Aqueous Titration

Titration is a strategy for minimising the body’s potential unfavourable reactions to medications in medicine. Most importantly, non-aqueous titrations have grown relevant in pharmaceutical analysis and have been recognised as an official analytical method by most modern pharmacopoeias, including the British pharmacopoeia. 

Aqueous titrations are analytical procedures that use water as the sample’s solvent to quantify the amount of the desired ingredient contained in the sample. Acid-base titrations, redox titrations, complexometric titrations, and precipitation titrations are examples of aqueous titrations used in analytical chemistry.

Furthermore, the non-aqueous titration technique is straightforward to use in quality control laboratories in developing countries where current and expensive tools are not accessible to determine GBP (gabapentin) content in milligrammes.

The current study outlines two easy and accurate titrimetric approaches for determining GBP in pure medication and capsules. The procedures entail titrating an acetous GBP solution with perchloric acetic acid in an acetic acid medium and detecting the endpoint either visually using crystal violet as an indicator or potentiometrically with a combination glass electrode.

What is titration in pharmaceutical analysis?

Titration is a typical quantitative chemical analysis method used in laboratories to determine the unknown quantity of a known reactant. Volumetric analysis is also known because volume measurements are essential in titration. The titrant or titrator is a reagent with a known concentration (a standard solution) and volume that reacts with an unknown analyte or titrant solution. When the endpoint is reached, we can use a calibrated burette or chemical pipetting syringe to ascertain the amount of titrant consumed. As defined by an indicator, the endpoint is the point at which the titration is complete.

In the pharmaceutical sector, titration, like many other fields of chemistry, has long been a standard method of analysis. It makes determining the number of active components and basic materials for medication manufacture easier. Volumetric analysis plays a key part in four separate stages, starting with medication formulation and ending with drug production:

Purity Analysis of Active Ingredients: Titration is being extensively utilised to evaluate the level of active ingredients in pharmaceuticals, such as aspirin or vitamin C in multivitamin pills, and the content and purity of medicine additives used in the manufacturing of medicinal compounds.

Content Analysis by Redox Titrations: Raw ingredients, fillers, and preservatives are also tested for purity using oxidation-reduction (redox) titrations. The bromatometric measurement of methyl-4-benzoate, a p-hydroxybenzoic acid ester, is a good example. This substance is utilised as a preservative in ophthalmic preparations and external ointments.

Precipitation Titrations: Some active compounds precipitate with an appropriate titrant to generate consumable medication due to their structure. Clotrimazole and benzalkonium chloride are two examples.

pH-Stat Titrations: To describe pharmaceuticals, assess the purity of enzyme products, and explore the kinetics of chemical reactions, pH-stat titration is used. The term “pH-stat” refers to a pH value that has been held constant for a while. This approach is beneficial for determining reaction kinetic characteristics such as enzyme reactivity.

Why are aqueous titrations not suitable for pharmaceutical analysis?

Organic acids and bases are water insoluble. These are incredibly weak and cannot be studied using standard titrimetric techniques. As a result, a non-aqueous titrimetric approach is employed.

Applications of Aqueous Titration

Hydrochlorothiazide, Aminophylline, niacinamide, chlorpheniramine maleate, and Chlorpromazine hydrochloride are effectively analysed using aqueous thermometric titration standard HCI, NaOH, or AgNO3 as titrant. The majority of the results were based on titration volumes. The quantitative result was derived from the temperature change due to the reaction when the enthalpogram curvature in the endpoint region was severe.

Exploratory studies of applying simple aqueous thermometric titration to measure solid and liquid dosage forms of the substances mentioned above were done without prior separation of constituents. There were no inert ingredient interferences, but one of the solid dosage formulations was studied. The vehicles interfered with the titrations in some of the liquid dosage form systems examined but not others.

Conclusion

Because of their resilience, low cost, and excellent precision, titrimetric methods are still commonly employed in pharmaceutical analysis. This is significant because everyone reacts to pharmaceutical medications differently depending on their age, comorbidities, weight, allergies, immunology, and general biochemistry.

Although aqueous titrations are no longer widely utilised in medicine, non-aqueous titrations, such as those detailed here, are still employed to analyse acids and salts of weak bases. However, titrating weak bases as their salts in a mixed non-aqueous/aqueous media employing potentiometric endpoint detection is often easier. The protonated base behaves like a weak acid when titrated with sodium hydroxide.