Chromatography Forum

Dear all,

I was hoping if anyone can give me some help on this, and thank you in advance!

We have a Shimadzu GC-2010+, and installed an Agilent GC Gaspro 60 m x 0.320 mm. We want to detect methane and ethane in Ar. We use a gas syringe to draw samples from a gas bag and inject into the GC manually. We tried different size syringe (0.1 mL, 1 mL, 5 mL)

We see the methane and ethane peaks, but they always split into 2 peaks. Sometime they split equally and sometimes they split into a big and a small. However, the split ratio between those two peaks are always very similar.

The Method

https://i.postimg.cc/fRTG8xbQ/Weixin-Im ... 184605.jpg

https://i.postimg.cc/nhPPTg5q/Weixin-Im ... 184614.jpg

Problem Pictures

https://i.postimg.cc/W1S4JHLg/Picture1.jpg

https://i.postimg.cc/QtRYs7sC/Weixin-Im ... 184221.jpg

https://i.postimg.cc/bYk3ksp0/Weixin-Im ... 184224.jpg

Does anyone know what happened? Why would the peak split in such a way?

Thank you!!

It looks to me like you have plenty of signal, if I'm you I would try a split injection. You can adjust the split ratio to get the sensitivity you need. I bet your peak shapes improve dramatically if you split the injection.

claserj,

I'm with rb6banjo. YOu can certainly stand to go to a split injection at a minimum of something like 10:1 based on what I see. The other thing I notice is your column flow is really low. 0.32's run best around 2-4 mL's min and you are supplying less than 1. Try taking that up to around 2 or 3 and see what happens.

Best regards,

Dear rb6banjo and AICMM,

Thank you for your help. We injected the samples in split mode 1:10 and the peaks no longer split. We also adjusted (reduced) the flow rate, and now the peaks have less tailing. Thank you!


https://i.postimg.cc/pXggRqr6/20230723115028.png


https://i.postimg.cc/3N2bRHdf/20230723115028-1.png


https://i.postimg.cc/YCvYfzxM/20230723115028-2.png


https://i.postimg.cc/Qx2xwg3X/20230723115028-3.png