Deproteination of serum samples for LC-MS/MS analyses by applying magnetic micro-particles.

Investigation of the practicability and performance of a magnetic micro-particle based method for protein depletion of serum samples, preceding the quantitative analysis of small molecules by LC-MS/MS. A commercially available kit including a protein denaturation reagent and functionalized magnetic particles together with a magnetic separator device was tested by addressing the quantification of amiodarone in serum as an exemplary analyte by LC-MS/MS with on-line SPE. A standard method validation protocol was applied. The sample preparation protocol was found to be convenient, straightforward and robust. Validation data characterized the entire analytical method - combining particle-based protein depletion and two-dimensional chromatography - as compatible with the analytical needs regarding selectivity, accuracy (102-106%), linearity (r(2)≥0.99), reproducibility (CV<7%), and control of ion suppression. Since this novel approach of sample preparation does neither require centrifugation nor the technically demanding application of positive or negative pressure, as in conventional solid phase extraction protocols, it seems highly attractive for developing fully automatized preparation systems for LC-MS/MS analyzers.