Pharmaceutical Analysis

Pharmaceutical analysis

Different techniques of analysis

Analytical chemistry Are mainly divided into two types

Qualitative analysis – it gives information about atomic and Molecular species are the functional group in the sample. e.g  M.P, B.P specific Gravity, viscosity, optical rotation.

Quantitative analysis – give the relative amount of one or more of the analyte in numerical terms.

Analytical methods: are divided into the following types

  • Chemical  methods
  • Physico Chemical methods
  • Microbiological methods
  • Biological methods
  1. Chemical  methods

 

Methods of expressing concentration

In all the technique of quantitative analysis, the use of solution requires some basis for the expression of a solution concentration

  1. Normality
  2. Molarity
  3. Molality
  4. Percent solution
  5. Formal concentration
  6. Parts per Million (PPM)

Normality

The number of Gram equivalent of solute (substances) dissolves in 1 liter (1000ml) of a solution is called normality (N)

e.g molecular weight of NaOH is 40

1 N = 40gm of NaOH is dissolved in1000ml of water (H2O)

0.1 N = 4gm of NaOH is dissolved in 1000ml of water (H2O)

Molarity (M)

The number of moles of solute (substances) diesel in 1 liter (1000ml) of the solution is called molarity

1gm in 1000ml =1 mol

 

e.g molecular weight of HCL is 36.5

1M = 36.5gm of HCL is dissolved in a thousand ml of water.

Molality

A molal Solution contains one mole of solute per one kilogram of solution (1 litre of solvent) is called as Molality. (M)

 

e.g molecular weight of NaOH = 40

1M = 40gm of NaOH is dissolved in 1000gm of water (H2O)

Percent(%) solution

Sometimes the concentration is expressed in terms of % also % composition of a solution can be expressed as

1.% w/w → weight of solute/weight of solution × 100

2.% v/v → volume of solute/volume of solution × 100

3.%w/v = weight of solution/volume of solution × 100

e.g 1 % → 1gm in 100ml of H2O

Formal concentration

The concentration unit formal is similar to the more familiar molar concentration in that it is calculated as the number of moles of a substance in a liter of solution

The Formal concentration (formality) is applicable to the ionic substances

Parts per million is frequently employed to express the concentration of the very dilute solution and is expressed as PPM

Concentration in PPM  = mass of solute/ mass of solution × 10 raise to 6

 

Primary and secondary standard

Standard,

In pharmaceutical analysis, the word standard means a material containing a substance of our interest with a known concentration. We can express this with a definite number with proper units

Function

  1. We can determine the unknown concentration of the solution
  2. Standardization of volumetric solution
  3. Preparation of secondary standard
  4. To calibrate an instrument

Primary standard

The primary standard is a reagent that is very pure generally representative of the number of moles of the substance contain and easily weighed

A primary standard is a reagent that stable it’s not a hydrate has no water of hydration and has a high molecular weight

The primary standard is typically used in titration to determine an unknown concentration and in the other analytical techniques

High level of purity, low reactivity, high stability high covalent weight (to reduce error from mass measurement)

Nonhydroscopic, non-toxic, inexpensive, and readily available

It should have a higher relative molecular weight so that weighing errors may be negligible

The substance should be readily soluble under the conditions in which it is employed

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Secondary standard

A secondary standard is a chemical that has been standardized against a primary standard for use in a specific analysis

Secondary standard are commonly used to calibrate the analytical method

A secondary standard that is prepared in the laboratory for a specific analysis and is used to standardize against a primary standard

It follows that a secondary standard solution is a solution in which the concentration of dissolved solute has not been determined from the weight of the compound dissolve but by reaction (titration) of the volume of the solution against the major volume of primary standard solution

Properties

  • The secondary standard has less purity than the primary standard
  • less stable and more reactive than primary standard but IT Solution remains stable for a long time
  • Titrated against a primary standard

Acid-Base Titration notes