Benzoic acid

Boba milk tea and the added ingredients (egg pudding, jelly, tapioca “boba” balls) were purchased at a local boba chain store located in a densely populated Asian community in Los Angeles, California. The milk tea boba and components purchased were the most typical boba drink as described by the proprietor and came in the standard size (473 mL or 16 ounces). The added ingredients of tapioca “boba” balls, egg pudding, and jelly were chosen because they represented the common add‐on ingredients in boba drinks. Three samples each of equivalent lots of each component were purchased. After purchase, drinks or individual components were refrigerated in preparation for analyses. Sugar standards, acetic acid, and benzoic acid (Fisher Scientific, Hanover Park, IL, USA) were ACS grade or better and used without further purification. Water was deionized by ion exchange to a resistivity >16 MΩ‐cm and filtered to 0.2 μm (Barnstead Nanopure II).
Solid‐phase extraction cartridges were purchased from Phenomenex (Torrance, CA). For reversed‐phase extractions, 3‐ mL cartridges packed with 500 mg of Strata C18‐E (55 μm, 70Å) sorbant were utilized. For ion‐exchange extractions, 6‐ mL cartridges packed with 1 g of Strata ABW (55 μm, 70Å) mixed‐bed ion‐exchange resin were used.

4-chloroPhenol (C₆H₅ClO, 99+ %) and palladium catalyst (Pd/Al₂O₃, 1% Pd on alumina powder, with a specific surface area of 150 m²g⁻¹) were purchased from Acros and Alfa Aesar, respectively. Phenol (C₆H₅OH, 89.6%), sodium sulfate anhydrous (Na₂SO₄, 99%), sulfuric acid (H₂SO₄, 98%), sodium bicarbonate (NaHCO₃, 99–100%), acetonitrile (99.8+ %), sodium hydroxide (NaOH, 96%), benzoic acid (C₇H₆O₂, 99.9+%), 4-hydroxylbenzoic acid (C₇H₆O3, 99.9+%), o- Phosphoric acid (H₃PO₄, 85%), and Acetic Acid (Glacial, HPLC grade) were acquired from Fisher Scientific. Ferrous sulfate (FeSO₄.7H₂O, pro analysis) was obtained from J.T. Baker Analyzed. palladium catalyst (1% on carbon 4 to 8 mesh), Potassium-hydrogen phthalate (C₈H₅KO₄), HPLC grade water, and methanol were bought from Sigma-Aldrich. The syringe filters with 0.22 μm and 0.45 μm pore sizes were purchased from Millex. Titanium sulfate (TiSO₄, 65%) was obtained from GFS Chemicals. All solutions were prepared in de-ionized water (18.2 mΩ.cm), obtained from a Millipore Milli-Q system.

All reagents used in this study were purchased from Sigma-Aldrich (Saint Quentin Fallavier, France) unless otherwise noted. 2,2-bis(hydroxymethyl)propionic acid (bis-MPA, 98%), p-toluenesulfonic acid monohydrate (PTSA.H₂O, >98.5%), 4-(dimethylamino)pyridine (DMAP, 99%), Dowex^®50WX8 hydrogen form (50–100 mesh), ethyl chloroformate (97%), 8-diazabicyclo[5.4.0]undec-7-ene (DBU, 98%), benzoic acid (99.5%), acetone (99.9%), dichloromethane (DCM, 99.5%), tetrahydrofuran (THF, 99.9%), diethyl ether (99%), methanol (CH₃OH, 99.8%), water (HPLC grade), N,N-dimethyl formamide (DMF, 99.9%), diethyl (3-bromopropyl)phosphonate (95%), copper(I) bromide (CuBr, 98%), N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA, 99%), sodium azide (NaN₃, 99%), and dimethyl (2-hydroxyethyl)phosphonate (95%) were purchased from Acros Organics (Geel, Belgium). 2,2-dimethoxypropane (>98%), N,N’-dicyclohexyldicarbodiimide (DCC, >98%), and triethylamine (TEA, >99%) were purchased from TCI (Zwijndrecht, Belgium). Benzyl alcohol (BnOH, 99%, Alfa Aesar, Karlsruhe, Germany) and dialysis membrane (Standard RC, 3500 Da, Spectrum Laboratories, Racho Dominguez, CA, USA) were used as received. 1-(3,5-bis(trifluoromethyl)phenyl)-3-cyclohexylthiourea (TU) and 5-methyl-5-propargylxycarbonyl-1,3-dioxane-2-one (MPC) were synthesized according to the literature procedures [19 (link),20 (link),21 (link)].

High-purity grade benzoic acid (C₆H₅COOH, BA, 99.6%) was purchased from Acros Organics (Belgium). Nitrobenzene (C₆H₅NO₂, NB, 99%) and silver nitrate (AgNO₃, 99%) were obtained from Sigma-Aldrich (Germany). Acetonitrile (CH₃CN, 99.9%), ammonium molybdate tetrahydrate ((NH₄)₆Mo₇O₂₄·4H₂O, 99%), tert-butanol ((CH₃)₃COH, 99.5%), methanol (CH₃OH, UHPLC grade), nitric acid (HNO₃, 70%), potassium hydroxide (KOH, pure), potassium persulfate (K₂S₂O₈, reagent grade), sodium bicarbonate (NaHCO₃, 99.5%), sodium nitrate (NaNO₃, 99%) and sodium sulfate (Na₂SO₄, 99%) were acquired from Acros Organics (Belgium). Acetic acid (CH₃COOH, ≥99.9%), orthophosphoric acid (H₃PO₄, 85%), potassium iodide (KI, ≥99.5%) and sodium acetate trihydrate (NaCH₃COO·3H₂O, ≥99%) were purchased from VWR Chemicals (Belgium). Potassium ferrocyanide trihydrate (K₄Fe(CN)₆·3H₂O, ≥98%) was obtained from Alfa Aesar (Germany). Working solutions were prepared with Milli-Q water purified using a Milli-Q®-Reference system (18 MΩ cm) from Merck (Germany).