Ionized calcium in human milk determined with a calcium-selective electrode.

1983 ◽  
Vol 29 (5) ◽  
pp. 858-861 ◽  
Author(s):  
J C Allen ◽  
M C Neville
Keyword(s):  
Ionic Strength ◽  
Human Milk ◽  
Blood Plasma ◽  
Calibration Curve ◽  
Calcium Ion ◽  
Ionized Calcium ◽  
Selective Electrode ◽  
Electrode Response ◽  
Glass Capillaries ◽  
Other Substances

Abstract We measured the concentration of ionized calcium in human milk with a Radiometer ionized calcium analyzer at 37 degrees C. This instrument is designed to use simultaneous outputs from a pH electrode and a calcium ion-selective electrode to obtain the true ionized calcium in blood plasma. Because both the ionic strength and the pH of human milk differ significantly from that of plasma, we used a calibration curve that corrected for these variables. No other substances in milk interfered with the electrode response to Ca2+. The Ca2+ concentration of milk decreased and the pH increased as CO2 was lost to the atmosphere. Samples collected in glass capillaries, which minimized CO2 loss, contained 2.84 (SD 0.56) mmol of Ca2+ per liter at pH 6.98. We emphasize the importance of maintaining physiological CO2 concentrations when Ca2+ is being measured in milk.

Ion effects in measurement of ionized calcium with a calcium-selective electrode.

1980 ◽  
Vol 26 (5) ◽  
pp. 640-644
Author(s):  
R A Kaufman ◽  
N W Tietz
Keyword(s):  
Ionic Strength ◽  
Osmotic Pressure ◽  
Calcium Ion ◽  
Important Variable ◽  
Ionized Calcium ◽  
Selective Electrode ◽  
Electrode Response ◽  
Ion Activity ◽  
Ion Effects ◽  
Significant Direct Effect

Abstract We examined the performance characteristics of an improved electrode for measurement of ionized calcium (Orion Research, Inc.) with respect to interferences by Na+, K+, Li+, Mg2+, and H+, as well as the effect of changes in ionic strength and osmolality. At physiologically observed concentrations, all ions except Na+ insignificantly affected ionized-calcium measurements. The decrease in ionized Ca2+ with increased Na+ concentration is caused by the increase in ionic strength and the associated decrease in Ca2+ activity. Sodium had no significant direct effect in concentrations below 250 mmol/L. A previously published (Clin. Chem. 23: 690, 1977) equation for the Na+ correction is invalid for this improved electrode. Changes in osmotic pressure negligibly affect electrode response. Significant changes in ionic strength, as would be observed in severe hypo- and hypernatremic sera, increase or decrease, respectively, values for ionized calcium by changing Ca2+ activity. With aqueous Ca2+ solutions, changes of less than or equal to 3% were observed for Na+ concentrations that deviate from 140 mmol/L by not more than 20 mmol/L. Because the calcium ion activity is considered to be the physiologically important variable, we suggest that no correlation be made for ionic strength effects.

Ion effects in measurement of ionized calcium with a calcium-selective electrode.

1980 ◽  
Vol 26 (5) ◽  
pp. 640-644 ◽  
Author(s):  
R A Kaufman ◽  
N W Tietz
Keyword(s):  
Ionic Strength ◽  
Osmotic Pressure ◽  
Calcium Ion ◽  
Important Variable ◽  
Ionized Calcium ◽  
Selective Electrode ◽  
Electrode Response ◽  
Ion Activity ◽  
Ion Effects ◽  
Significant Direct Effect

Abstract We examined the performance characteristics of an improved electrode for measurement of ionized calcium (Orion Research, Inc.) with respect to interferences by Na+, K+, Li+, Mg2+, and H+, as well as the effect of changes in ionic strength and osmolality. At physiologically observed concentrations, all ions except Na+ insignificantly affected ionized-calcium measurements. The decrease in ionized Ca2+ with increased Na+ concentration is caused by the increase in ionic strength and the associated decrease in Ca2+ activity. Sodium had no significant direct effect in concentrations below 250 mmol/L. A previously published (Clin. Chem. 23: 690, 1977) equation for the Na+ correction is invalid for this improved electrode. Changes in osmotic pressure negligibly affect electrode response. Significant changes in ionic strength, as would be observed in severe hypo- and hypernatremic sera, increase or decrease, respectively, values for ionized calcium by changing Ca2+ activity. With aqueous Ca2+ solutions, changes of less than or equal to 3% were observed for Na+ concentrations that deviate from 140 mmol/L by not more than 20 mmol/L. Because the calcium ion activity is considered to be the physiologically important variable, we suggest that no correlation be made for ionic strength effects.

Comparative evaluation of two calcium ion-selective electrode systems, and their utility for monitoring steady-state changes in [Ca2+].

1982 ◽  
Vol 28 (1) ◽  
pp. 129-133 ◽  
Author(s):  
L J Drop ◽  
L N Tochka ◽  
D R Misiano
Keyword(s):  
Steady State ◽  
Whole Blood ◽  
Calcium Ion ◽  
Ionized Calcium ◽  
Normal Range ◽  
Selective Electrode ◽  
Human Volunteers ◽  
Normal Human ◽  
State Changes ◽  
Electrode Systems

Abstract We compared ionized calcium concentrations ([Ca2+]) as measured with two ionized-calcium analyzers: the NOVA 2 and the Orion SS-20. Samples were obtained from 43 human volunteers, 213 patients, and five dogs (106 samples). In the [Ca2+] range of 0.85 to 1.8 mmol/L, [Ca2+] measurements in whole blood with the NOVA 2 consistently exceeded those measured with the Orion SS-20. However, in the normal range, this difference appeared to be smaller when we compared values for plasma or serum, and was absent over the entire range when we compared aqueous solutions. The normal human [Ca2+] in whole blood as measured with the NOVA 2 is 1.22 +/- 0.01 mmol/L (mean +/- SEM) and that with the Orion SS-20 is 1.12 +/- 0.01 mmol/L (p less than 0.0001 by paired t-test); the 95% confidence intervals were from 1.14 to 1.30 and from 1.02 to 1.22 mmol/L, respectively. Using dogs, we also tested the usefulness of the ionized-calcium electrode for monitoring [Ca2+] during infusion of either citrate or calcium chloride solutions, to produce steady-state alterations in [Ca2+] equilibrium. Frequent successive [Ca2+] measurements were essential to appropriately adjust the infusion rates of these solutions to achieve steady-state [Ca2+].

Titration of sulphates and lead using lead ion selective electrode

1981 ◽  
Vol 46 (2) ◽  
pp. 368-376 ◽  
Author(s):  
Josef Veselý
Keyword(s):  
Ionic Strength ◽  
Electrode Surface ◽  
Salt Content ◽  
Ion Selective Electrode ◽  
Lead Ion ◽  
Selective Electrode ◽  
Limit Of Determination ◽  
Total Salt Content ◽  
Automatic Titration

Titration of sulphates with lead perchlorate employing lead ion selective electrode indication was studied using additions of various organic solvents at different pH' and ionic strength values. As the optimum emerged systems with 60-70% 1,4-dioxane, pH' 5.3-5.6. After dehydration with sodium hydroxide, dioxane must be freed from the electrode surface-oxidizing impurities by their reduction with sodium metal and subsequent distillation. The method was applied to determination of sulphates in mountain spring waters. Units of ppm can be determined; the limit of determination, however, depends considerably on the content of dioxane, total salt content in the sample, and speed of the semi-automatic titration. Lead can be determined with EDTA in concentrations down to c(Pb2+) = 5 . 10-6 mol l-1.

Automated Fluoride Ion Determination

1977 ◽  
Vol 14 (1-6) ◽  
pp. 269-274 ◽  
Author(s):  
David C. Cowell
Keyword(s):  
Continuous Flow ◽  
Ion Concentration ◽  
Fluoride Ion ◽  
Selective Electrode ◽  
Automated Method ◽  
Electrode Response ◽  
Kinetics Of ◽  
Fluoride Ion Selective Electrode ◽  
Flow Techniques

An automated method is described, using standard continuous flow techniques, for the determination of urine fluoride ion concentration using a fluoride ion selective electrode. It is shown that the kinetics of the electrode response to changes in fluoride ion can be used for the accurate measurement of fluoride ion concentration in urine, and that equilibration of the electrode response is not a prerequisite for the measurement of fluoride ion. Recovery experiments are in the range 83 to 90%; in-batch precision is between 0·9 and 1·6% and carryover 2·5% or less.

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