Pretreatment:
Water-based cream-
Dissolve 1 g sample in 10 mL DI water containing 1% formic acid. Mix well. Centrifuge. Take 5 mL of supernatant for SPE.
Oil-based cream-
Dissolve 1 g sample in 10 mL DI water containing 1% formic acid. Add 10 mL hexane. Mix well. Centrifuge. Allow bisphasic layer to form. Take 5 mL of aqueous supernatant for SPE.
To a 500 mg Strata X-C cartridge,
Condition/Equilibrate with 5 mL of methanol, and then deionized water
Load 10 mL of pretreated sample slowly
Wash with 5 mL of deionized water with 1% formic acid
Wash with 5 mL of methanol
Dry cartridge on full vacuum for 10 minutes
Elute with 2x 5 mL 5% NH4OH in methanol/water (20:80)
Reconstitute in appropriate solvent for analysis
Collect and analyze load and wash fractions to monitor analyte movement throughout the method. The method can be further optimized based on your initial results.
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