How do I prepare my sample for a reversed phase SPE method?

It is common to use methanol or other aqueous miscible, stronger solvents to perform an initial extraction.  However, reversed phase SPE requires the sample to be loaded in a mostly aqueous solution.  You can either evaporate most of the methanol and dilute the sample with deionized water prior to sample loading, or simply dilute the sample with a lot of deionized water.  

Ideally, the methanol composition of the sample should be <20% for loading. If the target analytes are particularly hydrophilic, the methanol content will need to be even lower (e.g. <10%).