manual vs autosampler injection

Hi all, 

Quick question here regarding manual vs using an ALS for injection. 

I have been looking at a method to injection MDEA, methyl diethanolamine in a water matrix (unfortunately its an enviromental sample so cant avoid water). 

2 scenarios below that I have seen:

1. Manual injection 1.5 uL gives an area of of ~ 150 for the high standard
2. ALS injection of 0.8 uL gives an area of ~ 12 for the high standard

Both injections are using the same pressure pulsed mode (28 psi until 0.75 min then to 10 psi). Based on calculations 1.5 uL would cause severe backflash due to liner vol being approx 870 uL. 

Can anyone help me understand this scenario ? Do i need to further optimize my ALS injection to increase sensitivity ? Or injecting 1.5 uL is the way to go despite backflash ?

  • Hello  

    I’m sorry for the delayed reply to your message.  Do you still need assistance with this? If you do, please take into consideration the notes below. However, if the issue was resolved, could you please share what the resolution was? 

    Based on the details above, one thing I would look into is addressing the backflash. If the calculations are telling you the vapor volume surpasses the liner volume, you can use the vapor volume calculator to see what pulse you need to use to not exceed the volume. In other words, the easy solution would be to increase the pulse for the injection.

    Unfortunately I don't think I can provide much detail on the injection volume, as I do not know what method you are following and if it requires 1.5 for ALS injections or not. 

    Let me know if you have additional questions, details, or if anything is unclear.

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