Impact of Ficoll density gradient centrifugation on major and trace element concentrations in erythrocytes and blood plasma

• Ficoll-separated erythrocytes and plasma contained highly elevated concentrations of iodine and Ba, and markedly decreased concentrations of Ca.
• Ficoll-separated erythrocytes are suitable to use for the analysis of Mg, P, S, K, Mn, Fe, Zn, Se, Rb, Cd, Cs, and Pb, but the Ficoll-separated blood plasma should not be used for measurements of these elements.
• Concentrations of Mn, Cd, and Pb in blood plasma may be also affected by pre-analytical contamination of blood samples.
• This study provides information about the constituent consistency (or variations) of blood samples obtained with different centrifugation approaches, in terms of elemental concentrations.

ProjectFicoll density gradient centrifugation is widely used to separate cellular components of human blood. We evaluated the suitability to use erythrocytes and blood plasma obtained from Ficoll centrifugation for assessment of elemental concentrations.ProcedureWe determined 22 elements (from Li to U) in erythrocytes and blood plasma separated by direct or Ficoll density gradient centrifugation, using inductively coupled plasma mass spectrometry.ResultsCompared with erythrocytes and blood plasma separated by direct centrifugation, those separated by Ficoll had highly elevated iodine and Ba concentration, due to the contamination from the Ficoll-Paque medium, and about twice as high concentrations of Sr and Mo in erythrocytes. On the other hand, the concentrations of Ca in erythrocytes and plasma were markedly reduced by the Ficoll separation, to some extent also Li, Co, Cu, and U. The reduced concentrations were probably due to EDTA, a chelator present in the Ficoll medium. Arsenic concentrations seemed to be lowered by Ficoll, probably in a species-specific manner. The concentrations of Mg, P, S, K, Fe, Zn, Se, Rb, and Cs were not affected in the erythrocytes, but decreased in plasma. Concentrations of Mn, Cd, and Pb were not affected in erythrocytes, but in plasma affected by EDTA and/or pre-analytical contamination.ConclusionsFicoll separation changed the concentrations of Li, Ca, Co, Cu, As, Mo, I, Ba, and U in erythrocytes and blood plasma, Sr in erythrocytes, and Mg, P, S, K, Fe, Zn, Se, Rb and Cs in blood plasma, to an extent that will invalidate evaluation of deficiencies or excess intakes.