Ultrapure water system

Drug release was investigated via high-performance liquid chromatography (HPLC). For that purpose, the masses of the GP-RNI (n = 3) were determined on a Kern 770 microbalance (KERN & Sohn, Balingen, Germany), as shown in Table 1.
The GP-RNIs were placed in 4 mL glass vials and stored at 37 °C in 2 mL isotonic saline (B.Braun, Melsungen, Germany) on a lab shaker (Heidolph, Schwabach, Germany) at 100 rpm. For sampling, the medium was exchanged completely after defined time periods of 0.25; 0.75; 1.5; 3; 6; 13; 24; 29; 101; 197 and 317 h and then every 7 days for an additional 6 weeks. The medium was subsequently mixed 1:1 (v:v) with methanol (Carl Roth, Karlsruhe, Germany) and distilled water (Ultrapure water system (Sartorius, Göttingen, Germany)) prior to the HPLC measurements. Quantification of DEX was performed on a HPLC system (Knauer Wissenschaftlicher Gerätebau Dr. Ing. Herbert Knauer GmbH, Berlin, Germany) equipped with a Chromolith FastGrad RP-18e 50-2 column (Merck KGaA, Darmstadt, Germany). methanol/Water 1:1 was used as the mobile phase in an isocratic chromatographic method at a flow rate of 0.8 mL/min. Detection occurred with a UV-Detector at the wavelength λ = 254 nm [39 (link)]. For calibration, DEX standards with concentrations of 0.1, 0.5, 1.0, 2.0, 5.0, 10 and 50 µg/mL were used.

Two commercial products of dried hemp inflorescences were purchased from a company that produces hemp products. The products (known as cookie and gelato strains) were certified as industrial hemp with a THC content of less than 0.2%. Both of them were indica dominant hybrid (60% indica, 40% sativa) strains, differentiated by their genetic precedence. While the cookie strain came from the cross of OG Kush with Durban poison strains, the gelato sample was obtained by crossing the Sunset Sherbet with the thin Mint Girl Scout cookie strains.
All solvents used were LC–MS grade. Acetone was purchased from Sigma-Aldrich (Darmstadt, Germany), acetonitrile and methanol were acquired from VWR (Darmstadt, Germany), and formic acid was bought from Fisher Scientific (Schwerte, Germany). Ultrapure water (resistivity 18.2 M Ω cm⁻¹) was obtained from a Sartorius Ultrapure water System (Goettingen, Germany).

Chemical standards shaftoside, isoorientin, orientin, isovitexin, and vitexin (all primary grades) were purchased from Chromadex (Irvine, CA, USA). Solvents acetonitrile and ethanol (both HPLC grade) and ethyl acetate, acetic acid, and formic acid (analytical grade) were purchased from Merck (Merck Co., Darmstadt, Germany). Water was purified with an ultrapure water system (Sartorius, Germany).

Dichloromethane for HPLC grade (99.8%) was purchased from Thermo Fisher Scientific (Dreieich, Germany), while MilliQ water was obtained from a Sartorius ultrapure water system (Goettingen, Germany) (resistivity 18.2 M Ω cm⁻¹). 1,4-Dichlorobenzene (≥ 99.9%), used as recovery standard, and Supelco 37-component FAMES mix (200–600 mg L⁻¹), used as internal standard, were acquired from Merck (Darmstadt, Germany). The working solutions were prepared by adequate dilution of the recovery and internal standards in dichloromethane and stored at  − 20 °C before the analyses. Sodium chloride for analysis (100%) was obtained from Bernd Kraft (Duisburg, Germany). Moreover, helium Alphagaz 1 (≥ 99.999%), used as the carrier gas, argon Arcal Prime Smartop (≥ 99.999%), employed as the discharge gas, and nitrogen Alphagaz 1 (≥ 99.999%), used as the auxiliary gas in the TPI source, were supplied by Air Liquide (Oberhausen, Germany).

Azobisisobutyronitrile (AIBN, 98%), imidacloprid PESTANAL analytical standard (IMD) ethylene glycol dimethacrylate (EGDMA, 98%), hydrogen peroxide (30 wt%), methacrylic acid (MAA, 99%), tyramine (99%), dipotassium hydrogen phosphate (K₂HPO₄, ≥ 98%), 1-dodecanethiol (≥ 98%), trimethylamine (≥ 99%), sodium dodecyl sulphate (SDS) and potassium ferricyanide (K₃[Fe (CN)₆]) were purchased from Sigma Aldrich (Bornem, Belgium). Methanol (MeOH, LC–MS grade) and acetonitrile (ACN, LC–MS grade) were purchased from Biosolve BV (Valkenswaard, Netherlands). Acetone (99.5%) was obtained from Fiers (Kuurne, Belgium) and ethanol (EtOH absolute, Analar Normapure) from VWR International (Leuven, Belgium). Ultrapure water was obtained with the ultra-pure water system from arium pro, Sartorius (Goettingen, Germany). Gold electrodes were provided by CapSenze AB (Lund, Sweden). A 25 mL quartz glass round flask was purchased from Witeg Labortechnik GmbH (Wertheim, Germany). All the electrochemical measurements were carried out using a PGSTAT 101 potentiostat (Metrohm, Utrecht, The Netherlands) coupled to a computer using NOVA software (version 2.0) for data acquisition. An automated flow injection capacitance system based on current pulse capacitive measurements was used to perform the analysis (CapSenze HB, Lund, Sweden).