3.4. Correlation of Py–GC–MS to traditional methods
3.4.1. Protein analysis
The protein content of the 26 microalgae strains was analysed using the Lowry method and plotted in Fig. 3a on the X-axis. The same microalgae samples were also pyrolysed using the analytical pyrolyser and GC–MS. The peak areas of Indole were quantified and divided by the mass of sample pyrolysed (mg) in order to normalise the data points between samples. This resulting peak area value was plotted on the Y-axis and a linear relationship between the two analysis techniques was calculated. The linear regression of the two methods is shown to fit very well with a R2 value of 0.8. This value surpasses that obtained by comparing two traditional and commonly accepted methods for protein analysis presented by Laurens et al. [7]. The equation provided, now allows researchers to estimate the absolute protein content of any microalgae sample with reasonable accuracy. The advantage of this technique over others is that only 0.1 mg of sample is required. This is beneficial when microalgal growth trials are conducted on small scale and the scientist wants to know the change in protein content over time. Fig. 3b shows the data points for Scenedesmus and Chlorella samples only. It is expected that the same strains of microalgae have an improved relationship when this novel technique is applied. The data shows that R2 values now increase slightly compared to when the entire range of microalgae samples are investigated. This suggests that different amino acid profiles of different microalgae strains could have an effect on this proposed analysis technique. It is therefore beneficial to have a unique linear equation for each microalgae strain. Nevertheless this simple technique is expected to allow a quick estimation of any microalgae strain, even though only 26 different samples were investigated.