A COMPARISON OF THREE METHODS FOR DETERMINING CALCIUM ION ACTIVITY IN SOIL SOLUTIONS

1988 ◽  
Vol 68 (2) ◽  
pp. 433-441 ◽  
Author(s):  
GERALD W. LUTWICK ◽  
GORDON R. WEBSTER ◽  
BYRON KRATOCHVIL
Keyword(s):  
Relative Error ◽  
Calcium Ion ◽  
Colorimetric Method ◽  
Calculation Methods ◽  
Selective Electrode ◽  
Soil Extracts ◽  
Soil Solutions ◽  
Ion Activity ◽  
Aqueous Species ◽  
Good Agreement

Calcium ion activity, (Ca2+), in 37 soil solutions was determined using species calculation, potentiometric (ion selective electrode), and colorimetric (tetramethylmurexide) methods. Agreement among the three estimates of (Ca2+) was tested by comparing the potentiometric and colorimetric methods to the species calculation method. Good agreement was observed between (Ca2+) estimates using the potentiometric and species calculation methods. Percent relative error between the two methods was less than 5% for 76% of the soil extracts and less than 10% for 85% of the soil extracts. Differences are thought to be related to interference from H+, Na+, K+, and Mg2+ above certain concentrations. The colorimetric and species calculation methods agreed poorly in their estimates of (Ca2+) in soil solutions. Relative error was less than 20% for only 39% of the estimates. Sodium interference is thought to be a major contributor to error in estimating (Ca2+) using the colorimetric method. Key words: Calcium ion activity, methods comparison, aqueous species distribution, selective ion electrode, tetramethylmurexide

scholarly journals Complexometric titration with potenciometric indicator to determination of calcium and magnesium in soil extracts¹

2011 ◽  
Vol 35 (4) ◽  
pp. 1331-1336 ◽  
Author(s):  
Claudia Mara Pereira ◽  
Cristhiane Anete Neiverth ◽  
Shizuo Maeda ◽  
Marcela Guiotoku ◽  
Luziane Franciscon
Keyword(s):  
Flame Atomic Absorption Spectrometry ◽  
Calcium Ion ◽  
Analytical Techniques ◽  
Absorption Spectrometry ◽  
Selective Electrode ◽  
Soil Extracts ◽  
Complexometric Titration ◽  
Flame Atomic Absorption ◽  
Calcium And Magnesium

This study proposes a method of direct and simultaneous determination of the amount of Ca2+ and Mg2+ present in soil extracts using a Calcium Ion-Selective Electrode and by Complexometric Titration (ISE-CT). The results were compared to those obtained by conventional analytical techniques of Complexometric Titration (CT) and Flame Atomic Absorption Spectrometry (FAAS). There were no significant differences in the determination of Ca2+ and Mg2+ in comparison with CT and FAAS, at a 95 % confidence level. Additionally, results of this method were more precise and accurate than of the Interlaboratorial Control (IC).

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.

Determination of Aluminum Ion Activity in Soil Extracts

1959 ◽  
Vol 23 (4) ◽  
pp. 266-269 ◽  
Author(s):  
W. L. Lindsay ◽  
Michael Peech ◽  
J. S. Clark
Keyword(s):  
Soil Extracts ◽  
Aluminum Ion ◽  
Ion Activity

Effect of calcium chelators on heat coagulation and heat-induced changes of concentrated micellar casein solutions: The role of calcium-ion activity and micellar integrity

2012 ◽  
Vol 26 (2) ◽  
pp. 112-119 ◽  
Author(s):  
Esther de Kort ◽  
Marcel Minor ◽  
Thom Snoeren ◽  
Toon van Hooijdonk ◽  
Erik van der Linden
Keyword(s):  
Calcium Ion ◽  
Micellar Casein ◽  
Ion Activity ◽  
Induced Changes

scholarly journals The Ionic Associate of Metamizole as an Electrode-Active Component of a PVC Plasticized Membrane Electrode

Chemosensors ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 17
Author(s):  
Sarizhat D. Tataeva ◽  
Kurban E. Magomedov ◽  
Ruslan Z. Zeynalov ◽  
Naida D. Baygishieva ◽  
Viktorya S. Magomedova ◽  
...  
Keyword(s):  
Active Component ◽  
Limit Of Detection ◽  
Membrane Electrode ◽  
Ionic Associate ◽  
Selective Electrode ◽  
Coefficients Of Variation ◽  
Ion Associate ◽  
Phase Functions ◽  
Good Agreement

The technology for manufacturing a film membrane of the metamizole-selective electrode containing ion associate metamizole-octadecylammonium ODAH+MT− as an electrode active component (EAC) has been proposed. The main potentiometric characteristics of the metamizole-selective electrode have been determined. The expediency of the proposed design of the metamizole selective electrode for the determination of metamizole in dosage forms has been substantiated. The best composition of the membrane (wt.%) of the metamizole-selective electrode has corresponded to: ODAH+MT−—5.3; 2-nitrophenyloctylether—63.1; poly(vinyl chloride)—31.6. Electrode-active component in the membrane phase functions as an ion associate ODAH+MT−. Potentiometric characteristics of metamizole-selective electrode have been determined, which corresponded to: linear range 1 × 10−2–1 × 10−4 with limit of detection 4.58 × 10−5 M, electrode function slope −48.5 mV/dec., working interval pH 4.5–7.3, response time 60 s. The potentiometric coefficients of selectivity of the metamizole-selective electrode with respect to various ions have been determined. The possibility of determining metamizole in a medicinal product has been tested. The results of the analyses show good agreement between the two methods (relative error less than 7.0%) with coefficients of variation less than 5% for MT-SE and iodometric methods.

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