Medicine

Methodical instruction

Methodical instruction

for the students of pharmaceutical faculty

LESSON 2 (practical – 6 hours)

 

THEME: Refractometry and polarimetry: a theory, practical application, metrology descriptions.

AIM: To familiarize with the physical methods of analysis. To learn classification methods of analysis and classification of physical methods of analysis, theoretical bases of refractometry and polarimetry, learn  to determine content of substances medications by the method of refractometry and polarimetry.

 

PROFESSIONAL MOTIVATION OF STUDENTS

Large advantage of instrumental: physical and physical and chemical methods of analysis – expression, high sensitivity and in many cases high selectivity. In this connection they are all wider inculcated in practice of pharmaceutical analysis. The large section of physical methods of analysis is optical methods. Refraction of light and rotation of plane polarization is optical properties of the systems, which are closely related to chemical composition.

 

THE SELF-PREPARATION PROGRAM

1.     Classification methods of analysis, advantage and lacks of  physical methods of analysis (PhMA)

2.     Metrology descriptions of PhMA and physical and chemical methods of analysis (PhChMA) .

3.     Refractometry.

4.     Polarimetry.

 

TESTS AND REAL-LIFE SITUATIONS FOR SELF-ASSESSMENT

 


1. The relative index of refraction is determined of method:

A. Polarimetry.

B. Thermoanalysis.

C. Refractometry.

D. Polyarografiya.

E. Gravimetry.

2.  In the refractometry method of analysis the size of index of refraction depends:

A. Lengths of falling light.

B. Nature of substance.

C. Density of solution.

D. From all factors.

E. Temperature and pressure.

3. The refractometry method is used in pharmacies for:

A. Qualitative determination of cations.

B. Quantitative determination of medicinal substances.

C. Qualitative determination of anions.

D. Determination of admixtures in the substances .

E. Determination of very small concentrations of substances.

4. The determination content of substance of the polarimetry method:

A. Molar concentration.

B. Thithre.

C. Volume concentration.

D. Mass-volume  part.

E. Mass part in solution.

 


 1. To define the concentration potassium of iodide in water solution, if index of refraction of solution 1,3450, and the index of refraction of water is equal 1,3330. The refractometrion factor is equal 0,00130.

2. To define the concentration of water solution of glucose (%), if it is known that the index of refraction of this solution is equal 1,3557.  The refractometrion factor 0,00142.

3. To define the concentration of solution of glucose, if the corner rotation for this solution is equal +7,05°, the thickness of layer 10 sm, specific rotation of glucose is equal +53,1°.

4. To define the specific rotation of glucose, if it is known that the corner rotation of the polarized ray is equal +18,60° at measuring 35,00 % to solution in the cuvette, it is long 10 sm.

 

ANSWERS ON THE SELF-ASSESSMENT

Tasks: 1. 9,23 %, 2. 16,00 %, 3. 13.27 %, 4. +53,1°.

Tests: 1. C., 2. D., 3. B.,4. D,5.

REFERENCES:

1. The lecture’s material.

2.  Bolothov V.V. and other. Analitical chemistry. – Charciv «Osnova», 2000.-p. 332-347.

METHOD OF IMPLEMENTATION OF PRACTICAL WORK

 

Work 1. Determination the concentration  of glucose in  the water solution.

         In the flasks  of 50 ml place exact  mass of glucose  1,25; 2,50; 3,75; 5,00; 6,25 g,  dissolve in the distilled water, lead to the volume of solution water to the mark and mix.

         Measure the index of refraction of water, and then each of the prepared solutions. After the got solutions will be dependence in coordinates: an index of refraction to concentration.

         Measure the indexes of refraction of the investigated solutions and expect their concentration by the chart and calculation method, preliminary preparation 1 % solution of glucose and expecting the refractometrion factor.

Work 1. Refractometrion determination of concentration of ethanol in the alcohol-water solutions

              On the prism of refractometr is inflicted 4-5 drops of alcohol-water solution at once measure the index of refraction and determine after tables the concentration of alcohol in the investigated solution.

С, %

n

С, %

n

1

1,33345

17

1,34209

2

1,33400

18

1,34270

3

1,33440

19

1,34330

4

1,33493

20

1,34390

5

1,33535

21

1,34452

6

1,33587

22

1,34512

7

1,33641

23

1,34573

8

1,33700

24

1,34634

9

1,33760

25

1,34697

10

1,33808

40

1,35500

11

1,33870

45

1,35700

12

1,33924

50

1,35900

13

1,33977

55

1,36060

14

1,34043

60

1,36180

15

1,34096

65

1,36300

16

1,34158

70

1,36380

 

BASIC LEVEL OF KNOWLEDGE AND SKIILS

A STUDENT MUST KNOW:

1. Classification methods of analysis, advantage and lacks of  physical methods of analysis (PhMA)

2.     Metrology descriptions of PhMA and physical and chemical methods of analysis (PhChMA) .

3.     Refractometry.

4.     Polarimetry.

A STUDENT MUST BE ABLE:

1.   To conduct measuring and calculations of content of the determined substances as the result of measuring of index refraction.

2.   To conduct measuring and calculations of specific rotation and content of the determined substances as the result of measuring of corner rotation.

 

Prepared by assist. Burmas N. I.

Adopted at the Chair Sitting Minutes № 12

04” June, 2007, Revised