Optimizing Splitless Injections in Gas Chromatography, Part I: What It Is and What Happens When We Inject

In gas chromatography (GC), injecting samples is seemingly among the simplest steps in the analysis. For trace quantitative analysis, the splitless technique is most used as an inlet capable of performing both split and splitless injections, and is standard equipment on most gas chromatographs. In this and upcoming installments, we take a closer look at splitless injection, which is not as simple as it seems. Beginning with the syringe and autoinjector, the sample is subjected to passage of the syringe needle through a septum, ejection from the needle, deposition onto a surface in the inlet, evaporation, transfer to the column, condensation of the sample vapor in the column, and finally, temperature programming. All of this typically occurs in the first 30–60 s of the separation. If unwanted chemistry occurs in any of these steps, the injection may not be reproducible enough for precise quantitation. As we proceed, we will discuss some straightforward optimizations that can be performed to assist in obtaining reproducible splitless injections.