Sodium chloride pa

Analytes used for the measurements included l‐tryptophan reagent grade ≥98% HPLC (Sigma‐Aldrich, St Louis, MO, USA), 2‐deoxy‐d‐ribose ≥99.0% TLC (Sigma‐Aldrich, Steinheim, Germany) and triphenylene ≥98.0% HPLC (Fluka, Buchs, Switzerland). As MALDI matrices, 2,5‐dihydroxybenzoic acid 98% (DHB), 2,4,6‐trihydroxyacetophenone hydrate 98% (THAP) and sinapic acid ≥98% (SA) all purchased from Sigma‐Aldrich (Steinheim, Germany) were used. As solvents, tert‐butyl methyl ether ≥99% (Aldrich Chemical, Milwaukee, WI, USA), ultrapure water (UHQ water, 18.2 MΩ cm resistivity at 25°C) obtained from a Μillipore Simplicity UV apparatus (Millipore, Billerica, MA, USA), acetonitrile (ACN) ACS reag. Ph. Eur., methanol hypergrade for LC‐MS (MeOH) and acetone ACS reag. Ph. Eur. (all from Merck, Darmstadt, Germany) were used. Red phosphorus ≥97.0% (Sigma‐Aldrich, St Louis, MO, USA) was used for mass calibration of the intermediate‐pressure MALDI/LDI instrument. Some sample preparations were doped with sodium chloride pA from Merck.

Superparamagnetic silica colloids in water with a diameter (specified by the manufacturer) of 0.51 μm ± 0.03 μm and iron oxide content ≥30% were purchased from microParticles GmbH (Berlin, Germany). Poly(ethylene oxide) (PEO, 600 kDa) was purchased from Sigma-Aldrich (St. Louis, MO, USA), sodium chloride (p.a.) from Merck (Kenilworth, NJ, USA) and sodium azide (≥99%) from Fisher Scientific (Hampton, NH, USA). All chemicals were used as received. All water used was purified by a Milli-Q water purification system.