Lambda 35 uv vis spectrophotometer

Elemental analyses were carried out in a Carlo-Erba microanalyser at the Microanalytical Laboratory of the University of Vienna. Electrospray ionisation mass spectrometry (ESI MS) was carried out with amaZon speed ETD Bruker instrument (Bruker Daltonik GmbH, Bremen, Germany, m/z range 0–900, ion positive/negative mode, 180 °C, heating gas N₂ (5 L/min), Capillary 4500 V, End Plate Offset 500 V). UV–Vis spectra were measured on Perkin Elmer UV/Vis spectrophotometer Lambda 35. IR spectra were reported on a Bucker Vertex 70 Fourier transform IR spectrometer (4000–400 cm⁻¹) using the ATR technique. 1D (¹H, ¹³C) and 2D (¹H-¹H COSY, ¹H-¹H TOCSY, ¹H-¹H NOESY, ¹H-¹³C HSQC, ¹H-¹³C HMBC, ¹H-¹⁵N HSQC, ¹H-¹⁵N HMBC) NMR spectra were measured on a Bruker AV NEO 500 or AV III 600 spectrometers (Bruker BioSpin GmbH, Rheinstetten, Germany) in DMSO-d₆ at 25 °C at NMR spectroscopy Centre of the Faculty of Chemistry of the University of Vienna.

Total carbohydrate concentration was determined on 30 mg of dried algal powder with the phenol-sulfuric acid method, slightly modified from [38 (link)]. The dried biomass was re-suspended in 1.8 mL of 1 M sulfuric acid and heated at 95 °C for 2 h. After cooling at room temperature, the tubes were centrifuged (14,000× g for 10 min). Phenol (0.2 mL) was added to 0.4 mL of sample, then 1 mL of concentrated sulfuric acid was added. After 30 min at room temperature, the absorbance was read at 490 nm using a UV-VIS spectrophotometer (UV/VIS Spectrophotometer Lambda 35, Perkin Elmer). The total carbohydrates concentration was quantified referring to a calibration curve using glucose as standard.

Fourier-transform
infrared (FTIR) spectroscopy was carried out on a Spectrum One model
FTIR spectrometer (PerkinElmer, Connecticut, USA) between 650 and
4000 cm^–1 using the attenuated total reflection
(ATR) mode. DXR Raman model of Thermo Scientific with 532 nm laser
was used in the study. Raman analysis is carried out at room temperature
without preparation. TEM images of samples were taken on JEOL/JEM
ARM 200 with an acceleration voltage of 200.0 kV. Thermal gravimetric
analyses (TGA) were carried out under a nitrogen atmosphere using
a Diamond model TGA (PerkinElmer, Massachusetts, USA) in the temperature
range of room temperature to 800 °C with a 10 °C/min heating
range under nitrogen. A PerkinElmer 4000 differential scanning calorimetry
(DSC, PerkinElmer, Massachusetts, USA) was used to determine the thermal
properties of the samples under a nitrogen atmosphere at −10
to 150 °C with a 10 °C/min screening rate. PerkinElmer UV–vis
lambda 35 Spectrophotometer (PerkinElmer Corp, Waltham, MA, USA) was
used to detect the opacity of the hydrogels. 10 mm wide samples were
cut and placed in the chamber. %Transmittance was measured at 550
nm and the opacity was calculated by using eq 1.^{6 (link),62 (link)}

For total flavonoid concentration we used photocolorimetric method with 5% methanolic aluminum chloride solution (AlCl₃). The mixture was kept in the dark for 30 min at room temperature and absorbance was measured at 425 nm in UV–Vis Lambda 35 spectrophotometer (Perkin Elmer, Inc., Waltham, MA, USA). The concentration was calculated from the calibration curve constructed with standard quercetin solution (Merck, Darmstadt, Germany) (1–30.00 μg/mL) and expressed as quercetin equivalent (%). The analyses were performed in triplicate [55 (link)].