Model Perfumes Research Articles

Fixative effect of 2‐oxo‐2‐phenylacetates in fine fragrance and eau‐de‐toilette applications

AbstractThe evaporation of fragrances with volatilities spanning over several orders of magnitude results in a shift of the olfactive impression of a perfume over time. Fixatives have repeatedly been used to slow fragrance evaporation in multiple perfumery applications. We developed a simple and reliable method to measure the evaporation kinetics of individual fragrances in a model perfume and analysed the fixative effect of 2‐oxo‐2‐phenylacetates (α‐ketoesters) on perfume evaporation. 2‐Oxo‐2‐phenylacetates, some of which have been described as light‐sensitive profragrances, are commercially available or readily prepared by esterification or transesterification of commercial starting materials. (−)‐Menthyl 2‐oxo‐2‐phenylacetate afforded single crystals that were suitable for X‐ray crystal structure analysis. 2‐Oxo‐2‐phenylacetates were found to have a fixative effect on the evaporation of fragrances with volatilities below 5000 μg L−1 in fine fragrance and eau‐de‐toilette applications. The molecular structure of the compound rather than its molecular weight had an impact on the fixative effect to some extent.

Effect of pH adjustment and ratio of oppositely charged polymers on the mechanistic performance and sustained release of volatile perfume in interpolyelectrolyte complex microcapsules

In this study, volatile perfume was encapsulated in microcapsules (MCs) via interpolyelectrolyte complexes (IPECs) of oppositely charged polymers, with high encapsulation efficiency, to be delivered in a sustained manner. Positively charged chitosan (CTS) and negatively charged Eudragit® S100 (ES100) were used as eco-friendly biopolymers. Limonene (LMN) was selected as the model perfume. First, the solution of LMN in ethyl acetate and poloxamer 407 (POX407) in acidic solution was emulsified using ultrasonication. CTS and ES100 were added in that particular order to form o/w emulsion. LMN-loaded microcapsules (LMN-MCs) were prepared by adjusting the pH and freeze-drying for solidification. The electrostatic interactions of CTS and ES100 to form IPECs were highly dependent on pH, changing in the microscopic images of emulsion droplets and zeta potential. The NH3+ group of CTS and the COO– group of ES100 caused the electrostatic interactions at a specific pH. The formation mechanism of LMN-MCs was successfully validated using instrumental analysis, charge density, and energy dispersive X-ray spectrometer (EDS) mapping. Encapsulation efficiency, loading content, and release rates of LMN-MCs varied according to the ratios of CTS and ES100, demonstrating optimal performance at a 1:1 ratio. The current LMN-MCs could provide a simple manufacturing process with high performance in terms of encapsulation efficiency (>94%), drug loading, yield and sustained release of volatile perfume for 120 h.

Two-membrane air fresheners for continuous non-energized perfume delivery

We have developed two-membrane air fresheners for continuous non-energized air freshener perfume delivery with significantly superior delivery consistency over a conventional membrane air freshener. In this study, a model perfume is used to investigate the conventional air freshener as functions of temperature and air velocity. The release rate of the conventional air freshener varies greatly from its initial use to its end-of-life under a fixed ambient condition. In order to regulate the evaporation rates of the volatile compounds, the new air freshener consisting of an inner membrane and an outer membrane. The outer membrane is used as the regulation membrane to create a vapor reservoir between the inner wet membrane and the outer membrane so that the vapor generated from the inner membrane can be regulated. Comparing the conventional air freshener to the new air freshener, the outer membrane impregnated with polyethylene glycol (PEG) shows significantly better consistency of perfume delivery rates under different air velocities and temperatures. In addition, a model has been employed to predict the perfume release from the conventional air freshener. The perfume release from the newly developed air fresheners is regulated by vapor transport through the outer membrane which may be predicted through the Knudsen flow or solution diffusion model.

Membranes for Continuous Nonenergized Air Freshener Perfume Delivery

Membrane-based liquid air fresheners are attracting significant market interest because of their small size and ability to allow continuous delivery of perfume compounds without the need of external energy sources. However, the air freshener membranes that enable the nonenergized delivery are rarely reported in the literature except in patents. For the first time, we investigated a commercial air freshener membrane systematically to provide thorough characterizations of the membrane materials, morphology, and pore information. The interaction between a model perfume containing four compounds and the membrane was also studied through liquid wetting and contact angle measurements. Long-term tests to track the air freshener revealed that the perfume release rate was dependent on the perfume reservoir composition in a controlled external environment. Lastly, perfume transport through the membrane was investigated for the correlation of membrane properties and liquid flux through the membrane. This pioneering ...

Probing the surface of aqueous surfactant-perfume mixed solutions during perfume evaporation

The rate of release or evaporation of perfume molecules from surfaces is a key factor in determining the impact of the perfume in a range of applications relating to home and personal care products. For mixtures of the anionic surfactant sodium dodecylsulfate and the model perfume linalool the rate of change of adsorption with time due to forced air flow over a fixed headspace was evaluated using neutron reflectivity over a period of up to ∼250min. The measurements were made in the limit of the high flow rates where the evaporation is independent of the air flow rate. The amount of perfume at the interface decreases with time, and this occurs at a faster rate as the initial amount of perfume in solution is decreased. The variation of the perfume adsorption with time for different surfactant/perfume solution compositions illustrates the increasing importance of diffusion to the surface as the perfume concentration in solution decreases.

Spatial Modeling and Mapping of Tuberculosis Using Bayesian Hierarchical Approaches

Global spread of infectious disease threatens the well-being of human, domestic, and wildlife health. A proper understanding of global distribution of these diseases is an important part of disease management and policy making. However, data are subject to complexities by heterogeneity across host classes. The use of frequentist methods in biostatistics and epidemiology is common and is therefore extensively utilized in answering varied research questions. In this paper, we applied the hierarchical Bayesian approach to study the spatial distribution of tuberculosis in Kenya. The focus was to identify best fitting model for modeling TB relative risk in Kenya. The Markov Chain Monte Carlo (MCMC) method via WinBUGS and R packages was used for simulations. The Deviance Information Criterion (DIC) proposed by [1] was used for models comparison and selection. Among the models considered, unstructured heterogeneity model perfumes better in terms of modeling and mapping TB RR in Kenya. Variation in TB risk is observed among Kenya counties and clustering among counties with high TB Relative Risk (RR). HIV prevalence is identified as the dominant determinant of TB. We find clustering and heterogeneity of risk among high rate counties. Although the approaches are less than ideal, we hope that our formulations provide a useful stepping stone in the development of spatial methodology for the statistical analysis of risk from TB in Kenya.

Manipulating perfume delivery to the interface using polymer–surfactant interactions

Enhanced delivery of perfumes to interfaces is an important element of their effectiveness in a range of home and personal care products. The role of polyelectrolyte–surfactant mixtures to promote perfume adsorption at interfaces is explored here. Neutron reflectivity, NR, was used to quantify the adsorption of the model perfumes phenylethanol, PE, and linalool, LL, at the air–water interface in the presence of the anionic surfactant sodium dodecylsulfate, SDS, and the cationic polyelectrolytes, poly(dimethyldiallyl ammonium chloride), polydmdaac, and poly(ethyleneimine), PEI. The strong SDS–polydmdaac interaction dominates the surface adsorption in SDS–polymer–perfume (PE, LL) mixtures, such that the PE and LL adsorption is greatly suppressed. For PEI–SDS–perfume mixtures the PEI–LL interaction competes with the SDS–PEI interaction at all pH at the surface and significant LL adsorption occurs, whereas for PE the PEI–SDS interaction dominates and the PE adsorption is greatly reduced. The use of the strong surface polyelectrolyte–ionic surfactant interaction to manipulate perfume adsorption at the air–water interface has been demonstrated. In particular the results show how the competition between polyelectrolyte, surfactant and perfume interactions at the surface and in solution affect the partitioning of perfumes to the surface

Enhanced perfume surface delivery to interfaces using surfactant surface multilayer structures

Enhanced surface delivery and retention of perfumes at interfaces are the keys to their more effective and efficient deployment in a wide range of home and personal care related formulations. It has been previously demonstrated that the addition of multivalent counterions, notably Ca2+, induces multilayer adsorption at the air–water interface for the anionic surfactant, sodium dodecyl-6-benzenesulfonate, LAS-6. Neutron reflectivity, NR, measurements are reported here which demonstrate that such surfactant surface multilayer structures are a potentially promising vehicle for enhanced delivery of perfumes to interfaces. The data show that the incorporation of the model perfumes, phenylethanol, PE, and linalool, LL, into the surface multilayer structure formed by LAS-6/Ca2+ results in the surface structures being retained up to relatively high perfume mole fractions. Furthermore the amount of perfume at the surface is enhanced by at least an order of magnitude, compared to that co-adsorbed with a surfactant monolayer.

Electrostatic‐spray ionization mass spectrometry sniffing for perfume fingerprinting

The perfume market is growing significantly, and it is easy to find imitative fragrances of probably all types of perfume. Such imitative fragrances are usually of lower quality than the authentic ones, creating a possible threat for perfume companies. Therefore, it is important to develop efficient chemical analysis techniques to screen rapidly perfume samples. Electrostatic-spray ionization (ESTASI) was used to analyze directly samples sprayed or deposited on different types of paper. A linear ion trap mass spectrometer was used to detect the ions produced by ESTASI with a modified extended transfer capillary for 'sniffing' ions from the paper. Several commercial perfumes and a model perfume were analyzed by ESTASI-sniffing. The results obtained by paper ESTASI-MS of commercial fragrances were compared with those obtained from ESI-MS. In addition, a commercial fragrance was first nebulized on the hand and then soaked up by blotting paper, which was afterwards placed on an insulating plate for ESTASI-MS analysis. Analysis of peptides and proteins was also performed to show that the paper ESTASI-MS could be used for samples with very different molecular masses. Paper ESTASI-MS yields a rapid fingerprinting characterization of perfume fragrances, avoiding time-consuming sample-preparation steps, and thereby performing a rapid screening in a few seconds.

The impact of alkyl sulfate surfactant geometry and electrolyte on the co-adsorption of anionic surfactants with model perfumes at the air–solution interface

The impact of surfactant geometry and electrolyte on the co-adsorption of anionic surfactants and model perfumes at the air–solution interface has been studied by neutron reflectivity. The more hydrophobic perfume linalool, competes more favourably for the surface with sodium dodecylsulfate than was previously reported for the anionic surfactant, sodium dodecyl 6-benzenesulfonate. Due to an increase in surface activity of the sodium dodecylsulfate, the addition of electrolyte results in a reduction in the linalool adsorption. Changing the alkyl chain length affects the relative adsorption of linalool and surfactant at the interface. Similar measurements for the different alkyl sulfates and with electrolyte with the more hydrophilic perfume phenyl ethanol, reveal broadly similar trends. Although the relative adsorption of phenyl ethanol with sodium dodecylsulfate is substantially enhanced compared to sodium dodecyl-6-benzenesulfonate the effects are not as significant as was observed with linalool. The variations with alkyl chain geometry show the importance of the hydrophobic interaction between the perfume and surfactant and changes in the packing constraints on the relative adsorption. The results highlight the importance of the specific interaction between the surfactant and perfume, and the surfactant and perfume geometries on the relative adsorption at the interface.

Impact of Model Perfume Molecules on the Self-Assembly of Anionic Surfactant Sodium Dodecyl 6-Benzene Sulfonate

The impact of two model perfumes with differing degrees of hydrophobicity/hydrophilicity, linalool (LL) and phenylethanol (PE), on the solution structure of anionic surfactant sodium dodecyl 6-benzene sulfonate, LAS-6, has been studied by small angle neutron scattering, SANS. For both types of perfume molecules, complex phase behavior is observed. The phase behavior depends upon the concentration, surfactant/perfume composition, and type of perfume. The more hydrophilic perfume PE promotes the formation of more highly curved structures. At relatively low surfactant concentrations, small globular micelles, L1, are formed. These become perfume droplets, L(sm), stabilized by the surfactant at much higher perfume solution compositions. At higher surfactant concentrations, the tendency of LAS-6 to form more planar structures is evident. The more hydrophobic linalool promotes the formation of more planar structures. Combined with the greater tendency of LAS-6 to form planar structures, this results in the planar structures dominating the phase behavior for the LAS-6/linalool mixtures. For the LAS-6/linalool mixture, the self-assembly is in the form of micelles only at the lowest surfactant and perfume concentrations. Over most of the concentration-composition space explored, the structures are predominantly lamellar, L(α), or vesicle, L(v), or in the form of a lamellar/micellar coexistence. At low and intermediate amounts of LL, a significantly different structure is observed, and the aggregates are in the form of small, relatively monodisperse vesicles (i.e., nanovesicles), L(sv).

Adsorption of Model Perfumes at the Air–Solution Interface by Coadsorption with an Anionic Surfactant

The adsorption of the model perfumes phenyl ethanol, PE, and linalool, LL, at the air-solution interface by coadsorption with the anionic surfactant sodium dodecyl 6-benezene sulfonate, LAS-6, has been studied primarily by neutron reflectivity, NR. The variation in the mixed surface adsorption with solution composition is highly nonideal, and the more hydrophobic LL is more surface active. At a LAS-6 concentration of 0.5 mM the adsorption of PE and LL is broadly similar but with the LL systematically more surface active, and at 2 mM the LL completes more effectively for the surface than the PE. The variation in surface composition with solution composition and concentration reflect the greater hydrophobicity and hence surface activity of LL, and the greater solubility of PE in aqueous solution. Changing the geometry of the LAS isomer, from the symmetrical LAS-6 geometry to the more asymmetrical LAS-4, results in the LL competing more effectively for the surface due to changes in the packing constraints associated with the hydrophobic region. The results provide insights into the factors that affect coadsorption that can be more broadly applied to the surface delivery of a wide range of molecules other than perfumes.

Impact of Model Perfumes on Surfactant and Mixed Surfactant Self-Assembly

The impact of some model perfumes on surfactant self-assembly has been investigated, using small-angle neutron scattering. A range of different model perfumes, with differing degrees of hydrophilicity/hydrophobicity, have been explored, and in order of increasing hydrophobicity include phenyl ethanol (PE), rose oxide (RO), limonene (LM), linalool (LL), and dihydrogen mercenol (DHM). The effect of their solubilization on the nonionic surfactant micelles of dodecaethylene monododecyl ether (C12EO12) and on the mixed surfactant aggregates of C12EO12 and the cationic dialkyl chain surfactant dihexadecyl dimethyl ammonium bromide (DHDAB) has been quantified. For PE and LL the effect of their solubilization on the micelle, mixed micelle/lamellar and lamellar regimes of the C12EO12/DHDAB mixtures, has also been determined. For the C12EO12 and mixed DHDAB/C12EO12 micelles PE is solubilized predominantly at the hydrophilic/hydrophobic interface, whereas the more hydrophobic perfumes, from RO to DHM, are solubilized predominantly in the hydrophobic core of the micelles. For the C12EO12 micelles, with increasing perfume concentration, the more hydrophobic perfumes (RO to DHM) promote micellar growth. Relatively modest growth is observed for RO and LM, whereas substantial growth is observed for LL and DHM. In contrast, for the addition of PE the C12EO12 micelles remain as relatively small globular micelles, with no significant growth. For the C12EO12/DHDAB mixed micelles, the pattern of behavior with the addition of perfume is broadly similar, except that the micellar growth with increasing perfume concentration for the more hydrophobic perfumes is less pronounced. In the Lbeta (Lv) region of the DHDAB-rich C12EO12/DHDAB phase diagram, the addition of PE results in a less structured (less rigid) lamellar phase, and ultimately a shift toward a structure more consistent with a sponge or bicontinuous phase. In the mixed L1/Lbeta region of the phase diagram PE induces a slight shift in the coexistence from Lbeta toward L1. The addition of LL to the Lbeta (Lv) region of the DHDAB-rich C12EO12/DHDAB phase diagram also results in a reduction in the lamellar structure (less rigid lamellae), and a shift toward a structure more consistent with a sponge or bicontinuous phase, or a coexisting phase of small vesicles. For the mixed L1/Lbeta region of the phase diagram LL induces a shift toward a greater L beta component.

Phototumorigenesis studies of 5-methoxypsoralen in bergamot oil: Evaluation and modification of risk of human use in an albino mouse skin model

The skin of the female hairless albino mouse (Skh 1) was used to study the enhancement of solar simulated radiation (SSR) tumorigenesis by 5-methoxypsoralen (5-MOP) in model perfumes that contain bergamot oil. This work was done in association with yeast mutagenicity studies and human skin phototoxicity studies. Analyses of time-to-onset of tumour observation with 5-MOP at 0, 5, 15 and 50 ppm show a highly significant 5-MOP dose effect and the data indicate that 5-MOP has phototumorigenic potential even at 5 ppm. The addition of 0.5% UVB and 0.5% UVA sunscreens significantly reduces the tumorigenicity associated with the vehicle ( i.e. 5-MOP at 0 ppm) and 5-MOP at all concentrations. Pairwise comparisons of 5-MOP (at 5 or 15 ppm) plus sunscreens with vehicle plus sunscreens show that the sunscreens afford total protection at the lower 5-MOP concentrations. Additional studies show that a 5–6 h delay between 5-MOP application and SSR exposure defers the time-to-onset of tumours as does intermittent 5-MOP and SSR treatment. A comparison of 5-MOP at 50 ppm in bergamot oil with 5-MOP at 50 ppm prepared from pure 5-MOP crystals shows identical results, indicating that the active phototumorigenic agent in bergamot oil is 5-MOP and not other related compounds, which may be present at greater concentrations. Analyses of tumour histology at death show, in general, similar patterns of malignancy for all groups. Thus although it is possible to delay tumorigenesis by various strategies, the tumours that eventually develop are just as likely to be malignant, if not more so, when compared with non-delayed groups.

Phototoxic properties of perfumes containing bergamot oil on human skin: Photoprotective effect of UVA and UVB sunscreens

As part of an international cooperative study of the photophysical, photomutagenic and photocarcinogenic properties of bergamot oil and the effect of UVA and UVB sunscreens, the phototoxic properties of model perfumes containing 5, 15 and 50 ppm 5-methoxypsoralen (5-MOP) in bergamot oil with and without a suncreen have been investigated on human skin. It has been confirmed that the photosensitivity of human skin is maximal 2 h after perfume application. Interestingly the addition of a UVA sunscreen is more efficient for decreasing the phototoxic properties of bergamot oil than is a UVB suncreen. The addition of sunscreens in a model perfume containing 50 ppm 5-MOP in bergamot oil can reduce the phototoxic properties of this perfume to a toxicity equivalent to that produced by the application of a model perfume containing 15 ppm 5-MOP without sunscreens. However, despite their promising protective effect in vitro, UVB and UVA sunscreens at low concentration (0.5%–1%) in perfumes cannot suppress the phototoxicity of bergamot oil on human skin