Division 3.17 Calibration standard solution of tryptophan and internal standard:

Take 2,0 ml concentrated solution of tryptophan (3.15), and 2,0 ml of concentrated internal standard (α-methyl-tryptophan) solution (3.16). Dilute with water (3.1) and methanol (3.8) to approximately the same volume and to approximately the same concentration of methanol (10 %-30 %) as the finished hydrolysate.

This solution must be prepared freshly before use.

Protect from direct sunlight during preparation.