Photochromic and luminescence properties of isomeric forms of the hydronaphthyl radicals

The optical properties of the hydronaphthyl radicals produced upon radiolysis and photolysis of rigid naphthalene solutions in boric acid at 300 K and alcohol, ether and methylcyclohexane at 77 K were investigated. The ESR, absorption and luminescence spectra of the two different isomeric forms of hydronaphthyl radicals have been observed. The estimated values of the lowest electronic transition in α- and β-hydronaphthyl radicals are, respectively: E_α = 2.42 ± 0.03 eV, E_β = 2.66 ± 0.05 eV. It has been found that a reversible photo-induced interconversion between two hydroradicals takes place as well as a dark conversion from the β- to the α-isomer. Analogous photochromic behaviour of the absorption bands of biphenyl, phenanthrene, chrysene and fluorene rigid solutions have also been identified as reversible interconversion between isomeric hydroradicals.     

On the odour shift from bitter almond odour to cinnamic-floral notes

Summary The structural differences between bitter almond odour substances and molecules with cinnamic or floral odour notes were investigated by comparison of a number of compounds with various synthetic modifications. An attempt was made to find a systematic principle for the change of the odour notes.Dedicated to Prof. Dr. K. Schlögl on the occasion of his 70^th anniversary     

Immunoanalyser for Candida albicans based on the human olfactory function

A novel immunoanalyser system based on the human olfactory function has been developed and successfully applied to immunoassay for Candida albicans. After the immunoreaction of C. albicans and its antibody (IgG), the reaction solution was added gently to a phosphate buffer solution in a conical reaction vessel. The buffer in this vessel was previously saturated with Versalide (1,1,4,4-tetramethyl-6-ethyl-7-acetyl-l,2,3,4-tetrahydronaphthalene) as an odour marker and its odour was sensed by the nose of a tester immediately above the vessel. The addition of a sufficient amount of the reaction solution caused the disappearance of the odour. As the buffer level was raised and the surface area increased, the odour appeared again. A relationship was obtained between the change in buffer level until the odour reappeared and the concentration of C. albicans in the reaction solution. Based on this principle, C. albicans could be determined in the range 10²– 10⁵ cells ml^?1.     

Development and validation of an SPE-GC-MS/MS taste and odour method for analysis in surface water

The goal of this research was to develop a robust method for taste and odour compounds that can be implemented by laboratories with mass spectrometers lacking chemical ionisation capabilities or specialised sample introduction hardware that are commonly used for taste and odour methods. Development, optimisation, and validation of a solid-phase extraction method using liquid injection and gas chromatography – tandem mass spectrometry detection with electron impact ionisation are described. Camphor was used as an internal standard, and through method development and robustness testing it was shown to extract similarly to other taste and odour compounds, making it a cost-effective alternative to deuterated analogs. The instrumental parameters and extraction procedure were fully optimised prior to assessing the method’s linearity, precision, and accuracy. Using a 2000-fold enrichment factor, method recoveries for priority compounds geosmin (GSM) and 2-methylisoborneol (2-MIB) were >90%. Excellent linearity was obtained from the reportable detection limits up to 200 ng L^?1 and precision %relative standard deviations were 8.5% and 10.9% for GSM and 2-MIB, respectively. Detection limits of 0.9 and 5.5 ng L^?1 for GSM and 2-MIB respectively were deemed fit-for-purpose in comparison to their odour thresholds. Validation data were also obtained for other commonly analysed taste and odour compounds, including 2,4,6-trichloroanisole, 2-isopropyl-3-methoxypyrazine, and 2-isobutyl-3-methoxypyrazine. The validated method was used to screen surface waters in Nova Scotia, Canada for presence of taste and odour compounds, highlighting the presence of GSM on the east coast of Canada.     

Synthesen in der Isocamphanreihe, 37. Mitt.: Analytik und Geruch isomerer cyclischer Acetale mit Norbornanstruktur

Summary The separation of a complex mixture of a fragrance material into its isomers is described. Instead of an odour of sandalwood the mixture exhibits mainly a mushroom odour but also the pure isomers show other organoleptic qualities. The structure of two isomers could be ascertained mainly by¹³C- and¹H-NMR-measurements, for two isomers a structure proposal is given.

Herrn Prof. Dr. Wilhelm Fleischhacker mit den besten Wünschen zum 60. Geburtstag gewidmet     

Complementary use of GCxGC–TOF–MS and statistics for differentiation of variety in biosolid samples

Formation of biosolid cakes, which are one of the main wastes generated in wastewater treatment plants, is connected with emission of many hazardous chemical compounds, including odoriferous ones. To optimize particular processes of biosolid cake processing, it is necessary to assess chemical composition of the gas mixtures containing the compounds released from the cakes. The paper proposes application of two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC–TOF–MS) to identification of the compounds released from four main types of biosolid cakes and to quantitative determination of the markers characteristic for particular types of cake. Based on the analysis of variance, the following compounds, which could be potential markers of the investigated biosolid cakes, were selected: 1-propanol, 2-hexanone, toluene, o-xylene, p-xylene, and organosulfur compounds (methanethiol, ethanethiol, dimethyl sulfide, dimethyl disulfide, and diethyl disulfide). Theoretical odour concentrations of four investigated types of biosolid cakes were determined, based on measured concentrations and olfactory thresholds of the aforementioned compounds. The highest concentration was revealed for a primary cake (634 ou/m³), whereas the lowest concentration was found for an excess cake (136 ou/m³) (ou/m³—odour unit per m³; one odour unit is equivalent to collective odour threshold of odorants mixture present in 1 m³). The proposed methodology allows preliminary evaluation of the odour nuisance markers connected with formation of the biosolid cakes, without a need for quantitative analysis of all determined compounds.

Graphical abstract

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Asymmetric catalysis in fragrance chemistry: a new synthetic approach to enantiopure Phenoxanol®, Citralis® and Citralis Nitrile®

A new approach to the synthesis of the single stereomers of the fragrances Phenoxanol^®, Citralis^® and Citralis Nitrile^® is reported. The key step of the synthesis is the asymmetric hydrogenation of (Z)- or (E)-3-methyl-5-phenyl-pent-2-en-1-ol, which leads to the single enantiomers of Phenoxanol^® from which both enantiomers of Citralis^® are obtained by oxidation. Treatment of these compounds with hydroxylamine finally led to Citralis Nitrile^® without any loss of enantiopurity. The odour profiles of the single enantiomers of these fragrances are reported as well.     

Chemical, sensory and microbiological changes of gamma irradiated coconut cream powder

A study was carried out to determine optimum decontamination dose for a locally manufactured coconut cream powder. Samples were gamma irradiated (0–15 kGy) and ageing process was achieved using GEER oven at 60 °C for 7 days, which is equivalent to one-year storage at room temperature. Iodine value (IV), ranging from 4.8 to 6.4, was not affected by radiation doses and storage, however peroxide value and thiobarbituric acid (TBA) generally increased with radiation doses. In most samples, peroxide value (meq/kg) reduced after storage, whilst the TBA (mg malonaldehyde/kg), indicator for product quality, slightly increased. The sensory evaluation conducted using 25 taste panellists indicated that scores on odour, creamy taste and overall acceptance for all irradiated samples at more than 5 kGy were significantly lower (P<0.05) than the control. However, the panellists could not detect any significant differences among the irradiation doses (P>0.05). All stored products were significantly different in colour, creamy taste, odour and overall acceptance (P<0.05) when compared to the non-stored non-irradiated control. Microbiological count of the samples prior to irradiation was in the range of 1×10²–1.7×10³ cfu/g with no detection of Salmonella sp. and Escherichia coli. No microbial colonies were detected after irradiation. Based on the TBA and overall sensory acceptance, gamma irradiation of 5 kGy was found to be the optimum dose and lower doses can be considered to decontaminate coconut cream powder.     

Correlations between odour activity and the structural modifications of acrylates

Acrylates (acrylic esters) are versatile monomers that are widely used in polymer formulations because of their highly reactive α,β-unsaturated carboxyl structure. Commonly used acrylates such as butyl acrylate are known to emit a strong unpleasant odour, and the monomers are therefore potential off-odorants in acrylic polymers. However, up to now, the odour properties of structurally related acrylic esters have not been characterised in detail. To obtain deeper insights into the smell properties of different acrylates, we investigated the relationship between the molecular structure and odour thresholds as well as the odour qualities of 20 acrylic esters, nine of these synthesised here for the first time. The OT values of 16 acrylates fell within the range from 0.73 to 20 ng/L_air, corresponding to a high-odour activity. Moreover, sec-butyl acrylate and 2-methoxyphenyl acrylate showed even lower OT values of 0.073 and 0.068, respectively. On the other hand, the OT values of the hydroxylated acrylates 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate were 5–244 times higher than those of the other compounds, demonstrating that the presence of a hydroxyl group obviously favours odour inactivity.

     

DIALKYL THIOPHOSPHONATE DERIVATIVES OF TRIORGANOTIN(IV)

Abstract

The reaction of triorganotin chlorides with sodium dialkyl thiophosphites proceeds to completion on refluxing the reactants in a 1:1 molar ratio for about ten hours. Similar reactions of triorganotin chloride with dialkyl thiophosphonate do not give comparable yields in the presence of triethylamine. The products formed are colorless volatile liquids having pungent odour, are miscible with common organic solvents and are found to be monomeric. Exposure of these compounds to atmospheric oxygen the thiophosphite [Sn-S-P] linkage was oxidized to a thiophosphate [Sn-O-P(S)] linkage. These complexes have been characterized by elemental analyses, molecular weight determination, IR, ¹H NMR and ³¹P NMR spectral data.     

Synthesis and preliminary odour evaluation of 5α-androst-16-en-7-one: a new androstenone analogue

5α-Androst-16-en-3-one has been prepared from 5α-androstane-7,17-dione in a five-step sequence, via selective ketalisation at C-7 with bis-trimethylsilyloxyethane and trimethylsilyl triflate as the key step, followed by introduction of the Δ¹⁶ bond by reaction of the 17-hydrazone with iodine to give the vinyl iodide, and deiodination with sodium in ethanol, with acid-catalysed deprotection of the 7-oxo group as the final step. The compound has a mild sandalwood odour.     

Synthese und Geruch von (E)- und (Z)-bis-homo-ß-Santalol

Summary The synthesis of the title compounds is described. Guided by theoretical considerations and molecular modeling studies, the influence of the bulky group opposite to the osmophorically important primary hydroxyl function on the odour impression is determined. The organoleptic evaluation proved the predicted sandal like odour of the (Z)-isomer and its also predicted absence with (E)-isomer. A moderate increase of the volume of the bulky group shows no influence on the sandalwood odour of the new analogue.

     

Application of zNosetrade mark for the analysis of selected grape aroma compounds

A novel and portable gas chromatograph (GC, zNose™) has been evaluated for the measurement in grape berries of selected six-carbon compounds; namely, hexanal, cis-2-hexen-1-ol, cis-3-hexen-1-ol and trans-2-hexenal. The zNose™ is a handheld GC which uses purge and trap for concentration, and has a surface acoustic wave (SAW) sensor as a detector. Operation of the zNose™ using direct aspiration of the sample failed to detect the compounds at the reported odour threshold values. Pre-concentration by Tenax^® trapping and solid-phase microextraction (SPME) were investigated to improve the zNose™ sensitivity. Use of a Tenax^® pre-trap with the zNose™ allowed detection of the compounds at concentration levels in the order of their threshold values. Excessive bleed from the SPME fibre prevented the use of SPME with zNose™.     

Electrochemical response of Lactuca stolonifera leaf to CO2 gas and some odour compounds

The leaf of L. stolonifera responded drastically to CO₂ gas by changing the cellular potential as detected with a micro-electrode inserted in a leaf cell. Reproducible response patterns were obtained from the same position of the leaf. The magnitude of the response was correlated with the CO₂ concentration in the range of 0–20% under illumination. The leaf responded also to some odour compounds such as menthone, formaldehyde, and 1,2-dichloroethane. At the same time, the exposure to odour compounds altered the response pattern to CO₂ gas.     

Camphor-derived amber/woody odorants: 1,7,7-trimethyl-2′-iso-propylspiro[bicyclo[2.2.1]heptane-2,4′-(1,3-dioxanes)]

Six stereoisomers of a new camphor-derived 1,7,7-trimethyl-2′-iso-propylspiro[bicyclo[2.2.1]heptane-2,4′-(1,3-dioxane)] odorant were prepared. Their design with the help of an amber olfactophore model and structure–odour relationship are reported. The (1R,2S,4R,2′S) isomer has by far the strongest and the most characteristic amber-like odour.     

Determination of trace volatile fatty acids in ambient air by capillary gas chromatography–mass spectrometry in SIM mode

A simple, rapid and sensitive method was developed and validated for the analysis of C₂–C₅ volatile fatty acids (VFAs) in ambient air. This method involves preconcentration of VFAs with a sodium carbonate-impregnated silica gel tube, ultrasonic extraction with pure water, partition of VFAs to diethyl ether and determination using gas chromatography with a mass selective detector in the selected ion monitoring mode. A water-resistant free fatty acid phase capillary column was used to directly separate C₂–C₅ VFAs without the time-consuming derivatisation process. The limits of detection ranged from 0.001 to 0.003 µg m^?3 and the limits of quantification ranged from 0.003 to 0.010 µg m^?3. The validated method was successfully applied to the analysis trace-level VFAs in ambient air and in air samples from a landfill with perceived odour pollution.     

The enantiomers of Iralia®: preparation and odour evaluation

The enantiomers of methyl ionones 1 and 2 were prepared by an enzyme-catalysed approach. Their odour properties were evaluated by skilful perfumers.     

Odour‐causing compounds in air samples: Gas–liquid partition coefficients and determination using solid‐phase microextraction and GC with mass spectrometric detection

A quantification method based on solid‐phase microextraction followed by GC coupled to MS was developed for the determination of gas–liquid partition coefficients and for the air monitoring of a group of odour‐causing compounds that had previously been found in wastewater samples including dimethyl disulphide, phenol, indole, skatole, octanal, nonanal, benzothiazole and some terpenes. Using a divinylbenzene/carboxen/polydimethylsiloxane fibre, adsorption kinetics have been studied to define an extraction time that would avoid coating saturation. It was found that for an extraction time of 10 min, external calibration could be performed in the range of 0.4–100 μg/m³, with detection limits between 0.1 and 20 μg/m³. Inter‐day precision of the developed method was evaluated (n = 5) and RSD values between 12 and 24% were obtained for all compounds. The proposed method has been applied to the analysis of air samples surrounding a wastewater treatment plant in Catalonia (Spain). In all air samples evaluated, dimethyl disulphide, limonene and phenol were detected, and the first two were the compounds that showed the highest partition coefficients.     

An alternative evaluation method for accumulated dead leaves of Posidonia oceanica (L.) Delile on the beaches: removal of uranium from aqueous solutions

Posidonia oceanica (L.) Delile is an important endemic sea plant in the Mediterranean Sea. Its dead leaves are accumulated in the beaches and cause bad view and also odour in the touristical beaches. Therefore, these dead leaves accumulated on the beaches are collected and then burned in some beaches in Turkey. In the present study, the adsorption between dead leaves and uranium were studied in the aqueous solutions. The adsorption data obeyed the pseudo-second order kinetics. Among the studied isotherms, the data were well in line with the Freundlich and Dubinin-Raduschkevich models and the maximum adsorption capacities obtained from these models were found as 5.67 and 9.81?mg?g^?1, respectively. Negative values of Gibbs free energy showed that the adsorption was in spontaneous nature. In conclusion, the dead leaves of P. oceanica from touristic beaches might be collected and evaluated as a low-cost adsorbent for removal of uranium(VI) from aqueous solutions.