Hplc grade water

6,8-Dimethoxycoumarin, tomentin, and diosmetin were isolated from L. chinensis by column chromatography and used as reference standards. Their structures were confirmed by nuclear magnetic resonance (NMR) [46 (link),47 ,48 (link)], and their purities by HPLC (≥98.0%). Other reference standards, namely, diosmin (≥98.0%) and linarin (≥98.0%), were purchased from ChemFaces Biochemical Co., Ltd. (Wuhan, China). HPLC-grade water, acetonitrile, and methanol were purchased from Honeywell Burdick and Jackson (Muskegon, MI, USA). Formic acid was from DAEJUNG Chemicals & Metals Co., Ltd. (Siheung-si, Korea).

Four reference compounds, NCGA, CGA, CCGA, and rutin, were purchased from ChemFaces (Wuhan, Hubei, China). HPLC-grade water, acetonitrile, and analytical-grade phosphoric acid were acquired from Honeywell (Republic of Korea).

IMI (N-[1-[(6-Chloro-3-pyridyl)methyl]-4,5-dihydroimidazol-2-yl]nitramide) and [¹³C₆]-IMI (>99% isotopic purity; >97% total purity) were obtained from AK Scientific (Union City, CA, USA) and IsoSciences (King of Prussia, PA, USA), respectively. Authentic standards of IMI-Ole (N-[1-[(6-chloro-3-pyridyl)methyl]-1,3-dihydro-2H-imi-dazol-2-ylidene]nitramide) and IMI-5-OH (N-(1-[(6-chloro-3-pyridyl)methyl]-5-hydroxyimidazolidin-2-ylidene]nitramide) were provided by Bayer CropScience AG (Monheim, Germany). Sucrose was obtained from Chem-Supply (Gillman, SA, Australia) and glacial formic acid from AnalaR (supplied by BDH, Poole, Great Britain). HPLC grade acetonitrile, ethyl acetate,and HPLC grade methanol were obtained from Merck (Kenilworth, NJ, U.S.A.). 18.2 M ℧ HPLC grade water was obtained from Honeywell (Morristown, NJ, USA).

Certified mycotoxin standards were purchased as follows: AOH from Alternaria sp. (purity >96%), AME from Alternaria alternata (>98%), TeA copper salt from Alternaria alternata (>98%), and TEN from Alternaria tenuis (>95%) were obtained from Sigma-Aldrich (St. Louis, MO, USA); ALT (>98%) was purchased from ChemFaces (Wuhan, China), and ATX- I (>97%) was obtained from Cayman (Ann Arbor, MI, USA). All mycotoxin standards were prepared at 1 mg/mL in acetonitrile (ACN) and kept at −20 °C. HPLC-grade water, ACN, and methanol (MeOH) from Honeywell Burdick and Jackson (Muskegon, MI, USA) were used for sample preparation. LC/MS-grade water and methanol from Fisher Scientific (Cleveland, OH, USA) were used as the mobile phase. LC/MS-grade ammonium acetate was purchased from Merck (Darmstadt, Germany) and glacial acetic acid (≥99.7%, HPLC grade) for pH adjustment was obtained from Fisher Scientific (Cleveland, OH, USA).

PFOS (CAS: 1763-23-1, 97% purity, Santa Cruz Biotechnology, Dallas, TX, USA), PFOA (CAS: 335-67-1, 95% purity, Millipore Sigma, St. Louis, MO, USA), PFHxA (CAS: 307-24-4, 97% purity, Toronto Research Chemicals, North York, ON, Canada), and PFBA (CAS: 375-22-4, 98% purity, Millipore Sigma, St. Louis, MO, USA) were dissolved in deionized (DI) water and stored at room temperature in a dark environment. Optima-grade methanol (Fisher Chemical, Pittsburgh, PA, USA), HPLC-grade water (Honeywell Burdick and Jackson, Muskegon, MI, USA), and ammonium acetate (Thermo Scientific, Waltham, MA, USA) were used for chromatographic analyses of PFAS in exposure solutions.

U.S. Pharmacopeia (USP) reference standards for citric acid (CA, ≥99% purity), malic acid (MA, ≥99% purity), acetic acid (AA, ≥99% purity), glutaraldehyde (GLT, Grade I, 25% in H₂O), and formaldehyde (FAL, 37% stabilized with methanol) were used for high-performance liquid chromatography (HPLC) analysis. A phosphorus standard solution (1,000 mg/L) was purchased from Sigma–Aldrich (St. Louis, MO, United States) for inductively coupled plasma optical emission spectroscopy (ICP-OES). HPLC-grade water was obtained from Honeywell Burdick and Jackson (Morristown, NJ, United States). For the titration method validation, potassium peroxymonosulfate (PPMS, 99% purity), hydrogen peroxide (H₂O₂, 35% in H₂O), and GLT (Grade I, 25% in H₂O) were purchased from Sigma–Aldrich, and other active ingredients were obtained from the manufacturers. The standard solutions of quaternary ammonium compounds (QACs), sodium hypochlorite (NaOCl, 5.50% available chlorine), and copper sulfate pentahydrate (CuSO4.5H₂O, 99.6% purity) were provided by the manufacturers. The QACs of didecyl dimethyl ammonium chloride (DDAC), alkyl dimethyl benzyl ammonium chloride (ADBAC), and coco dimethyl benzyl ammonium chloride (CDBAC) were of 81%, 50.58%, and 50.12% purity, respectively. All other reagents were of analytical grade.