Issues with 525.2 surrogates

Discussion created by bigbear on Jan 7, 2019
Latest reply on Sep 19, 2019 by bigbear

I've been doing 525.2 for close to 16 years, and lately been having issues with perylene d 12, and triphenyl phosphate failing the +/- 30% of targeted concentration. I don't think the issue is due to my sample concentration step, as the nitro xylene recovers very well. The triphenyl phosphate sometimes recover over 130% and the perylene d 12< 70%.


With what I see it may be due to the way I handle my surrogate mix. The mix is a commercial 3 component mix @ 500ppm in acetone.Manufacturer's storage requirements are ambient temp. I store it in a freezer that is usually about -15C. Prior to use I warm it and then vortex.


My theory is that the perylene d12 falls out of solution in the freezer and warming and mixing is not enough. the other week I prepared a continung calibration std. using the mix of compounds used to spike my LFM/Bs. I combined this mix, the IS and surrogates and brought to volume. When I ran it against the initial calibration everything was very much in range with the exception of the perylene d12, which recovered in the mid 70%. I see similar results using the con cal prepared with the initial calibration.


The implication is that I am not completely reconstituting the perylene d12.


Any thoughts?