I have a bit of a problem with setting up our organochlorine pesticide analysis. First, a bit of info on my set up:
I'm running on a Agilent 6890B The front column is a Restek CLPesticides 2 and the rear is the CLPesticides column. For a liner I am using a Restek Topaz single taper ("gooseneck") liner (cat # 23302).
Here's a bit of background. We are a hazardous waste incinerator and this analysis will be done on ash generated by the kiln. This as comes in two forms, a powdery spray-dryer residue, and a coarse, rocky black substance referred to as "slag". Here is my problem:
At the beginning of a batch I run a series of standards, including a DDT/ endrin breakdown standard. These look good. Then I run a slag sample, followed by two hexane rinses, and the same standards. The problem is two fold. First, the early eluting compounds on the rear column (CLPesticides) have splitting they did not have earlier. Second, the later eluting compounds such as methoxychlor and endrin ketone come in below our acceptance criterion of 15%.
As far as my sample prep is concerned, I extract using a 1:1 mixture of hexane and acetone and, after evaporation, perform a copper cleanup using two grams of copper to a final volume of five ml extract. I'm considering adding a florosil cleanup after the copper.
Can anyone offer additional suggestions as to why I am having this peak splitting problem and how I can remedy it? Attached is a copy of the rear column chromatogram to show the spltting. The upper window is a standard run before the sample. The lower shows the standard after running a sample and two hexane rinses immediately after the standard in the upper window was run.