Amino Acids Working Group Meeting Book (July 3, 2018)

Existing Methods – Cys(CSSC)

Modified Hydrolysis • Performic acid oxidation to cysteic acid prior to hydrolysis. In addition to Trp, Tyr is destroyed by this procedure. Typically paired with IEX/Ninhydrin • Disulfide exchange using DTDPA, concurrent with hydrolysis, to form a mixed disulfide that can be quantitatively determined. Only Trp is destroyed. Mostly paired with pre-column derivatization/RP HPLC, but compatible with IEX/Ninhydrin

Existing Methods – Trp

Modified Hydrolysis • Alkaline hydrolysis – Still some losses, may require use of internal standard. • Enzymatic hydrolysis. Analysis • Regardless of prep, Trp can be determined directly by HPLC, based on either absorbance or fluorescence detection