2 4 6 trihydroxyacetophenone

Ammonium acetate (NH₄Ac), Triton X-100, l-arabinose, xylose, potassium chloride (KCl), 50% sodium hydroxide (NaOH, for HPLC), sodium acetate (NaAc), Sodium chloride (NaCl), 2,4,6-trihydroxyacetophenone (THAP), glucose, maltose, maltodextrins mixture (DP 3–30), potassium sodium tartrate (KNa-tartrate), para-hydroxy benzoic acid hydrazide (PAHBAH), acetonitrile (ACN), D₂O (99.9 atom% D), and methanol were purchased from Sigma Aldrich (St. Louis, Missouri, USA). MilliQ was prepared with a MILLI-Q ACADEMIC 230V/50HZ purchased from Merck (Darmstadt, Germany). HCl and NaOH were purchased from Merck (Darmstadt, Germany). Low-viscosity wheat arabinoxylan (AX), arabinan (AB) from sugar beet, rhamnogalacturonan (RG) from soybean, azurine-cross-linked (AZCL) xylan (beechwood), 3-α-l-plus 2-α-l-arabinofuranosyl-xylotetraose (XA₃XX/XA₂XX) mixture, 2,3-di-α-l-arabinofuranosyl-xylotriose (A_2,3XX), 3-α-l-arabinofuranosyl-xylotetraose (XA₃XX), 2-α-l-arabinofuranosyl-xylotriose (A₂XX), xylobiose (X2), xylotriose (X3), xylotetraose (X4), xylopentaose (X5), and xylohexaose (X6) were purchased from Megazyme (Bray, Wicklow County, Ireland). Insoluble corn fiber, defatted by hexane extraction and destarched by amylase treatment, was supplied by Novozymes A/S (Lyngby, Denmark). Finally, 10 mM NH₄Ac buffer was prepared and adjusted to pH 5.0 using 2 M HCl.

Solvents for LC–MS/MS, such as acetonitrile (ACN), methanol, and water were HPLC or MS grade and were obtained from Carl Roth (Karlsruhe, Germany). All other chemicals used were HPLC or analytical grade (p.a.). The solvent additives ammonium hydroxide and ammonium acetate were purchased from Carl Roth and Honeywell Riedel-de Haën (Seelze, Germany), respectively. Matrices for MALDI-TOF MS, such as DAN, 9-aminoacridine (AA), α-cyano-4-hydroxycinnamic acid (CHCA), 2,4,6-trihydroxyacetophenone (THAP), and multiwalled carbon nanotubes, as well as standard explosive solutions of 2-amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrotoluene (4-ADNT), 1,3,5-trinitrobenzene (TNB), 1,3-dinitrobenzene (DNB), 2-nitrotoluene (NT), and 5-chloro-2,4-dinitrotoluene (CDNT) were obtained from Sigma-Aldrich (St Louis, MO, USA). TNT, 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) were provided by terracon (Jüterbog, Germany). Mefenamic acid and chlorogenic acid were from Sigma-Aldrich. Citric acid was purchased from Merck (Darmstadt, Germany). Standard stock solutions were prepared as a mixture of each explosive at 50 ng/μL (TNT, 2-ADNT, 4-ADNT, 2,4-DNT, 2,6-DNT, TNB, DNB, NT) in ACN for LC–MS/MS measurements. For MALDI-TOF MS, a stock solution consisting of TNT, TNB, DNB, NT, 1:10 2-ADNT/4-ADNT, and 1:1 2,4-DNT/2,6-DNT each at 100 ng/μL in ACN was used.