Use of ion-exchange resin in preparing erythrocytes for magnesium determinations.

A rapid, accurate method is described for determining magnesium in red blood cells. Dowex 50 resin was used to separate magnesium from calcium and other cellular constituents. Magnesium in the eluate was titrated with EDTA, with Eriochrome Black T as indicator; the end point was determined spectrophotometrically. Magnesium in the erythrocytes of 17 healthy adults averaged 4.57 ± 0.16 (SD) mEq/liter of packed cells, with a range of 4.32 to 4.88, narrower than reported before in the literature.