Training - Fast GC analysis

• Fast GC: run times in 5-10 minutes
• Very fast GC: run times in a few minutes
• Ultra fast GC: run times less than one minute (usually several seconds)

Faster analysis can be achieved in any of the following ways:

• A fully optimized separation
• A non-optimized separation
• All peaks are equally important
• Only a small number of peaks are important
  

• Shorter run times
• Greater sample throughput
• Cheaper columns
• Higher signal to noise ratio
• Lower bleed (thinner films)

• Difficult to use for conventional GC/ MS
• Easy to overload the phase (less sample capacity)
• Careful attention required for splitless injections
• Conventional Van Deemter curves don’t apply (high pressure drop)

• Shorter columns
• Higher velocities
• Temperature program rates
• Pressure programming
• Vacuum outlet
• Selectivity
• Narrow bore columns
• Carrier gas selection
• Turbulent flow

The low carrier gas flow rates used with fast columns can cause band broadening in the injection port, especially during splitless injections.

If a liner with a small internal volume is used, the velocity of the carrier gas through the liner will be increased. This reduces the amount of time the sample spends in the injection port minimizing band broadening.

A liner with an internal diameter of 2 mm or less needs to be used in splitless mode to reduce mass discrimination.

This calculation is only good for isothermal analysis, but use as a guide.

There are two options

• Reduce the number of plates – lose resolution, faster analysis times
• Keep the number of plates constant – maintain resolution, longer run time
• If Beta and Total Plates are the same – chromatography can be identical

Conditions to reduce analysis time by a factor of 2 to 3

• HP 5890 GC
• Fast GC capillary column
• Manual pressure regulator (30 psi max)
• Helium carrier gas
• 20 Hz FID data acquisition
• 30°C/min max oven program rate