Amino acid enantiomers are separated by reverse phase HPLC (following a modified method of Kaufman & Manley, 1998). Samples are derivitised with o-phthaldialdehyde and thiol N-isobutyryl-L-cysteine automatically prior to injection. The resulting diastereomeric derivatives are then separated on Hypersil C18 BDS column (sphere d. 5 µm; 250 x 3mm) using a linear gradient of a sodium acetate buffer, methanol and acetonitrile on an Agilent 1100 or 1200 Rapid Resolution liquid chromatograph. The fluorescence intensity of derivitised amino acids are measured (Ex=230nm, Em=445nm) and normalised to the internal standard, L-homo-arginine. All samples are run in duplicate. Amino acid standards and chemical blanks are also run daily.