fractionation Distillation Expression Headspace sampling Marco Stöckli, Eva Gleißner

14 Headspace sampling Static sampling: sample in closed system (p, T= const.), until equilibrium vapour pressure is reached Dynamic sampling: air is passed through or over the sample: T= const., equilibrium will never be reached; slow stripping out of volatiles Marco Stöckli, Eva Gleißner

15 Headspace sampling Static sampling: sample in closed system (p, T= const.), until equilibrium vapour pressure is reached Dynamic sampling: air is passed through or over the sample: T= const., equilibrium will never be reached; slow stripping out of volatiles Marco Stöckli, Eva Gleißner

16 Headspace to GC? Direct injection possible + fully automated + high level of accuracy + reproducibility - unsatisfactory sensitivity to heavy volatiles (increase of sensitivity would require increase of vapour pressure risk of decomposition or chemical reactions) Marco Stöckli, Eva Gleißner

17 Headspace Trapping Sample Enrichment Cooling traps - unacceptable partial losses due to fog formation - interruption of vapour flow from water-rich material can lead to ice formation - heat desorption only if volatiles are thermostable Adsorption trap: porous polymer beads + Various sorbents tuneable properties + complete sample transfer without separation loss + simple device, easy to handle + aliquots of the sample extract can be used in different experiments - sometimes correct quantitation difficult if solvent peak is interfering with highly volatile compound Marco Stöckli, Eva Gleißner

18 Analysis (preparative or chiral) GC or HPLC for separation MS Scent identification by professional sniffer NMR Raman / IR / CD Comparison with reference library off-note: determined Update of reference library for future analyses Marco Stöckli, Eva Gleißner

19 Overview Natural product sample extraction of fragrance compounds distillation, headspace sampling/trapping Prepared sample separation and enrichment (preparative, chiral) GC, olfactory detection Analysis Separated fractions MS, IR, NMR, Raman, CD, reference compounds... Marco Stöckli, Eva Gleißner

20 Analysis of Flavour Compounds in Peppermint Chewing Gum (qualitatively) Sample preparation freeze drying (N 2(l) ), grinding extraction: solvent extraction by apolar (Et 2 O) and polar (EtOH) solvent Analysis HPLC-MS (for not sufficiently volatile substances) GC-MS with FID and Sniff detection Interpretation of results Comparison to: - sniffing database (odour profile) - MS database Marco Stöckli, Eva Gleißner