Determination of water samples and ene-diols or thiols in samples inaccessible for direct K.Fischer titration

Sherman, F. B.; Kuselman, Ilya; Shenhar, A.

doi:10.1016/0039-9140(96)01852-8

Cited by 12 publications

(16 citation statements)

References 3 publications

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“…Crude oil may contain significant amounts of oxidants containing sulfur as well as unsaturated hydrocarbons that may react with iodine. Although a brief reference to a coulometric method using a trichloroacetic acid-buffered SO 2 -free reagent has appeared [8,9], no well-documented and validated coulometric method analogous to the method of Sherman et al [4] exists for the measurement of the amounts of substances that react with iodine in a reagent similar to the Karl Fischer reagent. In this manuscript a coulometric method for measuring substances that interfere with the coulometric Karl Fischer method for the determination of water is described.…”

Section: Introductionmentioning

confidence: 99%

“…Sherman et al [4] reported an alternative method for volumetrically measuring water in ene-diols and thiols as well as the actual reducing agent. Their volumetric method [4] consisted of first measuring the reducing agent by using a dry SO 2 -free iodine reagent similar to the Karl Fischer reagent and then measuring the water by the Karl Fischer method using the same amperometric end point for both determinations. Both reagents were buffered with sodium acetate and the solvent was methanol.…”

Section: Introductionmentioning

confidence: 99%

“…Both reagents were buffered with sodium acetate and the solvent was methanol. This method was used for determining the water in pharmacologically important reductants such as ascorbic acid and thiols [4]. The economically important measurement of water in crude oil and oils containing additives presents a similar problem because these oils contain substances that react with iodine and as a result interfere with the measurement of water by the Karl Fischer reaction.…”

Section: Introductionmentioning

confidence: 99%

“…In this manuscript a coulometric method for measuring substances that interfere with the coulometric Karl Fischer method for the determination of water is described. This coulometric method uses a reagent similar in composition to that used in the volumetric method [4]. It complements the coulometric Karl Fischer method for measuring water by coulometrically measuring these materials which react with I 2 or I G and result in the inaccurate measurement of the water content.…”

Section: Introductionmentioning

confidence: 99%

“…Because the kinetics of some of these reactions are much slower than the Karl Fischer reaction, the extent of their interference with the measurement of water can be quantified by subtracting the contribution of the slower secondary reaction from the faster Karl Fischer reaction. It has been demonstrated and validated that the rapid interfering or side reactions can be volumetrically titrated independently by using a reagent that is similar to the volumetric Karl Fischer reagent but lacks the sulfur dioxide and is thus incapable of reacting with water [4].…”

Section: Introductionmentioning

confidence: 99%

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A coulometric method for determining substances that interfere with the measurement of water in oils and other chemicals by the Karl Fischer method

2002

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In order to fulfill a need to measure water in crude oils containing materials that interfere with the measurement of water by the Karl Fischer method, by reacting with iodine or iodide, a coulometric method has been developed and validated using 0.1 mol L(-1) Sodium thiosulfate as a calibrant. These interfering substances were measured in water-mass-equivalents, which were expressed as the mass of water that reacts with an equal mass of iodine in the Karl Fischer method. The SO(2)-free reagent that has been modified reacts quantitatively with sodium thiosulfate, cysteine and ascorbic acid but does not react with vinyl acetate. The level of interfering substances was measured in five transformer oils (including Reference Materials RM 8506 and RM 8507), a high and a low sulfur crude oil (Standard Reference Materials SRM 2721 and SRM 2722 respectively), a white oil, a high-vacuum oil and a high-viscosity base-stock oil. One oil contained less than 10 mg kg(-1) (water-mass-equivalents of interfering substances in oil) and two oils (RM 8507 and Drakeol 35) contained no measurable amount of interfering material (<0.2 mg kg(-1)). SRM 2271, a sour crude oil contained 834 mg kg(-1) (standard deviation (SD)=25 mg kg(-1)) (water-mass-equivalents of interfering substances in oil). Approximately 20% of this material was volatile and an additional 20% appeared to undergo some degradation (possibly oxidation) once the oil was exposed to air. These results indicate that this is a general method for measuring substances in oils that react with iodine and that it is capable of measuring in a variety of oils, using commercial instrumentation, interfering substances that inflate water measurements.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A coulometric method for determining substances that interfere with the measurement of water in oils and other chemicals by the Karl Fischer method

2002

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Assessment of limits of detection and quantitation using calculation of uncertainty in a new method for water determination

Kuselman

Sherman

1999

Measurement Uncertainty in Chemical Analysis

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The determination of water in crude oil and transformer oil reference materials

Margolis

Hagwood

2003

Anal Bioanal Chem

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The measurement of the amount of water in oils is of significant economic importance to the industrial community, particularly to the electric power and crude oil industries. The amount of water in transformer oils is critical to their normal function and the amount of water in crude oils affects the cost of the crude oil at the well head, the pipeline, and the refinery. Water in oil Certified Reference Materials (CRM) are essential for the accurate calibration of instruments that are used by these industries. Three NIST Standard Reference Materials (SRMs) have been prepared for this purpose. The water in these oils has been measured by both coulometric and volumetric Karl Fischer methods. The compounds (such as sulfur compounds) that interfere with the Karl Fischer reaction (interfering substances) and inflate the values for water by also reacting with iodine have been measured coulometrically. The measured water content of Reference Material (RM) 8506a Transformer Oil is 12.1+/-1.9 mg kg(-1) (plus an additional 6.2+/-0.9 mg kg(-1) of interfering substances). The measured water content of SRM 2722 Sweet Crude Oil, is 99+/-6 mg kg(-1) (plus an additional 5+/-2 mg kg(-1) of interfering substances). The measured water content of SRM 2721 Sour Crude Oil, is 134+/-18 mg kg(-1) plus an additional 807+/-43 mg kg(-1) of interfering substances. Interlaboratory studies conducted with these oil samples (using SRM 2890, water saturated 1-octanol, as a calibrant) are reported. Some of the possible sources of bias in these measurements were identified, These include: improperly calibrated instruments, inability to measure the calibrant accurately, Karl Fischer reagent selection, and volatilization of the interfering substances in SRM 2721.

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Determination of water samples and ene-diols or thiols in samples inaccessible for direct K.Fischer titration

Cited by 12 publications

References 3 publications

A coulometric method for determining substances that interfere with the measurement of water in oils and other chemicals by the Karl Fischer method

A coulometric method for determining substances that interfere with the measurement of water in oils and other chemicals by the Karl Fischer method

Assessment of limits of detection and quantitation using calculation of uncertainty in a new method for water determination

The determination of water in crude oil and transformer oil reference materials

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