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. 2017 May 11;7:1759. doi: 10.1038/s41598-017-01956-1

Figure 3.

Figure 3

UV-Vis absorption spectra and calibration curve of bromothymol blue/PBS solutions with different pH values. (a) Traditional UV-Vis absorption spectra of bromothymol blue/PBS solutions (10 mM) with varied pH values. The inset is the normalized UV-Vis absorption spectra of 350–500 nm for bromothymol blue/ PBS solutions (10 mM) with varied pH values. (b) The calibration curve of bromothymol blue solutions in terms of the pH-dependent UV-Vis absorption peak for pH measurements. Inset shows the calibration curve from pH 4.5 to 7.5. The error bars illustrate the relative standard deviation (RSD) over three replicates.