Determination of emodin by hexadecyl trimethyl ammonium bromide sensitized fluorescence quenching method of the derivatives of calix[4]arene

The fluorescence quenching effect of emodin (EMO) on the derivatives of p-tert-butyl-calix[4]arene with o-phenanthroline (TBCP) in 1.0% hexadecyl trimethyl ammonium bromide (CTAB) medium was investigated. The fluorescence of TBCP was quenched by EMO due to the formation of the weak fluorescent inclusion complex (EOM-TBCP), and the fluorescence quenching (ΔF = FTBCP–FEMO–TBCP) was sensitized in CTAB. Under the optimal conditions, the linear range of calibration curve for the determination of EMO was 1.17–23.40 μg/mL. The detection limit estimated and RSD was 0.34 μg/mL, 3.63% (n = 3, c = 4.74 μg/mL). The quantum yield Yu of TBCP was approximately 2.0 times higher in the presence of CTAB than that in the absence of CTAB. The method has been applied for the determination of EMO in samples with satisfactory results.

Graphical abstractThe fluorescence emission spectra of TBCP (present of or absent of EMO) in CTAB and H2O media were shown in Fig. 2. It could be seen that (1) the fluorescence intensity of TBCP (FTBCP) was enhanced in presence of CTAB and the maximum emission wavelength was red shifted (curve 1 and 3); (2) the fluorescence intensity of TBCP (FTBCP,FTBCP-CTAB) was diminished when EMO was added (curve 2 and 4); and the ΔF1 = FTBCP–CTAB–FEMO–TBCP–CTAB was larger than that ΔF2 = FTBCP-FEMO–TBCP with the same concentration of EMO; (3) the FTBCP-CTAB gradually decreased with an increase of EMO concentration (auxiliary Fig. 2, curve 1–5). Curve 5 was the fluorescence spectrum of EMO–TBCP with the excess EMO, which indicated that inclusion complex of TBCP–EMO had the weak fluorescent property. Hence, there was the sensitizing effect in CTAB.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A novel method for the analysis of emodin (EOM). ► FTBCP was quenched by EMO due to the formation of EOM-TBCP. ► ΔF = FTBCP–FEMO–TBCP was sensitized in CTAB. ► Yu of TBCP was approximately 2.0 times higher in the presence of CTAB than that H2O. ► This method was applied for the analysis of EOM in samples with satisfactory results.