Thermo flash 2000 elemental analyzer

Infrared (IR) spectra were recorded on a ThermoFisher Scientific Nicolet iS10 Fourier transform infrared (FTIR) spectrometer with a monolithic Diamond, Attenuated Total Reflection (ATR) accessory and absorption in cm⁻¹ (Thermo Scientific, Waltham, MA, USA). ¹H and ¹³C-NMR spectra were recorded at 400 MHz on a Bruker Advance 400 instrument. Molar mass was determined with Agilent 6470 triple quadrupole mass spectrometer. RP–HPLC analyses were performed on a Chomolith^® C18 column (Merck, Kenilworth, NJ, USA, 50 mm), using an Agilent 1200 Liquid Chromatograph (Agilent, Omaha, NE, USA). Chemical shifts are reported in ppm, using the solvent residual signal. Melting points were measured on a Stuart apparatus (Cole-Parmer, Stafford, UK) and are not corrected. The elemental analysis for carbon and hydrogen was carried out using a Thermo Flash 2000 elemental analyzer (Thermo Scientific, Waltham, MA, USA).

All chemicals used for the synthesis of compounds (Ph1–Ph10) were purchased from Sigma Aldrich (St. Louis, MO, USA). Melting points were determined using a Digimelt MPA 160, USA apparatus and are reported uncorrected. The FTIR spectra were recorded with Shimadzu FTIR–8400S spectrometer (Kyoto, Japan, υ, cm⁻¹). Elemental Analysis (C, H) was carried out on a Flash 2000 series elemental analyzer with thermal conductivity detector (TCD) system (Thermo Flash 2000 elemental analyzer, Thermo Fisher Scientific Inc., Waltham, MA, USA) and results are with ±0.3%. The ¹H NMR and ¹³C NMR spectra (DMSO-d₆) were recorded using a Bruker 400 MHz spectrometer (Bruker, Freemont, CA, USA). Chemical shifts (δ) are reported in ppm downfield from the internal standard tetra methyl silane (TMS). The purity of the compounds was checked by thin layer chromatography (TLC) on silica gel plate using n-hexane and ethyl acetate as mobile phase. Mushroom tyrosinase, l-DOPA and 2-(4-methoxyphenyl)ethan-1-amine were purchased from Sigma Aldrich (St. Louis, MO, USA). Stock solutions of the reducing substrates were prepared in phosphate buffer (20 mM, pH 6.8).

The moisture content was determined gravimetrically by drying samples in a freeze dryer (VirTis Ultra 35L, SP Scientific, Stone Ridge, NY, USA). Samples were loaded to pre-weighed 50 mL plastic conical centrifuge tubes (Fisher Scientific, Fairlawn, NJ, USA), frozen at − 80 °C, and then freeze-dried for 72 h. The samples were weighed and masses were recorded. Then, they were re-dried for an additional 2 h. The weight check procedure was performed several times until no further weight changes were observed. Water content was calculated by the mass difference between samples before and after freeze drying.
The ash content was determined gravimetrically by burning the sample in a muffle furnace at 550 °C for 1 h, followed by cooling down in desiccator following ASTM D5347-95 [15 ]. The weight was then recorded and the sample was reheated in the muffle oven at 550 °C for another 1 h. The cool down and weight check procedures were repeated several times until there was no change of weight.
The CHNS analysis was conducted by the Department of Chemistry, University of Alberta using a Thermo Flash 2000 Elemental Analyzer (Thermo Fisher, Milan, Italy). The metal content was determined by inductively coupled plasma mass spectrometry (ICP-MS; Elan 6000, Perkin-Elmer SCIEX, Toronto, ON, Canada) in the Department of Earth and Atmospheric Sciences, University of Alberta.