A kind of acid-base indicator and preparation method thereof

Abstract

The invention discloses an acid-base indicator and a preparation method thereof. The acid-base indicator is a solution containing alkannin and curcumin, wherein the mass ratio of alkannin to curcumin is 80 to (45-100). The preparation method of the acid-base indicator comprises the following steps: dispersing alkannin and curcumin into an organic solvent; and dissolving and filtering impurities to obtain the acid-base indicator. Alkannin and curcumin display different colors in an acid-base solution; alkannin and curcumin are mixed in the solution in a certain ratio, so that an indication range of the acid-base indicator is expanded, a mutational range is narrow and the acid-base indicator is sensitive to pH change indication; and meanwhile, the change of the colors is obvious so that the intensity of acid-base properties of the solution can be easily identified.

Description

technical field

[0001] The invention relates to an acid-base indicator, in particular to a compound acid-base indicator of shikonin and curcumin and a preparation method thereof. Background technique

[0002] Acid-base indicators are a class of compounds that change color as the pH of the solution changes within a specific pH range, usually organic weak acids or organic weak bases. Commonly used acid-base indicators include litmus, phenolphthalein, methyl orange, methyl red, etc., but due to these acid-base indicators have some shortcomings, for example: litmus color change range pH 5.0-8.0, phenolphthalein The pH value of the color change range is 8.2-10.0, which is insufficient for the indication of acidic and strong alkaline solutions; the color change range of the pH value of methyl orange is 3.1-4.4, and the color change range of methyl red is 4.8-6.0, neither of which can indicate alkaline solutions. It can be seen from the above examples that the existing acid-base i...

Examples

Embodiment 1

[0016] Take 1 g of shikonin with a content (ie, purity, the same below) of 80% and 0.71 g of curcumin with a content of 90%, add 80 milliliters of ethanol to dissolve, and filter. Add two drops of the filtered solution into 100 ml of acidic aqueous solution with pH less than 1, add dilute sodium hydroxide solution drop by drop, and observe the color and pH changes. The specific pH of the test solution was measured with a pH meter.

Embodiment 2

[0018] Take 1 g of shikonin with a content (ie, purity, the same below) of 80% and 0.53 g of curcumin with a content of 90%, add 80 milliliters of ethanol to dissolve, and filter. Add two drops of the filtered solution into 100 ml of acidic aqueous solution with pH less than 1, add dilute sodium hydroxide solution drop by drop, and observe the color and pH changes. The specific pH of the test solution was measured with a pH meter.

Embodiment 3

[0020] Take 1 g of shikonin with a content (ie, purity, the same below) of 80% and 1.07 g of curcumin with a content of 90%, add 80 ml of ethanol to dissolve, and filter. Add two drops of the filtered solution into 100 ml of acidic aqueous solution with pH less than 1, add dilute sodium hydroxide solution drop by drop, and observe the color and pH changes. The specific pH of the test solution was measured with a pH meter.

technical field

[0001] The invention relates to an acid-base indicator, in particular to a compound acid-base indicator of shikonin and curcumin and a preparation method thereof. Background technique

[0002] Acid-base indicators are a class of compounds that change color as the pH of the solution changes within a specific pH range, usually organic weak acids or organic weak bases. Commonly used acid-base indicators include litmus, phenolphthalein, methyl orange, methyl red, etc., but due to these acid-base indicators have some shortcomings, for example: litmus color change range pH 5.0-8.0, phenolphthalein The pH value of the color change range is 8.2-10.0, which is insufficient for the indication of acidic and strong alkaline solutions; the color change range of the pH value of methyl orange is 3.1-4.4, and the color change range of methyl red is 4.8-6.0, neither of which can indicate alkaline solutions. It can be seen from the above examples that the existing acid-base i...

Examples

Embodiment 1

[0016] Take 1 g of shikonin with a content (ie, purity, the same below) of 80% and 0.71 g of curcumin with a content of 90%, add 80 milliliters of ethanol to dissolve, and filter. Add two drops of the filtered solution into 100 ml of acidic aqueous solution with pH less than 1, add dilute sodium hydroxide solution drop by drop, and observe the color and pH changes. The specific pH of the test solution was measured with a pH meter.

Embodiment 2

[0018] Take 1 g of shikonin with a content (ie, purity, the same below) of 80% and 0.53 g of curcumin with a content of 90%, add 80 milliliters of ethanol to dissolve, and filter. Add two drops of the filtered solution into 100 ml of acidic aqueous solution with pH less than 1, add dilute sodium hydroxide solution drop by drop, and observe the color and pH changes. The specific pH of the test solution was measured with a pH meter.

Embodiment 3

[0020] Take 1 g of shikonin with a content (ie, purity, the same below) of 80% and 1.07 g of curcumin with a content of 90%, add 80 ml of ethanol to dissolve, and filter. Add two drops of the filtered solution into 100 ml of acidic aqueous solution with pH less than 1, add dilute sodium hydroxide solution drop by drop, and observe the color and pH changes. The specific pH of the test solution was measured with a pH meter.

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