Not official USP-NF text
TRYPTOPHAN
PF LGS# Brand Type of Test Additional Information
33(6) L1 Ultrasphere ODS Chromatographic purity 4.6 mm x 25 cm, 5 µm.
33(6) L1 Delta-Pak C18 Limit of . . . . . . . . . Limit of tryptophan related compound A. 3.9 mm x 15 cm, 5 µm.
18(3) G43 None Cited Organic volatile impurities See Method IV 467