Reagent Preparation

A reagent is a chemical substance used in preparing a product, in detecting a component, and in developing photographs. It is added to a system to discern the presence of another substance. Examples of common laboratory reagents include Tollens’ reagent, Fehling’s reagent, and Millon’s reagent. The terms “reactant” and “reagent” are not identical, but are frequently used interchangeably. A reactant is present at the start of a chemical reaction that is later altered in the course of that chemical reaction.

Reagents

• In organic chemistry, reagents are distinct substances formed by chemical union of two or more inorganic or small organic ingredients in definite proportion by weight. Examples of common organic reagents include Grignard reagent, Collins reagent, and Fenton’s reagent.

  -Acetate Buffer

  In the laboratory, a sodium acetate solution of 0.2 (M) (M refers to molarity) is prepared. In a one-liter volumetric flask, a solution of sodium acetate trihydrate is weighted for the desired 27.2 gm reading. Approximately 800 milliliters of deionized water is added to the mixture of sodium acetate and sodium acetate trihydrate solution. The entire mixture solution is acidified with glacial acetic acid (an acetic acid that is at least 99.8 percent pure and tends to crystallize on cold days) while simultaneously reducing the pH of the solution to 4.0. Lastly, the volume of the mixture is adjusted to one liter by adding deionized water.

  -Phosphate Buffer

  A monobasic potassium phosphate solution of 0.25 (M) is prepared. The initial pH of the solution must be approximately 4.8. Phosphate buffer is formed when the initial pH 4.8 is further adjusted to 6.0 by adding dibasic sodium phosphate solution of 0.25 (M).

  -Hepes

  Hepes refers to N-Hydroxyethyl Plperazine N2 Ethanesulfonic Acid. It is mixed and dissolved into deionized water and the volume is adjusted to one liter. Hepes reagent is prepared when the pH is brought up to 8.2 by the help of 2(N) sodium hydroxide solution.

Precautions

• In the laboratory, all solvents must be HPLC grade. Furthermore, all solvents should be tested for peroxide contamination before use, otherwise they may change chemically when reacted with an oxidizing agent. It's better to examine each new batch of solvents for contamination by drying down a few milliliters of the solvent and converting it into a derivative (called derivatization), if possible.