GluFib lockmass signal intensity gradually degrades when delivered by ACQUITY UPLC M-Class ASM - WKB65892

SYMPTOMS

• [Glu1]-fibrinopeptide B peptide (GluFib) signal is initially as expected when its delivered to nanoLockSpray source, but it degrades and is eventually gone

ENVIRONMENT

• nanoLockSpray source
• ACQUITY UPLC M-Class Auxiliary Solvent Manager (ASM)

CAUSE

The pump heads of the ASM are titanium, which binds to certain peptides such as GluFib. Addition of ion pairing agents such as maleic acid prevents binding of GluFib with titanium surfaces.  

FIX or WORKAROUND

To prevent this problem, use the following lockmass solution:

0.5 ng/µL leucine enkephalin (LeuEnk), 0.5 ng/µL GluFib and 5mM maleic acid in 50:50 water/acetonitrile + 0.1% formic acid

ADDITIONAL INFORMATION

- Other multiprotic organic acids might work.

- Be aware of cluster formation, as seen with citric and succinic acids.

- Addition will cause ionization suppression of LeuEnk.