PH Indicators

Pyranine (HPTS; Solvent Green 7) is a cell-impermeant pH-sensitive fluorescent indicator. Pyranine acts as a class of fluorescent chemosensor for the Cu⁺ ion. Pyranine is used as a coloring agent, biological stain, optical detecting reagent, and pH indicator (Ex/Em = 450/510 nm).

Carboxy-SNARF 1 (5/6-mixture) (SNARF 1) is a fluorescent probe that is sensitive to pH (Ex: 488 nm). Carboxy-SNARF 1 (5/6-mixture) can be used for measurement pH. Carboxy-SNARF 1 (5/6-mixture) exhibits a significant emission shift from yellow-orange (Em: 580 nm) to deep red fluorescence (Em: 640 nm) under acidic and basic conditions (pH=7-8), respectively.

Phenol red (Phenolsulfonephthalein) is a pH indicator dye, relying on a distinct color change from pink to yellow in case of a positive reaction .

BCECF is a cell-impermeant pH-sensitive fluorescent dye. BCECF allows measurements in the physiological pH range 6.0-8.0. Excitation ratio: 490/440 nm; Emission intensity: 535 nm.

BCECF Acetoxymethyl ester is a cell membrane permeable compound widely-used as a fluorescent indicator for intracellular pH. BCECF Acetoxymethyl ester could diffuse through the cell membrane and intracellular esterase cleave the ester bond releasing BCECF (HY-101882). BCECF allows measurements in the physiological pH range 6.0-8.0. Excitation ratio: 490/440 nm; Emission intensity: 535 nm.

Thymolphthalein is a phthalocyanine dye with electrochemical activity that can serve as an acid-base indicator, appearing colorless under acidic pH conditions and blue under alkaline pH conditions. Thymolphthalein acts as a signal molecule in co-assembled AMP/TP nanoparticles (NPs) for the visual and colorimetric detection of Escherichia coli. Thymolphthalein can form a non-conductive porous polymer coating via electropolymerization.

CouCyCF3 is a fluorescent probe for bacterial cytoplasmic pH, with a pKa of 7.0. CouCyCF3 can be taken up by both Gram-positive and Gram-negative bacteria. Under acidic conditions, the fluorescence of CouCyCF3 in the red channel increases, while its fluorescence in the blue channel increases with elevated pH. A linear quantitative response is achieved via the I_red/I_blue ratio within the pH range of 5.0-7.5, with excitation/emission wavelengths of 445/472 nm (blue) and 640/708 nm (red). CouCyCF3 can be used for studies on bacterial acid tolerance and phagolysosome acidification.

BTC1070 is an anti-quenching pentamethine cyanine NIR-II fluorescent probe. BTC1070 exhibits high brightness and excellent photostability in aqueous solution (Ex/Em = 1015/1065 nm). BTC1070 can clearly visualize lymphatic structures after intradermal injection, and produces a ratiometric fluorescence response in the acidic range to non-invasively quantify gastric pH. BTC1070 is applicable to studies related to in vivo deep tissue imaging and gastric pH sensing.

9-Amino-6-chloro-2-methoxyacridine is a pH sensitive fluorescent probe. 9-Amino-6-chloro-2-methoxyacridine has been frequently used to measure changes in vacuolar pH when a specific substrate crosses the tonoplast through a putative H⁺/solute antiport system.

9-Aminoacridine, a fluorescent probe, acts as an indicator of pH for quantitative determination of transmembrane pH gradients (inside acidic). 9-Aminoacridine is an antimicrobial. 9-Aminoacridine exerts its antimicrobial activity by interacting with specific bacterial DNA and disrupting the proton motive force in K. pneumoniae. 9-Aminoacridine is a HIV-1 inhibitor and inhibits HIV LTR transcription highly dependent on the presence and location of the amino moiety. 9-Aminoacridine inhibits virus replication in HIV-1 infected cell lines. 9-Aminoacridine is used as a Rifampin (RIF; HY-B0272) adjuvant for the multidrug-resistant K. pneumoniae infections.

Methyl Orange is a soluble azo dye commonly used as an acid-base indicator and for staining cells and tissue sections, as well as for dyeing textiles. Methyl Orange appears red at a pH of 3.1 and changes to bright yellow as the pH increases to 4.4. Methyl Orange (500 mg/L) exhibits cytotoxicity and can cause DNA damage.

DHPDS disodium salt is a pH-sensitive fluorescent dye. DHPDS disodium salt is used to measure intracellular pH (pHi) from the surface fluorescence of the isolated perfused rat liver.

DND-189, a low-pH fluorescent probe, is sensitive to neutral and low pH range. DND-189 can be used to measure the pH of acidic organelles.

Indigo carmine is an efficient reagent for the determination of ozone by chemlluminescence (CL).

5(6)-Carboxynaphthofluorescein is a pH-dependent fluorophore. 5(6)-Carboxynaphthofluorescein shows good sensitivity in an alkaline pH range and it can be exploited in the construction of fiber-optic pH sensors. 5(6)-Carboxynaphthofluorescein can be used as a fluorescent pH indicator (Ex/Em=593/668 nm).

OG 488, acid, a fluorescent pH indicator, has many applications in biochemistry and neurosciences.

Thymol blue is a reversible pH indicator that responds to the pH of the solution through structural changes of protonation and deprotonation. Thymol blue is red (HI^- form) under acidic conditions and blue (I^2- form) under alkaline conditions. Quantitative detection is achieved through the absorption peak shift (435 nm/596 nm) of the UV-visible spectrum. Thymol blue selectively responds to pH changes, changing from red to yellow at pH 1.2-2.8 and from yellow to blue at pH 8.0-9.6. Thymol blue can be fixed in a silica gel matrix through sol-gel technology to form a solid-state sensor for in-situ pH measurement in the marine environment and acid-base monitoring in the biomedical field[1][2].

Thymol Blue sodium is an acid-base indicator used to indicate changes in pH. Thymol Blue sodium fades from red to yellow at pH 1.2 to 2.8 and from yellow to blue at pH 8.0 to 9.6. Quantitative detection is achieved through the absorption peak shift (435 nm/596 nm) of the UV-visible spectrum. Thymol blue sodium can be fixed in a silica gel matrix through sol-gel technology to form a solid-state sensor for in-situ pH measurement in the marine environment and acid-base monitoring in the biomedical field.

Bromophenol blue sodium is a pH indicator. It changes from yellow at pH 3.0 to blue at pH 4.6. Bromophenol blue sodium is also used as a tracking dye to monitor the process of agarose gel electrophoresis and polyacrylamide gel electrophoresis.

Alizarine Yellow R (Mordant orange 1), Salicylic acid derivative (HY-B0167), is an azo dye. Alizarine Yellow R is used as a pH indicator and a biological stain in chemical examinations and dyeing industries.