BIO-309 BIOCHEMISTRY LABORATORY I VII.WEEK

7th WEEK Titration

TITRATION It is the determination of the amount and concentration of the solution (ACID-BASE) of unknown concentration reacted with a known solution (ACID-BAZ). The point where one of the species reacts completely in a titration is called EQUALITY POINT. http://kimyaygs.blogspot.com.tr/2014/01/titrasyon.html

Acid base titration is the process of adding certain amounts of acid to a solution known to be acidic, or adding a certain amount of acid to a solution known to be basic. The main purpose is to determine the concentration of acid or base. From here we can easily calculate the pH of the solution. In order to precisely capture the time at which the solution is equilibrated, an indicator is placed in the unconscious solution. As soon as the indicator changes color, the titration is stopped. The choice of indicator varies according to the type of acid or base, because the pH ranges in which the indicators show color change are different. There are many indicators that can be used for titration. When selecting indicators, we must consider the following items: 1) The reaction of strong acid with strong base will be the neutralization reaction and pH is 7. 2) Strong acid and weak base reaction results in a pH value of less than 7. 3) Reaction of weak base with strong base results in a pH value of 7.

If we take a brief look at the calculation process, let's assume that there is an unknown acid solution with a known volume and a concentration which is known for its volume. Since we balance the base and acid by titration, we can find the concentration of the base by applying the following formula: M1 x V1 = M2 x V2 Once we have found the concentration of the base, we can also easily find the pH value. Its formula is pH = -log (OHü). Of course, it is important to determine how much (OH) is in the base. Let me write down the names of some acid base indicators and their pH ranges. Timol blue: pH 1.2 - 2.8 while acid is red, base while yellow Methyl yellow: pH 2.9 - 4.0 while acid is red, base while yellow Methyl orange: pH 3.1 - 4.4 acid while red, base while orange Bromphenol blue: pH 3.0 - 4.6 while acid is yellow, while base is dark blue, purple Bromkresol green: pH 4.0 - 5.6 acid while yellow, base while blue Chlorphenol red: pH 5.4 - 6.8 while acid is yellow, while base is red Phenol red: pH 6.4 - 8.0 while the acid is yellow, while the base is red Kresol red: pH 7.2 - 8.8 while the acid is yellow, while the base is red Timol blue: pH 8.0 - 9.6 acid while yellow, base while blue Phenolphthalein: pH 8.0 - 10.0 acid while colorless, base while red

TITRATION OF AMINO ACIDS AND DETERMINATION OF ISOELECTRIC POINT Amino acids, which are amphoteric substances, have two functional groups. These are carboxylic acid (-COOH) and amino (-NH 2) groups. These functional groups form the inner salt in the neutral medium.

The amino group of amino acids can accept hydrogen ions and the carboxyl group may give hydrogen. Thus, amino acids can be titrated with both acids and bases, i.e. they show amphoteric properties. The presence of at least two groups that can be titrated in amino acids corresponds to at least two equilibrium constant (K) and two ionization constants. The isoelectric point (pI) is the pH at which the plus and minus loads in the amino acid are equal to each other, ie the net charge of the amino acid is 0, ie the point at which K1 and K2 are in equilibrium.

Acid-base titrations are the gradual addition or removal of protons Acid-base titrations are the gradual addition or removal of protons. Titration of glycine is given below Glycine appears to have two buffering intervals. They are shown as areas with pH range of pH 2.34 and pH 9.6 centered +/- 1. Glycine can be used as the buffer solution at these pH ranges. The theoretical value of the isoelectric point of glycine is 5.97.