LC-MS analysis combines two powerful techniques, liquid chromatography, and mass spectrometry. This highly selective technique isolates and measures target analytes in highly complex samples. The LC component differentiates based on physicochemical properties, whereas the MS unit differentiates by its mass to charge ratio. Such duality makes LC-MS such a robust technique in the drug development process. Besides, the MS unit not only acts as a detector but also identifies the chromatography peaks and corresponds them to unique masses.
Although there are different f LC and MS unit manufacturers ,they all follow the same principles. However, some lc ms analysis can find it challenging to set up LC-MS systems during different drug development timeline. Hence, we share seven steps to overcome challenges faced when setting up LC-MS units. Each tip covers a particular component of the LC-MS system. These tips will be beneficial, irrespective of the timeline of a drug development process.
Tune source parameters: Source tuning parameters can easily affect ion transmission. Hence, first, check against installation values. If the same issue persists, consider a fresh tune page as files become corrupted over time. Besides, having a fresh tune solution is always convenient because having an old tune solution with the wrong pH and wrong organic composition guarantees failure in sensitivity.
ESI Emitter position/stability/leaks: Spray stability and emitter position are vital in detecting and fixing problems. Record micrometer settings to adjust ESI position at the right place. Besides, replace or clean the sprayer component. And always check for leaks.
Poor vacuum: MS systems operate in a vacuum, and therefore, an incomplete vacuum can generate erroneous signals. Ensure appropriate and stable vacuum levels by checking the vacuum gauges against installation values. Avoid poor pumping, flawed gauge, or a leak.
MS analyzer tune parameters: Minor modifications in tune parameters can resolve issues. In these cases, first, load the backup tune page. If this does not resolve the issue, fall back to hard copy values. Often resolution issues are instrument specific. However, they can relate to the reflector tuning and pusher of TOFs..
No collision gas (MS/MS fragmentation): Review the pressure of the gas inlet and ensure that the collision gas is turned on in the tune page. Also, confirm that the collision cell pressure corresponds to the installation values. Besides, keep a check on collision energy.
The nebulization process: The nebulization process can impact the quantification of LC-MS/MS systems. Researchers can optimize the charges on the droplet and droplet radius to produce a maximum number of ions and thus increase the sensitivity of LC-MS systems. The formation of stable nebulization aerosols depends on three factors:
- The flow of nebulizer gas
- Position of the sprayer relative to the sampling orifice
- Composition and flow rate of an eluent.
Nominal mass calibration off: Remove the default calibration and crosscheck the nominal mass with a known standard. Follow the instructions provided for correcting the nominal mass value. Moreover, corrupt tune pages can lead to calibration failures. In such cases, start a new tune page or load a backup.