Retrospective Recovery Thresholds and Nonlinear Kinetic Modelling of n-hexane Soxhlet Extraction from Moringa oleifera and Irvingia gabonensis

Selecting a Soxhlet extraction time from the last observed maximum can prolong processing after most of the final extract has been collected. This exploratory study compared n-hexane extraction from Moringa oleifera and Irvingia gabonensis prepared batches. Oven-dried, 1-mm-sieved powders (15 g) were extracted with 250 mL n-hexane; the reported solvent temperature in the flask was 70 °C. Separate extractions were stopped after 1–10 or 1–12 siphon cycles, respectively, with two extractions per endpoint. Mean times and gravimetric yields were fitted directly to Peleg, first-order and Weibull functions. Final observed mean yields were 44.20% and 78.86% on a prepared-material basis. The first means exceeding 95% of these final means occurred at six cycles/89 min and seven cycles/78 min, respectively. These retrospective thresholds do not represent independently determined total extractable oil. With residual variance included in the corrected Akaike criterion, the three time-based models were not clearly separated for M. oleifera; first-order was favoured for I. gabonensis, with Weibull close. Individual duplicate readings, moisture, extract purity and constant-mass evidence were unavailable to the analysis. The thresholds are batch-specific laboratory candidates for confirmation, not validated stopping rules.