sensitivity change

make new mobile phase A with pH modifier(aqeuous solution) rational: the pH promote the charged state of the analyte over its neutral species. mobile phase was contaminated attributing to rising baselines, noise or spikes.

chromatography:

Troubleshooting strategy:

1. isolate area. [sample preparation, mass spectrometer, HPLC, monitoring]
2. rule out simple problem.

Questions to be answered:

1. Did electrospray ionization work properly?
2. Did mass spectrometer work properly? [autotune reports, such as declustering potential, collision energy, collision exit cell potential, pressure]
3. Did LC work properly? [mobile phase ageing

Steps:

1. check mass spectrometer performance. (autotune reports, parameters, asymmetric spray (blockage))

Useful diagnostic tools:

1. a known standard
2. unschedule method
3. monitoring plots of internal standards, blank, instrument parameters
4. infusion the tuning solution to check mass spectrometer
5. check autotuning reports.