Environmental Engineering Reference
In-Depth Information
Fig. 8.9 Microchip ESI QTOF MS of the
Ty
mixture of
O
-glycosylated amino acids and peptides
from human urine. ESI voltage 2.8 kV; sampling cone potential 100 V; signal acquisition 20 scans.
Solvent: methanol; average sample concentration: 1.25 pmol
l
1
. Reprinted with permission
μ
from [
29
]
the microchip ESI QTOF MS methodology afforded the identification of 13 differ-
ent components in the mixture with a fair S/N ratio. The potential raised from the
high sensitivity and the advantage regarding the minimization of the in-source
decay of the labile attachments such as
N
-acetyl neuraminic acid (Neu5Ac) of the
microchip ESI-MS, make suitable the use of this microchip platform in clinical
applications for comparative compositional analysis of homologous biological
glycoconjugate mixtures from either tissues/body fluids or natural products.
Another study based on the polymer microchip coupled this time with a FTICR
9.4T mass spectrometer has been designed and implemented for compositional
mapping of highly heterogeneous mixtures of
O
-glycosylated sialylated peptides
from the urine of a healthy individual (denoted
Ty2
) and an age-matched patient
(denoted
Gy2
) diagnosed with Schindler disease type I [
30
]. In the reported case,
special considerations of the thin chipESI FTICR MS parameters with respect to the
direct spray configuration of the FTICR instrument were necessary. The negative
ion mode electrospray process could be initiated by applying 1,500 V to the transfer
capillary, while the fine positioning of the microsprayer toward the MS inlet turned
out to be crucial for efficient transfer of the ionic species into the MS and long-term
stability of the electrospray.
For the
Ty2
mixture of
O
-GalNAc glycosylated sialylated peptides was used a
concentration of approximately 7 pmol
l
1
in methanol, and the chosen conditions
for ionization generated a constant and stable spray accompanied by a high ion
μ
