Objectives of sample introduction
- Representative aliquot from bulk sample
- Fast vaporization in inlet liner
- Expanded sample gas volume contained within inlet liner
- Homogeneous mixing in liner
- Representative transfer to column
Important considerations when selecting inlet liners
- Must ensure complete vaporization of the sample before it reaches the column entrance
- Must not react with the sample
- The liner volume must be larger than the volume of vaporized sample
- Should minimize discrimination not promote it
- Adding quartz wool will increase the surface area of the sample and promote mixing
- Liner should be deactivated especially for analysis of polar solutes and for splitless injections
- Quartz wool should be placed in the optimum position
Benefits of SGE inlet liners
- Range covers all applications and all popular instrument makes/models
- Range covers vaporizing and cool on-column injection techniques
- Inlet liners ensure complete transfer of sample from syringe to the column without loss
- Improved liner designs have improved both precision and accuracy of sample transfer
Inlet liner geometry
- ◄ Narrow straight through inlet liners
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Advantages
- Great for Fast GC applications
- Great for gaseous samples. (e. g. Purge and Trap)
- Great for small injections 0.5 µL or less
Disadvantages
- Not suitable for >1 μL injections
- Can give high and low boiling point discrimination
- Only suitable for split injections
- ◄ Straight through inlet liners
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Advantages
- Cheap.
- Good for gaseous samples (e.g. Purge and Trap)
- OK for split injections of non-active samples
Disadvantages
- Allows the sample to contact the base seal
- Not for small ID columns
- Can give high and low boiling point discrimination
- Not the best reproducibility
- ◄ Single taper inlet liners
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Advantages
- Doesn’t allow the sample to contact the base seal
- Great for active compounds
- Good response for high boiling point compounds
- Performs well in split or splitless mode
Disadvantages
- Can give low boiling point discrimination
- Not the best reproducibility
- ◄ Double taper inlet liners
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Advantages
- Doesn’t allow the sample to contact the base seal
- Great for active compounds
- Good response for high boiling point compounds
- Performs well in split or splitless mode
Disadvantages
- Can give low boiling point discrimination
- Not the best reproducibility
- ◄Using quartz wool
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Advantages
- Increases surface area for vaporization
- Collects non-residue material from dirty samples
- Wipes the sample from needle tip
Disadvantages
- Decreased inertness for very active compounds
- ◄ FocusLiner inlet liners
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Advantages
- Wipes the sample from the tip of the needle for complete transfer
- Gives accurate and reproducible results
- Performs well in split or splitless mode
- Promotes vaporization of sample
- Minimizes Mass Discrimination
- Prevents non-volatile material entering the column (acts as a filter)
Disadvantages
- Not suitable for extremely active compounds
- ◄ Conventional quartz wool plug inlet liners
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a) Quartz wool plug is in the correct position to wipe needle tip.
b) Quartz wool plugs can be moved in either direction, preventing the needle wiping or sample vaporization process.
- ◄ FocusLiner wool positioning
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Two tapered sections
a) Secure wool plug. The two glass baffles secure the positon of the glass wool preventing shifting in either direction.
b) Positioned correctly to ensure wiping of the sample off the end of the syringe needle and ensuring good reproducibility.
Injection mode
- ◄ For split injection
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Quartz wool in liner
- Promotes mixing of analytes and results in better quantitation
- Provides a large surface area which aids the vaporization of liquid samples
- Acts as a trap to collect non-volatile residue in the sample
- Protects capillary column from ‘dirty’ samples
- Prevents sample hitting the bottom of the injector before volatilization
Quartz wool in the liner located at the optimum position (FocusLiner)
- Excellent reproducibility results from wiping the sample from the syringe needle and preventing droplet formation
- Results in lower mass discrimination
- Quartz wool prevents the sample hitting the bottom of the injector
Double glass baffling (FocusLiner™)
- Ensures quartz wool remains in the correct position in the liner
- Top baffle prevents quartz wool shifting towards septum
- Bottom baffle prevents quartz wool being pushed down into the liner
- ◄ For splitless injection
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Taper at the bottom of liner
- The taper minimizes contact of analytes with the bottom of the injection port. This is especially important in splitless injection mode because the residence time of the sample in the liner is longer
- Column installation into the liner becomes more robust because the taper ‘channels’ the analytes into the column. The distance the column is inserted into the liner is not so critical
- ◄ For splitless injection - very active compounds
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- The taper minimizes contact of analytes with the bottom of the injection port. This is especially important in splitless injection mode because the residence time of the sample in the liner is longer
- No quartz wool
- ◄ For Fast GC analysis - narrow internal diameter
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- Results in smaller peak widths
- Especially suited for (0.1 mm ID) Fast GC columns