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A new, miniature device that extracts trace ions from just one drop of blood with minimal sample preparation could vastly simplify the analysis of blood samples for certain components. The device enabled researchers to quickly measure two physiologically important ions in blood samples from volunteers (Anal Chem. 2015, DOI: 10.1021/acs.analchem.5b01681).

Analyzing blood for ions, such as electrolytes or basic nutrients like iron, currently requires drawing several milliliters of blood and removing large molecules and cells via methods like centrifugation. But Kei Toda of Kumamoto University, in Japan, and his colleagues devised a method that needs little blood and eliminates the separation step, all in a 3- by 3-cm device.

The scientists place a drop of human blood into a sample well, below which lies a dialysis membrane that keeps out large molecules and cells and another membrane that allows either positively or negatively charged ions to pass through. They apply an electric field for a minute, drawing ions of that charge through the membranes into water on the other side, which they then analyze using ion chromatography-mass spectrometry for ions of interest.