Chromatography Forum

Hi,
I'm having poor recovery for o-Toludine in my SPE for method 530. Anyone running this method and willing to share info??

Are you rinsing your sodium sulfate with acetone? Acetone is necessary to release all of the o-toluidine.

Don

I just ran it exactly as the method state for solvent usage by the Oasis cartridges. Drying time I extended. The more moisture in the extracts the lower the recovery it seems, just don't over dry. I made several runs using different dry times and also tried drying with the positive pressure manifold mentioned in EPA541. There is a sweet spot you can find that will improve recoveries, also be certain to rinse the bottles as noted and pass through the lines into the cartridge.

Also, turn off the flow as soon as the bottle is empty, leaving the line full of water before the water rinse step, otherwise it takes a lot more vacuum to get the flow going again before the final DI rinse. I also do this with the first rinse with DI, and leave the cartridge full to the top before inserting the lines to draw the sample from the bottle, this way you cartridge remains full almost to the level of the end of the transfer lines. I elevate the bottles so that the bottom of the bottle is even with the lid of the extraction manifold so the sample transfers mostly by siphon once the flow is established, that way any micro leaks will not draw in air and let the water level go below the top of the packing material during extraction.