Hplc grade acetic acid

Racecadotril was purchased from Ferrer Therapeutics, S.A. de C. V. (Hidrasec, Rac-racecadotril; capsule of 100 mg); dimethyl sulfoxide (DMSO), cholera toxin from Vibrio cholerae (>90 %, SDS-PAGE, lyophilized powder, C8052), Coomassie-blue (B0149), Muller-Hinton agar (70191), chloramphenicol (C0378), acetonitrile HPLC grade, acetic acid HPLC grade were purchased from Sigma-Aldrich, St. Louis, MO, USA. EtOH, dichloromethane, hexane, and MeOH AR grade were purchased from JT Baker, Mexico City, Mexico.

MGO, acetic acid (HPLC grade) and HMF were purchased from Sigma-Aldrich (St. Louis, MO, USA). Acrylamide and 3-DG were supplied by TRC (Toronto, Canada). d₃-Acrylamide was supplied by Cambridge Isotope Labs (Cambridge, MA, USA), while o-phenylenediamine (OPD) was obtained from J & K Scientific (Beijing, China). Potassium hexacyanoferrate and zinc acetate were supplied by Sinopharm (Beijing, China). Water (HPLC grade) was prepared using a Milli-Q Integral purification system (Molsheim, France). Acetonitrile (HPLC grade) was supplied by Merck (Darmstadt, Germany). Skimmed milk powder (Fonterra, Taranaki, New Zealand) was purchased from the local supermarket. Lactobacillus casei 01 was supplied by Chr. Hansen (Beijing, China). Oasis HLB solid phase extraction (SPE) cartridges (6 mL, 200 mg) were supplied by Waters (Milford, MA, USA).

The 3′-SL (98.55%) and 6′-SL (98.75%) were provided from GeneChem (Daejeon, Korea). An internal standard, [1,2,3-¹³C₃]3′-sialyl[3-¹³C^glc]lactose sodium salt (97.00%), was purchased from Omicron Biomedicals (South Bend, IN, USA). Methanol and acetonitrile (HPLC grade) were purchased from Burdick & Jackson (Muskegon, MI, USA). Acetic acid (HPLC grade) was purchased from Sigma-Aldrich (St. Louis, MO, USA). Ammonium acetate (HPLC grade) was purchased from Fluka (Muskegon, MI, USA). Purified water was obtained with the Elix & Milli-Q Biocel system (Milford, MA, USA).