Comparison of high precision coulometric and West-Gaeke methods with the gravimetric method for preparation of standard sulfur dioxide gas blends using permeation tubes

Cedergren, Anders; Wikby, Anders; Bergner, Kurt.

doi:10.1021/ac60351a006

Cited by 26 publications

(7 citation statements)

References 23 publications

(18 reference statements)

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“…Before use the reagents were nearly decolored with water. Coulometric determination of the effective concentration of sulfur dioxide, [SO 2 ] eff , (i.e., the sum of all tetravalent species obtained from the added sulfur dioxide) was performed iodometrically according to the procedure described by Cedergren et al using an LKB 16300 coulometric analyzer. The titration medium consisted of an aqueous solution of 0.4% potassium iodide and 0.68% acetic acid.…”

Section: Methodsmentioning

confidence: 99%

Coulometric Study of Reaction Rates of Water in Pyridine- and Imidazole-Buffered Methanolic Karl Fischer Reagents Containing Chloroform

Cedergren

1996

Anal. Chem.

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The influence of additives like chloroform, methylene chloride, and carbon tetrachloride on the reactivity of pyridine- and imidazole-buffered methanolic Karl Fischer (KF) reagent has been investigated. For all reagents studied, including a variation in the concentration of pyridine between 1 and 5 M and imidazole between 1 and 8 M, chloroform was found to have an accelerating effect on the KF reaction. The most pronounced effect was found for 5 M imidazole-buffered reagents containing 30% chloroform for which the reaction rate constant was determined to be as high as 1.0 × 109 M-2 s-1 provided that the iodine concentration was kept in the range 10-9−10-10 M. The analytical advantages of such a rapid reagent were demonstrated by rapid titrations of nanogram amounts of water in a coulometric procedure in which the end-point concentration of iodine was controlled at 10-9 M. Generally, it was found that the reaction rate for iodine concentrations below 10-5−10-6 M was much higher when the rate of the reaction was determined on the basis of a method using continuously generated iodine as compared to the value for the corresponding iodine level evaluated by means of direct potentiometry. However, the latter method was found to be more affected by a competitive, reversible reaction (probably the formation of iodate) which leads to an underestimation of the rate constant for the KF reaction when different iodine excesses are considered. It could be concluded that the KF reaction is first order with respect to iodine, water, and sulfur dioxide only in the case of pyridine at pH values that correspond to low nonprotonated concentrations of this base.

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Section: Methodsmentioning

confidence: 99%

Coulometric Study of Reaction Rates of Water in Pyridine- and Imidazole-Buffered Methanolic Karl Fischer Reagents Containing Chloroform

Cedergren

1996

Anal. Chem.

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“…Th e chamber air was co ntin uo us ly a na lyzed with an electrochemi cal method , with which SOz is oxidized to sulfa te and the cur rent is regi stered on a recorder. The method ha s previo usly been de scribed in detail (15). The su bje cts wer e exposed to SO z in the cha m be r for 20 min .…”

Section: Sulfur Dioxide Exp Osurementioning

confidence: 99%

Cell response in bronchoalveolar lavage fluid after sulfur dioxide exposure.

Sandström¹,

Stjernberg²,

Andersson³

et al. 1989

Scand J Work Environ Health

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“…The reagents were prepared by dissolving 1−8 mol/L of imidazole, 0.1−2 mol/L of sulfur dioxide, 0.1 mol/L of iodine in methanol. Coulometric determinations of sulfur dioxide (i.e., the sum of all S IV species obtained from the added sulfur dioxide) was performed iodometrically, according to the procedure described by Cedergren et al, using an LKB 16300 coulometric analyzer. The titration medium for the SO 2 determinations consisted of an aqueous solution containing 0.4% KI and 0.68% acetic acid.…”

Section: Methodsmentioning

confidence: 99%

Determination of Kinetics of the Karl Fischer Reaction Based on Coulometry and True Potentiometry

Cedergren

1996

Anal. Chem.

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A new measurement technique based on a combination of coulometry and zero-current potentiometry is described for determination of the kinetics of rapidly reacting Karl Fischer (KF) reagents. This makes it possible to determine the order as well as the rate constant for large variations in the concentrations of iodine and water present during a titration. It was shown that for imidazole-based methanolic reagents exposed to a large variation in the concentration of water, the KF reaction is first order with respect to iodine, sulfur dioxide, and water only for reagents in which the concentration of nonprotonated imidazole is very low. The rate constant determined for such a reagent (1 M imidazole, 0.8 M sulfur dioxide, 0.1 M iodine) was equal to that reported earlier in the literature. Regions showing first-order kinetics were also found for low concentrations of water when imidazole concentrations up to 2 mol/L were used, provided that these reagents had a quotient [Im](free)/[ImH(+)] around 4. In the interval 2-8 mol/L of imidazole, the order of the reaction with respect to iodine was, in most cases, one-half, while it was changed to between one-half and one with respect to water. The rate of the KF reaction was found to increase by nearly 5 orders of magnitude for a reagent in which the concentration of nonprotonated imidazole was increased from 0 (rate constant equal to 2.6 × 10(3) L(2) mol(-)(2) s(-)(1)) to about 7 mol/L. For most of these reagents, a recovery rate close to 100% was attained. A high concentration of nonprotonated imidazole in combination with a high concentration of sulfur dioxide could, however, lead to a change in stoichiometry of the KF reaction when larger amounts of water were determined (250 μg of water added to 3.4 mL of reagent solution). A reaction scheme is proposed which might explain this change in stoichiometry observed for some reagent compositions. By use of the described most rapidly reacting reagents, it was shown to be possible to carry out titrations even at such a low end-point concentration as 10(-)(10) M of iodine within 1-2 min.

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Comparison of high precision coulometric and West-Gaeke methods with the gravimetric method for preparation of standard sulfur dioxide gas blends using permeation tubes

Cited by 26 publications

References 23 publications

Coulometric Study of Reaction Rates of Water in Pyridine- and Imidazole-Buffered Methanolic Karl Fischer Reagents Containing Chloroform

Coulometric Study of Reaction Rates of Water in Pyridine- and Imidazole-Buffered Methanolic Karl Fischer Reagents Containing Chloroform

Cell response in bronchoalveolar lavage fluid after sulfur dioxide exposure.

Determination of Kinetics of the Karl Fischer Reaction Based on Coulometry and True Potentiometry

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