ELISA kit reveals classification of indicators - Database & Sql Blog Articles

1. Acid-base indicator. Indicates the change in H+ concentration in the solution, which is an organic weak acid or an organic weak base, which has different colors of acidity and alkalinity.

Elisa kit

The dissociation constant of the indicator acid HIn in solution is Ka=[H+][In-]/[HIn], ie the color of the solution is determined by [In-]/[HIn], and [In-]/[HIn] is determined again. At [H+]. Take

Methyl orange

(Ka=10-3.4) As an example, when the pH of the solution is <3.1, it is acidic and has a red color; when the pH is >4.4, it is alkaline and has a yellow color; and at a pH of 3.1 to 4.4, a mixed color of red and yellow appears. Orange, called the discoloration range of the indicator. Different acid-base indicators have different ranges of discoloration.

2. Metal indicator. The indicators used in complexometric titration are mostly dyes which, at a certain pH, can complex with metal ions to present a completely different color than the free indicator to indicate the end point.
3. Redox indicator. It is an oxidizing agent or a reducing agent, and its oxidized form has a different color from the reduced form, and when it is oxidized (or reduced) in the titration, it is discolored, indicating a change in the solution potential.
4. ELISA kit precipitation titration indicator. Mainly the titration of Ag+ and halogen ions, using potassium chromate, ferric ammonium or fluorescent yellow as an indicator.