Spitless injection

Long needles, releasing the sample near the column entrance, for spitless injection and for split injection with low split flow rates. 

Gas chromatography of the soil extract was carried out on a Varian 3700 instrument equipped with a flame ionization detector and a fused silica capillary column (25in, 0.25mm i.d.) coated with CP-SIL 5. Samples were injected spitlessly, and nitrogen was used as a carrier gas. The oven temperature was programmed from 40°C (5min) to 300°C at 5°C/min. 

Two approaches are used to overcome the problem of large vapor volumes for capillary columns. With the split-splitless injector (Figure 4.20), the sample is introduced via a syringe into the heated injector and evaporated. Then either only part of the evaporated sample is allowed to enter the capillary column (the so-called split mode), or alternatively most of the solvent is separated in the injector from the analytes (splitless mode). In the latter mode the analytes (usually considerably less volatile than the solvent) are re-condensed at the entrance of the column and the more volatile solvent is swept away the analytes are then flash heated to start the elution. The alternative to the split-spitless injector does not use an injector that is already heated, but rather one at around ambient temperature which, following sample injection, is heated in a controlled fashion so as to preferentially evaporate the solvent. An advantage of the heated injector is that it can be used in either mode to best suit the sample under analysis at the time. A more complete comparison of the two approaches is given below. 

---

See also in sourсe #XX -- [ , ]

---