Sensitivity
Flat Film Degasser
January 3, 2022
Systematic Method Development and Troubleshooting
October 15, 2022
Method Development,
Sensitivity,
Assessment of Matrix Effects,
Trifluoroacetic Acid,
TFA,
Buffer,
Ion Pairs
Tips: Frequently, resolving the problem requires a combination of individual experimental solutions and systematic and logical investigation.
Part 1 highlights rational method development and validation and includes troubleshooting tips for sound sample preparation, for analyte stability in biological matrices, and for chromatographic conditions and injection solvents.
Part 2 further discusses development strategies for LC/MS/MS analysis of biopharmaceutical products including proteins and peptides. It will present troubleshooting tips for carryover, recovery and matrix effects, and selectivity; and for automation where possible to improve the overall reliability and efficiency of LC/MS/MS.
...APCI General Review
March 17, 2022
The LC elute passing through a nebulizing needle, creates a fine spray. The spray passes through a heated ceramic tube, where the droplets are fully vaporized. The resulting gas/vapor mixture is then passed over a corona discharge needle, where the solvent vapor is ionized to create reagent gas ions.
For successful APCI, the analyte must be volatile and thermally stable and the mobile phase must be suitable for gas-phase acid–base reactions.
To vaporize the solvent and analyte, the APCI source is typically operated at vaporizer temperatures of 400 to 500 0C.
...ESI General Review
March 17, 2022
The LC eluate is sprayed into a spray chamber at atmospheric pressure in the presence of a strong electrostatic field and heated drying gas.
The electrostatic field occurs between the nebulizer, which is the ES probe, and the capillary. Aerosol of charged droplet formation at right angles to the capillary.
Ionization takes place as a result of imparting the strong electrical field and the superheated nitrogrn sheath gas, with Agilent AJS (Jet Stream) technology.
...The influence of electrospray ion source design on matrix effects
March 17, 2022
Conclusion:
The Turbo Ion Spray (off-axis geometry), Turbo VTM Source (orthogonal geometry) and the Standard Z-Spray Source (double orthogonal geometry) did not differ much in their susceptibility to MEs.
The Jet Stream ESI (orthogonal geometry) reaches a higher sensitivity by an additional heated sheath gas, but suffers at the same time from significantly stronger signal suppressions than the comparable Standard ESI (orthogonal geometry) without sheath gas. No relation between source geometry and extent of signal suppression was found in this study.
...Ion Pair Reagents
June 27, 2022
Gas Leaks
March 10, 2022
Split vs. Splitless Injection
March 10, 2022
Restek - Effective LC Troubleshooting Symptom-based Strategies and Solutions
January 12, 2022
Summary of sensitivity reduction
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Simple potential causes:
1.1) sample preparation,
abnormal storage temperature,
storage time,
abnormal extraction,
abnormal clean-up,
1.2) LC system,
Dilution error,
autosampler needle not reaching sample,
incorrect injection volume,
abnormal LC back pressure,
Leak,
mobile phase unstable (modifier, prepared date, )
1.3) Mass spectrometer system,
non-asymmetric spray (due to clog)
Electron multiplier voltage error,
the declustering potential error,
the collision energy error
the collision exit cell potential error
GS1 pressure - nebulizer gas error
GS2 pressure - turbo gas error
Curtain gas pressure error
Ion spray voltage error
test
1.4) System monitoring,
monitoring charts of internal standards, blank, calibrators,
1.5) Data processing,
Calculation error (dilution factor),
Peak integration error (baseline issue, noise),
Retention time shift,
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Complex potential causes:
Analyze new known standard
Analyze blank
Infuse standard in 50-50 mobile phase solution to the mass spectrometer
Dry run