Octanophenone

Uracil (99%), phenol (99%), acetophenone (99%), butyrophenone (99%), valerophenone (99%), hexanophenone (99%), heptanophenone (98%), octanophenone (99%), and benzanthracene (99%) were purchased from Sigma-Aldrich (Bornem, Belgium).
Acetonitrile (ACN, HPLC grade) was obtained from Biosolve (Valkenswaard, The Netherlands). Ultra-pure water (18.2 MΩ•cm) was generated by a Milli-Q water purification system (Millipore, Molsheim, France). Uracil (t0 marker), acetophenone, butyrophenone, valerophenone, hexanophenone, heptanophenone, octanophenone, and benzanthracene were dissolved separately in 70:30% (v/v) ACN:H2O at 1 g/L as stock solutions. The sample was prepared by mixing and diluting aforementioned solutions in 70:30% (v/v) ACN:H2O yielding 5 μL/L for acetophenone, 10 mg/L for Uracil, 10 μL/L for phenol and butyrophenone, 20 μL/L for valerophenone, hexanophenone, heptanophenone, 20 mg/L for benzanthracene, and 30 μL/L for octanophenone.

Toluene (HPLC grade, ≥99.8%), urea, tetramethoxysilane (TMOS), metyltrimethoxysilane (MTMS), 1 M aqueous acetic acid solution, polyethylene glycol (PEG) of molecular weight (MW) = 10,000 g/mol, thiourea, acetophenone, propiophenone, butyrophenone, valerophenone, hexanophenone, heptanophenone and octanophenone were purchased from Sigma-Aldrich (Overijse, Belgium). Trifluoroacetic acid (TFA, LC-MS Ultra grade) was purchased from Fluka (Buchs, Switzerland). Octadecyldimethyl-N,Ndimethylaminosilane (ODS-DMA) was purchased from ChemPur Feinchemikalien und Forschungsbedarf GmbH (Karlsruhe, Germany). Acetonitrile (ACN, HPLC supra-gradient grade) was purchased from Biosolve B.V. (Valkenswaard, the Netherlands). N-(Trimethylsilyl)-imidazole (TMSI) was obtained from Merck Schuchardt OHG (Hohenbrunn, Germany). Deionized water was produced in-house with a Milli-Q water purification system of Merck Millipore (Billerica, MA, USA). PTFE filters (0.20 µm × 25 mm) were purchased from Macherey-Nagel (Düren, Germany). MassPREP Peptide Mixture was purchased from Waters (Milford, MA, USA). Fused-silica capillaries of 20 µm i.d. (90 µm outer diameter (o.d.)) and 40 µm i.d. (105 µm o.d.) were purchased from Polymicro Technologies (Phoenix, AZ, USA).