We offer two different methods for the determination of amino acids as contaminants. A qualitative identification of present contaminant amino acids and a quantitative determination of contaminating amounts of amino acids. A method selection guide on which method to choose can be found at the end this section.
This method gives only an indication if additional amino acids could be present. Amino acids are determined in a fast screening without application of any substance-specific response factors. All proteinogenic amino acids (Alanine, Valine, Glycine, Threonine, Isoleucine, Leucine, Proline, Serine, Cysteine, Aspartic acid, Methionine, Phenylalanine, Glutamic acid, Tyrosine, Lysine, Arginine and Tryptophan) with the exception of Histidine are covered by this method.This method is only available as additional service to method A.0.1. A.0.3. or A.0.4.
Recovery of Cysteine, Methionine and Tryptophan could be influenced by the properties of the sample matrix and could lead to false-negative results.
Please contact us for a substance specific validation
Amino acids, which are suspected to be present in the sample are determined via enantiomer labelling coupled with analyte detection and quantification by GC-MS. All proteinogenic amino acids are covered by this method – including Histidine and Cysteine. Quantification is based on traceable standards from the National Institute of Standards and Technology (NIST), except Tryptophan.
In general, A.0.6. only gives a rough overview of which amino acid could be present as a contaminant. Histidine as a contaminating amino acid cannot be detected by this method. Matrix effects which could impede with the detection of Cys, Met and Trp are not covered by this method and could lead to false-negative results. Coelution of non-amino-acid contaminants could give rise to false positive results. However, A.0.6. is well suited for samples of low complexity such as free amino acids and when the expected concentration of contaminating amino acid is lower than 0.3%.
A.0.6.3. is the more robust method as it is based around analyte identification and quantification by GC-MS. The method covers all proteinogenic amino acids and is less prone to artefacts due to e.g. matrix effects.