Open-Split Inlet (Older Technology)

Open-Split Inlet (Older Technology)

What is an Open-Split Inlet?

When a gas flow is too large, a hardware arrangement which allows a portion of the column flow to enter the ion source is used. A restrictor is positioned between a GC column and the vacuum  system, restricting the column flow. Two types of split inlet implementations which could be used are open-split and effluent split.

An open-split inlet has a purge flow which is typically the same as the carrier gas.This improves system performance, although additional purge hardware and a special interface are required.

Open-Split Inlet Advantages

  • accommodates wide-bore or narrow-bore columns 
  • no need to vent to change columns
  • no vacuum effects on chromatography or retention time

Open-Split Inlet Disadvantages

  • sample is split - only allows a small portion of the sample to enter the mass spectrometer
  • more flows to set
  • more places to leak
  • a plug can occur in the restrictor
  • split ratio is slightly temperature dependent

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