For some years now, so-called peptides have been of interest as active ingredients, as they are easy to produce synthetically and influence a wide range of processes in the body. Peptides are chains of up to 100 amino acids that are linked via peptide bonds. Their biological properties depend on the number of amino acids and their position in the chain. There are peptides that have an anti-cancer, cholesterol-lowering or anti-inflammatory effect. This makes them attractive to the pharmaceutical industry and as additives in cosmetics or food supplements.

Peptides are usually supplied as a freeze-dried powder. However, 1 milligram of this powder contains only 60 to 80 percent peptide material. In order to incorporate the peptide powder into a therapeutic agent in the correct dosage, the amount of peptide in the powder must be precisely determined - i.e. the net peptide content. As peptides are very expensive, only minimal sample quantities may be used to determine the net peptide content. The analysis needs to minimise manual work and costs, and still comply with GMP guidelines, meaning that the peptide content of the powder must be measured with maximum accuracy and precision. This sounds like a major challenge for an analytical laboratory, but thanks to modern analytical techniques, sample quantities of far less than 1 mg of peptide powder are now sufficient to meet these requirements.

The absolute nitrogen content of the peptide powder is determined using elemental analysis. The net peptide content can be easily calculated from this formula: Net peptide content = absolute nitrogen content of the powder ×100/(%N in the peptide). Here, "%N in the peptide" is a known quantity derived from the chemical formula of the peptide. You can see ow the sample preparation and analysis works in this video from CUP Laboratorien Dr. Freitag GmbH.

Apart from weighing and packing the peptide powder in tin foil, the analysis is fully automated and only takes about five minutes. Elemental analysis has now become the gold standard for net peptide determination. As is usual with this method, the sample is burned and completely converted into gas. The nitrogen content of the peptide is then detected using a thermal conductivity detector and determined using specialized analysis software.

In addition to elemental analysis, TOC analysis supports pharmaceutical manufacturers in GMP-compliant production, for example in cleaning validation. This is a procedure used to prove that cleaning methods for production facilities and medical devices have worked effectively. Manufacturers often use multi-purpose facilities in which both medicinal and non-medicinal products are produced. In order to avoid unwanted cross-contamination, these systems must be reliably cleaned and the results of this cleaning proven.

The determination of total organic carbon (TOC) is suitable for this purpose, as this is a sum parameter that determines all organic contamination, for example from active ingredients or cleaning agents. In practice, TOC is analyzed both in the rinse water from the last cleaning sequence ("final rinse") and in swab samples from areas that are particularly difficult to clean. 

In summary, when it comes to applications under GMP standards, it is important that we can fully rely on the safety of the pharmaceutical products used in order to stay healthy or become healthy.