Buffers and Degassing
Posted: Mon Jun 13, 2005 2:07 pm
Greetings,
I are performing gradient RP HPLC for environmental analysis. I usually pump pure solvents with low pressure mixing, and He sparging.
I am seeing some unacceptable retention time shifts with a new method. The shifts appear to be sample matrix related. I suspect a pH effect since we are running unbuffered with pure solvents.
I would like to try buffering the water. Phosphate is not a good choice since the samples contain calcium chloride. I want to try a formate buffer, but I am concerned about its volatility. Since we generally use pure solvents, we just sparge continuously. Am I right in thinking that continuous sparging of a formate buffer may change its pH over time due to evaporation of the formic acid? Can I sparge for 30 minutes and then maintain a He blanket in the vessel?
ravenwork
I are performing gradient RP HPLC for environmental analysis. I usually pump pure solvents with low pressure mixing, and He sparging.
I am seeing some unacceptable retention time shifts with a new method. The shifts appear to be sample matrix related. I suspect a pH effect since we are running unbuffered with pure solvents.
I would like to try buffering the water. Phosphate is not a good choice since the samples contain calcium chloride. I want to try a formate buffer, but I am concerned about its volatility. Since we generally use pure solvents, we just sparge continuously. Am I right in thinking that continuous sparging of a formate buffer may change its pH over time due to evaporation of the formic acid? Can I sparge for 30 minutes and then maintain a He blanket in the vessel?
ravenwork