By uberto on Friday, October 11, 2002 - 05:30 am:
Dear all members,
Does anyone have the experience in using Agilent GC6890 5973N MSD instrument in operating the negative chemical ionization mode. Recently I find the instrument sensitivity dropped significantly and the service engineer suggested me to clean the ion source. After cleaning, the instrument sensitivity dropped by approx half the initial response when I analyse the standard solution. Can someone tell me what wrong with my system?
By Anonymous on Friday, October 11, 2002 - 09:10 am:
5973s have a very large door opening which may be difficult to seal correctly. If you are running NCI any oxygen or water leaking in will kill sensitivity very quickly. The ion gauge is about the only way to find this leak, since the Agilent source and lens stack is designed in such a way that the level of water seen in a tune or in an air and water check does not reflect the true level of water in the vacuum chamber.