Acetic acid

Chitosan of medium molecular weight, M-Chit, (Mw: 190,000–375,000; 75–85% deacetylated chitin), chitosan of low molecular weight, L-Chit, (Mw: 50,000–190,000; ≥75% deacetylated chitin), poly (vinyl alcohol) (Mw: 89,000–98,000; 99+% hydrolyzed), and gelatin from cold-water fish skin (40–50% in H₂O) were purchased from Sigma-Aldrich (Darmstadt, Germany) and used as received. Acetic acid (min 99.8%, PA) and ethanol (min 99.8%, PA) from Riedel-de Haën (Munich, German), were used as chitosan solvent and neutralizer agent respectively.

Anhydrous sodium sulfate was purchased from AppliChem GmbH (Darmstad, Germany); dichloromethane (99.9%) was supplied by Honeywell Riedel-de Haën (Steinheim, Germany) and silanized glass wool by Supelco (Steinheim, Germany). 2-Octanol (≥99.5%), used as an internal standard was purchased from Sigma-Aldrich (St. Louis, MO, USA).
GC-FID and GC-MS used standards: acetic acid was purchased from Riedel-de-Haen (Seelze, Germany); isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol,benzyl alcohol, 2-phenylethanol,propanoic acid, butanoic acid, isovaleric acid, octanoic acid, hexanal, ethyl propanoate, isobutyl acetate, ethyl 2-methylbutyrate, ethyl hexanoate, ethyl decanoate, phenethyl acetate, ethyl dodecanoate, eugenol were acquired from Fluka (Buchs, Switzerland);1-propanol, 2,3-butanediol, 1,2-propanediol, glycerol, isobutyric acid, ethyl butyrate, ethyl octanoate were purchased from Merck (Darmstadt, Germany); e-ethoxy-1-propanol, methional, ethyl isobutyrate, ethyl isovalerate, isoamyl acetate, ethyl hydrogen succinate, furfural were bought from Aldrich (Steinheim, Germany) and 2,3 butanedione was acquired from Sigma-Aldrich (Saint Louis, MO, USA).

All chromatographic solvents were of high-performance liquid chromatography (HPLC) grade. Ethanol, acetone, acetonitrile, mEthanol (≥99.9%), l-ascorbic acid, gallic acid, (+)-catechin, (−)-epicatechin, and quercetin were obtained from Sigma-Aldrich (Johannesburg, South Africa). quercetin-3-glucoside was obtained from Fluka (Buchs, Switzerland), malvidin-3-glucoside from Polyphenols Laboratories AS (Norway), and acetic acid and orthophosphoric acid from Riedel-de Haën (Seelze, Germany). Purified water was obtained from a Milli-Q filtration system (Millipore Filter Corp., Bedford, MA, USA).

The reagents used were all of analytical grade (purity > 98%): DL-lactic acid and butyric acid purchased from Fluka (Buchs, Switzerland), acetic acid from Riedel-de-Haën (Seelze, Germany), L-(+)-tartaric acid, formic, citric acid, benzoic acid, succinic acid, malic acid, propionic acid, DL-p-hydroxyphenyllactic acid (HO-PLA), sodium hydroxide, sodium chloride, glycerol, and phenyllactic acid (PLA) bought from Sigma-Aldrich (Germany). Phosphoric acid 85% and oxalic acid were supplied by Merck (Hamburg, Germany), cetyltrimethylammonium bromide (CTAB) from LOBA Chemie (Fischamend, Austria), HPLC-grade water and 0.1 and 1 N sodium hydroxide solutions were purchased from Agilent Technologies (USA). All solvents (Merck, Darmstadt, Germany) and solutions were filtered through 0.2-μm membranes (Millipore, Bedford, MA, USA). Peptone water and MRS broth media were purchased from Oxoid Ltd. (Hampshire, UK).

Loba Chemie (Mumbai, India) provided acetone, sodium hydroxide, n-hexane, and methanol, while Alfa Agar (Binfeld, UK) provided Ninhydrin solution, Benedict’s, and Millon’s reagents. Alfa Aesar (Lancaster, UK) also provided iodine solution, sulfuric acid, and Molisch’s reagent. Sigma-Aldrich (Steinheim, Germany) provided the Folin-Ciocalteu’s reagent, hydrochloric acid, aluminum chloride, potassium acetate, chloroform, and 2,2-diphenyl-1-picrylhydrazyl (DPPH). Riedel-De-Haen (Teningen, Germany) provided magnesium ribbon, acetic acid, ferric chloride, and dimethyl sulfoxide (DMSO). Trolox ((s)-(-)-6-hydroxy-2,5,7,8-tetramethychroman-2-carboxylic acid) and quercetin were also obtained from Sigma-Aldrich (Sborg, Denmark). α-amylase, on the other hand, was brought in from Sigma (Mumbai, India). Sigma (St. Louis, USA) provided the DNSA (3,5-dinitro salicylic acid) reagent, Acarbose, p-nitrophenyl butyrate, Orlistat, tris–HCl buffer, and Porcine pancreatic lipase type II.

A total of 8 samples of wet wipes of different brands were obtained from different stores in Riyadh. Distilled and deionized water was used in all experiments. All chemicals used in the experiments were of HPLC grade. Methanol was obtained from Merck (Rahway, NJ, USA), and acetic acid was obtained from Riedel-de Haën (Seelze, Germany). For reference materials, pure materials of methylisothiazolinone (MIT) and methylchloroisothiazolinone (CMIT), HPLC grade were obtained from Merck (Darmstadt, Germany). The analytical standard Kathon^TM CG, a mix standard of methylisothiazolinone (MIT) and methylchloroisothiazolinone (CMIT), was purchased from SIGMA-ALDRICH (St. Louis, MO, USA). The diluent used was a mixture of 0.4% solution of acetic acid (CH₃COOH) and Methanol (CH₃OH). The mobile phase consisted of 80% of the acetic acid solution (0.4% solution) and 20% Methanol. The column used for separation was Thermo Scientific™ (Waltham, MA, USA) 250-4.6 Hypersil™ BDS (Base-Deactivated Silica) RP-C18 (5 µm) column. A SHIMADZU (Kyoto, Japan) Prominence-i series High-Performance Liquid Chromatography (HPLC) system was employed which is equipped with an autosampler, degasser, and quaternary solvent delivery unit and a PDA detector.