Lambda 265 uv vis

Babassu oil was diluted in HPLC grade hexane at a concentration of 10 g/L and from stock solution, we prepared different dilutions for spectra reading at 1 × 10⁻³ g/mL and 0.05 g/mL. Absorbance in the UV-Visible range was measured using a spectrophotometer (Lambda 265UV-VIS, Perkin Elmer, Waltham, MA, USA). An optical cuvette made from quartz with a 10 mm optical path and with four optical sides was used as a sample holder. The collection of UV-Vis absorption spectra was in the 220–420 nm range. All analyses were performed at room temperature.
Excitation-emission matrix fluorescence spectra were measured using a spectrofluorometer (Cary Eclipse, Varian). The excitation-emission maps of fluorescence were obtained by exciting the samples in the wavelengths from 200 to 375 nm in 5 nm steps and collecting the emission between 250 and 500 nm in 1 nm steps. The excitation and emission slits were 5 nm, and the sensitivity of the detector was 600 V. The samples were diluted in HPLC grade hexane at a concentration of 10 g/L. A four-sided quartz cell with a 10 mm optical path was used.

Buriti oil samples were diluted in hexane (spectroscopic grade, 99.9%) at 5 g/L. We utilized a quartz cuvette with a 10 mm optical path and four polished sides for optical measurements. The UV–vis absorption measurements were performed using a spectrophotometer (Lambda 265 UV/Vis, Perkin Elmer, Waltham, USA). The UV–vis absorption spectra were collected in the 200–600 nm range.
The fluorescence map (excitation/emission) of the oil was obtained utilizing a bench spectrofluorometer, FS-2 (Scinco, Seoul, Korea). The fluorescence excitation/emission matrices were obtained by exciting the samples in the 250–400 nm range, with steps of 5 nm, and the emission was collected between 250 and 600 nm, with a 1 nm resolution. For all tests, the excitation and emission slits were set at 5 nm, and all measurements were performed at room temperature.

Algal growth was determined daily by OD₈₀₀, at which pigment absorbance is negligible, using a UV-visible spectrophotometer (Perkin-Elmer lambda™ 265 UV/VIS, United States) in cuvettes of an optical path of 1 cm. Dilutions have been performed to reach an OD₈₀₀ between 0.1 and 0.3. OD measurements were extrapolated as dry biomass using an OD/biomass correlation. Biomass was estimated by centrifuging 25–50 ml of culture (3000×g; 3 min) once during exponential phase and once in stationary phase. Samples were washed twice in distilled water, centrifuged again, transferred in an aluminum cup pre-weighted and weighted after 48 h in a 70°C oven.
Specific growth rate (μ) expressed in day^–1, was calculated as the slope of the linear regression of the natural log dry weight number as a function of time in exponential phase. Doubling time (Td), expressed in day was calculated as the natural log of 2 divided by the specific growth rate. Maximum biomass productivity expressed in g DW.L^–1.day^–1, was calculated by subtracting the dry biomass concentration after 3 days from dry biomass concentration after 4 days of growth. Biomass to substrate yield expressed in g DW.g substrate^–1 was calculated dividing the dry biomass concentration after carbon source depletion to the initial carbon source concentration.