The Effect of Drying on The Homogeneity of DBS

BACKGROUND: Inhomogeneous sample distribution in DBS is a problem for accurate quantitative analysis of DBS, and has often been explained by chromatographic effects. RESULTS: We present a model describing formation of inhomogeneous DBS during drying of the spot caused by higher evaporation rates of water at the edge as compared with the center. Color intensity analysis shows that the relative humidity and DBS card position affect the homogeneity of DBS. CONCLUSION: The so-called 'coffee-stain effect' explains the typical distribution pattern of analytes with higher concentrations measured along the edge of DBS as compared with the center. The driving mechanism and potential influencing factors should be considered when addressing the inhomogeneity of DBS in the future.