Chromatography Forum

we install a new PTV inlet and We did all of optimization parameters (include temperature,pressure,vent time and flow)
we use SOLVENT VENT mode and we inject 5ul for pesticide analysis
but our Repeatability is not good and our repeated injection from 1 sample have very high RSD.
Could you please help me about this problem?

Watch the injection process and see if the timer begins when the needle goes down into the inlet or when the plunger has finished injecting.

I had an autosampler that it would begin the timer when the needle went into the inlet, and the inlet would begin heating and the vent valve would change before the sample had completed injecting into the inlet, which causes a lot of problems. I added time to the hold before the temperature program began (and vent valve change) to compensate for this and the injections became much more reproducible.

Welcome to the forum.

We need a lot more detail than that before anyone can begin to troubleshoot your problem. Make and model of instrument, length, diameter and stationary phase of the column, and the temperatures and pressure would be a good place to start.

Peter