[1] This phenomenon plays an important role in pseudohyponatremia, an error affecting measurements made by either flame photometry or indirect potentiometry but not by direct potentiometry.
[2][3] The volume of total solids (primarily protein and lipid) in a plasma sample is approximately 7%, so that only 93% is water.
[1] This phenomenon produces only a slight difference as volume fraction of water in plasma is sufficiently constant.
But, in patients with severe endogenous or exogenous hypertriglyceridemia and in patients with high plasma protein concentration (usually due to paraproteinemia), water portion of plasma is replaced with either lipid or protein causing falsely low electrolyte value (pseudohyponatremia).
[4] Conversely, in patients with low plasma protein concentration (a finding often seen in critical care), the water content of plasma is higher than normal, resulting in the reciprocal artifact, a falsely high electrolyte value (pseudohypernatremia).