Analyzing the vitamin D3 content in milk is not easy. A prerequisite for correct vitamin D3 analysis, regardless of the choice of analysis method, is the complete recording of the vitamin in the substrate to be examined. Both free vitamin D3 and vitamin D3 bound to fat, for example, must be recognised. Purification steps that eliminate e.g. fractions containing vitamin D3 before the actual analysis lead to incomplete results. So far, high-performance liquid chromatography in conjunction with tandem mass spectroscopy (HPLC-MS/MS) has proven to be the method of choice for determining the vitamin D3 content.* This method is cumbersome, takes a long time, is expensive and is used in HPLC-MS /MS form hardly offered by laboratories in Germany.
A cheaper and faster method based on the immunological detection method ELISA (Enzyme-linked Immunosorbent Assay) has now been developed for the first time by the laboratory Dr. Scheller GmbH, Augsburg for vitamin D3 determination in the milk medium in Germany. The method is not new. It has already been in use in the USA and Canada for years and is accredited according to ISO/IEC 17025:2005 (ANAB).
Table 1 shows the agreement of analytical results between the methods.
See AOAC Research Institute e.g. n. SciMed Technologies Inc. (2016): Technical Information VitaKit® A &D Vitamin D & A Analysis by Elisa
The ELISA method for determining vitamin D3 in milk was included in the accreditation certificate according to DIN EN ISO/IEC 17025:2005 for a laboratory accredited by the German Accreditation Body (Dakks) for the first time in 2018. You can find the certificate here.
The laboratory Dr. Scheller GmbH, Augsburg carried out the procedure. A round robin test, on which the accreditation is based, with 16 laboratories, 14 of which used the HPLC method and two used the ELISA method, was successful.
You can find the current analysis protocols for dDrei milk and a comparison of conventional milk here