2 ethyl 1 hexanol

1-Propanethiol (Aladdin, Shanghai, China, 99%), carbon disulfide (Sigma, Metairie, LA, USA, 99%), potassium ferricyanide (K₃Fe(CN)₆, Aladdin, Shanghai, China, 99%), 4,4′-azobis (4-cyanovaleric acid) (ACVA, Sigma, Metairie, LA, USA, 98%), 2,2′-Dithiodipyridine (Aladdin, Shanghai, China, 98%), 2-Mercaptoethanol (Sigma, Metairie, LA, USA, 99%). N′-dicyclohexylcarbodiimide (DCC, Sigma, Metairie, LA, USA, 99%), 4-(dimethylamino)pyridine (DMAP, Sigma, LA, USA, 99%), Tris(2,2-bipyridine) dichlororuthenium(II) hexahydrate (Aladdin, Shanghai, China, 98%), N-isopropylacrylamide (NIPAAm, Sigma, LA, USA, 98%) were recrystallized twice in hexane and toluene prior to use. 2-ethyl-1-hexanol (Sigma, LA, USA, ≥98%), ALP and 4-nitrophenyl phosphate (pNPP) (Sigma, Metairie, LA, USA), PEG-bis (N-succinimidyl succinate) (Sigma, Metairie, LA, USA), Chloroauricacid (HAuCl₄·H₂O, Energy Chemical, Shanghai, China, 98%), sodiumhydroxide (NaOH, Sigma, Metairie, LA, USA) were purchased from Guangfu Technology Development Co. Ltd., Tianjin, China). Albumin from bovine serum (BSA, isoelectric point = 4.6) (Sigma, Metairie, LA, USA, ≥98%) were used as received without further purification.

All reagents utilized in this assay were of analytical quality. Sodium chloride (NaCl, 99.5%), and calcium chloride (CaCl₂, >99.0%) were obtained from Panreac (Spain, Barcelona). Ultrapure water was supplied from a Milli-Q^® system (Millipore); the 3-octanol used as internal standard and other VOCs for identification, namely, 1-butanol, 1-heptanol, 1-octanol, 1-propanol, (E)-2-hexenal, 2-methyl-butanal, 2-ethyl-1-hexanol, 2-methyl-1-propanol, 2-phenylethanol, acetaldehyde, benzaldehyde, ethanol, ethyl acetate, ethyl butanoate, ethyl decanoate, ethyl hexanoate, ethyl octanoate, ethyl propanoate, ethyl 3-hydroxybutanoate, hexyl acetate, and pentanal with purity up to 98% were acquired from Sigma Aldrich (Madrid, Spain). Helium gas purity of 5.0 (Air Liquide, Portugal) was utilized as the GC carrier gas. Solid-phase microextraction holder and divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber were supplied from Supelco (Bellefonte, PA, USA). The Kovats index (KI) was calculated by the injection of a series of C₈ to C₂₀ straight-chain n-alkanes (at 40 mg L⁻¹ in n-hexane) produced by Fluka (Buchs, Switzerland).

Some building materials such as pieces of deteriorated plastic carpets were also analysed as such. Chemicals such as emodin, glyoxal, methylglyoxal, 2-ethyl-1-hexanol and 1-octen-3-ol were purchased from Sigma–Aldrich (St. Louis, MO, USA) and diluted into ethanol as indicated. The surfactants included the anionic detergent SDS (sodium dodecyl sulphate, Sigma–Aldrich), the cationic detergent DDDAC (didecyldimethylammonium chloride; Merck, Darmstadt, Germany) and three nonionic detergents, Genapol X-080 (polyethyleneglycol monoalkyl ether), Triton X-100 (polyethyleneglycol-p-is-octylphenyl ether) and Tween 80 (polyethylene glycol sorbitan monooleate), all from Sigma–Aldrich. DDDAC was diluted into methanol and other surfactants into water.

2-Ethyl-1-hexanol and n-butanol of purity higher than 99% were supplied from Sigma-Aldrich
and used as received. The chemical structures of the investigated
alcohols are presented in the insets to Figure 1.

The following compounds were used as authentic standards in the GC-MS and GC-FID assays. Ethyl propanoate (99% purity), 2,3-butanediol isomers (98%), ethyl 2-methylpropanoate (≥ 98%), ethyl 2-methylbutanoate (≥ 98%), n-propyl 2-methylpropanoate (≥ 97%), 4-heptanone (98%), 2-ethyl-1-hexanol (≥ 99.6%), diethyl succinate (99%), 2-bornanone (≥ 97%), methyl dodecanoate (≥ 98%), ethyl dodecanoate (≥ 98%), methyl tetradecanoate (≥ 98%), ethyl tetradecanoate (99%), ethyl (Z)-9-tetradecenoate (97%), ethyl hexadecanoate (≥ 99%), ethyl (Z)-9-octadecenoate (98%) and n-hexane (≥ 97%) were procured from Sigma-Aldrich (St. Louis, MO, USA). Ethyl (Z)-9-hexadecenoate and ethyl (E)-9-octadecenoate, N-(2-methylbutyl)acetamide, N-(3-methylbutyl)acetamide, N-(2-methylbutyl)propanamide, N-(3-methylbutyl)propanamide, N-(2-methylbutyl)-2-methylpropanamide and N-(3-methylbutyl)-2-methylpropanamide, all at ≥ 98.0% purity (by GC), were synthesised previously [53 (link), 55 (link)].