Glossary
183
Reducing the amount of vaporization from the needle may result in unexpected
changes in your chromatogram.
• 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 you introduce is richer in low boiling
components than 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 called needle fractionation or
discrimination.
The following chromatograms compare manual injection with automatic fast
injection from the automatic liquid sampler for a 1 µl sample of C10 to C40 in
hexane.
Automated
injection
Manual
injection
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