Silica gel 60 coated plates

A semi-quantitative analysis of non-edible or waste frying olive oil was also assessed using TLC. Silica gel 60 coated plates (Merck, Darmstadt, Germany) were activated for 30 min at 100°C and 0.5 µl samples were applied. The ternary mixture n-hexane∶ethyl acetate∶acetic acid (90∶10∶1 v/v/v) was used as the eluting phase [33] (link). After chromatography development (about 40 min), plates were air dried at room temperature, and then immersed for 1 min with gentle orbital shaking in a solution of 0.02% (w/v) Coomassie Blue R-350 [34] (link), prepared in acetic acid∶methanol∶H₂O (1∶3∶6 v/v/v) as indicated by the manufacturer. Finally, the plates were air dried at room temperature. Spots corresponding to substrates and products of the transesterification reaction were identified by using appropriate reference external standards (triolein, 1,3-diolein, 1-oleyl-rac-glycerol, oleic acid and propyl oleate) run in parallel.

A semi-quantitative analysis of biodiesel and biosurfactant was also assessed using TLC. Silica gel 60 coated plates (Merck, Darmstadt, Germany) were activated for 30 min at 100°C and 0.5 μ l samples were applied. For biodiesel analysis, the ternary mixture n-hexane:ethyl acetate:acetic acid (90:10:1, v/v/v) was used as eluting phase (Samakawa et al., 2000 (link)). After chromatography development (about 40 min), plates were air dried at room temperature, and then immersed for 1 min with gentle orbital shaking in a 0.02% (w/v) solution of Coomassie Blue R-350 (Nakamura and Handa, 1984 (link)), prepared in acetic acid:methanol:H₂O (1:3:6, v/v/v) as indicated by the manufacturer. Finally, the plates were air-dried at room temperature. Spots corresponding to substrates and products of the transesterification reaction were identified by using appropriate reference external standards run in parallel. For biosurfactant analysis, the eluting phase was composed of a mixture of toluene:ethyl acetate:ethanol (2:1:1, v/v/v). Spots corresponding to sucrose and SMP were detected by spraying the plates with a solution of urea (1 g urea, 4.05 ml phosphoric acid and 48 ml water-saturated 1-butanol) and heating them at 100°C for 15 min.