3.4.3. Lipid analysis
Total lipids were measured using the Folch method as described previously. The results for all 26 strains of microalgae are plotted on the X-axis in Fig. 5a. The algae range from very low levels (~ 5%) to very high levels above 55%. Each microalgae was pyrolysed and the peak areas for heptadecane quantified and normalised. These normalised areas are plotted on the Y-axis in Fig. 5a. The linear correlation between the two methods resulted in a R2 value of 0.65. The R2 value is reasonably good for such a unique method. It can be seen however that some values are largely overestimated, especially the two samples at around 57% lipids. Equally there are samples which were underestimated, notably the 45% lipid sample. Over and under estimations are most likely due to different fatty acid profiles or different lipid classes amongst different microalgae samples. Using just one alkane as a marker compound rather than the sum of all alkanes is likely the cause of the deviance. Nevertheless a clear general trend between the two analysis methods can be seen and a relatively good R2 value is obtained. The method could likely be improved by taking the sum of all alkane peaks observed in chromatograms. This presents a trade-off between accuracy and simplicity and speed. In the course of the current work the aim was to keep the data analysis as simple as possible for high throughput.