5975 Sensitivity questions..

[cjm]

Well I am doing an extra acid cleanup as well as a water rinse. Seems to help some but still having difficulty with passing standards. I still can't believe method 680 requires a closing standard.

@walkerd2: I'm still relatively new to the MS world but I'm willing to try tweaking the MS if it means injecting less and getting better response. I do have to continue using the PTV however. My newest problem: congener run, I am doing 4x5uL injections in hexane, concentration range 1-100 ng/mL each of all 209 pcb congeners, plus IS: phenanthrene-d10, chrysene-d12, and perylene-d12. Chrysene and Perylene are nice and stable the way I have system set up, and chromatography looks perfect. Phenanthrene is ALL OVER the place, responses (in thousands) for all 7points:

730
821
581
539
530
768
973

The interesting thing is: all compounds relative to phenanthrene calibrate nicely. It's the compounds relative to chrysene and perylene that are out RF RSD>30%. I have made the calibration up several times thinking it was my error, but no one here can understand why my calibration looks the way it does. More to come....

[tlahren]

Just curious:

What do your SIM windows look like? Dwell times for each ion, cycles/s, etc. How many data points do you have per peak at the beginning of the run and at the end of the run? (count data points by looking at scan number in the spectral view for the end of a peak minus the scan number at the beginning of the peak).

Ty

[Bigbear]

I don't like the Agilent DFTTP tune, m/z 430 sometimes does not respond at all. I run an autotune, then manually adjust it (drop ion focus) to get the 442/198 ratio in. I then add EMv to get my 69 area to be about 600000 counts. I'm using a 5973 so you may not need to up the EM.