Artificial human plasma

Strychnine (purity > 98%), Strychnine N-oxide (purity ≤ 100%) were obtained from Sigma (Sigma-Aldrich, Gillingham, UK). Phosphoric acid, Hydrochloric Acid, Glacial acetic acid and Potassium Hydroxide were obtained from Fisher Scientific (Loughborough, UK); and Sodium Chloride from Sigma Aldrich, UK. Britton-Robinson buffer solution (Phosphoric acid, Glacial acetic acid and Sodium Chloride) had the pH adjusted using sodium hydroxide and Hydrochloric Acid. Potassium ferricyanide from Sigma-Aldrich (St.Louis, MO, USA) was used to for the cyclic voltammetry testing of the polished glassy carbon electrode. Fumed silica (particle size 0.007 μm) and aluminium oxide (particle size 0.05 μm), used for polishing the glassy carbon electrode, were obtained from Sigma-Aldrich. Acetonitrile (HPLC grade) from Fisher Scientific, (Loughborough, UK); used in the sonication of the GC electrode. Water was purified using an ELGA purification system to a specific resistance 18 MΩ and used to prepare all solutions. Artificial human plasma was purchased from sigma (Sigma Aldrich, UK). The urine sample (ethics permission obtained) used was freshly supplied by a volunteer.
Pyrrole (Py) was obtained from Sigma (Sigma-Aldrich, UK). Brucine and scopolamine used in selectivity tests were bought from Sigma (Sigma-Aldrich, UK).

Coumaphos, 3-chloro-4-methyl-7-hydroxycoumarin (Chlorferron), and 4-methylumbelliferone were ordered from Sigma (Sigma-Aldrich, Leicestershire, UK). Acids used in this work were: hydrochloric, phosphoric and glacial acetic acids and were purchased from Fisher Scientific (Leicestershire, UK). Disulfoton-sulfoxide (DSX) and propoxur (PPX) were also delivered by Sigma-Aldrich and used for testing the selectivity of fabricated GC electrode with electro-polymerisation of pyrrole. Potassium hydroxide was also obtained through Fisher Scientific (Leicestershire, UK). Sodium chloride was acquired from Sigma-Aldrich, UK. Britton-Robinson buffer was freshly prepared every day, and the pH was adjusted as required to obtain the different pHs used in this work. Potassium ferricyanide was purchased from Sigma-Aldrich (Leicestershire, UK) and helped in assessing the state of the electrode surface. Fumed silica (0.007 μm) and Al₂O₃ (0.05 μm) used to polish the working electrode were both from Sigma-Aldrich (Leicestershire, UK). Acetonitrile (HPLC grade) was obtained from Fisher (Fisher Scientific, Leicestershire, UK). Deionised water (18 MΩ) was used to prepare all solutions. Artificial human plasma was obtained from Sigma Aldrich, UK. Urine samples were obtained from healthy volunteers.
The reagents used for the metabolic system can be found as described by Qader [16 (link)].