*2.2. Solubility*

The solubility of EFV in different vegetable oils was determined by adding an excess amount of efavirenz to 5 mL of flaxseed, sunflower, soybean, macadamia, grapeseed and olive oil in Kimax® test tubes with Teflon®-lined crew caps (DWK Life Sciences, Hattenbergstr, Mainz, Germany). The tubes were agitated with the aid of cylindrical BRAND® (Wertheim, Germany) PTFE, length 5 mm, diameter 2-mm magnetic stirring bars at 100 rpm for 48 h at laboratory air-conditioned room temperature (22 ± 2 ◦C) using an FMH STR-MH magnetic stirring hot plate purchased from (Lasec® Group, Cape Town, South Africa). The samples were removed and centrifuged using a Damon IEC HN-SII centrifuge (Thermo Scientific, Waltham, MA, USA) at 3000 rpm for 15 min after which a 500-µL aliquot of the supernatant was collected and added to 50 mL ethanol and water in a ratio of 3:2 ratio prior to filtration through a Millipore® automation compatible 0.45-µm PVDF membrane syringe filter from (Merck Group, Darmstadt, Germany). The concentration of EFV in the oils was determined using the validated HPLC method described in Section 2.1.
