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Fluorescence Microscopy Techniques
Published in Margarida M. Barroso, Xavier Intes, In Vivo, 2020
Mehmet S. Ozturk, Robert Prevedel
pH indicators bring forth image contrast because of a pH change in their environment. One exemplary indicator (a modified fluorescein, bis-carboxyethyl-carboxyfluorescein [BCECF]) has both pH-sensitive and pH-insensitive parts, which enables ratiometric imaging. Others, such as 3,6-dihydroxy phthalonitrile and various naphthofluorescein derivatives, yield a pH dependent shift in their emission spectra (Urano et al., 2009). Recent research is actively pushing the emission spectrum toward the NIR for deep-tissue imaging (Myochin et al., 2011).
Sensing pH for the Perfect Tomato
Published in Denise Wilson, Sensing the Perfect Tomato, 2019
The simplest pH sensors use litmus or pH indicators to generate color representations of pH at coarse resolutions (on the order of 1 pH unit or greater). The most common instruments for measuring pH use an electrochemical approach with a glass electrode that includes a stable reference solution to ensure high-resolution, accurate, and consistent measurements. A wide range of other pH sensors are also available commercially. They are based on an equally broad range of sensing strategies and have attributes that are not available in glass electrodes, pH indicators, or other traditional pH sensors. And, many are smaller than glass electrodes while providing comparable accuracy and resolution, thus making them more attractive for integration into the IOT.
Glossary of scientific and technical terms in bioengineering and biological engineering
Published in Megh R. Goyal, Scientific and Technical Terms in Bioengineering and Biological Engineering, 2018
Litmus is a pH indicator paper (range 4.5–8.3) impregnated with an extracted lichen pigment. It turns red in acidic and blue in alkaline solutions. However, the use of litmus paper as an indicator is not a precise method of pH measurement.
Applications of aged powders of spray-dried whey protein isolate and ascorbic acid in the field of food safety
Published in Drying Technology, 2023
Chao Zhong, Songwen Tan, Zelin Zhou, Xia Zhong, Timothy Langrish
Microbial contamination causes reductions in food shelf life, and it increases the possibility of food-borne illnesses. For consumers, the changed texture, flavor and color of the food may be unacceptable. To deal with this problem, some food sensors[6–8] have been developed, which also help to mitigate food waste.[9] With the help of specific reactions, food sensors may be used to indicate food quality or safety. The pH of the chemical environment for foods can be changed by microbial spoilage.[10] When food is stored, transported or distributed, a pH indicator can be used to monitor its pH condition and give information about its quality. An indicator may respond through visible color development in response to pH changes.[11,12] The pH may be detected using an indicator, and a simple, low-cost, rapid and environmentally friendly sensor is helpful.[5] In order to detect volatile compounds that are acidic or basic, changes in the visual appearance of some pH dyes may be considered. Colorimetric pH indicator dyestuffs may be used, including bromothymol blue, bromophenol blue, bromocresol purple, methyl red, bromocresol green, methyl orange, methyl yellow, phenol red.[13] As pH indicators, methyl red (MR) and bromocresol purple (BCP) are toxic.
Real-time colorimetric detection of dissolved carbon dioxide using pH-sensitive indicator based on anthocyanin and PVA coated green iron oxide nanoparticles at room temperature
Published in Inorganic and Nano-Metal Chemistry, 2022
Derya Aksu Demirezen, Dilek Demirezen Yılmaz
The pH indicator consists of two parts: a support and a pH-responsive dye. Various synthetic dyes such as methyl red, cresol red, bromocresol green/purple, chlorophenol, bromothymol blue, and xylenol have been used for the preparation of pH-responsive color-changing indicators.[10–12] However, most synthetic dyes can be a serious threat to life and the environment. Therefore, it is necessary to replace these dyes with renewable and natural pigments.[13] Recently, a variety of natural pigments such as anthocyanin,[14–16] curcumin,[17] alizarin,[18] and green tea extract[19] have been used as pH indicator dyes.