Electronic Nose Applications in the Fragrance Industry

1. Electronic Nose Applications in the Fragrance Industry Rachel M. Bukowski, Ph.D.

2. Outline • Presentation Goals and Objective • Background • Current E-Nose Technology • Evolution and present applications • Molecular Imprinting Technology • Xerogels • Fluorescence-based sensors • Previous results • Data Acquisition and Analysis Methods • Applicability to Fragrance Industry • Conclusions

3. Presentation Goals and Objective • Definition of an E-nose • Review of current available technologies • Benefits of fluorescence-based MIPs • How can a fluorescence-based MIP E-nose platform be applied to the fragrance industry? • Benefits of E-nose over human sensory evaluation

4. What is an E-Nose? • Electronic nose: a device intended to detect, identify and quantify odors and flavors • Consists of three major parts: • Sample delivery system: generates headspace and injects sample into detection system • Detection system: react to presence of VOCs, undergo chemical change and produce useable signal • Computing system: combines the responses of individual sensor elements and generated sample information

5. Background • Optically-based electronic noses are most common (vapor phase) • Generally consist of an array of sensors • Wealth of research and experience for a diverse set of applications • Although it is difficult to copy the mammalian nose, a sensor array system most closely resembles it • Current products consist of combinations of various technologies

6. Current Applications • Food/beverage safety and security • Food quality • Olive oil • Wine • Coffee/Tea • Homeland security • Explosives detection • Bio/Chem WMD detection • Drug detection • Medical screening and diagnostics

7. Array-Based E-Noses Signal Raw data acquisition Sample Feature extraction and pattern recognition [Analyte] Sensor Array - Generally, combinations of signals from several different sensor elements allow the user to obtain the identity of a sample

8. Sample X Sample Y Optical Sensor Systems • Optical sensor: sensor based on the emission of photons, which are detected and converted into a useable signal • Most closely resemble the sensor array systems • Various methods can be exploited • Changes in photon properties • High number of available technologies for light sources and detectors

9. Other Systems • Mass Spectrometry • Ion Mobility Spectrometry • Gas Chromatography • Infrared Spectroscopy • These technologies, although preferable to use in many applications, generally fall short of the advantages offered by an optically-based detection system.

10. Current Products • Alpha MOS Gemini • Smell and VOC analyzer • Automated headspace sampling • 6 pre-selected sensors according to customer applications • Chemsensing Colorimetric Array • Sensor array of chemically reactive dyes • Sensitive to presence of VOCs and changes in VOC concentration • Application-specific arrays can be developed

11. Current Products • GSG MOSES II • Takes a “fingerprint” of a particular odor without separating the individual components • Useful for objective odor comparison • Modular system design • Sacmi EOS Ambiente • Uses electrochemical sensors to take a fingerprint of an odor and identify its concentration • Initially developed to measure concentrations of environmental and industrial plant malodours • Highly sensitive and robust

12. Transducer Recognition Chemistry

13. ≡Si = Si Xerogel Technology • Hydrolysis: • Si(OR)4 + nH2O  Si(OR)4-n(OH)n + nROH • Condensation: • ≡Si-OH + HO-Si≡≡Si-O-Si≡ + H2O • ≡Si-OR + HO-Si≡≡Si-O-Si≡ + ROH • Polycondensation: • x(≡Si-O-Si≡)  (≡Si-O-Si≡)x

14. The sol-gel process applied to analyte sensing: Sensor elements (fluorophores, dyes, indicators, proteins, etc.) introduced into sol-gel matrix. Sensor element is entrapped within the xerogel matrix. Sensor element maintains its functionality and accessibility. 1 2 3 4 Xerogels as Sensor Platforms Anal. Chem. 1994, 66, 1120A

15. Molecular Imprinting Technology • Modeled after enzyme-like recognition of molecules by receptor sites • “Lock-and-key” • Involves using the target analyte (TA) or derivative of the TA to create recognition sites within a porous polymer matrix • Since the TA is used to create these sites, they are highly selective towards the analyte of interest

16. Fluorescence-Based MIPs • Involves the installation of a chemically responsive fluorophore at or near the templated site • Upon binding of TA, change in fluorescent properties is observed and quantified • Emission maxima, emission wavelength, fluorescent lifetime, etc. • Highly selective • More sensitive than electrochemical methods

17. Simplified Schematic: Fluorescence-Based MIP

18. Previous Results: Edminston et. Al. • Drawback to molecular imprinting techniques: • Molecules had to be small with at least two polar functional groups to create templated sites • Edminston created a MIP for fluorene • High sensitivity and selectivity • Irreversible • Opens the door for MIPs for aroma chemicals

19. Previous Results:Bright et. Al. • Created first fluorescence-based MIP with selective reporter installation • Fluorescent reporter molecule is selectively installed in the templated site • Upon binding, target analyte is very close to reporter molecule • Higher sensitivity to target analyte achieved

20. Applications to the Fragrance Industry • Strong drive to apply E-nose technology to olfaction • Toxic nature of some aroma chemicals • Sensitization of the perfumer • Odor fatigue • Irritation • Current technology is time-consuming and costly • ie: human test panels

21. Malodour Detection and Identification • Common malodorous molecules include: • Indole, skatole, methanethiol: toilet and animal malodours • Piperidine, morpholine: urine • Pyridine, triethylamine, diamines: kitchen and garbage odors (fish) • H2S, nicotine, pyrroles: cigarette smoke • Short chain fatty acids: axilla malodours • Malodours are small molecules with polar functional groups • Ideal for molecular imprinting applications

22. Possible Detection Scheme for Example Malodour React with functional monomers Lauric Acid Entrap in polymer Remove TA Selectively install reporter Reintroduce TA Change in signal from reporter

23. Malodour Counteractants • Various approaches have been used to counteract malodors: • Masking via a more pleasant odor • Blocking malodour olfactory receptors • Elimination or absorption of malodour via chemical reaction • Association and complexation • Physical absorption of malodour into other materials • Malodour suppression • Malodour formation inhibition

24. Counteractant Effectiveness • Electronic noses can be used to measure malodor counteractant effectiveness • MIPs could provide an excellent platform • Robust • Selective • Sensitive • Must be application-specific • Example 1: determine the effectiveness of a malodour-eliminating candle on typical household odors (skatole, indole, amines) • Example 2: quantify the effectiveness of deodorant on axillary malodour (short chain fatty acids)

25. Counteractant Effectiveness (II) • Direct measurement • Measure the amount of malodour present prior to testing, at various points during testing, and at conclusion of testing • Indirect measurement • In the case of counteractants reacting with malodour to eliminate malodour molecules, measure the rate of decay of counteractant molecules

26. - H2S - CH3SH - Allyl mercaptan - Methanethiol - Dimethyl sulfide Sample Platform Volitile Sulfur Compound Sensor No counteractant 5 min. after counteractant introduced 30 min. after counteractant introduced

27. Conclusions • There is a need for a robust, consistent and economically practical electronic nose system in the fragrance industry • Quality Assurance • Research and Development • The electronic nose system cannot be a “black box” • Must be application specific • Malodour counteractant effectiveness assessment presents a feasible application for electronic nose technology

28. Acknowledgements • Maesa Home • Dr. Ron Newman (Maesa Home) • Jill Belasco (Maesa Home) • Steve Herman (Fairleigh Dickinson University) • Udo Weimar (University of Tuebingen )