Commissioned by a large international non-profit research institute, we developed a GC-MS method for analysing DDT in soil samples. The customer wanted to measure the concentrations of each DDT, DDD and DDE isomer separately. This meant that a straightforward report on the total DDT content would not suffice.
The additional information was used to investigate the antiquity of the sample and/or the influence of storage conditions.
For the analytical method this was a complication factor because it is well known that DDT, next to the natural breakdown, also partly breaks down during GC-MS analysis. In order to report the accurate sample contents a distinction had to be made between the naturally occurring breakdown and the analytical breakdown. The problem could be solved by developing a novel and innovative model by which the analytical breakdown could be determined in terms of the decrease in p,p DDT content and increase in p,p DDE respectively p,p DDD content. After correction the “real” natural contents were reported to the client. The validity of the method was tested thoroughly by means of fortified samples. Unfortunately, the details of the model are for the time being confidential.
