Chromatography Forum

Does anyone have a cleanup method for PAH soil/sediment extracts using SPE or a similar convient method. The PAHs are microwave extracted with 1:1 hexane:acetone solvent which gives us good recoveries. We will be analysing the extracts using reverse phase UPLC with UV/fluoresence. When we get a method sorted we may also run them through our LC-MS/MS with APPI.

Most of the SPE cartridges seem to be designed for PAHs in waters which have different problems to soil extracts. Looking through the literature there seems to be a great deal of variety in cleanup procedures, some of which I find a bit dubious. The old EPA methods seem a bit dated and more appropriate for GC analysis. There are suggestions of NH2 SPE or just a C18 SPE for soil but if possible I want to avoid solvent exchange/blow down of the extracts.

Any suggestions or protocols would be welcome.

Could be difficult. The acetone in your sample is likely to react with an NH2 column. If possible, I suggest to evaporate to dryness, redissolve in hexane / methylene chloride and follow established SPE protocols for the NH2, which will probably mean washing with some composition and elution with acetonitrile to get a sample that is compatible with your RP technique.

Alternatively, and if the SPE protocol is not supposed to remove anything relevant, you could inject the sample in small volumes directly into your RP method. The hexane is not miscible with RP solvents, but the large proportion of acetone will help.

We use Acetonitrile to extract and clean up with a strong anion phase SPE. We got the method from Macherey-Nagel and it works good with HPLC-Fluorescence.