Fluorescence quantum yields and lifetimes of annatto aqueous solutions dependent on hydrogen potential: Applications in adulterated milk

Fluorescence Quantum Yields and Lifetimes of Aqueous Natural Dye Extracted from Tradescantia pallida purpurea at Different Hydrogen Potentials

“…The η average result for samples at different pH values in the range of (~4.0-8.0) was η = (0.28 ± 0.02). For comparison, for annatto that was extracted from the fruit of the Bixa Orellana trees at a pH between 5.4 and 11.5, the average value of η = (0.40 ± 0.08) was reported [41], and for the Carthamus tinctorius L. petal, η ≈ 0.004 was obtained for the main colored species that was extracted [65]. The time-resolved fluorescence (TRFL) spectroscopy measurements were also performed for natural dyes that were extracted in different pH values.…”

“…The TRFL setup was tested by using the sodium fluorescein (Synth, molecular weight 376.28) in an alkaline aqueous solution (pH 11.24), and the transient emission was adjusted with a single exponential (τ = (4.13 ± 0.01) ns and χ 2 = (1.03 ± 0. 01)) [41,42]. Figure 6 shows the TRFL for aqueous natural dye that was extracted at different pH values (Figure 6 (a) 3.98, (b) 5.34, (c) 6.75, and (d) 7.99) from ornamental leaves of Tradescantia pallida purpurea.…”

“…Time-resolved fluorescence lifetimes (TRFL) were performed by using a light source PLS 450 LED (λ = 460 ± 10 nm, 40 μW average power at 40 MHz and 800 ps). TRFL results for liquid samples were analyzed within a FluoTime 100 time-resolved fluorescence spectrometer from PicoQuant (Berlin, Germany) using a 1 cm thick quartz cuvette [41]. A Ludox solution was used as a scattering sample for prompt measurements [41,42].…”

“…TRFL results for liquid samples were analyzed within a FluoTime 100 time-resolved fluorescence spectrometer from PicoQuant (Berlin, Germany) using a 1 cm thick quartz cuvette [41]. A Ludox solution was used as a scattering sample for prompt measurements [41,42].…”

“…The η parameter plays an important role in studying fluorescent materials and developing new materials for light-emitting devices [39,40]. In addition, the extracted natural dye was tested as a possible probe for milk prepared at different pH values to simulate adulterated food, due to its colorimetric and/or fluorometric properties that change as a function of pH, which allows future use as a possible pH-dependent biosensor [29,30,41].…”