Direct potentiometric measurement of sodium and potassium in whole blood.

1977 ◽  
Vol 23 (10) ◽  
pp. 1912-1916 ◽  
Author(s):  
J H Ladenson
Keyword(s):  
Whole Blood ◽  
Potassium Concentration ◽  
Residual Liquid ◽  
Liquid Junction Potential ◽  
Liquid Junction ◽  
Significant Difference ◽  
Potentiometric Measurement ◽  
Capillary Liquid ◽  
Sodium And Potassium ◽  
Junction Potential

Abstract I compared results for sodium and potassium in whole blood and plasma as measured with a newly available potentiometric analyzer, the "Orion SS-30". No significant difference was found for either sodium or potassium in 207 such comparisons. With use of the flowing, high mixing-velocity liquid junction of the Orion SS-30, the residual liquid junction potential due to blood cells was found to be less than 0.1 mV and to be independent of the hematocrit. This is in contrast to the hematocrit-dependent residual liquid junction potential of approximately 0.6 mV noted by others at normal hematocrit values with the open capillary liquid junctions now commonly used in pH instruments. I also found that the potassium concentration can increase significantly during the mixing of whole blood, and such samples should be mixed gently, if at all. Evidently sodium and potassium can be accutately and easily measured directly in heparinized blood.

Ion-selective electrodes for sodium and potassium: a new problem of what is measured and what should be reported.

1985 ◽  
Vol 31 (3) ◽  
pp. 482-485 ◽  
Author(s):  
A H Maas ◽  
O Siggaard-Andersen ◽  
H F Weisberg ◽  
W G Zijlstra
Keyword(s):  
Activity Coefficient ◽  
Theoretical Calculations ◽  
Pair Formation ◽  
Ion Selective Electrodes ◽  
Residual Liquid ◽  
Liquid Junction Potential ◽  
Liquid Junction ◽  
Normal Plasma ◽  
Sodium And Potassium ◽  
Junction Potential

Abstract For clinical purposes the activities of Na+ and K+ obtained with ion-selective electrodes in undiluted whole blood or serum should be multiplied by an appropriate factor to obtain the same values as the substance concentrations obtained by flame photometry. The factor is primarily dependent on the mass concentration of water in normal plasma divided by the molal activity coefficient of Na+ (or K+) of normal plasma. We discuss the value of the molal activity coefficient of Na+ obtained by theoretical calculations and by direct measurement. The discrepancies between theory and measurement (gamma Na+ of 0.747 and 0.73, respectively) may be due to some binding of Na+ (protein binding or ion pair formation), a small and variable residual liquid-junction potential, or certainty about the appropriate value for the ionic strength of normal plasma (0.16 mol/kg or somewhat higher).

scholarly journals Influence of Erythrocytes on Direct Potentiometric Determination of Sodium and Potassium

1983 ◽  
Vol 20 (2) ◽  
pp. 116-120 ◽  
Author(s):  
P Bijster ◽  
H L Vader ◽  
C L J Vink
Keyword(s):  
Whole Blood ◽  
Potassium Concentration ◽  
Reference Electrode ◽  
Sodium Concentration ◽  
General Phenomenon ◽  
Liquid Junction ◽  
Direct Potentiometry ◽  
The Difference ◽  
Sodium And Potassium

We have shown that the sodium concentration in whole blood measured by direct potentiometry is higher than in plasma. The ‘erythrocyte-effect’, already described by Siggaard Andersen, is most pronounced for instruments equipped with a reference electrode with an open static liquid junction and is thus a general phenomenon. Instruments with a modified liquid junction show less interference. The same phenomenon appears for the determination of the potassium concentration, although the difference between whole blood and plasma, when measured with instruments equipped with a modified liquid junction, can be neglected in practice.

Potentiometric measurements of ionized calcium in anaerobic whole blood, plasma, and serum evaluated.

1985 ◽  
Vol 31 (6) ◽  
pp. 856-860 ◽  
Author(s):  
J Wandrup ◽  
J Kvetny
Keyword(s):  
Whole Blood ◽  
Volume Fraction ◽  
Salt Bridge ◽  
Sodium Formate ◽  
Ionized Calcium ◽  
Liquid Junction ◽  
Paired Samples ◽  
Significant Difference ◽  
Junction Potential ◽  
Venous Plasma

Abstract The measurements of ionized calcium and pH in paired samples of anaerobic capillary whole blood, venous whole blood, venous plasma, and venous serum have been evaluated with a modified ICA 1 analyzer and compared with those of an unmodified ICA 1 analyzer. The unmodified instrument showed a significant difference between measurements in anaerobic venous whole blood, venous plasma, and venous serum, but the modified instrument did not. Statistically significant differences between the two instruments were found for whole blood (magnitude of mean difference magnitude of = 0.053 mmol/L) and for venous serum (0.016 mmol/L), but not for venous plasma. The error of residual liquid junction potential due to blood cells, previously found in the unmodified ICA 1 (salt bridge: KCl, 2.68 mol/kg) was eliminated and independent of the erythrocyte volume fraction in the modified ICA 1 (salt bridge: sodium formate, 4.56 mol/kg). From studies of procedures for measurements of ionized calcium in anaerobically handled samples, we recommend the use of anaerobic whole blood for measuring ionized calcium.

Determination of sodium and potassium with ion-selective electrodes.

1984 ◽  
Vol 30 (3) ◽  
pp. 433-436 ◽  
Author(s):  
N Fogh-Andersen ◽  
P D Wimberley ◽  
J Thode ◽  
O Siggaard-Andersen
Keyword(s):  
Whole Blood ◽  
Venous Blood ◽  
Ion Selective Electrodes ◽  
Liquid Junction ◽  
Sample Handling ◽  
Blood Ph ◽  
Ionic Binding ◽  
Sodium And Potassium ◽  
Junction Potential

Abstract We compared different sample-handling techniques for measurement of Na+ and K+ with ion-selective electrodes (ISE). Imprecision was less for venous blood (with a minimum of heparin) than for plasma, serum, or capillary blood. The results for K+ were higher for serum than for whole blood, and higher for whole blood than for plasma. The latter difference was apparently due to release of K+ during the analysis. Values were more stable for whole blood stored at 20 degrees C than at 4 degrees C or 37 degrees C. The molality of Na+ in the plasma of mixed whole blood changed by -10.5 mmol/kg per unit change in blood pH. This could be explained by the different H+ buffering capacities of plasma and erythrocyte fluid, because when the pH is changed, the concentration of small anions in erythrocytes changes more than it does in plasma, with a consequent osmotic movement of water across the erythrocyte membrane. When we took into account the residual liquid-junction potential and the mass concentration of water in each of 65 patients' sera, the molality determined for Na+ was 1% lower and that of K+ 3% lower by ISE than by flame photometry--differences that may be related to ionic binding or to a lower molal activity coefficient in serum than in the calibrator.

Effects of residual liquid junction potential in direct potentiometry of potassium.

1984 ◽  
Vol 30 (3) ◽  
pp. 482-484 ◽  
Author(s):  
J W Winkelman ◽  
C Merritt ◽  
W J Scott ◽  
A Kumar ◽  
G Baum
Keyword(s):  
Ionic Strength ◽  
Residual Liquid ◽  
Small Decrease ◽  
Liquid Junction Potential ◽  
Solution Composition ◽  
Liquid Junction ◽  
Reasonable Estimate ◽  
Direct Potentiometry ◽  
Plasma Electrolyte ◽  
Junction Potential

Abstract To further the accurate direct potentiometry of plasma electrolyte concentrations, we investigated the effects of solution composition on the residual liquid junction potential (RLJP) during measurement of K+. Assuming that the binding constant between K+ and proteins or bicarbonate is no greater than with Na+, we calculate that the amount of bound K+ can be neglected. A significant RLJP exists between simple solutions containing Na+, K+, and Cl- ions and solutions containing Na+, K+, Cl-, and HCO3- ions. Replacing Cl- with HCO3- leads to an increase in the RLJP, which in turn contributes to a negative error in K+ analysis. A small decrease in RLJP is observed as the ionic strength is increased. The Henderson equation gives a reasonable estimate of the magnitude of the observed RLJP, even though the liquid junction does not meet the conditions under which the equation is rigorously applicable. Errors attributed to RLJP may be substantially minimized by using a calibrator solution that contains an anion with mobility similar to that of HCO3-.

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