Different Techniques of Analysis

Qualitative Analysis

Qualitative analysis in pharmaceutical analysis refers to the process of identifying the components present in a pharmaceutical sample, without measuring or calculating their exact amounts or concentration.

This type of analysis focuses on determining the presence, quality or the nature and the type of substances present in drugs or formulations.

This type of analysis is used to detect and identify chemical substances—such as drug molecules, excipients, or contaminants—by their physical, chemical, or biological properties.

Quantitative Analysis

Quantitative analysis in pharmaceutical analysis refers to the precise measurement and determination of the amount or the concentration of a drug or chemical compound present in any pharmaceutical formulations or biological samples using numerical, graphical or statistical methods.

Methods of Qualitative Analysis:

The following are some methods for performing qualitative analysis of a chemical compound:

Change in Colour:

An appearance or shift in color could indicate the presence of specific elements in the form of ions. Many substances have distinct color changes when they react with specific reagents, which indicate their presence in any sample.
For instance, the presence of iron ions (Fe3+) can be detected by adding potassium thiocyanate (KSCN), which forms a deep red complex. This visual confirmation indicates the presence of iron.
Example: Fe³⁺ + KSCN → deep red complex indicates iron presence.

Flame Test:

When a solid substance is exposed to a flame, it emits colors that are unique to each element. A flame test can be used to determine the presence of a specific metal or its ions.
Depending on the metal atoms present, the flame takes on different colors. The flame produced color when a portion of the sample is burned in the Bunsen burner can be used to assess the presence of some metal ions. For example:
Zn = Green,
Sr = Crimson,
Ca = Brick Red,
K = Violet.

Precipitation Reactions:

These tests involve the formation of insoluble compounds when two solutions are mixed. The formation of a precipitate, indicates the presence of specific ions.
For example, when silver nitrate (AgNO3) is added to a solution containing chloride ions (Cl-), a white precipitate of silver chloride (AgCl) forms, indicate the presence of chloride ions.
Example: Ag⁺ + Cl⁻ → AgCl (white precipitate).

Chromatography:

Chromatographic techniques, such as thin-layer chromatography (TLC) and gas chromatography (GC), allow for the separation and identification of components in a mixture. In these methods, the different rates of movement of substances on a stationary phase reveal their identities based on retention factors (Rf values) or elution order.

Methods of Quantitative Analysis:

Gravimetric Analysis

This traditional technique helps in quantifying substances by converting them into a stable and measurable form, usually through precipitation. The mass of the precipitate formed, after filtration and drying, is used to calculate the quantity of the original substance.

The analyte (the substance to be measured) is converted into an insoluble precipitate by adding a suitable reagent.


• The precipitate is filtered, washed to remove impurities, and dried (or ignited) to a constant weight.
• The final, pure compound is weighed accurately.
• By using specific formula and calculation the mass of the analyte in the original sample is calculated.

For example, Chloride ions can be precipitated as silver chloride (AgCl) by adding sodium chloride solution into silver nitrate (AgNO₃). The precipitate of AgCl is obtained in pure form and from the weight of AgCl, the amount of chloride ion (Cl⁻) present in the sample can be calculated

Spectrophotometry

Measures light absorbance at specific wavelengths to determine concentration.

Spectrophotometry measures the intensity of light of a specific wavelength, absorbed by a chemical or compound present in any solution.

By establishing a calibration curve using known concentrations, we can determine the concentration of unknown samples based on their absorbance.

• Initially by measuring the absorbance of any particular chemical by using spectrophotometer, a calibration curve / graph was prepared of different known quantity.
• Then by using the same spectrophotometer, the absorbance of the same chemical was measured in any sample solution (in which the same chemical is present in unknown concentration).
• Then this absorbance of unknown concentration solution is compared with the standard curve / graph to calculate the exact quantity of that chemical which is present in any sample in unknown concentration.

Electrochemical Analysis

Techniques such as potentiometry and voltammetry allow for the determination of analyte concentrations through their electrochemical properties. These methods are particularly useful for measuring the levels of ions and small organic molecules.

This analytical technique involves the study of chemical reactions that cause electrons to move. These methods are based on measuring electrical quantities—such as potential (voltage), current, or charge—produced by chemical reactions in an electrochemical cell.

The resulting electrical signal (current or potential) is used to calculate to the concentration or nature of the analyte.

Main types of electrochemical methods include:

• Potentiometry: measures the potential (voltage) of a solution at zero current (e.g., pH meter) determine the concentration of an analyte.
• Conductometry: measures the electrical conductivity of a solution to determine the concentration of an analyte.
• Coulometry: Measures total electric charge.
• Voltammetry: Measures current proportional to analyte concentration.

Titration Method

One of the most widely used quantitative methods. A titrant (known concentration) is added to analyte (unknown concentration) until reaction endpoint (often color change which is facilitated by an indicator added to the titration solution) is reached.

• Acid-Base Titration: This method focuses on the neutralization reaction between an acid and a base. For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), the reaction can be represented as:
  HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)
  The amount of NaOH used to neutralize HCl, used to calculate the concentration of HCl.
• Redox Titration: Redox titration (also called oxidation-reduction titration) is a type of volumetric analysis based on a redox reaction — a chemical reaction in which oxidation (loss of electrons) and reduction (gain of electrons) occur simultaneously between the titrant and the analyte.
  In a redox titration, one reagent acts as an oxidizing agent and the other as a reducing agent. During the titration, electrons are transferred from the reducing agent to the oxidizing agent until the reaction reaches a stoichiometric endpoint.
  The amount of titrant required to reach the endpoint is directly proportional to the amount of analyte present. This allows for quantitative determination of the analyte’s concentration.