Pulse coulometric titration in continuous flow

Dakashev, Anastas Dimitrov; Dimitrova, Veselina Todorova

doi:10.1039/an9941901835

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…The results for conversion efficiency by this study were about the same as the previous one, so one has to suppose that generation process itself goes with a conversion efficiency less than 100%. It was found earlier [7] that the conversion efficiency does not depend on the flow rate used. It depends on the current.…”

Section: Resultsmentioning

confidence: 71%

Continuous flow system and method for electrochemical preparation of metal-ion standard solutions

Dakashev

Dimitrova

1998

Lab. Robotics Autom.

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Standard metal-ion solutions for analytical purposes are obtained by electrochemical dissolution of a porous metal anode in a continuous flow of an appropriate supporting electrolyte. Dissolution is performed at a constant flow rate and a constant current. Different solution concentrations are achieved choosing proper current values. Standard solutions of Cr(VI), Cu(II), Ag(I), Zn(II), Bi(III), Sn(II), Fe(II), Pb(II), Co(II), and Ti(III) were generated. The standard solution concentrations as prepared were compared with the same solution concentrations made by the conventional way, and a statistical identity was proved.

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Section: Resultsmentioning

confidence: 71%

Continuous flow system and method for electrochemical preparation of metal-ion standard solutions

Dakashev

Dimitrova

1998

Lab. Robotics Autom.

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“…The method presented in this paper was extended to the electrolytic preparation of Fe 2+ (aq) and Sn 2+ (aq). These reagents were produced by electrolytic reduction of Fe 3+ (aq) and Sn 4+ (aq) reagent precursors, respectively. ,− In each case, the neutralization of electrolytically produced H + (aq) by Na 2 CO 3 was used as a common counter reaction to determine the amount of reagent produced at the cathode. Relevant electrolytic reductions at the cathode are described below.…”

Section: Experimental Overviewmentioning

confidence: 99%

Quantitative Cathodic Preparation of Selected Aqueous Reagents Used in an Undergraduate Laboratory

Melaku

Dabke

2015

J. Chem. Educ.

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A guide for instructors and laboratory assistants to prepare several aqueous reagents used in an undergraduate laboratory is presented. Dilute reagents consisting of OH − (aq), Fe 2+ (aq), and Sn 2+ (aq) were prepared by electrolytic reduction of the respective precursors at the cathode. Concurrently, water was electrolyzed at the anode. A known mass of anhydrous Na 2 CO 3 (a primary standard) was added to the anode compartment. Electrolytically produced H + (aq) ions were titrated in situ against Na 2 CO 3 using bromophenol blue indicator. The electrolysis was promptly stopped when the indicator changed color from blue to yellow. The amount of H + (aq) produced at the anode was determined from the mass of Na 2 CO 3 . Because the same current passed through the electrolysis cell, the stoichiometric relation between the cathode and anode reactions facilitated the determination of the reagent prepared at the cathode. The concentration of reagent prepared at the cathode was independently confirmed by the volumetric titration method. The electrolysis cell, powered by 18 V dc power supply, eliminated the requirement of a coulometer or a constant current power source. Setup of an electrolysis cell and experimental details for preparing reagents are presented.A variety of reagents are prepared for volumetric titrations in an undergraduate laboratory. If a reagent is available in the pure from, its molarity can be directly determined from its mass. However, if a reagent is not available in the pure form or if its mass alters due to its hygroscopic nature, the reagent must be standardized prior to use in a titration. NaOH(aq) is commonly used in an undergraduate laboratory for the volumetric titration of CH 3 COOH(aq) in vinegar. 1,2 However, due to the hygroscopic nature of NaOH, it cannot be weighed accurately and needs to be standardized with standard HCl or with potassium hydrogen phthalate (C 8 H 5 O 4 K). 3 Fe 2+ (aq) is used for volumetric or potentiometric titrations in a quantitative analysis laboratory. 4,5 Fe 2+ (aq) is standardized with KMnO 4 or Ce(SO 4 ) 2 ; however, these reagents necessitate their independent standardization. 6 Potentiometric titrations of Ce 4+ (aq), MnO 4 − (aq), or Cr 2 O 7 2− (aq) involving Sn 2+ (aq) are of practical importance in view of applying redox chemical reactions for quantitative analysis. 4 Amperometric titration of Cu 2+ (aq) with Sn 2+ (aq) also exemplifies the pedagogy of redox reactions for chemical analysis. 7 However, additional titrations owing to the standardization of Sn 2+ (aq) or other reagents are required. 6 Several practical considerations related to preparing and storing chemicals make the standardization of various reagents less straightforward.We recently presented an alternative approach for preparing and standardizing some common aqueous reagents used in an undergraduate laboratory. 8 In this approach, the reagent was prepared by an electrolytic oxidation of a precursor at the anode. The amount of reagent prepared at the anode was determined from the amoun...

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“…In this way, the analyte concentration was determined based on analytical calibration (a set of standard solutions was subjected to the titration procedure in the same instrumental conditions as the sample) [9,10] or on the relationship between the time necessary to achieve the endpoint of titration and the flow rate of the titrant (introduced using a double-plunger micropump) measured at the endpoint of titration [11]. The other approach is based on changing the flow rates of the sample and titrant streams while keeping the sum of the flow rates constant [12][13][14][15][16][17][18][19][20][21][22]. In this (latter) case, a single concentration gradient with analytical calibration [12] or a triangle-programmed concentration gradient of the analyte was formed [12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

“…The other approach is based on changing the flow rates of the sample and titrant streams while keeping the sum of the flow rates constant [12][13][14][15][16][17][18][19][20][21][22]. In this (latter) case, a single concentration gradient with analytical calibration [12] or a triangle-programmed concentration gradient of the analyte was formed [12][13][14][15][16][17]. To this end, e.g., two streams of titrant and analyte were introduced into the system using peristaltic pumps, first increasing the titrant flow rate from zero to a value corresponding to zero sample flow rate and then, at the same rate, reducing to zero again.…”

Section: Introductionmentioning

confidence: 99%

“…The method enabled the determination of analyte concentration using an appropriate formula [14,16] or analytical calibration [15,16]. Coulometric titration with a continuous sample flow in which the concentration gradient of the analyte was associated with the magnitude of the rectangular [17] or triangular [18][19][20] current pulse generating the titrant in a flow-through electrolytic vessel was also proposed.…”

Section: Introductionmentioning

confidence: 99%

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Novel Approach to Automated Flow Titration for the Determination of Fe(III)

et al. 2020

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A novel approach to automated flow titration with spectrophotometric detection for the determination of Fe(III) is presented. The approach is based on the possibility of strict and simultaneous control of the flow rates of sample and titrant streams over time. It consists of creating different but precisely defined concentration gradients of titrant and analyte in each successively formed monosegments, and is based on using the calculated titrant dilution factor. The procedure was verified by complexometric titration of Fe(III) in the form of a complex with sulfosalicylic acid, using EDTA as a titrant. Fe(III) and Fe(II) (after oxidation to Fe(III) with the use of H2O2) were determined with good precision (CV lower than 1.7%, n = 6) and accuracy ( | RE | lower than 3.3%). The approach was applied to determine Fe(III) and Fe(II) in artesian water samples. Results of determinations were consistent with values obtained using the ICP–OES reference method. Using the procedure, it was possible to perform titration in 6 min for a wide range of analyte concentrations, using 2.4 mL of both sample and titrant.

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Pulse coulometric titration in continuous flow

Cited by 6 publications

References 8 publications

Continuous flow system and method for electrochemical preparation of metal-ion standard solutions

Continuous flow system and method for electrochemical preparation of metal-ion standard solutions

Quantitative Cathodic Preparation of Selected Aqueous Reagents Used in an Undergraduate Laboratory

Novel Approach to Automated Flow Titration for the Determination of Fe(III)

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