Instrumental Analysis Exam 2 questions with
verified answers
Advantage to desorption sources? Ans✓✓✓ applicable to nonvolatile
and thermally unstable samples.
advantage to ECD? Ans✓✓✓ - extremely sensitive
advantages and disadvantages of hard-ionization sources; example?
Ans✓✓✓ Advantage: provides useful information about the kinds of
functional groups/structure of the analytes
Disadvantage: too much fragmentation
**Electron ionization (EI)
advantages and disadvantages of soft-ionization sources; example?
Ans✓✓✓ Advantages: little fragmentation and provides accurate info
about the molecular mass of the analyte
Disadvantage: limited information about the structure
**Chemical ionization (CI)
Advantages to FID detectors? Ans✓✓✓ - insensitive to noncombustible
gases (CO2, CO, SO2, noble gases)
- high sensitivity
- large linear response
,- low noise
- easy to use
Advantages to hyphenated MS? Ans✓✓✓ - gain ret. time and mass
spectrum for each solute eluted
- spectrometer can be highly selective for analyte of interest
- selectivity eases requirements for sample prep or complete
chromatographic separation of components in mixture
Advantages to TCD? Ans✓✓✓ - simple and universal
- large linear range
- responds to organic and inorganic species
- nondestructive to sample
Common support material in HPLC column? Ans✓✓✓ *Silica is most
common
- surface modified with thin polymer layers to create desired
interaction chemistry
Construction of GC column? Ans✓✓✓ - from fused silica and stainless
steel or glass and teflon
- formed as coils 10-30cm diameter
, def. base peak Ans✓✓✓ most abundant peak in the mass spectrum
assigned a value of 100
def. detector (transducer) mass spec Ans✓✓✓ (Detector amplifies ion
current as a funct. of m/z) amplifies ion current when different species
of ions impinge on detector at different times. mass spec shows
detector current as func. of m/z.
def. eluent strength Ans✓✓✓ the measure of the solvent adsorption
energy on the S phase
def. Gas-liquid chromatography (GLC/GC) Ans✓✓✓ - based on liquid S
phase
- retention of analyte due to partition between gaseous M phase and
liquid S phase
- wide applications; most widely used separation technique
def. Gas-solid chromatography (GSC) Ans✓✓✓ - based on solid S phase
- retention of analyte due to physical adsorption
- limited application
def. hyphenated MS Ans✓✓✓ separation coupled with MS detection
verified answers
Advantage to desorption sources? Ans✓✓✓ applicable to nonvolatile
and thermally unstable samples.
advantage to ECD? Ans✓✓✓ - extremely sensitive
advantages and disadvantages of hard-ionization sources; example?
Ans✓✓✓ Advantage: provides useful information about the kinds of
functional groups/structure of the analytes
Disadvantage: too much fragmentation
**Electron ionization (EI)
advantages and disadvantages of soft-ionization sources; example?
Ans✓✓✓ Advantages: little fragmentation and provides accurate info
about the molecular mass of the analyte
Disadvantage: limited information about the structure
**Chemical ionization (CI)
Advantages to FID detectors? Ans✓✓✓ - insensitive to noncombustible
gases (CO2, CO, SO2, noble gases)
- high sensitivity
- large linear response
,- low noise
- easy to use
Advantages to hyphenated MS? Ans✓✓✓ - gain ret. time and mass
spectrum for each solute eluted
- spectrometer can be highly selective for analyte of interest
- selectivity eases requirements for sample prep or complete
chromatographic separation of components in mixture
Advantages to TCD? Ans✓✓✓ - simple and universal
- large linear range
- responds to organic and inorganic species
- nondestructive to sample
Common support material in HPLC column? Ans✓✓✓ *Silica is most
common
- surface modified with thin polymer layers to create desired
interaction chemistry
Construction of GC column? Ans✓✓✓ - from fused silica and stainless
steel or glass and teflon
- formed as coils 10-30cm diameter
, def. base peak Ans✓✓✓ most abundant peak in the mass spectrum
assigned a value of 100
def. detector (transducer) mass spec Ans✓✓✓ (Detector amplifies ion
current as a funct. of m/z) amplifies ion current when different species
of ions impinge on detector at different times. mass spec shows
detector current as func. of m/z.
def. eluent strength Ans✓✓✓ the measure of the solvent adsorption
energy on the S phase
def. Gas-liquid chromatography (GLC/GC) Ans✓✓✓ - based on liquid S
phase
- retention of analyte due to partition between gaseous M phase and
liquid S phase
- wide applications; most widely used separation technique
def. Gas-solid chromatography (GSC) Ans✓✓✓ - based on solid S phase
- retention of analyte due to physical adsorption
- limited application
def. hyphenated MS Ans✓✓✓ separation coupled with MS detection
