Gravimetric Analysis Is Applied in Pharmacy

The term ‘Gravimetric Analysis’ can be defined as a quantitative method that is used to precisely determine the quantity of a particular chemical substance in an aqueous solution. Gravimetric analysis is performed with the selective precipitation of the respective component. Chemical analysis of ores and other industrial materials, equipment calibration, and elemental analysis of inorganic compounds are all applications of gravimetric analysis. It is also utilised in various sectors to inspect raw materials and finished goods and determine the chemical composition of rocks, minerals, and alloys. In the following section, we’ll go through the applications and steps of gravimetric analysis.

What Are the Applications of Gravimetry in Pharmacy?

• It can be used to calibrate other instruments since it can easily provide accurate and highly correct data.

• This method provides undergraduate students with hands-on experience in a graduate laboratory. It is a very beneficial tool for students considering medical school, as they will continuously employ the strategy throughout their education.

• One of the applications of gravimetric analysis is that it can provide extremely precise analyses. It has determined the atomic masses of many elements in the periodic table.

• Another benefit of gravimetric analysis is that it helps to limit the number of instrumental errors when measuring the mass of substances.

• It is used to measure the volume of plasma. Radioiodinated human serum, albumin, and red blood cells can be utilised in the same way to calculate plasma volume. In fact, this is one of the most widely used applications of gravimetry in pharmacy and biology.

• The method is helpful in chloride determination in a particular mixture.

Steps Involved in Gravimetric Analysis

• Preparation of the Solution

In this step, the pH of the solution is altered for precipitation to occur. Other procedures include removing interferences and adjusting the volume of the sample to suit the amount of the precipitating agent. 

• Precipitation

A precipitating agent solution is added to the sample solution, leading to supersaturation. Next, nucleation occurs when a few molecules of precipitate clump together to form a nucleus. Adding more precipitating agents at this point will either generate new nuclei or build upon existing nuclei, resulting in a precipitate.

• Digestion of the Precipitate 

To digest the particles, the precipitate is heated (below boiling) for 30 minutes to an hour. Digestion results in particle growth and improves precipitate properties by dissolving tiny particles and reprecipitating larger ones. Ostwald ripening is the name for this process. 

In colloidal precipitates, high concentrations of adsorbed ions cover a vast area of the precipitate. Digestion causes the small colloidal particles to clump together, reducing their surface area and, in turn, reducing adsorption.

• Washing and Filtering the Precipitate

Washing the precipitate will eliminate adsorbed ions that increase the precipitate weight. However, it is important not to use too much water, as some precipitates may be lost. Water should not be used as a washing solution for colloidal precipitates because it may lead to peptisation.

• Drying and Ignition

The goal of drying (heating at roughly 120-150°C in an oven) or ignition (heating at 600-1200°C in a muffle furnace) is to obtain a material with an exactly known chemical structure. Thus, the amount of analyte can be properly calculated.

How Is Gravimetric Analysis Performed?

Gravimetric analysis is a quantitative method for estimating the amount of a component in an aqueous solution by selective precipitation of the substance. Filtration separates the precipitate from the remaining aqueous solution, which is then weighed. Assuming that the precipitate chemical formula is known and that the precipitation reaction is completed, the mass of the material in the original sample can be calculated.

The following experiment shows how gravimetric analysis is performed to calculate the proportion by mass of sulphate in an unknown sulphate salt: 

• The unknown sulphate salt will first be dissolved in water in a pre-weighed sample. 

• The unknown salt’s aqueous solution is then diluted with the excess amount of barium chloride in an aqueous form. 

• Filtration is used to collect the barium sulphate precipitate, which is then dried and weighed. 

• We can presume that all of the sulphates from the initial unknown sample are transferred to the precipitate because barium chloride is supplied in excess. 

• Thus, the precipitation procedure is complete.

Conclusion

Gravimetric analysis is a chemical technique for determining the mass of a substance. The approach is based on the idea that every material has a mass that can be measured. 

In this method, a known mass of the chemical is weighed and then transferred to a vessel. The material is then evaporated by heating the vessel. Following that, the vaporised material is collected and weighed. This enables the mass of the original sample to be calculated.