Karl-Fischer Titration Research Articles

Coprecipitation of Aluminum Goethite and Amorphous Al-Hydroxy-Sulfate Using Urea and Characterization of the Thermal Decomposition Products

AbstractAluminum substitution is a common phenomenon in environmental iron oxides and oxyhydroxides, affecting the color, magnetic character, surface features, etc. Several methods for preparing Al-substituted iron oxyhydroxides can be found in the literature, resulting in samples with particular properties. In the present study, the synthesis of aluminum-substituted goethites, AlxFe1-xOOH with 0 ⩽ x ⩽ 0.15, by homogeneous precipitation and the transformation to aluminum-substituted hematites, (AlxFe1-x)O3, are presented. The goethite samples were produced at 90°C from solutions of urea and iron and aluminum nitrates in the presence of ammonium sulfate (GU series). Although attempts were made to incorporate up to 33 mole% of Al into the goethite, only ~15 mole% was found to be within the structure, due to the final pH, ~7, of the synthesis. Another feature of these goethites was a lateral alignment of the tabular particles. By heating batches of the GU samples at 400°C and 800°C, two series of Al-hematites were obtained, denoted here as the HX400 and HX800 samples, respectively. X-ray diffraction, thermal analysis, Karl-Fischer titration, transmission electron microscopy, and Mössbauer spectroscopy were used to characterize the samples. The X-ray patterns showed the samples to be pure iron phases, with particle sizes of ~10 nm for the GU and HX400 samples, and of ~70 nm for the HX800 samples. An inversion in the intensities of the (104) and (110) diffraction peaks of hematite was observed to be dependent on the aluminum substitution and was explained by small particle sizes, shape anisotropy, and the presence of nanopores. The cell parameters of both GU and HX samples showed a small decrease with increasing aluminum substitution up to x ≈ 0.15. The amount of adsorbed sulfate, presumably as an aluminum hydroxy sulfate gel, increased with aluminum substitution in all GU and HX samples, reaching a maximum of ~6.5 wt.% for the highest substitution. Heating at 100°C did not remove all of the adsorbed water, and significantly higher temperatures were required to achieve complete removal. Mossbauer spectra at 295 K and 80 K are typical for small-particle goethite and hematite, and revealed that Al-for-Fe substitution in all samples seems to be limited to ~15 mol.%.

Physical Stability of Freeze-Dried Isomalt Diastereomer Mixtures.

Isomalt is a sugar alcohol used as an excipient in commercially available solid oral dosage forms. The potential of isomalt as a novel freeze-drying excipient was studied in order to increase knowledge of the behavior of isomalt when it is freeze-dried. Isomalt was freeze-dried in four different diastereomer compositions and its physical stability was investigated with differential scanning calorimetry, Fourier-transform infrared and Raman spectroscopy, X-ray powder diffraction, Karl-Fischer titration and thermogravimetric analysis in order to verify the solid state form of isomalt after freeze-drying and observe any changes occurring during storage in three different relative humidity conditions. Isomalt was successfully transformed into the amorphous form with freeze-drying and three diastereomer combinations remained stable as amorphous during storage; one of the diastereomer compositions showed signs of physical instability when stored in the highest relative humidity condition. The four different crystalline diastereomer mixtures showed specific identifiable solid state properties. Isomalt was shown to be a suitable excipient for freeze-drying. Preferably a mixture of the diastereomers should be used, as the mixture containing only one of the isomers showed physical instability. A mixture containing a 1:1 ratio of the two diastereomers showed the best physical stability in the amorphous form.

English

Siparuna guianensis Aublet is a predominant species in the Brazilian Cerrado. Some studies found that its essential oil has properties that could be useful for manufacturing new products. Its quality depends on physicochemical properties, since its degradation, as well as water content and other volatile materials may cause several changes in its features. The differential scanning calorimetry (DSC) was used to determine the water content in the S. guianensis essential oil in order to evaluate its thermal parameters. The method is based on the hypothesis that the desolvation enthalpy (ΔH desol ) needed for removing n water moles from the essential oil is approximately the enthalpy needed for melting the same n water moles (nΔH f ). Thus, the current study considers the dissociation enthalpy (ΔH diss ) to be negligible. The total number of moles was calculated from the molecular mass value of the main essential oil components mentioned in the literature. The DSC curve in nitrogen atmosphere indicated the melting temperature of 1.6°C (ΔH=18.95 Jg -1 ). Based on the dehydration enthalpies demonstrated in the DSC curve, it was possible to infer that the calculations on the number of water moles and other constant volatile materials found in the S. guianensis essential oil were compatible with Karl Fischer Titration (KFT) method. This method is commonly used to determine the water content in substances. Key words: Siparuna guianensis , differential scanning calorimetry, thermogravimetric analyses.

Thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) and complexation with β-cyclodextrin.

The thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) as well as its β-cyclodextrin (β-CD) complexation ability has been verified for the first time. The main omega-3 fatty acids, EPA and DHA, were significantly degraded, even at 50 °C. Their relative concentrations decrease from 6.1% for EPA and 4.1% for DHA to 1.7% and 1.5% after degradation at 150 °C, respectively. On the other hand, the relative concentrations of monounsaturated and saturated fatty acids remained constant or slightly increased by a few percent after degradation (e.g., from 10.7% to 12.9% for palmitic acid). Co-crystallization of ASO with β-CD at a host–guest ratio of 1:1 and 3:1 from an ethanol–water mixture and kneading methods has been used for the preparation of β-CD/ASO complexes. The analysis of the complexes by thermogravimetry, differential scanning calorimetry (DSC), and Karl Fischer titration (KFT) as well as the decrease of the “strongly-retained” water content confirm the formation of the inclusion compound. Furthermore, the DSC parameters correlate well with the KFT kinetic data for β-CD/ASO complexes.

Formulation Characterization of Parathyroid Hormone PTH (1-34)Coated on a Novel Transdermal Microprojection Delivery System:Water Determination

This study assessed the feasibility of determining the water content of the PTH (1-34) formulation coated on a novel transdermal microprojection delivery system, ZP-PTH. Thermogravimetric analysis (TGA) and Karl Fischer (KF) titration were used for water analysis.Headspace moisture was determined by internal vapor analysis and a hand-held moisture sensor. The moisture sorption isotherm was established by moisture sorption analyzer. PTH (1-34) API and formulation showed several weight-loss phases in TGA thermograms. Water loss is not a single-phase event, occurring over a wide temperature range. The typical water amount in a single ZP-PTH coated array is below the sensitivity of TGA and KF titration. Combining 20 coated array samples together in a single extract made KF analysis is possible but impractical due to strenuous sample preparation requirements and controls. The moisture sorption isotherm allowed accurate prediction of water content when the headspace moisture level is known. We demonstrated that TGA and KF titration are not practically possible for determining the water content in ZP-PTH. Simple alternative approaches can ensure that the desired water content in the ZP-PTH coating is achieved without direct water measurement. This study provides scientific rationales to justify the application of unconventional approaches.

Water, the other network modifier in borate glasses

In the present study we have investigated whether the effect of water on properties of borate glasses resembles that of alkali oxide. Soda–lime–borate glasses with nominal compositions of x Na2O, 10 CaO, (90-x) B2O3 (x=5, 15 and 25mol%) were doped with up to 8wt.% H2O by processing glass powder+distilled water in platinum capsules in an internally heated gas pressure vessel at 1523K and 500MPa. The water content of hydrous glasses was determined by Karl-Fischer titration and near-infrared spectroscopy. The glass transition temperature Tg. was derived from DTA and micropenetration experiments for which the effect of water loss at the surface of the hydrous glasses was studied. Heating glass samples at 10Kmin−1 in the DTA resulted in Tg values which are close to T12 isokom temperatures confirming the equivalence of enthalpy relaxation and viscous relaxation for borate glasses. For all three glass series it is shown that Tg strongly decreases whereas the liquid fragility strongly increases upon the addition of water. These findings reveal that H2O primarily causes breaking of B–O–B bonds rather than supporting 4-fold coordinated boron as it is well-known for alkali oxides in this concentration range.

Water content in hydrated ethanol fuel measured by a photothermal chamber with a transparent transducer

Abstract A photothermal chamber with a transparent transducer and a 1450 nm laser were used to measure the water content of hydrated ethanol biofuel. The values of water content in the fuel samples assessed using the photothermal chamber were compared with reference values certified by Karl-Fischer titration. The results indicate good agreement between these two methodologies. Detection thresholds of 0.73 and 0.89 (% w/w) and sensitivity of 0.039 and 0.014 mV/(% w/w) were assessed at the laser powers of 340 and 125 mW, respectively. This study proves that the analytical approach based on the photothermal chamber with a transparent transducer is convenient to determine the water content in ethanol fuel because it is capable of providing reliable results in a quick and accurate way.

Probing Bias Reduction to Improve Comparability of Lint Cotton Water and Moisture Contents at Moisture Equilibrium

The Karl Fischer Titration (KFT) standard test method is specific for water in lint cotton and designed for samples conditioned to moisture equilibrium. There is no standard method for equilibrium moisture content by oven drying (OD). The KFT technique is specific for water; in the OD procedure the weight of the loss volatiles at 105 to 110°C is the measure of moisture content, all of which is incorrectly attributed to water. The results from OD we call "moisture content" and from KFT "water content". Different OD procedures, with dissimilar sample conditioning systems, drying ovens, size, and number of weighing bottles in the oven, currently are used to make measurements. Yet, no comprehensive study of the multiple causes of the difference between equilibrium water and moisture content has been reported. To assist with explaining the observed disparity, the present effort develops a list of six potential OD biases. The origin of these biases is incomplete drying and weight change due to side reactions in opposite directions. Using a control cotton, the biases were measured at moisture equilibrium in four different OD procedures. The corrections were applied to the moisture content data from a dozen Mississippi cotton samples analyzed by the same OD methods. Method grand mean results were 7.73% water compared to moisture content before/after bias correction, respectively: 7.19/7.80, 7.50/7.80, 7.42/7.69, and 7.79/7.92. By changing OD features it was possible to suppress one bias over the other. Samples were conditioned to more stringent specifications to provide precise data to test the hypotheses in this research.

Modulating the Solubilities of Ionic Liquid Components in Aqueous-Ionic Liquid Biphasic Systems: A Q-NMR Investigation.

Aqueous-ionic liquid (A-IL) biphasic systems have been examined in terms of deuterated water, acid, and IL cation and anion mutual solubilities in the upper (water-rich, in mole fraction) and lower phase of aqueous/IL biphasic systems at ambient temperature. The biphasic mixtures were composed of deuterated acids of various concentrations (mainly DCl, DNO(3), and DClO(4) from 10(-2) to 10(-4) M) and five ionic liquids of the imidazolium family with a hydrophobic anion (CF(3)SO(2))(2) N(-), that is, [C1 Cn im][Tf(2)N], (n=2, 4, 6, 8 and 10). The analytical techniques applied were (1) H NMR, (19) F NMR, Karl-Fischer titration, pH potentiometry for IL cations and anions, and water and acid determination. The effects of the ionic strength (μ=0.1 M NaCl and NaNO(3) as well as μ=0.1 M, 0.2 M and 0.4 M NaClO(4), according to the investigated acid), the nature of the IL cation, and the nature of the mineral acid on the solubilities of the (D(2)O, D(+), Tf(2)N(-), C1 Cn im(+)) entities in the lower or upper phases were determined. The addition of sodium perchlorate was found to enhance the Tf(2)N(-) solubility while inhibiting the solubility of the ionic liquid cation. Differences in IL cation and anion solubilities of up to 42 mM were evidenced. The consequences for the characterization of the aqueous biphasic system, the solvent extraction process of the metal ions, and the ecological impact of the ILs are discussed.

Influence of water on the tribological properties of zinc dialkyl-dithiophosphate and over-based calcium sulphonate additives in wet clutch contacts

Usually the wet clutch lubricant properties vary with different formulations of base oil types and additives. The aim of this paper was to evaluate the effect of water on the performance of additives in ATF. Simplified lubricants, ZDDP and over-based Ca-sulfonates detergent additives in an API Group I mineral base oil, were employed to compare with the commercial fully-formulated automatic transmission fluid (DEXRON®VI) during water-contamination. A full-scale wet clutch test rig was used to evaluate the frictional response due to water contamination of the lubricants. Fourier Transform Infrared Spectroscopy was utilized to evaluate the variation in the solubility of these polar organic additives in the water phase and Karl-Fischer titration was utilized to evaluate the post-test water content for different formulations.

Antibacterial Activity of Short-Chained 1-Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl) Imide Ionic Liquids

The antibacterial activity of a series of ionic liquids containing short-chained 1-alkyl-3-methylimidazolium cations ([Cnmim+]; n = 2, 4, 6 and 8) and bis (trifluoromethylsulfonyl) imide anion ([Tf2N]) against E. coli and B. subtilis was measured, for the first time. All ILs used in this work were synthesized and analyzed by Fourier transform infrared (FT-IR) spectroscopy, NMR, and Karl-Fischer titration. Antimicrobial activity was determined by the tube dilution method. The ILs investigated showed antibacterial activity against E. coli and B. subtilis. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were in the ranges of 0.041-6.39 mM and 0.67-12.78 mM, respectively. The antibacterial activity for ionic liquids with longer alkyl chain (n ≥ 4) increased with increasing alkyl chain length. The highest inhibition against E. coli was found for [C8mim][Tf2N] (MIC = 0.041 mM and MBC = 0.67 mM). The mechanism of action of these ionic liquids was bacteriostatic.

Adsorption of water from aqueous acetonitrile on silica-based stationary phases in aqueous normal-phase liquid chromatography

Excess adsorption of water from aqueous acetonitrile mobile phases was investigated on 16 stationary phases using the frontal analysis method and coulometric Karl–Fischer titration. The stationary phases include silica gel and silica-bonded phases with different polarities, octadecyl and cholesterol, phenyl, nitrile, pentafluorophenylpropyl, diol and zwitterionic sulfobetaine and phosphorylcholine ligands bonded on silica, hybrid organic-silica and hydrosilated matrices. Both fully porous and core-shell column types were included. Preferential uptake of water by the columns can be described by Langmuir isotherms. Even though a diffuse rather than a compact adsorbed discrete layer of water on the adsorbent surface can be formed because of the unlimited miscibility of water with acetonitrile, for convenience, the preferentially adsorbed water was expressed in terms of a hypothetical monomolecular water layer equivalent in the inner pores. The uptake of water strongly depends on the polarity and type of the column. Less than one monomolecular water layer equivalent was adsorbed on moderate polar silica hydride-based stationary phases, Ascentis Express F5 and Ascentis Express CN column at the saturation capacity, while on more polar stationary phases, several water layer equivalents were up-taken from the mobile phase. The strongest affinity to water was observed on the ZIC cHILIC stationary phases, where more than nine water layer equivalents were adsorbed onto its surface at its saturation capacity. Columns with bonded hydroxyl and diol ligands show stronger water adsorption in comparison to bare silica. Columns based on hydrosilated silica generally show significantly decreased water uptake in comparison to stationary phases bonded on ordinary silica. Significant correlations were found between the water uptake and the separation selectivity for compounds with strong polarity differences.

A comparison of the formation of bubbles and water droplets in vegetable and mineral oil impregnated transformer paper

Bubble formation from paper insulation during overload is important to understand because it can cause a transformer to fail. This phenomenon has been investigated in a mineral oil-paper system, but not in vegetable oil. This study investigated bubble formation during overload in a vegetable oil impregnated paper system and the results were compared to a mineral oil (Shell Diala B) which was studied previously using similar test equipment and method. The limiting hot-spot temperatures for bubbles and water droplets in vegetable oil for paper with water content between 1 - 6 % were determined. The water content of paper measurement which is critical when setting the winding temperature limit was evaluated using both a moisture sensor and Karl-Fischer titration method.

Detailed characterization of red oak-derived pyrolysis oil: Integrated use of GC, HPLC, IC, GPC and Karl-Fischer

Red oak bio-oil obtained from fast pyrolysis in a fluidized bed reactor was fully analyzed using gas chromatography/mass spectrometry (GC/MS), high-performance liquid chromatography (HPLC), ion chromatography (IC), gel permeation chromatography (GPC) and Karl-Fischer titration. Based on the chemical speciation, we achieved a high mass balance closure of bio-oil (92wt%). Of the analytical techniques, GC accounted for the largest portion of the bio-oil (25.7wt%), followed by HPLC (15.4wt%) and IC (8.1wt%). Monosaccharides and disaccharides (not detected by GC) were characterized by HPLC, and total sugars present in bio-oil were estimated by running acid-hydrolysable sugars in the HPLC. Quantity of pyrolytic lignin, oligomer of lignin-derived phenolic compounds, was determined as a GC-undetected portion of water-insolubles of a whole bio-oil. Small standard deviation of each compound between duplicate runs indicated a reproducibility of pyrolysis experiments and bio-oil characterizations validating the detailed analytical approach used.

Compositional and pressure effects on the solubility of H2O and CO2 in mafic melts

The effect of the anhydrous composition on the solubilities of H2O and CO2 in mafic melts varying from MORB to nephelinite was investigated experimentally between 50 and 500MPa at 1200 to 1250°C. In all compositions, CO2 is only present as carbonate species in the quenched glasses. The concentrations of dissolved H2O and CO2 have been analyzed by KFT (Karl–Fischer titration) and FTIR (Fourier-transform infrared spectroscopy). The Mid-Infrared (MIR) absorption coefficients for the H2O band at 3500cm−1 are identical within error for all investigated melt compositions and equal to 59.2±4L/(mol∗cm). The absorption coefficients for the carbonate bands vary in the range 306±32 to 360±24L/(mol∗cm) for the 1430cm−1 band and in the range 349±25 to 394±27L/(mol∗cm) for the 1520cm−1 band. However, a simple correlation with the melt composition could not be determined.Water solubility in mafic to intermediate melts increases slightly with the total alkali content and the effect of composition is more pronounced at higher pressures. At 500MPa, the solubility of H2O in melts coexisting with nearly pure H2O fluids varies from 8.8 to 9.5wt.% H2O. A strong effect of melt composition on the solubility of CO2 is observed at all investigated pressures. For instance, at 500MPa, mafic melts coexisting with nearly pure CO2 fluids can dissolve from around 0.32 to more than 1.30wt.% CO2 as melt composition changes from tholeiite to nephelinite. The compositional effect on the solubility of CO2 in melts coexisting with pure CO2 fluid is best described by non-linear (exponential) correlations with compositional parameters such as the parameter Π proposed by Dixon (1997; American Mineralogist, 82: 368–378) or structural parameters (e.g., nonbridging oxygen per tetrahedrally coordinated cation). The obtained relationships are used to propose empirically derived equations of the form ln(CO2)=1.150·lnP+6.71·Π*−1.345, where CO2 is the solubility of CO2 in silicate melts in wt.% (at 1200 to 1250°C), P is pressure in MPa and Π* is a compositional parameter (Π*=Ca2++0.8K++0.7Na++0.4Mg2++0.4Fe2+)/(Si4++Al3+) with cations expressed as cation fractions in melt.

Development of a certified reference material for the determination of perfluorooctanoic acid

A certified reference material (CRM) for the determination of perfluorooctanoic acid (PFOA) has been issued as NMIJ CRM 4056-a by the National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Purity (kg kg -1 ) based on a titration method was determined by subtracting the mass fractions of impurities measured using liquid chromatography/mass spectrometry (LC/MS) from those of acids expressed as PFOA measured by a neutralization potentiometric titration. To validate an obtained result, purity based on a mass balance method was determined by subtracting the mass fractions of impurities, measured using LC/MS, Karl-Fischer titration (KFT), and vacuum evapo- ration, from 1 kg kg -1 . Results from both titration and mass balance methods were in agreement within the accepted limits of uncertainty. The certified purity of NMIJ CRM 4056-a was determined to be 0.959 kg kg -1 , calculated as the mean of the results obtained with the two methods. The standard uncertainty of the certified purity was evaluated from purity evaluations as well as from sample homogeneity and stability obtained from LC/MS and KFT analyses. Consequently, the expanded uncertainty was estimated to be 0.005 kg kg -1 with a coverage factor of k = 2.

The Use of a Custom-Built Coulometric Karl Fischer Instrument for the Determination of Water Content in Chocolate

A Karl Fischer (KF) coulometric titration method was designed and optimized for the quantitative determination of water in chocolate. A number of essential KF experimental parameters were investigated and assessed, including a study of polar extraction solvents, extraction times, interfering side reactions, and a comparison of pyridine-free KF coulometric reagents. The optimized protocol was found to be applicable to a wide variety of chocolate samples. Typical coulometric titration times for the chocolate samples were between 1 and 5 min, translating to water contents from 0.18 to 0.38 % w/w. With this contribution, the quantification of water in chocolate using KF titration methods is now a simple, safe, and reliable process, comparable in terms of precision and accuracy to any commercially available KF coulometric apparatus.

Influence of temperature and moisture content on frequency response analysis of transformer winding

Frequency Response Analysis (FRA) has been in use since the last decade as a sensitive method for detecting transformer internal defects. This study is focused on the influence of temperature and moisture migration on the FRA response of transformer winding. It also discusses the feasibility of FRA capability in moisture diffusion recognition in transformer paper insulation. To conduct this study, a single phase model transformer involving concentric LV and HV windings and a 20/0.4 kV, 1.6 MVA threephase two windings transformer are taken as test objects. Experiments are carried out at different temperature and moisture conditions. FRA spectra are then recorded and analyzed. FRA spectra deviations as well as total capacitance variations due to the temperature and moisture changes in the test objects are calculated. Karl-Fischer Titration (KFT) is utilized to monitor the moisture migration within oil and paper insulations. Furthermore, a mathematical model is used to simulate one of the test object windings and verify the experimental result, and also clarify the main reason of FRA spectrum deviation in this circumstance. Finally, statistical indices in FRA evaluation are calculated to explore their capability in FRA spectrum interpretation once the moisture content of paper insulation is changed.

Water determination in active pharmaceutical ingredients using ionic liquid headspace gas chromatography and two different detection protocols

A rapid, accurate, precise and versatile analytical method was developed for the detection and quantification of water in solid active pharmaceutical ingredients (APIs). The headspace gas chromatography (HSGC) method utilized an ionic liquid (IL) based open tubular capillary GC column to increase sensitivity and ruggedness of this method. ILs are also utilized as the headspace solvent because of their low vapor pressure, unique physiochemical properties and high thermal stability. This method is not affected by side reactions and solubility problems which are common with Karl Fischer Titration (KFT) methods. Nor is it as limited as weight loss on drying approaches. The ability to use either/both modern thermal conductivity or barrier ion discharge GC detection provides flexibility, different dynamic ranges and sensitivity. The developed method also was shown to be broadly applicable.

Utilization of seeds from tomato processing wastes as raw material for oil production

The increase of waste quantities from tomato processing industry is an important ecological and also financial problem. Seeds are the major component of this waste and one valuable alternative of transforming them into raw materials is oil extraction. The isolated oil can be used for nutritive or industrial purposes. In this research, the influence of some extraction parameters (time, solvent and granularity of tomato milled seeds) on the fatty acid (FA) composition, water content and water reaction rate has been evaluated. The FA composition of tomato seed oil, determined by gas chromatography–mass spectrometry, has shown a high content of linoleic acid (20.8–39.9 mg/mL), followed by palmitic acid (6.3–19.3 mg/mL), oleic acid (2.5–14.2 mg/mL), linolenic acid (0.7–4.9 mg/mL), stearic acid (0.1–0.8 mg/mL), palmitoleic acid (0.03–0.5 mg/mL), arachidic acid (0.08–0.4 mg/mL), myristic acid (0.05–0.2 mg/mL) and margaric acid (0.02–0.11 mg/mL). The oil content of tomato seeds was registered in the range of 13.3–19.3 %. For evaluation of water content, a method using Karl Fischer titration (KFT) has been established. Comparing with the physical methods that do not distinguish the water content from volatile matter, KFT is an important technique, very accurate, that determines water content by a chemical reaction.