The amino acid L-carnitine plays an essential role in the energy metabolism of human, animal and plant cells. It functions as a receptor molecule for activated fatty acids in cytosol and in cell organelles such as the mitochrondia. The human body can form L-carnitine from the amino acids methionine and lysine, but also ingests it, predominantly from meat. L-carnitine is used in medicinal products and dietary supplement products.
L-carnitine is extracted from the sample material (eg milk powder-based baby food) using an acetonitrile/water mixture at 60°C. To determine the bound L-carnitine, the sample material is also subjected to an alkali fusion. After HPLC separation on a reverse phase, and after electrospray ionisation, the L-carnitine content is determined using mass spectrometry (MS/MS) on the basis of characteristic disintegration of the quasi-molecule ions. Quantification takes place with an isotype-labelled D3-Carnitine, which was added to the sample material to be extracted before extraction began.