LC/MS/MS Analysis of N-Terminal Protein Adducts with Improved Sensitivity: A Comparison of Selected Edman Isothiocyanate Reagents

Table 3

Measurements, limit of detection (LOD) on pure standards by LC/MS/MS (ESI) with LC/MS system no. 2.

Buffer/pH modifier (obtained pH)	TFA (~2)	Without buffer/pH-modifier		NH4OAc (~7)		NH3 (~9)
	Positive	Positive	Negative	Positive	Negative	Positive	Negative
FTH-MeVal (LOD, nM)	2.0	230	26	8.2	7.2	2.4	0.5
DABTH-MeVal (LOD, nM)	14	200	200	31	24	5.1	29
DNTH-MeVal (LOD, nM)	54	550	560	560	130,000	270	9,400
PTH-MeVal (LOD, nM)	4,100	19,000	470	7,500	3,400	310	470