Chromatography Forum

Hi, when I use the HPLC-MS system, the flow rate of the mobile phase (85%water and 15%MeOh) is 0.1ml/min, but so many moisture and droplets will appare on the window of the shield spray of the MS, Which not happen when I use the syringe inject to MS directly.
Could you give me some suggesions to solve this problem?
Thanks!

Hi,

I assume you work in ESI mode. It seems that the desolvation is not sufficient, which probably affect the spray quality. This is a bit strange because 0.1ml/min is not that high. But you have high water contents in the mobile phase, it is more difficult to evaporate.

We need more info to help you: Do you have pneumatically assisted desolvation, i.e. can you modify the desolvation gas flow and temperature? What are current values for the latter? Since there is a window, can you clearly see the formation of the spray in the chamber? What is the flow rate you use in direct infusion via the syringe?

Hi,

I assume you work in ESI mode. It seems that the desolvation is not sufficient, which probably affect the spray quality. This is a bit strange because 0.1ml/min is not that high. But you have high water contents in the mobile phase, it is more difficult to evaporate.

We need more info to help you: Do you have pneumatically assisted desolvation, i.e. can you modify the desolvation gas flow and temperature? What are current values for the latter? Since there is a window, can you clearly see the formation of the spray in the chamber? What is the flow rate you use in direct infusion via the syringe?

Thank you for youre reply.
Yes, I use the ESI mode. The sweedp gas flow rate is 2 arb, the capillary tempreture is 200 centigrade. The current tempreture is 200.80. I can not see the spray in the chamber, since there are so many droplets inside the window...
I try to increse the sweep gas flow rate, it's getting better now. Is it the right way?

I can't tell you much whether the desolvation gas flow is appropriate because you have arbitrary units. You may ask your manufacturer for standard source conditions according to different LC flow rates. You can also inject a mixture of standard compounds and see if the sensitivity increases when the gas flow is increased.

It is solved. Thank you!