Determination of Water by Karl Fischer Reagent

Seaman, Wm.; McComas, Wilbur H.; Allen, Geoffrey

doi:10.1021/ac60028a016

Cited by 44 publications

(9 citation statements)

References 13 publications

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“…The effect of different wt % of ClO 4 À (0.1, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 10.0, 15.0, 20.0, 30.0, 40.0 wt %) on TMAH pyrolysis at 600°C was studied. The calcium perchlorate was dried at room temperature under a dinitrogen flow for 3 h, and the water abundance in the sample was measured by the Karl Fischer method with an Aqua processeur radiometer (Seaman et al, 1949;Burns and Muraca, 1962;Bryan and Bhaskara, 1976;Galletti and Piccaglia, 1988;Ewa and Piotr, 2009). The calibration curve of the moisture detection is shown in Fig.…”

Section: Samples and Chemical Productsmentioning

confidence: 99%

Influence of Calcium Perchlorate on the Search for Martian Organic Compounds with MTBSTFA/DMF Derivatization

Buch

Szopa

et al. 2021

Astrobiology

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The Mars Organic Molecule Analyzer (MOMA) and Sample Analysis at Mars (SAM) instruments onboard the Exomars 2022 and Mars Science Laboratory rovers, respectively, are capable of organic matter detection and differentiating potentially biogenic from abiotic organics in martian samples. To identify organics, both these instruments utilize pyrolysis-gas chromatography coupled to mass spectrometry, and the thermochemolysis agent tetramethylammonium hydroxide (TMAH) is also used to increase organic volatility. However, the reactivity and efficiency of TMAH thermochemolysis are affected by the presence of calcium perchlorate on the martian surface. In this study, we determined the products of TMAH pyrolysis in the presence and absence of calcium perchlorate at different heating rates (flash pyrolysis and SAM-like ramp pyrolysis with a 35°C$min -1 heating rate). The decomposition mechanism of TMAH pyrolysis in the presence of calcium perchlorate was studied by using stepped pyrolysis. Moreover, the effect of calcium perchlorate (at Mars-relevant concentrations) on the recovery rate of fatty acids with TMAH thermochemolysis was studied. Results demonstrate that flash pyrolysis yields more diversity and greater abundances of TMAH thermochemolysis products than does the SAM-like ramp pyrolysis method. There is no obvious effect of calcium perchlorate on TMAH degradation when the [ClO 4 -] is lower than 10 weight percent (wt %). Most importantly, the presence of calcium perchlorate does not significantly impact the recovery rate of fatty acids with TMAH thermochemolysis under laboratory conditions, which is promising for the detection of fatty acids via TMAH thermochemolysis with the SAM and MOMA instruments on Mars. Key Words: Calcium perchlorate-TMAH thermochemolysis-Pyrolysis-GC-MS-Mars-SAM and MOMA. Astrobiology 21, xxx-xxx.

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Section: Samples and Chemical Productsmentioning

confidence: 99%

Influence of Calcium Perchlorate on the Search for Martian Organic Compounds with MTBSTFA/DMF Derivatization

Buch

Szopa

et al. 2021

Astrobiology

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“…Water content was measured by the Karl Fischer titration t net hod, the end point being determined electrometrically (24,26,30) with the aid of a Model HZ Beckman pH meter equipped with two plati~lu~n electrodes. Pure, dried methanol, stirred mechanically, was titrated in an enclosed beaker to the end point with standardized Karl Fischer reagent.…”

Section: Analysis For Water In Dried Cotton Lintersmentioning

confidence: 99%

The Reactivity of Cellulose: II.WATER Sorption, Heats of Wetting, and the Reactions With Thallous Ethylate in Ether, Nitration Mixtures, and Heavy Water of Cotton Linters Alternately Wetted With Water and Dried

Brickman¹,

Dunford²,

Tory³

et al. 1953

Can. J. Chem.

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Cotton linters dewaxed with benzene and alcohol possess a slightly expanded structure attributed to the swelling effect of the alcohol. Storage causes a partial collapse of the linters especially so when moisture is present. Wetting with water followed by rigorous drying produces a marked reduction in accessibility, but with each additional wetting-drying cycle accessibility of the dried linters increases slightly as measured by reaction with thallous ethylate in ether, a nitration mixture, and in hydrogen-deuterium exchange. Differences in nitration found for limited reaction times are obliterated when these reaction times are extended. Increasing accessibility due to repeated wetting and drying is accon~panied by lower water sorption and smaller heats of wetting. This anomaly is due to the fact that cellulose sanlples obtained by alternately wetting and drying dewaxed linters, when stored with a desiccant, compete for the limited amount of water present and adsorb moisture in proportion to their accessibility. Upon further exposure to water the sample of least accessibility, having adsorbed less water, can now adsorb to a greater extent than do the linters of somewhat greater accessibility.The evidence indicates that the difference in accessibility occasioned by repeated wetting and drying is of a physical rather than chemical nature. INTRODUCTIONThe accessibility of cellulose to reagents is a matter of colisiderable practical and theoretical importance and in recent years has been given a great deal of attention (6,12,16,19,21,28). I t has been shown quite conclusively that this accessibility is influenced by the previous history of the cellulose sufficiently that uniform reactivity is obtained only by the observation of great care in the choice and processing of the raw material (14, 25).The association of cellulose with water throughout most of its history has provoked enquiries regarding the influence that water has upon the properties of cellulose. I t is generally believed that water itself exercises only a swelling effect, producing nothing more than an increase in the amount of accessible cellulose a t the expense of that portion less highly organized. However, recent work indicates that a slight change in dimensions of the unit cell occurs when dry mercerized ramie, spun viscose, or regenerated acetate fibers are wetted (15). Furthermore, lengthy exposure of wet cellulose t o oxygen (air) or ozone is reported to produce some degradation of the macromolecule (3,4). The removal of water from cellulose by direct drying methods is accompanied by a decrease 1 n/Ia?~uscript

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“…In the determination of water the book "Aquametry'1 gives a literature survey as well as theory and practice (89). A variation of the Karl Fischer method which is stoichiometric may be of interest (121).…”

Section: Determinations By Elementsmentioning

confidence: 99%