| 4 |
Low metabolite signal |
Analyte loss due to
neuron damage during
isolation or culturing
because of a) excessive
enzymatic digestion; b)
cell membrane integrity
impacted by mechanical
or chemical treatment |
Optimize experimental conditions of
cell isolation and culturing for the
sample under investigation; use
stabilization solutions |
| 18 |
Unstable ES in ESI-
MS mode. MS signal
or spray current
exhibits regions of
low-to-no signal spikes, or chaotic fluctuation
|
The ES Taylor-cone is
destabilized by
bubbles in sheath flow supply (confirm via optical inspection), electrical circuit breakdown, or multijet/nonaxial conejet mode established (confirm via optical inspection)
|
Inspect/replace sheath flow connections In order of preference: increase ES emitter-sampling plate distance, decrease ambient humidity, decrease sampling plate potential, or clean/polish sampling plate and ES emitter tip In addition to b), inspect for perpendicular ES emitter-sampling plate alignment
|
| 19 |
Unstable ES in CE-
ESI-MS mode. MS
signal or spray current
has regions of
low-to-no signal, spikes (e.g., spray current reaching µA level), or chaotic fluctuation
|
The ES Taylor-cone is
destabilized by
electrolysis/solvent heating, producing bubbles adjacent to separation capillary (confirm under microscope), electric breakdown at emitter-MS inlet region (electric sparks/arcs may are also audible), or multijet/nonaxial conejet mode established (confirm under microscope)
|
In order of preference: Flush system and restart experiment, minimize/prevent electrolysis by lowering the CE voltage, decreasing ambient temperature, increasing sheath flow rate, or modifying the electrolyte composition increase ES emitter-to-sampling plate, decrease CE voltage or spray voltage, rinse ES emitter thoroughly, or clean sampling plate In addition to b), follow Troubleshooting advices given for 18 |
| 23 |
Separation capillary
inlet end is damaged |
Capillary inlet end has
been forced against the
sample-loading vial and
chips off or breaks
(confirm under
microscope) |
Avoid bending the capillary during
sample loading and separation. Cleave,
burn, and clean inlet end of the
capillary (Step 15). Alternatively,
install a new separation capillary into
the platform. Measure capillary length.
Note that shortening the capillary will
inherently shorten the migration time of
analytes, alter separation efficiency,
and increase CE current. |
| 25 |
Electric sparks audible
from the
CE platform, or ES emitter
|
Electrical circuit shorting
due to
liquid spillage or salt deposits around CE platform salt deposits on emitter
|
Lower ambient humidity, or
inspect connections; dry components and place a drying agent (e.g., calcium sulfate) in CE enclosure; clean platform surfaces and separation capillary with isopropanol and allow to air dry increase ES emitter-to-sampling plate distance; Sigma water- then methanol-rinse and air dry ES emitter and MS sampling plate; if problem persists, polish sampling plate.
|
| 28 |
Poor analytical
performance observed
for
test solution single-cell extract
|
Improper performance in
sample loading, CE separation, ion generation, or MS detection sample preparation
|
Clean system (Step 15). If problem persists, optimize ion generation and mass spectrometric analysis for the test solution (Step 18) as well as separation by analyzing decreasing amounts of analytes Validate system performance via Troubleshooting advice 28a. Analyze rinse solution, and if positive for the compound of interest, eliminate, or minimize the duration of the water rinse (Step 4A, iv). Optimize sample preparation including the volume and composition of the extraction solution, increase sample loading volume for analysis
|
