Analysis of the hydrolysates from cured and uncured urea-formaldehyde (UF) resins with two F/U mole ratios

Holzforschung ◽  
2018 ◽  
Vol 72 (9) ◽  
pp. 759-768 ◽  
Author(s):  
Muhammad Adly Rahandi Lubis ◽  
Byung-Dae Park
Keyword(s):  
Functional Groups ◽  
Degradation Products ◽  
Urea Formaldehyde ◽  
Chemical Species ◽  
Gel Permeation Chromatography ◽  
Hydrolysis Time ◽  
Water Hydrolysis ◽  
Hydrolysis Of ◽  
C Nmr

Abstract Uncured and cured urea-formaldehyde (UFcured) resins prepared with formaldehyde/urea (F/U) mole ratios of 1.0 and 1.2 and at the catalyst levels of 1, 2 and 3% NH4Cl were hydrolyzed for 5, 15 and 30 min and the degradation products were evaluated using gel permeation chromatography, Fourier-transform infrared (FTIR) and liquid carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopies. The molar masses of the degradation products, their functional groups and structures were determined. An extended hydrolysis time and higher catalyst levels resulted in compounds with higher molar masses. Similar functional groups and distribution of chemical species were found by both FTIR and 13C-NMR spectroscopies in the hydrolysates of UFcured, indicating water hydrolysis of hydroxymethyl groups and then methylene linkages. Methylene linkages and mono- and tri-hydroxymethyl ureas were mainly responsible for the liberation of formaldehyde from UFcured during hydrolysis. The indicated compounds are believed to contribute to the long-term release of formaldehyde from the resins. This is the first systematic report on the composition of UFcured hydrolysates.

Stereoselective epimerization of pilocarpine in aqueous solution as determined by 13C nuclear magnetic resonance spectroscopy

1976 ◽  
Vol 54 (13) ◽  
pp. 2094-2100 ◽  
Author(s):  
George A. Neville ◽  
Fariza B. Hasan ◽  
Ian C. P. Smith
Keyword(s):  
Degradation Products ◽  
Parent Compound ◽  
Imidazole Ring ◽  
Alkaline Treatment ◽  
Resonance Spectroscopy ◽  
Open Chain ◽  
Similar Treatment ◽  
13C Nuclear Magnetic Resonance ◽  
Hydrolysis Of ◽  
C Nmr

Cleavage and recyclization of the lactone ring of pilocarpine (1) and of isopilocarpine (2) in D2O with varying pD have been studied by 13C nmr spectroscopy. Alkaline treatment (pD 10–13) results in rapid epimerization of pilocarpine to form isopilocarpine (28 ± 3% at 30 °C) and hydrolysis of the parent compound(s) to form the open chain pilocarpinate (isopilocarpinate). By contrast, isopilocarpine does not epimerize to pilocarpine under similar treatment. A mechanism is discussed for the epimerization of pilocarpine and the nonepimerization of the isopilocarpine is rationalized. pKa values of 5.7 and 8.5, respectively, have been determined for pilocarpinic acid and for the dissociation of the protonated quaternary nitrogen of the imidazole ring of pilocarpine. A basis for assay of degradation products in aqueous pilocarpine solutions utilizing differences in 13C chemical shift for C-8 is discussed.

Influence of high hydrostatic pressure on the proteolysis of β-lactoglobulin A by trypsin

2006 ◽  
Vol 73 (1) ◽  
pp. 121-128 ◽  
Author(s):  
Rosa Chicón ◽  
Josefina Belloque ◽  
Isidra Recio ◽  
Rosina López-Fandiño
Keyword(s):  
High Pressure ◽  
Degradation Products ◽  
Thiol Group ◽  
Hydrolysis Time ◽  
Structural Modifications ◽  
Disulphide Bonds ◽  
Free Thiol Group ◽  
Β Lactoglobulin ◽  
Hydrolysis Of ◽  
Tryptic Hydrolysis

This work describes the effect of the hydrolysis time and pressure (0·1–400 MPa) on the proteolysis of β-lactoglobulin A (β-lg A) with trypsin, either conducting hydrolysis of β-lg under pressure or hydrolysing β-lg that was previously pressure treated. Pressurisation, before or during enzyme treatments, enhanced tryptic hydrolysis of β-lg. Trypsin degraded pressure-modified β-lg and pressure-induced β-lg aggregates, favouring proteolysis to the intermediate degradation products: (Val15-Arg40), (Val41-Lys69)S-S(Leu149-Ile162) and (Val41-Lys70)S-S(Leu149-Ile162). These were further cleaved at the later stages of proteolysis to yield: (Val15-Tyr20), (Ser21-Arg40), (Val41-Tyr60), (Trp61-Lys69)S-S(Leu149-Ile162) and (Trp61-Lys70)S-S(Leu149-Ile162). Particularly, in the tryptic hydrolysates of pre-pressurized β-lg, two other fragments linked by disulphide bonds: (Lys101-Arg124)S-S(Leu149-Ile162) and (Tyr102-Arg124)S-S(Leu149-Ile162), were found. These corresponded to rearrangement products induced by SH/SS exchange between the free thiol group of Cys121 and Cys160, that normally forms the disulphide bond Cys66-Cys160. In the light of these results, structural modifications of β-lg under high pressure are discussed.

scholarly journals A CHROMATOGRAPHIC STUDY OF HYDROLYSIS IN THE FEULGEN NUCLEAL REACTION

1957 ◽  
Vol 3 (1) ◽  
pp. 71-88 ◽  
Author(s):  
Philip S. Woods
Keyword(s):  
Deoxyribonucleic Acid ◽  
Degradation Products ◽  
High Rate ◽  
Chromatographic Technique ◽  
Chromatographic Study ◽  
Hydrolysis Time ◽  
Acid Hydrolysate ◽  
Tissue Sections ◽  
Labile Fraction ◽  
Hydrolysis Of

In a study on Feulgen hydrolysis of frozen-dried alcohol-fixed lily anthers, a chromatographic technique was developed to analyze the acid hydrolysate for some of the degradation products of nucleic acid. Hydrolysis was accomplished by 10 per cent perchloric acid at 20°C., and a typical hydrolysis time-Feulgen intensity curve was obtained, with maximum staining occurring at 19 hours. Microphotometric measurements indicated that the amount of stain per nucleus was no different from amount in nuclei fixed and hydrolyzed by more conventional procedures. Uracil-containing material (from ribonucleic acid) was almost completely separated from thymine-containing material (deoxyribonucleic acid) of tissue sections by acid treatment for 1½ hours. Adenine (purines), as the base, was effectively all removed from the deoxyribonucleic acid at the time of optimum hydrolysis. Detectable amounts of thymine-containing material appeared in the hydrolysate shortly after the onset of hydrolysis; and the amount increased rapidly with increased hydrolysis time. At the time of optimum hydrolysis approximately two-thirds of the total deoxyribonucleic acid thymine was lost. The removal of these thymine-containing fragments was linear with respect to time during the first 24 hours and occurred at a relatively high rate. Removal after 24 hours was also linear but was at a markedly lower rate. These results would suggest that two kinds of deoxyribonucleic acid exist in lily anthers; an acid-labile fraction amounting to approximately three-fourths of the total, and an acid-resistant fraction making up the remainder. In the Feulgen procedure much of the labile fraction is lost by the time of optimum hydrolysis and is not stained; most of the stable fraction remains in the tissue and is stained. In light of these findings the use of the Feulgen method as a means of determining cytochemically relative amounts of deoxyribonucleic acid in nuclei by measuring their Feulgen dye content was discussed.

scholarly journals Optimization of hydrolysis conditions for xylans and straw hydrolysates by HPLC analysis

2021 ◽  
Author(s):  
Alexander Beckendorff ◽  
Anne Lamp ◽  
Martin Kaltschmitt
Keyword(s):  
Sulfuric Acid ◽  
Acid Concentration ◽  
Hplc Analysis ◽  
Degradation Products ◽  
Sulfuric Acid Concentration ◽  
Corn Cob ◽  
Hydrolysis Time ◽  
Conversion Rates ◽  
Hydrolysis Temperature ◽  
Hydrolysis Of

AbstractOligosaccharide analysis is commonly done by acid hydrolysis and following HPLC analysis. A major problem is the incomplete hydrolysis of oligosaccharides and disaccharides and the increasing formation of volatile furfural from pentose monomers and hydroxymethylfurfural (HMF) from hexose monomers. This paper optimizes the conditions of hydrolysis approaches and proposes a method for oligosaccharide quantification. The optimal condition for hydrolysis of model xylan from corn cob was found to be for 100 °C hydrolysis temperature, 120 min hydrolysis time, and 2 wt% sulfuric acid concentration. Under these conditions, the total free and bound xylose yield was 77.4% and hemicellulose conversion 87.4% respectively; no degradation products were found. The optimal conditions for hydrolysis of model xylan from beech wood were found to be for 120 °C hydrolysis temperature, 120 min hydrolysis time, and 2 wt% sulfuric acid concentration. Under these conditions, the total free and bound xylose yield was 65.1% and hemicellulose conversion 70.5% respectively; no degradation products were found. For pentosan hydrolysate, conditions were further optimized (110 °C, 60 min, 2 wt% H2SO4). Standard addition of xylan from the corn cob for hydrolysation showed similar conversion rates (< 2% deviation); no matrix effects were detected.

Sub-critical water hydrolysis of hog hair for amino acid production

2010 ◽  
Vol 101 (7) ◽  
pp. 2472-2476 ◽  
Author(s):  
M.B. Esteban ◽  
A.J. García ◽  
P. Ramos ◽  
M.C. Márquez
Keyword(s):  
Amino Acid ◽  
Acid Production ◽  
Amino Acid Production ◽  
Water Hydrolysis ◽  
Hydrolysis Of

Effect of Palm Kernel Meal as Melamine Urea Formaldehyde Adhesive Extender for Plywood Application: Using a Fourier Transform Infrared Spectroscopy (FTIR) Study

2011 ◽  
Vol 121-126 ◽  
pp. 493-498 ◽  
Author(s):  
Huei Ruey Ong ◽  
Reddy Prasad ◽  
Md. Maksudur Rahman Khan ◽  
Md. Najmul Kabir Chowdhury
Keyword(s):  
Fourier Transform ◽  
Functional Groups ◽  
Chemical Interaction ◽  
Urea Formaldehyde ◽  
Palm Kernel ◽  
Fourier Transform Infrared ◽  
Blue Shift ◽  
Hot Press ◽  
Kernel Meal ◽  
Palm Kernel Meal

Increased demand for wood adhesives, environmental concerns, and the uncertainty of continuing availability of petrochemicals have led to recent attention on protein-based adhesives. This study was conducted to investigate the physico-chemical interaction of palm kernel meal (PKM) with melamine urea formaldehyde (MUF) resins in adhesive formulation by using Fourier Transform Infrared (FTIR) Spectroscopy. The effect of hot press on PKM extender has been investigated by FTIR and blue shift is observed due to the hot press indicating that the functional groups (such as C=O, -OH and NH) are become more free in the samples. In the case of PKM-MUF blend bonding interactions observed where, PKM played the role as an extender. Red shift of C=O and N-H groups stretching in PKM-MUF-Wood blend is observed which suggests the interaction of these functional groups through hydrogen bonding. The results suggest that PKM extender-based MUF adhesive resins have potential application for the production of exterior plywood.

Investigation of acid hydrolysis for carbohydrate analysis in kraft black liquor

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Silvia Maitz ◽  
Marlene Kienberger
Keyword(s):  
Acid Hydrolysis ◽  
High Performance ◽  
Degradation Products ◽  
Black Liquor ◽  
Amperometric Detection ◽  
Kraft Process ◽  
Kraft Black Liquor ◽  
Carbohydrate Degradation ◽  
Reliable Detection ◽  
Hydrolysis Of

Abstract Black liquor (BL) from the kraft process is considered a promising feedstock for several biorefinery scenarios. Besides lignin and carboxylic acids, this liquor also contains hemicelluloses and their degradation products. A simple and reliable detection of those is of importance for further processing of the liquor. The present paper presents a thorough investigation of quantitative analysis of carbohydrates, by performing acid hydrolysis experiments with a concentrated BL sample of 44% total dry solids. The hydrolysates were then analysed for the four monosaccharides arabinose, xylose, galactose and glucose, by high performance ion chromatography (HPIC) with pulsed amperometric detection. The amount of sulphuric acid needed for complete hydrolysis of the carbohydrates was determined in the range of 3.5–5 mol kg−1 of BL. A lower acid concentration led to insufficient liberation of galactose and glucose, while higher acid concentrations led to degradation of arabinose and xylose. The carbohydrate degradation was also investigated over time for different dilutions and hydrolysis temperatures. These experiments confirmed that the hexoses require considerably harsher conditions for complete liberation compared to xylose and arabinose. The use of internal recovery standards (RSs) was tested; the highest recoveries were obtained by direct spiking of the samples with the RS prior to hydrolysis.

47,49Ti NMR in Metals, Inorganics, and Gels

2000 ◽  
Vol 55 (1-2) ◽  
pp. 291-297 ◽  
Author(s):  
T. J. Bastow
Keyword(s):  
Solid State ◽  
Titanium Oxide ◽  
Recent Progress ◽  
Titanium Isopropoxide ◽  
Metallic State ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrolysis Of ◽  
C Nmr

Some recent progress in solid state 47,49Ti NMR is described and reviewed. The metallic-state work described covers metals such as hep titanium, TiB2 , a number of intermetallics such as TiAl2 and TiAl3· The inorganic work covers the various titanium oxide based materials including the TiO2 polymorphs, anatase, rutile and brookite. The gel work covers the evolution of crystalline titania from gels formed by hydrolysis of titanium isopropoxide. Some complementary data from 17O and 13C NMR and powder X-ray diffraction is also included.

Effect of Water Vapor and SOx in Air on the Cathodes of Solid Oxide Fuel Cells

2007 ◽  
Vol 1041 ◽  
Author(s):  
Seon Hye Kim ◽  
Toshihiro Ohshima ◽  
Yusuke Shiratori ◽  
Kohei Itoh ◽  
Kazunari Sasaki
Keyword(s):  
Water Vapor ◽  
Solid Oxide Fuel Cells ◽  
Degradation Mechanism ◽  
Chemical Species ◽  
Cell Voltage ◽  
Ambient Air ◽  
Open Circuit ◽  
Constant Current ◽  
Constant Current Density

AbstractAmbient air is used as an oxygen source in SOFCs to be commercialized. Various chemical species which can lead to poisoning of SOFC cathodes are included as minor constitutions in air, such as water vapor, SOx, NOx and NaCl etc. However, their effects on the cathode performance have not yet well known, even though they are expected to cause a degradation of the electrode performance and to reduce the long-term durability of SOFCs. Therefore, in this study, we focused on the poisoning caused by water vapor and SOx in the oxygen source to clarify their effects on SOFCs performances and to reveal the degradation mechanism of cathodes. SOFCs with typical electrolyte-supported structure were used in this work, which were composed with ScSZ (10 mol% Sc2O3, 1mol% CeO2, 89 mol% ZrO2) plate with the thickness of 200 µm as electrolyte, NiO-ScSZ (mixture of 56 wt% NiO and 44 wt% ScSZ) porous layer as anode, and two cathode layers of LSM ((La0.8Sr0.2)0.98MnO3) and LSM-ScSZ (mixture of 50 wt% LSM and 50 wt% ScSZ). Power generation characteristics of the cells had been analyzed by measuring cell voltage at a constant current density (200 mA/cm2) and by comparing changes in cell impedance, upon supplying the artificially-contaminated air with water vapor or SOx, to the SOFC cathodes at various operational temperatures. High-resolution FESEM (S-5200, Hitachi) was used to analyze microstructural changes caused by the impurities. Mg Kα radiation from a monochromatized X-ray source was used for XPS measurements (ESCA-3400, KRATOS). AC impedance was measured at various temperatures under the open circuit voltage condition by an impedance analyzer (Solatron 1255B/SI 1287, Solatron), in a frequency range from 0.1 to 105 Hz with an amplitude of 10 mV.

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