Disodium 3 hydroxynaphthalene 2 7 disulfonate

HPLC- or MS-grade solvents acetonitrile (ACN), methanol (MeOH), and chloroform (CHCl₃) were purchased from Merck (Darmstadt, Germany) or Sigma-Aldrich (Steinheim, Germany or St. Louis, MO). MS grade water or ultrapure water was purchased from Merck (Darmstadt, Germany) or using a Milli-Q purity system (Millipore, Billerica, MA).
MeOH-dissolved internal standard solution (ISS-1) containing L-methionine sulfone, D-camphor-10-sulfonic acid sodium salt, leucine-d3, phenylalanine-d5, tryptophane-d5, succinic acid-13C4, and cholic acid-d4 (all from Sigma-Aldrich, Steinheim, Germany) was used to normalize signal intensity of the CE-TOF/MS data. ACN-dissolved ISS-2 consisting of N,N-diethyl-2-phenylacetamide, trimesic acid, disodium 3-hydroxynaphthalene-2,7-disulfonate (all from Wako, Japan), and 3-aminopyrrolidine dihydrochloride (Aldrich, St. Louis, MO) was used to adjust the migration time of the CE-TOF/MS analysis. Internal standards of free fatty acid (FFA) 16:0-d4 (Cambridge Isotope Laboratories, Tewksbury, MA, USA), and FFA 22:0-d4 (ten Brink laboratories, Amsterdam, Netherlands) dissolved in CHCl₃/MeOH (2:1, v/v) were used to normalize signal intensity of the UHPLC-Q-TOF/MS-based FFA analysis.

The dialyzer with low flux used in this study was the Fresenius F6, and the dialyzer with high flux was the Fresenius F60. Liquid chromatography grade methanol and chloroform were purchased from Merck (Darmstadt, Germany). Liquid chromatography grade ammonium acetate was purchased from Sigma-Aldrich (St. Louis, Mo, USA), and 98% formic acid was purchased from Fluka (Darmstadt, Germany). Ultrapure Water (18.2 MΩ-cm, TOC = 6 ppb) was prepared with a Milli-Q system (Millipore, Billerica, MA, USA). 10 mM D-camphor-10-sulfonic acid sodium salt (Wako, Japan) and 10 mM L-methionine sulfone (Wako, Japan) in methanol were used as internal standard solution 1 (ISS1). A mixture of 1 mM disodium 3-hydroxynaphthalene-2,7-disulfonate (Wako, Japan), trimesic acid (Wako, Japan), N,N-diethyl-2-phenylacetamide (Wako, Japan), and 3-aminopyrrolidine dihydrochloride (Aldrich, USA) in water was used as internal standard solution 3 (ISS3). ISS1 was used to standardize the metabolite intensity and ISS3 was used to adjust the migration time of the metabolites.