D3 4 methylguaiacol

Analytical grade volatile phenols (guaiacol, 4-methylguaiacol, 4-ethylguaiacol and 4-ethylphenol), hexamethylene diisocyanate (HDI), N,N-dimethylformamide (DMF), dibutyltin dilaurate and deuterated NMR solvents (d₆-ethanol, D₂O and DCl) were purchased from Sigma-Aldrich (Castle Hill, NSW, Australia). Analytical grade chloroform was purchased from Chem-Supply (Adelaide, SA, Australia) for polymer precipitation. The deuterium-labelled normalising standard, d₃-4-methylguaiacol, was purchased from CDN Isotopes (Pointe-Claire, Quebec, Canada). Food grade (>98% purity) β-CD and γ-CD were sourced from the IMCD Group (Adelaide, SA, Australia). Stock solutions of volatile phenols and deuterated standards were made in pure ethanol (Thermo Fisher Scientific, Waltham, MA, USA) and stored at –20 °C. Working solutions were prepared in model wine containing 5 g/L of tartaric acid (Thermo Fisher Scientific) and 12% v/v ethanol, and were stored at –4 °C. A commercial red wine (a 2017 Barossa Valley Cabernet Sauvignon) was used for the adsorption study.

The following chemicals were of analytical reagent grade. Eugenol, 4-methylsyringol, 4-ethylguaiacol, 4-ethylphenol and hydrochloric acid (HCl) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Guaiacol, o-cresol, p-cresol, and m-cresol were obtained from TCI America (Portland, OR, USA). 4-methylguaiacol and syringol were purchased from Alfa Aesar (Tewksbury, MA, USA). Deuterated standards d3-guaiacol, d3-4-methylguaiacol, d7-o-cresol, d7-p-cresol, d7-m-cresol, d5-4-ethylguaiacol, and d4-4-ethylphenol were obtained from CDN Isotopes (Pointe-Claire, QC, Canada) and d6-syringol was purchased from EPTES (Vevey, Switzerland). Solvents ethyl acetate (EtOAc) and pentane were of HPLC grade and purchased from Millipore Corporation (Darmstadt, Germany) and Sigma-Aldrich (St. Louis, MO, USA), respectively. HPLC-grade ethanol used in this study was from Sigma-Aldrich (St. Louis, MO, USA). Water was produced by a Milli-Q Element system (Millipore, Rockville, MD, USA).

Analytical grade volatile phenols (guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, o-cresol, m-cresol, p-cresol, and eugenol) and deuterated NMR solvents (d₆-ethanol, D₂O, and DCl) were purchased from Sigma-Aldrich (Castle Hill, NSW, Australia). Deuterium-labelled internal standards (d₃-guaiacol, d₃-4-methylguaiacol, and d₄-4-ethylphenol) were sourced from CDN Isotopes (Pointe-Claire, Quebec, Canada). Analytical grade ethanol, tartaric acid, and sodium hydroxide were purchased from Thermo Fisher Scientific (Waltham, MA, USA). Food grade (>98% purity) α-, β-, and γ-CDs were supplied by IMCD Group (Adelaide, SA, Australia). Model wine was prepared by dissolving tartaric acid (5 g/L) in aqueous ethanol (12% alcohol by volume) and adjusting the pH to 3.5 by dropwise addition of 1 M sodium hydroxide. Stock solutions of internal standards and volatile phenols were prepared volumetrically in absolute ethanol and stored at −20 °C, with working solutions prepared in model wine and stored at 4 °C.