Identification tests for paracetamol (acetaminophen): a journey through different analytical techniques

Abstract

Introduction: Quality control is an essential part of Good Manufacturing Practice and it is present in all stages of production of a drug product aiming to remove or prevent any potential non-conformity. The identification test is one of the first tests to be performed when analyzing a drug product as it is necessary to verify the presence of the active substance in the product to proceed quantitative tests. This study aimed at presenting in an illustrative way different analytical techniques used for identifying acetaminophen. Five different analytical techniques described in the current national official compendia were explored: colorimetry, melting point, infrared spectrophotometry, ultraviolet spectrophotometry and high-performance liquid chromatography. The techniques were explored in samples (commercial paracetamol tablets) and the paracetamol primary standard was used for obtaining the results. All selected techniques showed acetaminophen identification in the samples, as proposed. The selection of an analytical technique for identification tests must be done considering the objective of the analysis, laboratory conditions and the number of different techniques needed for concluding the test. Infrared spectrophotometry, ultraviolet spectrophotometry and high performance liquid chromatography are generally conclusive/ confirmatory techniques. Alternatively, colorimetry is considered only as eliminatory. Each technique has its own peculiarities, advantages and disadvantages, hence, it is up to the analyst to consider all these points when evaluating which techniques will be chosen in the laboratory. Apart from the applied techniques, the greatest aim of a pharmaceutical analysis is to ensure the quality of the drug products available in society.