Elemental impurities are trace levels of metals present in finished drug products. Elemental impurities testing is critical to understand the levels of trace elements present in final drug products. This article will outline how elemental impurities testing is carried out and the benefits of various techniques.
Where do Elemental Impurities Come From?
Elemental impurities in pharmaceuticals are often transferred from catalysts, formulation ingredients, and process vessels. Impurities can alter the efficacy of a drug or have a direct toxic impact on the patient taking the drug.
The Legalities of Elemental Impurities Testing
For over a century, pharmaceutical regulators have required testing of heavy metal impurities. In recent years, global regulators have produced and distributed a modern, revised methodology and guideline for elemental impurities testing.
The elemental analysis testing guidelines specify twenty-four elemental impurities and their toxicity limit. To adhere to these standards, elemental impurities testing must be carried out using one of the following techniques:
ICP Elemental Impurities Testing
ICP-OES (inductively coupled plasma optical emission spectroscopy) and ICP-MS (inductively coupled plasma mass spectrometry)instruments are suited to applications that require low detection capabilities and the capacity to resolve complex spectra.
Elements such as arsenic, mercury, palladium, platinum, osmium, and iridium produce many emission lines when excited in the plasma. This must be resolved effectively to stop spectral interferences.
Atomic absorption spectrometer and graphite furnace atomic absorption spectrometer can also perform trace metal analysis. However, ICP can carry out elemental impurities testing for numerous elements at one time, with longer linear ranges than AAS and GFAAS because of the high temperature of the plasma.
ICP also has a lower level of matrix interference because of its mode of sample introduction and has a range of emissions lines to select. This reduces interference from other elements whilst enhancing sensitivity.
ICP provides a specific, sensitive, and reproducible means of elemental impurities testing in drug articles. This technology is increasingly important in the pharmaceutical industry. The main downside to ICP-OES is that it is extremely expensive, particularly when compared with other elemental impurities testing methods.
Flame Atomic Absorption Spectrometry
FAAS is a simple and fairly inexpensive way of carrying out elemental impurities testing. It has high detection limits but can only analyze one element at a time.
Vapor Generation Atomic Absorption Spectrometry
VG-AAS is an elemental impurities testing technique that involves a chemical reaction to emit metals as gaseous hydrides. It has high detection levels but can only be used for a few elements and only one at a time.
Graphite Furnace Atomic Absorption Spectrometry
GFAAS elemental impurities testing method slowly heats a small amount of sample to ash. The temperature is then raised quickly to volatize the metal. It is highly sensitive and can examine trace levels of analytes, however, chemical interference often impacts the outcome.
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