Water hipersolv chromanorm

All solvents and metabolite standards were obtained at highest purity. Hydrochloric acid [HCl, ≥32% (T), Fluka] and methanol (Chromasolv LC-MS Ultra) used for SPE were purchased from Honeywell (Seelze, Germany). For all other purposes, methanol [ultragradient high-performance liquid chromatography (HPLC)] was purchased from J. T. Baker (Norway). Acetonitrile (ULC/MS), methyl tert-butyl ether (MTBE, HPLC), hexane (HPLC), and formic acid (99%, ULC/MS) were purchased from Bio-Lab (Jerusalem, Israel). Acetone (≥99.8%, Chromasolv HPLC) was purchased from Sigma-Aldrich (Saint Louis, MO, USA). Water (HiPerSolv Chromanorm) used for SPE was purchased from VWR (Oslo, Norway). For all other purposes, water was purified by a Milli-Q system (resistivity of 18.2 megohm cm at 25°C, total organic carbon <5 parts per billion; Merck Millipore, Molsheim, France). Indole-3-acetic-2,2-d₂ acid (d₂-IAA; ≥98%) and N-hexanoyl-l-homoserine lactone-d₃ (d₃-C6-HSL; ≥99%) were used as isotopically labeled extraction standards (Santa Cruz Biotechnology, Dallas, TX, USA). Caffeine-(trimethyl-d₉) (98%; Sigma-Aldrich) and l-tryptophan-d₅ (98%; Cambridge Isotope Laboratories, Andover, MA, USA) were used as isotopically labeled injection standards for ultraperformance LC–HRMS (UPLC-HRMS) analysis.