Spectrophotometric determination of free, ionized, metal ion concentrations in solution by an indicator increment method. Application to the determination of free Mg2+ with calmagite

1995 ◽  
Vol 73 (2) ◽  
pp. 296-302
Author(s):  
Hongji Ren ◽  
Byron Kratochvil ◽  
Xiwen He
Keyword(s):  
Metal Ion ◽  
Ion Concentration ◽  
Multiple Equilibrium ◽  
Conditional Stability ◽  
Ligand Complex ◽  
Conditional Stability Constant ◽  
Visible Spectra ◽  
Free Magnesium ◽  
Free Metal

A spectrophotometric method, called the Indicator Increment Method, is described in which varying amounts of a complexing indicator are added to a sample and the visible spectra recorded after each addition. Through multiple equilibrium calculations the free metal ion concentration, as well as total metal and total ligand concentrations, can be estimated in systems that contain a single metal ion and one ligand. The technique was tested successfully for the determination of free magnesium in the presence of NTA, phosphate, or oxalate using calmagite as indicator. The method requires the approximate conditional stability constant of the metal–ligand complex to be known beforehand. Keywords: ionized magnesium, indicator increment method, spectrophotometry.

Ion Exchange Complexing Resins as Sensors for the Determination of Free Metal Ion Concentration at a Low Level

2008 ◽  
Vol 26 (3) ◽  
pp. 301-320 ◽  
Author(s):  
Maria Pesavento ◽  
Antonella Profumo ◽  
Raffaela Biesuz ◽  
Giancarla Alberti
Keyword(s):  
Ion Exchange ◽  
Metal Ion ◽  
Ion Concentration ◽  
Low Level ◽  
Free Metal ◽  
Free Metal Ion

scholarly journals Spectrophotometric determination of dothiepin hydrochloride in pharmaceuticals through ion-pair complexation reaction

2012 ◽  
Vol 18 (2) ◽  
pp. 339-347 ◽  
Author(s):  
Sameer Abdulrahman ◽  
Kanakapura Basavaiah
Keyword(s):  
Ion Pair ◽  
Pure Form ◽  
Bromocresol Green ◽  
Bromophenol Blue ◽  
Complexation Reaction ◽  
Conditional Stability ◽  
Conditional Stability Constant ◽  
Accuracy And Precision ◽  
Significant Difference

Two simple, sensitive and extraction-free spectrophotometric methods are described for the determination of dothiepin hydrochloride (DOTH) both in pure form and in pharmaceutical tablets. The methods are based on ion-pair complex formation between dothiepin base (DOT) and two acidic dyes, namely, bromophenol blue (BPB) or bromocresol green (BCG) with absorption maximum at 425 nm for BPB method or 430 nm for BCG method. Beer?s law is obeyed over the concentration ranges of 1.0-15.0 and 1.0-17.5 ?g mL-1 DOT for BPB and BCG methods, respectively. The molar absorptivity values and Sandell?s sensitivity values are reported for both methods. The limits of detection (LOD) and quantification (LOQ) were calculated to be 0.18 and 0.53 ?g mL-1 for BPB method, and 0.17 and 0.50 ?g mL-1 for BCG method, respectively. The stoichiometry of the complex in either case was found to be 1: 1 and the conditional stability constant (KF) of the complexes has also been calculated. The proposed methods were applied successfully to the determination of DOTH in pure form and in its tablet form with good accuracy and precision. Statistical comparison of the results was performed using Student's t-test and variance ratio F-test at 95% confidence level and there was no significant difference between the official and proposed methods with regard to accuracy and precision. Further, the validity of the proposed methods was confirmed by recovery studies via standard addition technique.

scholarly journals Spectrophotometric determination of nicradipine and isradipine in pharmaceutical formulations

2009 ◽  
Vol 15 (2) ◽  
pp. 69-76 ◽  
Author(s):  
S.M. Al-Ghannam ◽  
A.M. Al-Olyan
Keyword(s):  
Standard Deviation ◽  
Detection Limit ◽  
Reaction Pathway ◽  
Pharmaceutical Preparations ◽  
Pharmaceutical Formulations ◽  
Molar Absorptivity ◽  
Zinc Powder ◽  
Conditional Stability ◽  
Conditional Stability Constant

A sensitive spectrophotometric method was developed for the determination of some 1,4-dihydropyridine compounds namely, nicardipine and isradipine either in pure form or in pharmaceutical preparations. The method is based on the reduction of nicardipine and isradipine with zinc powder and calcium chloride followed by further reduction with sodium pentacyanoaminoferrate (II) to give violet and red products having the absorbance maximum at 546 and 539 nm with nicardipine and isradipine, respectively. Beer's law was obeyed over the concentration range 8.0-180 ?g/ml with the detection limit of 1.67 ?g/ml for nicardipine and 8.0-110 ?g/ml with the detection limit of 1.748 ?g/ml for isradipine. The analytical parameters and their effects on the reported methods were investigated. The molar absorptivity, quantization limit, standard deviation of intercept (Sa), standard deviation of slope (Sb) and standard deviation of the residuals (Sy/x) were calculated. The composition of the result compounds were found 1:1 for nicardipine and 1:2 for isradipine by Job's method and the conditional stability constant (Kf) and the free energy changes (?G) were calculated for compounds formed. The proposed method was applied successfully for the determination of nicardipine and isradipine in their dosage forms. The results obtained were in good agreement with those obtained using the reference or official methods. A proposal of the reaction pathway was presented.

scholarly journals Determination of the free-ion concentration of rare earth elements by an ion-exchange technique: implementation, evaluation and limits

2016 ◽  
Vol 13 (3) ◽  
pp. 478 ◽  
Author(s):  
Sébastien Leguay ◽  
Peter G. C. Campbell ◽  
Claude Fortin
Keyword(s):  
Ion Exchange ◽  
Natural Organic Matter ◽  
Metal Ion ◽  
Exchange Resin ◽  
Ion Exchange Resin ◽  
Ion Concentration ◽  
Free Ion ◽  
Free Metal ◽  
Free Metal Ion ◽  
Exchange Technique

Environmental context The lanthanides are a group of heavy elements (from lanthanum to lutetium) increasingly used in many electronic consumer products and little is known about their environmental mobility and toxicity. In natural systems, these elements will bind to natural organic matter but metal toxicity is usually defined by the free metal ion concentration. Here, we propose a method based on sample equilibration with an ion-exchange resin to measure the free lanthanide ion concentration in the presence of natural organic matter. Abstract An ion-exchange technique that employs a polystyrene sulphonate ion-exchange resin was developed for determining environmentally relevant free-ion concentrations of Ce, Eu, La and Nd. Owing to the high affinity of rare earth elements (REE) for the selected resin, this method requires the addition of an inert salt to increase the concentration of the counter-ions (i.e. cations that are exchanged with REE bound to the resin). The use of a batch equilibration approach to calibrate the resin allowed the implementation of the ion-exchange technique at reasonably low ionic strength (I = 0.1M). Several ligands were used to test the selectivity of the method, which proved to be highly selective for the free metal ion in presence of the tested cationic and anionic complexes (REE–nitrate, REE–malic acid and REE–nitrilotriacetic acid systems) and operational for very low proportions of REE3+, owing to the strong REE–resin interactions. The ion-exchange technique was also implemented to determine [Eu]inorg in the presence of natural humic matter (Suwannee River Humic Acid) and the results were compared with those obtained using equilibrium dialysis and those calculated with chemical equilibrium models. At pH 4.00, the measured [Eu]inorg values were in fairly good agreement with those predicted with the Windermere Humic Aqueous Model and Stockholm Humic Model, whereas the Non-Ideal Competitive Absorption model appeared to underestimate the [Eu]inorg. However, the inorganic europium concentrations were strongly underestimated (4 < [Eu]inorg, IET/[Eu]inorg, calc < 18) with the three prediction models at higher pH (5.3 and 6.2).

Ion-selective determination of total metal ion concentration in an excess of complexing ligand using the standard additions method

The Analyst ◽  
1985 ◽  
Vol 110 (4) ◽  
pp. 359 ◽  
Author(s):  
Liliana Ilcheva ◽  
Maria Polianova ◽  
Jordan Dalukov ◽  
Brian R Chapman
Keyword(s):  
Metal Ion ◽  
Ion Concentration ◽  
Selective Determination ◽  
Total Metal ◽  
Standard Additions

A study of the Ca2+ – Arsenazo III system and its application to the spectrophotometric determination of free calcium in solution

1990 ◽  
Vol 68 (11) ◽  
pp. 1932-1936 ◽  
Author(s):  
Byron Kratochvil ◽  
Xi-Wen He
Keyword(s):  
Ionic Strength ◽  
Calcium Ion ◽  
Calcium Binding ◽  
Metal Ion ◽  
Arsenazo Iii ◽  
Free Calcium ◽  
Ionic Calcium ◽  
Free Metal ◽  
Free Metal Ion

A two-wavelength method was applied to the determination of free, ionic calcium with Arsenazo III in solutions containing calcium-binding ligands. By this procedure impurities in the indicator can be corrected for, thereby allowing the use of commercial indicator preparations with purities as low as 80%. Only a 1:1 complex with a conditional log stability constant of 4.28 ± 0.13 at pH 4.6 and ionic strength 0.1 was found under the conditions studied. Key words: free metal ion determination, calcium ion speciation, spectrophotometry, arsenazo III, ion increment method for speciation.

scholarly journals Determination of Trace Metal Ions in Common Salt by Stripping Voltammetry

1999 ◽  
Vol 82 (6) ◽  
pp. 1413-1418 ◽  
Author(s):  
Azza M M Ali
Keyword(s):  
Metal Ion ◽  
Supporting Electrolyte ◽  
Standard Addition ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Ion Concentration ◽  
Common Salt ◽  
Trace Metal Ions

Abstract Sensitive voltammetric methods using cathodic and anodic differential pulse stripping techniques were applied for determination of trace ions cadmium(II), cobalt(II), copper(II), lead(II), manganese(II), nickel(II), and zinc(II), which are usually found in different grades of common salt as contaminants. The optimal conditions, i.e., deposition time, preconcentration potential, supporting electrolyte, and ionic strength, were investigated for each metal ion. Concentration of the metal ion was determined by the standard addition method. Metal content varied according to the quality of the table salt.

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