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LC-MS/MS tends to be used for what kind of molecules?
Larger ones like proteins
What are two advantages of tandem mass spec?
- 1. You can use a soft ionization followed by harder ionization to get molecular plus fragment information
- 2. You can use the first MS to clean up matrix interference
Chemical suppression is used for what technique? What does it do?
- Ion chromatography
- It reduces background conductivity of the eluant and so increases sensitivity
What are 6 detection methods used for IC?
- Mass spec
- Photo diode array
- Refractive Index
Both ICP-MS and LC-MS contain ___ and ___ cones at the interface to the MS
Flow rates for electro spray ionization are typically (small/large)?
Extremely Small, < 1 uL/min
Is ESI a soft or hard technique?
Which technique gives smaller HETP values? HPLC/UPLC
UPLC (therefore it has higher resolution)
Which has higher pressure? HPLC/UPLC
UPLC (max around 15,000 psi)
Which has shorter run times? HPLC/UPLC
If you don't have an MS detector for you IC and it's hard to see a peak, what could you do?
- Put other detectors back to back - maybe one of them will see the peak
- Example: DAD --> RI
Is refractive index a good detector for gradient elution?
No! You must use isocratic elution for an RI detector
UPLC uses ___ eluant than HPLC
- This can reduce costs and is environmentally friendly
Disadvantage of UPLC