Hyphenated Techniques

Question 1

whatre the advantages of GC-MS?

Answer 1

• high resolution power
• high sensitivity when used w/MS & other detectors
• short analysis time
• tolerant to sample quality
• good accuracy & precision
• library search possible (for EI)

Question 2

whatre the disadvantages of GC-MS?

Answer 2

• samples must be volatile & thermally stable
• EI/CI is limited to < 1000 Da
• [M+H]+ frequently not observed in EI
• no library search for CI

Question 3

why are normal phase and adsorption chromatography not compatible with HPLC-MS?

Answer 3

normal phase - due to the non-polar mobile phase that has low dielectric constant

adsorption - due to non-volatile salts & buffer components in mobile phase

Question 4

what liquid chromatographic techniques are compatible with -MS?

Answer 4

• reversed-phase
• ion-exchange
• size-exclusion

Question 5

what ionization techniques in incompatible with LC?

Answer 5

FAB, MALDI & EI
- FAB & MALDI techniques rely on solid samples
- LC has continuous flow of eluent/analyte
- EI requires

Question 6

whatre the advantages of LC-MS?

Answer 6

• very general, versatile approach
• high resolution power; tho lower than GC
• high sensitivity when used with MS & other detectors
• good accuracy & precision

Question 7

whatre the disadvantages of LC-MS?

Answer 7

• V. sensitive to impurities
• incompatible with non-polar solvents & compounds (normal-phase chrom.)
• expensive & not portable
• requires experienced technician
• limited throughput
• no library search; can create custom library tho of own analytes