JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Pharmacy I Year PHARMACEUTICAL INORGANIC CHEMISTRY-I Previous Question Paper (July-2021 - R17)

A pharmacopoeia is an officially recognized book containing directions for the identification, purity, and strength of drugs, along with standards for their preparation. Its history reflects the evolution of medicine from ancient herbal practices to modern standardized pharmaceutical science.

The early history of pharmacopoeias dates back to ancient civilizations. The Ebers Papyrus (c. 1550 BC) is one of the oldest medical documents, containing hundreds of herbal remedies. Later, the works of Dioscorides, specifically De Materia Medica, served as the foundation for western pharmacognosy for centuries.

The first formal pharmacopoeias appeared during the Renaissance. The Nuovo Receptario, published in Florence in 1498, is often cited as the first city-state pharmacopoeia. This marked a shift toward standardized compounding practices. Subsequently, national pharmacopoeias emerged, such as the London Pharmacopoeia (1618), which provided legal authority for the preparation of medicines within its jurisdiction.

In the 19th century, the need for international consistency led to the creation of national compendia. The United States Pharmacopeia (USP) was established in 1820 by a group of physicians to ensure the quality of drugs. Similarly, the British Pharmacopoeia (BP) was first published in 1864, consolidating previous regional pharmacopoeias into a single national standard.

The Indian Pharmacopoeia (IP) has a distinct history. Before independence, the British Pharmacopoeia was used in India. The Indian Pharmacopoeial List was published in 1946 as a precursor. The first official Indian Pharmacopoeia was published in 1955 under the guidance of the Indian Pharmacopoeia Committee, which was later institutionalized as the Indian Pharmacopoeia Commission (IPC). The IP is now updated regularly to include modern analytical techniques like HPLC, GC, and spectroscopic methods to ensure the safety and efficacy of pharmaceutical products in alignment with global standards like the International Pharmacopoeia (Ph. Int.) published by the WHO.

Limit tests for chloride and sulphate are designed to identify and control small quantities of impurities present in pharmaceutical substances. The modified limit test is specifically employed for substances that are coloured or exhibit properties that interfere with the standard opalescence or turbidity comparison.

Modified Limit Test for Chloride:

This test is used for substances that produce a coloured solution or interfere with the precipitation of silver chloride. The procedure involves:

1. Dissolve the specified quantity of the substance in water or a suitable solvent.
2. If the solution is coloured, add a small amount of activated charcoal, shake well, and filter to obtain a clear, colourless filtrate.
3. Transfer the filtrate to a Nessler cylinder and add dilute nitric acid to acidify the solution.
4. Add silver nitrate reagent.
5. Compare the opalescence produced with a standard chloride solution treated similarly.
6. If the substance itself is insoluble or interferes, it is dissolved in a solvent like ethanol or treated with specific reagents to mask the interference before adding the silver nitrate.

Modified Limit Test for Sulphate:

The standard test uses barium chloride to form barium sulphate turbidity. The modified approach for substances that interfere or are coloured includes:

1. Dissolve the substance in distilled water. If the substance is coloured, perform a decolorization step using activated charcoal or an ion-exchange resin.
2. Add a small amount of alcohol to the test solution to stabilize the turbidity of barium sulphate.
3. Add the sulphate reagent (barium chloride and a small amount of sulphate standard to act as a seed).
4. The addition of alcohol ensures the formation of a uniform, fine suspension of barium sulphate, which is crucial for accurate visual comparison in the presence of trace impurities.
5. Compare the turbidity against a standard prepared by using a known quantity of potassium sulphate.

In both cases, the modification ensures that the visual assessment of opalescence or turbidity is not obscured by the inherent colour of the sample or by chemical interference, thereby maintaining the sensitivity and accuracy of the limit test.