Formic acid hcooh

One-component model solutions were prepared by dissolving in 0.1 M HCl the required amounts of PtCl₄ (96%), PdCl₂ (99.9%), RhCl₃ (99.9%) and RuCl₃ (99.9%) supplied by Sigma Aldrich (Schnelldorf, Germany). Polyvinylpyrrolidone PVP (M_w ≈ 55000, Sigma Aldrich) was used as the stabilizing agent. Sodium borohydride NaBH₄ (>98.0%, Sigma Aldrich), ascorbic acid C₆H₈O₆ (AA, p.a., Chempur, Piekary Śląskie, Poland), sodium formate HCOONa, and formic acid HCOOH (p.a., Sigma Aldrich) were used as reducing agents in the study.
To obtain NPs, scientists proposed the use of PVP as a stabilizing agent. Depending on the synthesis, it can be used as a surface stabilizer, growth modifier, and dispersant for NPs. As a stabilizer, PVP prevents particle aggregation caused by repulsive forces. This is because the polymer contains hydrophobic carbon chains that extend into the solvents and interact with each other as a steric hindrance effect [40 (link),41 (link)].

Unless specified, all reagents were obtained from Bio-Rad Laboratories (Hercules, CA, USA). Solvents used for the sample preparation and LC–MS/MS analysis have >99.9% purity, as reported by the manufacturing companies. Acetonitrile (ACN) CHROMASOLV was obtained from Honeywell (Charlotte, NC, USA). Methanol (MeOH) and formic acid (HCOOH) were purchased from Sigma (St. Louis, MO, USA).

AFB₁, AFB₂, OTA (98% purity), AITC, and formic acid (HCOOH) were obtained from Sigma–Aldrich (St. Louis, MO, USA). Methanol and acetonitrile have been obtained by Fisher Scientific (Hudson, NH, USA). Deionized water (<18 MΩ cm resistivity) was produced by a water purification system (Millipore, Bedford, MA, USA). All the chromatographic solvents were filtered through a 0.22 µm membrane filter Scharlau (Barcelona, Spain). Barley, wheat, and corn were provided by Tot Agro (Barcelona, Spain). The peptone water and dextrose potato agar culture medium were obtained from Liofilchem (Teramo, Italy). The strains of A. flavus ITEM 8111 were provided by the Microbial Culture Collection of Institute of Sciences and of Food Production (ISPA, Bari, Italy) whereas the P. verrucosum VTT D-01847, was obtained from the VTT Culture Collection (Espoo, Finland).

The commercial amaranth protein concentrate (Amaranthus hypochondriacus L. Revancha variety) was supplied by Nutrisol (Hidalgo, Mexico). The amaranth protein isolate (API) was prepared based on the methodology previously reported [27 (link)]. Briefly, a water suspension of defatted commercial amaranth protein concentrate was adjusted to pH 9 with a 2 M NaOH. The mixture was centrifuged after stirring 30 min at room temperature. Then, the supernatant was adjusted to pH 5 with 2 M HCl, centrifuged at 4 °C, and the pellet was resuspended in water, adjusted at pH with 0.1 M NaOH, and freeze-dried. The protein content of the API was 85.5 ± 0.2% and consisted of a mixture of different proteins with molecular weights ranging from ~10 to ~83 kDa [27 (link)]. Sodium hydroxide (NaOH) was purchased from VWR International AB (Stockholm, Sweden). Formic acid (HCOOH) of 95% purity, glycerol and the surfactant Tween 80 were supplied by Sigma-Aldrich Co. (St. Louis, MO, USA). Freeze-dried CNCs (2012-FPL-CNC-043) were kindly supplied by USDA Forest Products Laboratory, Forest Service (Madison, WI, USA). The CNCs were produced from wood pulp using sulfuric acid and the dimensions were between 100–300 nm in length and around 5 nm diameter [28 (link)]. Milli-Q water was used as a solvent.

Acetonitrile (MeCN) and methanol (MeOH) were obtained from Merck (Darmstadt, Germany). A Milli-Q water purification system (Millipore Corporation, Bedford, MA, USA) was used to obtain deionized water (<18 MΩ cm resistivity). Ammonium formate (HCO₂NH₄, 97%), anhydrous magnesium sulphate, formic acid (HCOOH), mycotoxin stock standard solutions (AFs, OTA, FUS-X, STG, FBs, ENNs, and BEA), and sodium chloride were provided from Sigma-Aldrich (St. Louis, MO, USA). All solvents were filtered through a 0.22 µm cellulose filter (Membrane Solutions, Texas, TX, USA). The working standard solutions consisting of individual compounds were prepared by appropriate dilution of the stock solutions in MeOH or MeCN, depending on its solubility properties, in order to obtain multi-compound working standard solution. The new multianalyte working solution (ranging from 0.1 to 1000 µg/L of concentration for each compound) was stored in darkness conditions in glass-stoppered bottles at −20 °C. The working standard solution consisting in a mixture of the individual compounds was employed for method validation assays.

GO was obtained from Xfnano Materials Tech (Nanjing, China). CA242 and anti-CA242 antibodies were obtained from Fitzgerald Industries International. PVP, palladium chloride (PdCl₂), ascorbic acid, chloroauric acid (HAuCl₄), dopamine, formic acid (HCOOH), and uric acid were purchased from Sigma-Aldrich (St. Louis, MO, USA). Doubly distilled water was applied to prepare all detection systems.

The IS mixture (25 µmol/L for each SPLs in ethanol, catalog LM-6005) was purchased from Avanti Polar Lipids (Alabaster, AL, USA). It was composed of uncommon SPLs including So (d17:1), Sa (d17:0), S1P (d17:1), Cer (d18:1/12:0), C1P (d18:1/12:0), GlcCer (d18:1/12:0), and LacCer (d18:1/12:0), and SM (d18:1/12:0). Complete Freund’s adjuvant (CFA), ammonium acetate (NH₄Ac) and formic acid (HCOOH) were purchased from Sigma-Aldrich (St. Louis, MO, USA). LC-MS-grade methanol (MeOH), chloroform (CHCl₃), and isopropanol (IPA) were purchased from Merck (Darmstadt, Germany). Ultrapure water (18.2 MΩ) was purified with a Milli-Q system (Millipore, Burlington, MA, USA). All other chemicals used were of analytical grade. Indomethacin (IDM) was obtained from Shanghai Shyndec Pharmaceutical Co., Ltd. (Shanghai, China).