FTIR transmission spectroscopy for measurement of algae neutral lipids
Keywords:biofuels, FTIR spectroscopy, ATR spectroscopy, KBr pellets, Mid-infrared spectroscopy
Algae lipids can be used to produce biofuels and are considered a potential source of energy to supplant fossil fuel. Cultivation practices of algae grown in large ponds can be tailored to maximize lipid content. Laboratory methods of measuring lipid content are time-consuming and labor-intensive, so a real-time measuring technique is needed to efficiently control the addition of pond nutrients. The objective of this research was to determine the effectiveness of measuring algae lipid content with Fourier Transform Infrared (FTIR) transmission spectroscopy. Six algae samples (Nannochloropsis salina) with varying lipid contents were centrifuged and then dried in an oven at 40° C for 12 hours. Dried algae were mixed with potassium bromide (KBr) powder at a mass ratio of 1:150 (algae:KBr) and pressed into pellets. A Thermo-Nicolet 6700 FTIR spectrometer was used to collect spectral data in transmission mode. Three relevant absorption bands centered at 2920, 2855, and 1742 cm-1 were identified. A linear regression analyses showed that the band depth at 2920 cm-1 was strongly correlated (R2 = 0.92) with lipid content measured by gas chromatography (GC). The results of this research provide insight into the development of a real-time lipid-content sensor.