For 2NapFF-Na solutions prepared at a concentration of 40 mg/mL, solutions were also examined over a seven-day period but preparing the samples in 7 mL Sterilin vials instead of 50 mL Falcon tubes to establish if the containers used to prepare samples could also affect stirring and therefore sample viscosity. Seven lots of 3 mL 2NapFF-Na samples at a concentration of 40 mg/mL prepared using the quantities in Section 1.3. Solutions were made in 7 mL Sterilin vials, stirred with the same (13 x 3 mm) stirrer bars, and wrapped in Parafilm. Samples were then stirred at 1000 rpm for seven days. Viscosity measurements were performed every day for seven days, with day 1 representing the day following the creation of the samples. The pH was adjusted daily to 10.5 ± 0.1 using 0.1 M, 1 M and 2M NaOH; or 1 M and 2 M HCl as required for each solution.