splitless bad peaks shape

What are all the GC parameters? A 0.18 mmid column has very low capacity.  Big fronting on a later eluting peak could just be too much sample on the column. What is the scale of these two chromatograms? 

Hi Paul,

This is the Chromatogram of solution at 4 ppm with 1uL injection volume in 100% ACN. 

When I tried to inject 0.5uL:

we can see that we help the shape at 0.5uL

At 0.3 uL the fronting is almost eliminated :

Finally at 0.2uL, the shape was perfect: 

This morning I tried to dilute my 4 ppm to 0.4 ppm with ACN, And my peak shape was poor even at 0.5 uL.You 

It was ok when I injected again at 0.2 uL:

It seems not related to the quantity of the analyte (tridecane) but more about the amount of ACN injected. That's why the 0.2 uL is better because less ACN at the head of column. 

I also see that Restek article this weekend that it's exactly what I have seen so far. They tried to add non polar solvent like toluene compared to getting lower injection volume and it also helps to peak sharpness. 

They say that the mismatch polarity between highly apolar column like HP-5MS with highly polar solvent like ACN is the cause of that bad peak sharpness.  

I will to dilute my 4 ppm in ACN to 0.4 ppm with toluene and see if the problem persist or not at 1 uL and 0.5 uL 

If it's ok, it will confirm that ACN causes the splitting peak. 

I will let you know the result here. 

Thank you for your help 

It works well when I used toluene even with 1 uL. So I will change for apolar solvent. See this 0.4 ppm preparing by diluting 2 mL of 4 ppm in ACN to 20 mL with toluene. So just by diluting 10 time the amount of ACN, it allows me to inject 1 uL with peak splitting. 

Look at the scale. All of the individual chromatograms are really huge -  about 2.5 million counts tall.  The 0.3µL peak is taller than the 0.5µL or the 1.0µL injections. Are you using an autosampler or manually injecting?

ACN and splitless. Is your starting oven temperature about 50°C or lower?

Something else changed as the retention time is now more than 1 minute faster?  This peak is about 800,000 counts tall - still very tall...

yeah I need to increase a bit the oven for having the same solvent focusing delta around 25C below solvent boiling for ACN (50C) and toluene (80 C). That's why I have a faster retention time. For the area with ACN, peak splitting is affecting the highest data point. But if you looked at 0.3uL is more than the 0.2 uL.