Fig. 5b shows the data of two strains of microalgae, namely the seven Scenedesmus samples and eleven Chlorella samples. The larger data set and broader lipid distribution of Chlorella samples result in good linear relation between the two methods; a R2 value of 0.82 is achieved. The seven Scenedesmus samples have a much narrower range of only 10% difference in lipid content and result in a worse fitting linear relation, R2 is 0.69. Considering how close the lipid levels are clustered together for Scenedesmus, the average lipid analysis error of ± 0.7, shown in Table 1, could have a significant impact on the R2 value in this analysis. Another reason could be the variance in analysis of repeats in the Py–GC method itself, which is addressed in the subsequent section.