Uv 5500pc spectrophotometer

We examined the absorption spectrum of madder extracts in the 190 to 600 nm wavenumber range using a UV-5500PC spectrophotometer (Shanghai Metash Instruments Co., Ltd). Fourier transform infrared spectrometer (Nicolet iS10, ThermoFisher Scientific) confirmed the FT-IR spectra of madder extract, with 16 scans at 4 cm⁻¹ resolution in the spectral range of 4000–400 cm^-1. The method of KBr pellet was used for spectrum data^{16 (link)}.

To determine the β-carotene content, a standard curve was first generated. A β-carotene standard solution at a certain concentration (0–10 μg/mL), mixed with n-hexane, was prepared. Gradient dilution was then conducted, and the ultraviolet absorption value of the solution at 450 nm was measured using an ultraviolet-visible spectrophotometer (UV-5500PC spectrophotometer; Metash Instruments Co., Ltd., Shanghai, China). A standard curve was generated, with β-carotene concentration (μg/mL) as the abscissa and absorbance (A) as the ordinate.
Using Wright’s method, β-Carotene was extracted [19 (link)], with certain modifications. The process was as follows: up to 2 mL of absolute ethanol and 2 mL of n-hexane were added to 1 mL of the emulsion sample. The sample was oscillated on a vortex vortexer to fully demulsify and dissolve the sample and then allowed to stand for 10 min. The layers were separated, and the n-hexane phase was collected. The remaining samples were extracted twice with n-hexane until the n-hexane phase became less. The extraction was conducted under dark conditions. The extracts were combined and then diluted into a 25 mL brown volumetric flask, and the absorbance at 450 nm was measured for quantitative analysis.