Determination of substituent distribution of viscoses by GPC

Holzforschung ◽  
2006 ◽  
Vol 60 (5) ◽  
pp. 467-473 ◽  
Author(s):  
Axel Rußler ◽  
Antje Potthast ◽  
Thomas Rosenau ◽  
Thomas Lange ◽  
Bodo Saake ◽  
...  
Keyword(s):  
Enzymatic Degradation ◽  
Laser Light ◽  
Gel Permeation Chromatography ◽  
Narrow Molecular Weight Distribution ◽  
Substitution Pattern ◽  
Degradation Pattern ◽  
Long Time ◽  
Ultrasonic Degradation ◽  
Insight Into

Abstract Based on previous investigations on the substitution pattern of stabilized and fresh viscose, different viscoses were analyzed by gel permeation chromatography (GPC) with multiple-angle laser light scattering, refractive index (RI), and UV detection. Viscoses derivatized with N-methyl-N-phenyl-iodoacetanilide are stable over a long time and largely improve handling for analytical purposes. In addition, the derivatized xanthogenate groups exhibit UV absorbance that can be used to detect their distribution along the polymer molecule, once the polymer is dissolved. UV assay indicated that in technical viscoses the distribution of substituents is uniform. Enzymatic degradation with endoglucanases was followed by analysis of the degradation pattern by GPC. Even though the degree of substitution (DS) of xanthogenate groups ranged from γ=0.4 to 0.6, endoglucanases were able to slightly degrade the viscose. Ultrasonic degradation resulted in a narrow molecular weight distribution (MWD), notably without cleavage of substituents, and was also used to improve the solubility of the stabilized viscoses for further analysis. The techniques applied provide more insight into the xanthogenate distribution along the MWD. Remarkable differences in the degradation behavior of both viscose samples were observed.

Determination of absolute molecular weight of sodium lignosulfonates (NaLS) by laser light scattering (LLS)

Holzforschung ◽  
2013 ◽  
Vol 67 (3) ◽  
pp. 265-271 ◽  
Author(s):  
Yong Qian ◽  
Yonghong Deng ◽  
Yunqing Guo ◽  
Conghua Yi ◽  
Xueqing Qiu
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Laser Light ◽  
Gel Permeation Chromatography ◽  
Laser Light Scattering ◽  
Sodium Polystyrene Sulfonate ◽  
Sodium Lignosulfonate ◽  
The Absolute ◽  
Syringe Filter

Abstract The problems related to the determination of the absolute molecular weight (Mw) of sodium lignosulfonate (NaLS) are the focus of the present work. Four narrow-dispersed NaLS fractions were collected by filtration, ultrafiltration, and gel permeation chromatography (GPC), and their Mw measured by laser light scattering (LLSMw) was compared with that obtained by GPC (GPCMw). The LLSMw values were much larger than GPCMw, and this Mw difference increased with increasing Mw of NaLS. This finding confirms the known polyelectrolyte and aggregation effects of NaLS. The deviation is also partly due to the conformation differences between the GPC standard (sodium polystyrene sulfonate) and the NaLS molecules. The effects of polyelectrolytes and NaLS aggregates could be inhibited by adding enough NaCl salt in the NaLS solution and filtering the NaLS/NaCl solution through a syringe filter. As a result, the slow mode in dynamic LLS measurement disappeared. By this approach, the absolute LLSMw values were only slightly larger than that determined by GPC due to the conformation differences between the GPC standard and the NaLS molecules.

Tingkat Pemahaman Kompetensi Guru Pada Mahasiswa Pendidikan Geografi Sebagai Calon Guru Geografi

2020 ◽  
Vol 21 (1) ◽  
pp. 102-117
Author(s):  
Novia Zalmita ◽  
Muhajirah Muhajirah ◽  
Abdul Wahab Abdi
Keyword(s):  
Prospective Teachers ◽  
Prospective Teacher ◽  
Quantitative Description ◽  
Population Data ◽  
Geography Education ◽  
Teacher Competence ◽  
Education Department ◽  
Long Time

One that influences human resource indicators is education. The teacher is a profession as a job of academic specialization in a relatively long time in college. Understanding related to teacher competence is very important to have by a prospective teacher because it can affect the quality of performance as a professional teacher. The teacher's competence is known as pedagogic, professional, social and personality competencies. The issue in this study is how the competency of the teacher of the Department of Geography Education FKIP Unsyiah as a prospective teacher of geography? The purpose of this study was to determine the competence of teachers in the Department of Geography Education FKIP Unsyiah as prospective geography teachers. Quantitative description approach is used in this study to find answers to the issue. The population in this study were students of the Department of Geography Education FKIP Unsyiah class of 2015 and 2016 who had been declared to have passed the Micro Teaching and Magang Kependidikan 3 course totaling 50 people. Because the population is small and can be reached, the determination of the sample using total sampling techniques so that the sample in this study is the whole population. Data collection is done by distributing test questions to respondents. The data was analyzed using the descriptive statistics percentage formula. The results of the study indicate that the level of teacher competence of Geography Education Department students as prospective teachers is in the moderate category, namely as many as 22 respondents (44%). A total of 12 respondents (24%) were in the high category, 15 respondents (30%) were in the low category and 1 respondent (2%) were in the very low category.

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