Benzidine degredation: methods 8270C and 625 BNA analysis

[semivoadude]

Does anyone know any tips to calibrate a GC/MS for BNA compounds while minimizing benzidine degredation? We are considering running an acid only curve, base only curve and benzidines by itself. (very time consuming)
We are currently running all 83 BNA target compounds into one ICAL, but we lose benzidine and other labiles so quickly that we have to recal every week. How can we minmize our ICALs? How long does a BNA curve usually last?
Does anyone run this method that can help us?

thank you

[vballchemist]

I run 80 analytes together with the Benzidine compounds. I prepare a fresh daily calibration std from 2000ppm stock stds (Benzidine is in a separate stock) and I am sure to replace liner, septum, and the stainless steel disk every 100 injections ( about every 2 days). With these constants the Benzidine is fairly stable. It will drop off in response if very "dirty" samples are run which create active sites in the system. Benzidine will degrad in the presence of the other compounds in your std so a fresh std prep is necessary every day.
My BNA curve will last 2-3 months with this regime.

Good Luck

[varian]

I run 100 analytes together with the Benzidine compounds. high std 50ppm no problem.
injection temp must 250. make sure your liner is clean.if you are running bad samples active site will be present on the line or injection port.
Benzidine is verry stable. I run both acid and base as one run.
your extaction method must be Base first,Neautrual second and Acid for last.