Nonaqueous Titration of Acidic Groups of Lignins.  Titration in Pyridine Using Potassium Methoxide as Titrant.

Thompson, S. O.; Chesters, G.

doi:10.1021/ac60209a027

Cited by 8 publications

(4 citation statements)

References 10 publications

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“…Sharp potential breaks were obtained using platinized platinum and calomel electrodes. The acidic properties of the lignins varied with their source and method of isolation (184) Bases.…”

Section: Methods and Applicationsmentioning

confidence: 99%

Titrations in Nonaqueous Solvents

Harlow¹,

Morman²

1966

Anal. Chem.

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A lthoughthere have been no dra-_£\_ matic "breakthroughs" during the last two years there has been notable advance in several areas. Particularly gratifying is the number of outstanding papers devoted to the fundamentals of nonaqueous equilibria. Not only are some of the more commonly used solvents such as acetonitrile receiving continued attention, but theoretical studies are being extended to solvents of very low7 dielectric constant. There appears to be a trend toward utilizing the newer types of measurements such as nuclear magnetic resonance and toward using several different types of measurements in the same investigation. In some of the recent work, for example, one finds spectrophotometric, conductometric, potentiometric, and solubility measurements combined to achieve an understanding not possible with a single technique. In the area of study concerned with the effect of solvent and acid structure on acidity, new and imaginative ideas have been introduced.

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“…Sharp potential breaks were obtained using platinized platinum and calomel electrodes. The acidic properties of the lignins varied with their source and method of isolation (184) Bases.…”

Section: Methods and Applicationsmentioning

confidence: 99%

Titrations in Nonaqueous Solvents

Harlow¹,

Morman²

1966

Anal. Chem.

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“…Nitrogen was flowed in to protect the active groups, while the sample was stirred at 200 rpm. After 5 minutes, the titration was performed with a KOH-isopropyl alcohol solution, with the conductivity instrument used to record the conductivity curve until two equivalence points appeared [37]. The equivalence points M and N were determined using the conductivity curve (Fig 4).…”

Section: Principle and Process Of Nact Of Phenolic-hydroxyl And Carbomentioning

confidence: 99%

“…The non-aqueous conductivity titration (NACT) is the most common titrimetric procedure used in pharmacopoeial assays and it is suitable for the titration of very weak acids and very weak bases, which has been used to quantitatively analyze phenolic-hydroxyl and carboxyl groups in lignin [ 37 – 39 ]. Because humic acid and lignin have similar molecular structures and NACT can be applied to the measurement of weak organic acids [ 38 ], in this study, we attempted to adopt this method to measure the phenolic-hydroxyl and carboxyl-groups contents of humic acid by optimizing the humic-acid sample pH, concentration of the titrant, and nitrogen-gas flow rate.…”

Section: Introductionmentioning

confidence: 99%

An acidic-groups detection method and its application to analysis of Chinese humic acid samples

Peng-fei

Wang

et al. 2020

PLoS ONE

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The method of non-aqueous conductivity titration (NACT) of organic weak acids was applied to quickly and accurately determine the phenolic-hydroxyl and carboxyl-groups contents in humic acid. By varying the pH of the humic-acid sample, the concentration of the titrant, and the nitrogen-gas flow rate, the optimal titration conditions were determined to be a sample pH of 4, titrant concentration of 0.05 mol/L, and nitrogen-gas flow rate of 80 mL/min. Applying the detection method to p-hydroxybenzoic acid showed that its phenolic-hydroxyl content was 758.82±111.76 cmol/kg and carboxyl content was 744.44±51.11 cmol/kg. The theoretical phenolic-hydroxyl and carboxyl-groups contents of the p-hydroxybenzoic acid were 723.96 cmol/kg respectively, indicating that the method can accurately quantify the carboxyl and phenolic-hydroxyl groups in the sample. The NACT was used to measure the phenolic-hydroxyl and carboxyl-groups contents in humic acid quickly and accurately. In addition, 29 humic acid samples from 8 provinces of China covering the main humic-acid producing areas were collected and analyzed for acidic-groups content using the reported method.

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“…THE literature on the acidic pro erties of lignins, as revealed by solidstate cation exchange capacity E E C ) determination and by potentiometric and conductometric titration in various systems, has been reviewed briefly (Thompson et al, 1964; Thompson and Chesters, 1964). The wide range of values reported for the different methods of analysis employed indicates that neither the total acidi nor the A similar situation exists regarding knowledge of the acidic propedes of organic soil extracts.…”

Section: Introductionmentioning

confidence: 99%

Acidic Properties of Plant Lignins and Humic Materials of Soils

Thompson¹,

Chesters²

1969

Journal of Soil Science

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The acidic properties of lignins from the native vegetation of a virgin Ella loamy sand and the humic acids, the I, 4-dioxane extractable humic fraction and residual humic acids from the virgin and cultivated soils were investigated by determining solid-state cation exchange capacities for Cu and Ca and by nonaqueous potentiometric titration, using potassium methoxide in a benzenemethanol mixture as titrant. The lignins and soil dioxane extracts were titrated in pyridine; the humic acids in dimethylformamide. Platinized Pt and CHIOH modified calomel electrodes formed the electrode combination.The CEC of the humic acids were much higher than the CEC of lignins with both cations but the Cu:Ca absorption ratios were less for humic acids than for lignins. Titration curves of lignins showed two potential breaks with total acidities of 960 to 1,190 me/Ioo g. Titration curves of the humic acids showed three to six potential breaks while curves of the soil dioxane extracts showed three and four. The total acidities of the two types of humic isolates were 1,100-1,200 me/roo g. The equivalent weights of most lignins and humic materials were very similar although the acid groups might be different with respect to types and acid strength. Lignins from other plant materials and humic isolates from other soils were also investigated by non-aqueous titration to determine the general applicability of the results obtained with isolates from the Ella soils.

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Nonaqueous Titration of Acidic Groups of Lignins. Titration in Pyridine Using Potassium Methoxide as Titrant.

Cited by 8 publications

References 10 publications

Titrations in Nonaqueous Solvents

Titrations in Nonaqueous Solvents

An acidic-groups detection method and its application to analysis of Chinese humic acid samples

Acidic Properties of Plant Lignins and Humic Materials of Soils

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