GC liquid injection - the most frequently used GC injection technique

Modern GC systems allow two different liquid injection modes for the hot split/splitless injector, known as the 'hot needle' and the 'liquid band' injection, terms coined by Koni Grob and Maurus Biedermann from the Official Food Control Authority of the Canton of Zurich, Switzerland, already two decades ago [1].
The hot needle injection mode resembles the manual injection, but the liquid band mode is reserved for autosamplers.
The slower hot needle injection with its evaporation from aerosol droplets formed in the hot syringe needle is the gentlest injection technique for sensitive and absorptive compounds, and achieves the best reproducibility. However, hot needle injections tend to discriminate high boilers.
Highly linear responses for samples from analytes with a wide range of boiling point range are achieved by using the liquid band injection mode with fast autosamplers.
The unaltered liquid sample is deposited within about hundred milliseconds into a plug of deactivated glass wool into the hot injector liner. Here the solvent evaporation is cooling the glass wool. The analyte evaporation starts from the wool surface after the solvent is evaporated and leaving non-evaporative matrix behind.

While the analytical results of well experienced manual and the optimized automated hot needle injection can be very similar, the liquid band injection mode requires fast autosamplers and cannot be performed manual or with the regular slow autosamplers.
The PAL Systems provides optimized GC injection for both GC injection modes. The so-called "Normal" mode refers to the hot needle injection with best quantitative performance. The “Fast” mode uses the liquid band injection for the low discrimination of high boiling analytes.

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