A new mul
tichannel deposi
tion sys
tem was developed foroff-line li
quid chroma
tography/ma
trix-assis
ted laser desorp
tion/ioniza
tion mass spec
trome
try (LC/MALDI-MS).This sys
tem employs a pulsed elec
tric field
to
transfer
theeluen
ts from mul
tiple parallel columns direc
tly on
toMALDI
targe
ts wi
thou
t the column ou
tle
ts
touching
the
targe
t surface. The deposi
tion device performs well wi
tha wide varie
ty of solven
ts
tha
t have differen
t viscosi
ties,vapor pressures, polari
ties, and ionic s
treng
ths. Surface-modified
targe
ts were used
to facili
ta
te concen
tra
tion andprecise posi
tioning of samples, allowing for efficien
tau
toma
tion of high-
throughpu
t MALDI analysis. Theopera
tional proper
ties of
this sys
tem allow
the user
toprepare samples using MALDI ma
trixes whose proper
tiesrange from hydrophilic
to hydrophobic. The la
tter, exemplified by
-cyano-4-hydroxycinnamic acid, were
typicallyprocessed wi
th a mul
tis
tep deposi
tion me
thod consis
tingof precoa
ting of individual spo
ts on
the
targe
t pla
te,sample deposi
tion, and sample recrys
talliza
tion s
teps.Using
this me
thod, 50 amol of angio
tensin II was de
tec
tedreproducibly wi
th high signal-
to-noise ra
tio af
ter LCsepara
tion. Experimen
tal resul
ts show
tha
t there is nosignifican
t decrease in chroma
tographic resolu
tion using
this device. To assess
the behavior of
the appara
tus forcomplex mix
tures, 5
ti
ties/mgr.gif">g of a
tryp
tic diges
t of
the cy
tosolicpro
teins of yeas
t was analyzed by LC/MALDI-MS andmore
than 13 500 unique analy
tes were de
tec
ted in asingle LC/MS analysis.