Introduction to Operation 3
Installation, Operation, and Maintenance 77
Part 2, Operation
Fast Injection
This is a method of introducing a sample to a heated inlet without the negative
effect of needle fractionation.
If you are using the automatic liquid sampler for the first time, you may see
some changes in the resulting chromatograms. Most of the changes are due to
reducing the amount of vaporization from the needle during injection.
• The peak areas of your chromatograms may be smaller. Automatic fast
injection delivers the desired setpoint volume of sample. Without fast
injection, residual amounts of sample boil out of the needle and enter the
inlet. This extra amount could measure up to 1 µL.
• The peak areas of your chromatograms may show less differentiation
between the low boiling and high boiling components.
Without fast injection, the sample introduced is richer in low boiling
component than in high boiling ones because of fractional distillation in the
needle. Not only does residual sample in the needle enter the inlet, but the low
boiling components boil off first. This is needle fractionation or
discrimination.
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