Ca content of human erythrocytes. What is the true value?

It has been generally accepted that the Ca content of washed erythrocytes is in the range of 1 - 3 X 10(-5) mole/l cells (1-10). These values were obtained after samples were treated in various way for Ca measurement. However, by using a simplified careful preparation technique to avoid Ca contamination together with inductively coupled argon plasma emission spectroscopy, we have found that the Ca content of erythrocytes washed with nominally Ca2+-free solution, is one order of magnitude lower than the reported values, in the range of 1 X 10(-6) moles/l cells.