Phenylethyl Alcohol

Data were obtained from 9139 subjects [4928 females aged 5–96 years (M = 31.8, SD = 18.9) and 4211 males aged 5–91 years (M = 30.7, SD = 17.7)]. Among them, 3432 (37.5%) had been included in a previous study to establish normative data [15 (link)]. According to the inclusion criteria for the respective studies, all subjects were healthy and none reported histories for any olfactory disturbances.
Odors were delivered using felt-tip pens (“Sniffin’ Sticks”) of approximately 14 cm length and an inner diameter of 1.3 cm. These pens carry a tampon soaked with 4 ml of liquid odorant. For odor presentation, the cap was removed from the pen for approximately 3 s, the pen’s tip brought in front of the subject’s nose and carefully moved from left to right nostril and backwards [3 (link)].
The threshold was obtained in a three alternative forced choice paradigm (3 AFC) where subjects were repeatedly presented with triplets of pens and had to discriminate one pen containing an odorous solution from two blanks filled with the solvent. Phenylethanol (dissolved in propylene glycol) or n-butanol (dissolved in water) were used, with both odorants having been found equivalent in olfactory sensitivity testing: scores obtained with both are correlated [17 (link)]. The highest concentration was a 4% odor solution. Sixteen concentrations were created by stepwise diluting previous ones by 1:2. Starting with the lowest odor concentration, a staircase paradigm was used where two subsequent correct identifications of the odorous pen or one incorrect answer marked a so-called turning point, and resulted in a decrease or increase, respectively, of concentration in the next triplet. Triplets were presented at 20 s intervals. The threshold score was the mean of the last four turning points in the staircase, with the final score ranging between 1 and 16 points.
The discrimination task used the same 3 AFC logic. Two pens of any triplet contained the same odorant, while the third pen smelled differently. Subjects were asked to indicate the single pen with a different smell. Within-triplet intervals were approximately 3 s. As the odors used in this subtest were more intense, between-triplets intervals were 20–30 s. The score was the sum of correctly identified odors. Hence, the scores in this task ranged from 0 to 16 points. Importantly, subjects were blindfolded for the threshold and discrimination tasks to avoid visual identification of target pens.
Odor identification comprised common and familiar odorants (recognized by at least 75% of the population). Subjects were presented with single pens and asked to identify and label the smell, using four alternative descriptors for each pen. Between-pen intervals were approximately 20–30 s. The total score was the sum of correctly identified pens, thus subjects could score between 0 and 16 points.
The final “TDI score” was the sum of scores for Threshold, Discrimination and Identification subtests, with a range between 1 and 48 points.

GAUSSIAN09 (Frisch et al., 2009 ▸ ) was used to determine all pairwise intermolecular/interionic energies for calibration purposes, based on B3LYP-D2 calculations corrected for BSSE. For a very small number of crystal structures involving anion–cation pairs, supermolecule calculations at this level did not converge and these ion–ion pairs were not included in the fitting process, although energies for all other possible molecule/ion pairs in those structures were included. HF/3-21G monomer calculations also failed to converge for some open-shell molecules/ions [Cambridge Structural Database (CSD; Groom et al., 2016 ▸ ) refcodes ACACCR07, ACACVO04, CPNDYV07, IGACEC, JIYKEH, AFATAE and AGEFEX], and those structures were not included in the determination of scale factors for the CE-HF energy model. Perhaps of more consequence, the B3LYP-D2 counterpoise-corrected benchmark calculations provided quite obviously unacceptable energies for the crystalline salts ferrocenium tris­(hexa­fluoro­acetylacetonato)manganese(II) (AGEFEX), the 1,2-di­phenyl­ethylenediammonium N-phenyliminodiacetate ethanol sol­vate (KOLDUL), calcium α-ethylmalonate (CUZHEK) and sodium dihydrogen citrate (NAHCIT). For these crystal structures, the B3LYP-D2 counterpoise-cor­rected energies between pairs of ions were consistently much more binding than obtained with a simple electrostatic model; MP2/6-31G(d,p) counterpoise-corrected calculations were used as benchmark energies instead.

All reagents were used as received without further purification. Nickel chloride hexahydrate (NiCl₂·6H₂O), pyrazine, pyrimidine, 4,4-bipyridine, ethanol (≥ 99.7%), N,N-dimethylformamide, methanol, 2,2,2-trifluoroethanol, 2-phenylethanol, 1-propanol, 3-propanol, furfural, 1,4-butanediol, 1,6-hexanediol, ethylamine, 1-phenylethylamine, cyclohexanol, cyclohexylamine, 1-propylamine, 2-aminoethanol, urea, glycerol, glucose, 5-hydroxymethylfurfural (5-HMF), ethylene glycol and 1-hexanethiol were all purchased from Aladdin Industrial Corporation (China). Potassium hydroxide (KOH) was purchased from Sinopharm Chemical Reagent Co., Ltd. (China). 1,1,1-trifluoro-2-propanol, 1-phenylethanol, benzaldehyde and 2-propylamine were purchased from Innochem Alfa Acros (China). Methyl mercaptan was purchased from Macklin Biochemical Co., Ltd. (China). 2,2,2-trifluoroethylamine and benzylamine were purchased from Shanghai Titan Scientific Co., Ltd. (China). Ultrapure deionized water (18.2 MΩ·cm⁻¹, 25 ^oC) was obtained from ELGA purification system (China). Anion exchange membrane was obtained from Fumatech (FAB-PK-130, Germany). Carbon fiber paper was purchased from Hesen Electric Co., Ltd. (HCP020N, China).

Mechanical detection and pain thresholds and electrical detection and pain thresholds were obtained at baseline and after 3 months of olfactory training. Testing areas were the volar lower arms. The mechanical detection threshold (MDT) was measured with a standardized set of modified von Frey hairs that exert forces between 0.25 and 512 mN (21 (link)). Mechanical pain threshold (MPT) was measured using the PinPrick stimulators, which exert forces between 8 and 512 mN (21 (link)). For both tests, the geometric mean of five series of ascending and descending stimulus intensities was selected as the threshold value. For the electrical detection and pain thresholds, transcutaneous electrical nerve stimulation (TENS) equipment was used. TENS is used in a therapeutic setting, so it is a well-tolerated system to measure electric thresholds in children and adolescents (22 (link)). The electrical detection threshold was measured by a single stimulus of increasing electric current until participants detected the stimulus. After that, a stepwise increase in mA led to the level of perception of pain.
Olfactory testing was performed before and after the 3-month training period using the “Sniffin' Sticks” test kit (23 (link)), which involves tests for odor threshold, odor discrimination, and odor identification. The threshold test comprises 16 triplets of Sniffin' Stick pens, where one of the three pens is impregnated with N-butanol or phenylethylalcohol (BUT/PEA) diluted in a solvent according to a decreasing concentration. The children should specify the odor pen among the set of three pens presented. The second subtest assessed the ability of the patients to discriminate different odors. In this test, patients were also exposed to 16 triplets of odors, including two identical odors and one different odor. The task was to identify the odor, which differed from the other two pens. Eyes must be closed or blindfolded for both threshold and discrimination tests. The identification subtest consists of 16 common odors. The study participants were asked to choose from a list of four written proposals (24 (link)). The sum of the scores of the three subtests resulted in the Threshold, Discrimination, Identification (TDI) score, with a maximum of 48 points.

All extracts were analyzed using a GC fitted with a DB-5MS UI column (30 m × 0.25 mm ID × 0.25 μm film, product: 122-5532UI; Agilent Tech., Santa Clara, CA, USA) and coupled to a mass spectrometer (GC-MS; GC: 7890A, MS: 5062C, Agilent Tech.). Helium was used as a carrier gas flowing at 1 mL min⁻¹ with a temperature program beginning at 45–50 °C (held for 2 min), followed by an increase of 3 °C min⁻¹ to 70 °C, then 5 °C min⁻¹ to 130 °C, after that 12 °C min⁻¹ to 170 °C, and finally the column temperature was brought to 300 °C (held 2 min) at a rate of 30 °C min⁻¹. A 1 μL sample injection volume was used; the injector temperature was 250 °C, and samples were run in splitless mode. The Sim and Scan acquisition mode was conducted simultaneously; while Sim mode allows us to acquire low traces of VOC and terpene compounds, Scan mode is performed for identification purposes. The NIST 2017 Mass Spectral library version 2.3 was used for the verification of all compounds. All compounds were quantified based on the following standards availability: Monoterpenes: limonene (Chem Purity: >99%, racemic mixture), β-pinene (CP: >99%, RM), β-myrcene (CP: 90%), α-pinene (CP: 98%, RM), β-phellandrene (CP: 96%, RM), α-phellandrene (CP: 95%), p-cymene (CP: >99%), terpinolene (CP: 90%), 3-carene (CP: 98.5%, RM), camphene (CP: 90%, RM), α-terpinene (CP: 85%), γ-terpinene (CP: 97%), ocimene (CP: 90%), Oxygenated monoterpenes: (-)-borneol (>99%), camphor (CP: 95%), α-terpineol (CP: 90%, RM), linalool (CP: 97%), cis-grandisol (CP: >95%), verbenone (CP: >99%), Phenylpropenes: 4-allylanisole (CP: 98.5%), Sesquiterpenes: (+) aromadendrene (CP: 97%), caryophyllene oxide (CP: 95%), β-caryophyllene (CP: 80%), Aliphatics/others: iso-butanol (CP: >99%), phenethyl alcohol (CP: >99%), 2-methyl-1-butanol (CP: >99%), phenethyl acetate (CP: >98%), 3-methyl-1-butanol (CP: >98%), iso-amyl acetate (CP: >97%), acetoin (CP: >96%),. All standards were obtained from Sigma-Aldrich (Oakville, ON, Canada), except β-phellandrene from TRC Canada (Toronto, ON, Canada). For the quantitation of some sesquiterpene compounds, due to their unavailability in the market, we used some of the above-mentioned standards to quantify based on hydrocarbon groups along with unique ion masses.