Thermal Degradation of Deltamethrin During Splitless Injection

As mentioned in a previous post, having the splitless injection port at a temperature higher than 250°C is usually not necessary to maximize response of even relatively involatile compounds. In fact, sometimes having a higher temperature leads to deleterious effects, like thermal degradation.

In the accompanying graphic, Deltamethrin response is maximized at around 250°C splitless injector temperature (blue chromatogram), while the response of the isomeric degradation compound is minimized. Having the injector at 300°C not only decreases the Deltamethrin response (pink chromatogram), but increases the thermal degradation isomer, an undesirable situation. This effect is quite common in pesticide analysis, so lower splitless injector temperatures (225-250°C) are preferred.

The box on the left side of the graphic indicates the splitless injector temperatures, and matches those with the chromatograms.