Molecular weights by computer from gel permeation data on punched tape

A Fortran IV program has been written that reduces digitized data from gel permeation chromatography to number and weight average molecular weights. This computer program is suitable for routine calculations whenever corrections are unnecessary for axial diffusion and branching effects.     

Molecular weights of natural rubbers from selected temperate zone plants

Molecular weights and molecular weight distributions are compared by gel permeation chromatography for rubbers from 33 north temperate zone plants, guayule, and Hevea. Rubbers isolated from all the northern plants had much lower weight-average molecular weight (M _w) values (9.72 × 10⁴–4.95 × 10⁵) than milled Hevea (1.31 × 10⁶) or guayule (1.28 × 10⁶) rubber. Pycnanthemum incanum, Lamiastrum galeobdolon, Monarda fistulosa, and Vernonia fasciculata produced potentially useful natural rubbers having M _w values above 4 × 10⁵ and polydispersity factors of 3.1–4.5.     

Molecular weights and molecular weight distributions of liquefied wood obtained by acid-catalyzed phenolysis

By means of gel permeation chromatography analysis, the molecular weights and molecular weight distributions of liquefied wood obtained under various liquefaction conditions and species of catalysts were investigated in order to trace the change in the structural characteristics of the liquefied wood. The results indicated that during the liquefaction reaction, wood components were subjected to decomposition, phenolation, and recondensation. The intensities of these reactions depended greatly on the reaction conditions and the species of catalysts, and their competing result determined the structural characteristics of the resulting liquefied wood. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 351–357, 1997     

Removal of cellulose from sunflower meal by fractionation

The dependence of sunflower meal fractionation on the following factors was investigated: quality of original meals, 37.5%, 40.0% and 42.5% crude protein; screen hole size, 1.5 mm, 2.0 mm, 2.5 mm and 3.0 mm; and single-phase and two-phase fractionation. The following conclusions were drawn. The increased protein levels in original meals (from 37.5% to 42.5% crude protein) had considerably greater effects on the quality than on the yield of the protein fractions. Increased screen hole size (from 1.5 mm to 2.5 mm) increased the yield of the protein fractions by 16.4–22.3%, but reduced the protein level in these fractions by 2.3–2.8%. Two-phase fractionation of the original meals with 40.0% and 42.5% crude protein increased the protein yield in the resulting protein fractions by 15.5–22.8%. The most efficient fractionation procedures rendered high yields of attractive protein fractions that contained 44.0–47.5% crude protein. The protein fractions were analyzed for physico-functional constants and amino acid composition. The most efficient and applicable fractionation procedures, those that may be successfully used in oil refineries, were selected.     

Molecular weights of polyethylene and polypropylene by vapor pressure osmometry at elevated temperatures

The Wescan Model 232-A VPO was modified with a 12 volt regulated power supply for supplying bridge current and with thermocouples to allow for direct digital readout of the syringe box and measuring chamber temperatures. The modified instrument was used to measure M _n of standard (NBS) polyethylenes. Agreement with NBS values was good (within 10%) for M _n < 3 × 10⁴ and fair (within 20%) for M _n = 1 × 10⁵. Results on M _n of commercial polypropylenes are also reported.     

A simplified method of obtaining the backmixing coefficient of a solvent extraction column from tracer pulse data

A method based on transfer function matching is used to obtain the backmixing coefficient of a solvent extraction column. The method demonstrates the exploitation of the symbolic manipulation capability of the current generation of scientific computing software. It starts with the dynamic model of Dongaonkar et al. and makes use of a set of tracer pulse data of Dongaonkar for a Kühni column. Compared to the existing methods of evaluating backmixing coefficient, this new method is more direct and simple to implement on computers. It has the potential of being applicable to more elaborate dynamic models of plate columns.     

Molecular weights and molecular weight distributions of irradiated cellulose fibers by gel permeation chromatography

Radiation degradation of cellulose fibers was investigated by gel permeation chromatography (GPC). Scoured cotton of Mexican variety (cellulose I), Polynosic rayon (cellulose II), and their microcrystalline celluloses obtained by hydrolysis of the original fibers were irradiated by Co-60 γ-rays under vacuum or humid conditions. The irradiated samples were then nitrated under nondegradative conditions. The molecular weights and molecular weight distributions were measured by GPC using tetrahydrofran as solvent. The relationship between molecular weight and elution count was obtained with cellulose trinitrate standards fractionated by preparative GPC. The degree of polymerization of the fibers decreased with increasing irradiation dose, but their microcystalline celluloses were only slightly degraded by irradiation, especially in microcrystalline cellulose from cellulose I. Degradation of the fibers irradiated under humid conditions was less than that irradiated under vacuum. It was found that the G-values for main-chain scission for the irradiated cellulose I, cellulose II, microcrystalline cellulose I, and microcrystalline cellulose II were 2.8, 2.9, less than 1, and 2.9, respectively, but the G-value for main-chain scission for the irradiated cellulose II was increased to 11.2 at irradiation doses above 3 Mrad. Consequently, it is inferred that cellulose molecules in the amorphous regions are degraded more readily, and the well-aligned molecules in crystalline regions are not as easily degraded by irradiation.     

Analysing gas well production data using a simplified decline curve analysis method

Decline curves are one of the most extensively used forms of data analysis employed in evaluating gas reserves and predicting future production. The parameters determined from the classical fit of historical data can be used to predict future production and the most popular and widely accepted method is Arp's equation. In the present work, simple-to-use method, which is easier than existing approaches, less complicated with fewer calculations, is formulated to arrive at an appropriate estimation of nominal (initial) decline rate, and the Arp's decline-curve exponent. The results can be used in follow-up calculations for analysis of past trends of decline in production performance for gas wells as well as reservoirs. Using this method is quite simple and accurate to generate the coefficients of the equations instead of opting for ready-generated coefficients with uncertainty. The engineers can easily develop their own computer program to compute the coefficients and hence obtain the solution for gas reserves and production performance in reservoirs.     

Removal of trace Cu from aqueous solution by foam fractionation

A system for removal of Cu²⁺ from aqueous solution by foam fractionation is proposed. The effects of pH, gas flow rate, surfactant concentration and froth/solution ratio on the removal rate and the enrichment ratio were studied to optimize the conditions. The results show that the removal rate increased with gas flow rate decreased, surfactant concentration increased and the froth/solution ratio increased, and was higher at pH4.0-5.0 than at other pH value. The optimum separation conditions were pH5.0, 200 mL/min of gas flow rate, 0.15 g/L of surfactant concentration and 1.1 of froth/solution ratio. Under the optimum conditions, the removal rate was 97.2% and the enrichment was 53.0.     

The dietary score as a simplified methodology in processing and analyzing food consumption data

The purpose of this investigation was to evaluate the dietary score as a valid and rapid alternative procedure for the processing and analysis of food consumption data in Guatemala. The dietary score consists in assigning points to a diet based upon the number of servings the diet provides of each one of the eight groups in which food has been classified. The size of the serving for each food receiving points was estimated based on available data describing the food pattern of Guatemala. The caloric contribution of each of the eight groups to the total caloric intake was also calculated, and information on the caloric and nutrient needs of the Guatemalan population is discussed. In this communication, the dietary score was compared to the percentage of adequacy for energy and nutrients in 392 diets of women, and children between the ages of 24 and 60 months. Half of the dietaries were collected using the 24-hour recall method, while in the other half, the direct weighing method was used. Nutritional adequacy was estimated from food composition tables and based on the recommended energy and nutrient intake figures. In addition, by utilizing the adequacy indices for energy and nutrients, a binary variable was developed to describe the overall adequacy of the diet. This variable describes the probability a diet has of being adequate, given the dietary score obtained. In conclusion, the dietary score was found to be a valid, rapid and efficient alternative for the processing and evaluation of food consumption information, collected by means of either the direct weighing of foods or the 24-hour recall methods.     

Recovery,fractionation and study of oils from a lignite

Oils from a lignite (Teruel, Spain) were studied. They were obtained by catalytic depolymerization, by reacting an aromatic substrate (tetralin), Lewis acid catalyst (BF₃) and the lignite (oil A) or asphaltenes (oil B) at atmospheric pressure and temperatures <220 °C. The A and B oils were fractionated on an alumina-silica gel dual column into their saturated, mono- and diaromatic, polyaromatic and polar components by elution with hexane, hexane-benzene, benzene and methanol-diethyl ether-benzene respectively. The elemental analysis, average molecular weight, i.r. and ¹H n.m.r. spectroscopy and aromaticity data of these subfractions were studied.     

A graphic procedure for obtaining average molecular weights from a chromatogram

A simple graphic method is described for obtaining average molecular weights of a continuously distributed polymer from its GPC chromatogram. The method is based on the assumption that the weight distribution of the polymer may be approximated by a Schulz distribution. As an example, a polystyrene sample is analyzed graphically, and the results are compared with the traditional method of calculation.     

IgY isolation from a watery by-product obtained from an egg yolk fractionation process

The possibility of recovering IgY from a watery by-product produced during an egg yolk fractionation process was evaluated. The protocol employed for the extraction of IgY was the polyethylene glycol precipitation method. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was carried out to confirm the presence of IgY at the different steps of the IgY purification process. Finally, the amount of IgY obtained was quantified by means of anion exchange chromatography. Native egg yolk was employed as IgY reference source, and results showed that the by-product could be at least as suitable as egg yolk as an IgY source. Additionally, the use of the by-product as a source of biotechnological compounds, such as IgY, leads to an increase in the value added during the egg yolk fractionation process.     

Reactor design from batch data by a direct graphical method

A graphical method for reactor design is presented which uses the plot of concentration vs. time. This method can be used to compare stirred tank, plug flow and recycle reactors as well as various reactor combinations. With Monod Kinetics the concept of wash-out can be illustrated. A brief comparison with other graphical methods is made.     

The fractionation of milk fat from a solvent at low temperatures

Summary A procedure for fractionating milk fat from a solvent at low temperatures has been developed. This procedure consists of freezing out fractions of the fat from solvent (Skelly Solve A) at progressively lower temperatures —7°, —13°, —23°, —53°C., with the remaining filtrate taken as a final fraction. In physical appearance these fractions vary from a dry white powder to a reddish-yellow oil; in melting point from 53°C. to —10.6°C.; in iodine number from 8.29 to 58.37; and in saponification equivalent from 262.8 to 235.2. The saponification equivalents do not change in the same order as the other properties mentioned. This fat fractionation effects a simplification of milk fat and makes available less complex portions of the natural glyceride mixtures for detailed study of the composition, configuration, and other properties. Some of these studies are now being carried out and will be reported later.     

Removal of mercury by foam fractionation using surfactin, a biosurfactant

The separation of mercury ions from artificially contaminated water by the foam fractionation process using a biosurfactant (surfactin) and chemical surfactants (SDS and Tween-80) was investigated in this study. Parameters such as surfactant and mercury concentration, pH, foam volume, and digestion time were varied and their effects on the efficiency of mercury removal were investigated. The recovery efficiency of mercury ions was highly sensitive to the concentration of the surfactant. The highest mercury ion recovery by surfactin was obtained using a surfactin concentration of 10 × CMC, while recovery using SDS required < 10 × CMC and Tween-80 >10 × CMC. However, the enrichment of mercury ions in the foam was superior with surfactin, the mercury enrichment value corresponding to the highest metal recovery (10.4%) by surfactin being 1.53. Dilute solutions (2-mg L(-1) Hg(2+)) resulted in better separation (36.4%), while concentrated solutions (100 mg L(-1)) enabled only a 2.3% recovery using surfactin. An increase in the digestion time of the metal solution with surfactin yielded better separation as compared with a freshly-prepared solution, and an increase in the airflow rate increased bubble production, resulting in higher metal recovery but low enrichment. Basic solutions yielded higher mercury separation as compared with acidic solutions due to the precipitation of surfactin under acidic conditions.     

Determination of average molecular weights of a polyelectrolyte by meniscus-depletion sedimentation equilibrium

Long-column meniscus-depletion sedimentation equilibrium has been used to determine M?_n, M?_w and M?_z for the Na⁺ and (CH₃)₄N⁺ salts of a high molecular weight poly(styrene sulphonate). Consideration has been given to ways of avoiding the need for dialysis when dealing with polyelectrolyte solutions.     

大豆蛋白废水中乳清蛋白的泡沫分离实验

采用泡沫分离法回收大豆蛋白废水中蛋白,考察了pH值、气体的流速、进料浓度、液柱和泡沫层高度等因素对分离效果的影响.低进气速度、高泡沫层高度、适当的pH值以及低进料浓度有利于较好的分离.结果表明:当进料浓度为0.54 g/L、pH值为5、泡沫层与液池高度比4∶1,通气量为15.0 L/h 时,富集比可以达到3.25;当进料浓度为0.54 g/L、pH值为5、泡沫层与液池高度比3∶1,通气量为15.0 L/h,此时脱除率可以达到48.5%.