Red phosphorus

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.

Methanol (LC-MS grade), chloroform (HPLC grade), Ethanol (HPLC grade), norharmane (crystalline), and red phosphorus (≥99.99% purity) were purchased from Sigma Aldrich (Zwijndrecht, The Netherlands) and used without further purification.

Acetone and methanol (HPLC
grade) were obtained from Biosolve (Valkenswaard, Netherlands). Trifluoroacetic
acid (TFA, 99%), α-cyano-4-hydroxycinnamic acid (α-HCCA,
purity 97%), and red phosphorus (>97%) were purchased from Sigma-Aldrich
(Taufkirchen, Germany). The internal standard SPLASH LipidoMIX containing
deuterated lipids from different families was purchased from Avanti
Polar Lipids (Alabaster, Alabama) via Sigma-Aldrich.

An α-Cyano-4-hydroxycinnamic acid matrix, red phosphorus, and trifluoroacetic acid were purchased from Sigma-Aldrich (Poole, UK). Acetonitrile (ACN) was purchased from Fisher Scientific (Loughborough, UK). Double-sided conductive carbon tape was obtained from TAAB (Aldermaston, UK). Seven black gel pens from different brands were used, including a Uni Ball Signo, a UMN-207, a Pentel Energel BL77-A, a Pilot G-1, a Tesco home office gel pen, a Zebra Sarasa, a WHSmith rollerball gel pen, and an ASDA gel pen. Woodland Trust (75 g, uncoated) paper was used for the deposition of ink.

All
chemicals including cobalt(II) nitrate
hexahydrate (Co(NO₃)₂.6H₂O, ≥96%),
potassium hydroxide (KOH_(aq), ≥85%), copper(II)
sulfate pentahydrate (CuSO₄.5H₂O, ≥98%),
sodium chloride (NaCl, ≥99%), platinum (Pt, nominally 20% on
carbon black), red phosphorus (P, ≥99.99%), and ethanol (≥85%)
were purchased from Sigma-Aldrich and used without further purification.
Water used was purified through a Millipore ultrapure water system
(18.2 MΩ.cm at 25 °C).

Red phosphorus (99.999%), tin
(99.999%), and AlCl₃ (98%) were purchased from Sigma-Aldrich
(Czech Republic). Iodine (99.9%), and dimethyl sulfoxide (DMSO) were
obtained from Penta, Czech Republic. Carbon disulfide (CS₂) (99.99%) was acquired from Acros Organics, Germany. Gold (99.99%)
was acquired from Mateck, Germany. Tetrabutylammonium hexafluorophosphate
(TBAPF₆, 99%, powder) was purchased from Fluorochem. SnI₄ was made by reacting Sn with I₂ in chloroform
under reflux and then recrystallizing the product.
Black phosphorus
crystals were synthesized from Red phosphorus as described previously.^{19 (link)} Briefly, Red phosphorus and Sn/SnI₄ (mineralizing agent) were placed in a quartz glass ampule and subsequently
sealed using an oxygen/hydrogen torch. The ampule was placed horizontally
in a muffle furnace and heated to 400 °C for 2 h. After that,
the temperature was increased to 600 °C for another 24 h. Finally,
the sample was slowly cooled to room temperature overnight. The obtained
BP crystals with a metallic sheen were washed with CS₂ to
remove the byproduct of white phosphorus.

MS-grade water, solvents, and formic acid (FA) were purchased from Biosolve Chimie SARL (Dieuze, France). Red phosphorus and 2,5-DHB, trifluoroacetic acid (TFA) were purchased from Sigma-Aldrich (Darmstadt, Germany). Osimertinib and [¹³C,²H₃]-osimertinib were purchased from Alsachim (Illkirch, France).