Cesium triiodide

D-pinitol (95% mass), L-chiro-inositol (95% mass), myo-inositol (≥98% mass), D-glucose, D-fructose, and D-galactose were purchased from Sigma-Aldrich (Steinheim, Germany). Water, acetonitrile, methanol (all solvents were of LC-MS grade purity), trifluoroacetic acid (≥99% purity), and ammonium acetate (≥99% purity) were purchased from Sigma-Aldrich (Steinheim, Germany). MALDI matrices such as 2,5-dihydroxybenzoic acid (DHB), α-cyano-4-hydroxycinnamic acid (HCCA) as well as cesium triiodide for mass calibration were purchased from Sigma-Aldrich (Steinheim, Germany). Water was obtained with a Milli-Q RG apparatus by Millipore (Millipore Intertech, Bedford, MA, USA).

Thiamine hydrochloride (99%, MW 337.27), biotin (>99%, MW 244.31), vitamin B12 (>98%, MW 1355.37), and α-Cyano-4-hydroxycinnamic acid (>99%, MW 189.17), 4-Nitrophenol (>99%, MW 139.11) were supplied by Sigma-Aldrich (St. Louis, MO, USA). Hydrogen peroxide (30%, MW 34.01), sodium nitrate (>99%, MW 84.99), sodium dihydrogen phosphate monohydrate (>99%, MW 137.99), sodium molybdate dihydrate (>99%, MW 241.95), manganese (II) chloride tetrahydrate (>99%, MW 197.91), and cobalt (II) chloride hexahydrate (>99%, DW 237.93) were obtained from Chempur^® (Piekary Śląskie, Poland). Zinc sulfate heptahydrate (>99%, MW 287.54), iron (III) chloride hexahydrate (>99%, MW 270.32), EDTA disodium dihydrate (>99%, MW 372.24), and copper (II) sulfate pentahydrate (>99%, MW 249.68) were purchased from Scharlab (Barcelona, Spain). Sodium metasilicate nonahydrate (44–47.5% total solids, MW 284.19) were supplied by Acros Organics, ThermoFisher Scientific (Waltham, MA, USA). Deionized water was obtained by using a Milli-Q^® purification system (Millipore Co., Bedford, MA, USA). Standards of D-glucose (>99%), D-alanine (>99%) and cesium triiodide (>99%) were purchased from Sigma-Aldrich (Steinheim, Germany). Standard mixture of triacylglycerols (TG internal standard, Ultimate SPLASH^TM) was purchased from Avanti Polar Lipids (Alabaster, AL, USA).

Cesium triiodide (CsI₃, 99.9%), angiotensin I human acetate salt hydrate (90%), and α-cyano-4-hydroxycinnamic
acid (CHCA) were purchased from Sigma-Aldrich (St. Louis, MO, U.S.A.).
Organic solvents used in sample preparation, including acetonitrile
(99.9%) and ethanol (99.9%), were sourced from J. T. Baker Avantor
(Radnor, PA, U.S.A.). Distilled deionized water used in the experiment
(with a resistivity of 18.2 MΩ-cm) was produced by the Merck
milli-Q purification system (Darmstadt, Germany).
The CsI₃ analyte solution was prepared using 50% ethanol with a concentration
of 0.1 mmol/mL. One microliter of the analyte solution was directly
deposited onto the sample plate and dried in a vacuum chamber before
analysis. The preparation process did not involve any matrix mixing,
thereby avoiding interference of mass spectra from matrix signals.
The angiotensin I analyte solution was dissolved in distilled deionized
water at a concentration of 10 nmol/mL. The CHCA solution was prepared
using 50% aqueous acetonitrile solution, with a concentration of 0.1
mmol/mL. The CHCA matrix and angiotensin I solutions were premixed
in a final matrix-to-analyte molar ratio of 100:1. Finally, one microliter
of the premixed solution was deposited onto the sample plate and dried
in the vacuum chamber.