Fractionation of Lithium Isotopes in Cation-Exchange Chromatography

Abstract

Cation-exchange chromatography of lithium was carried out to investigate the lithium isotope effect in aqueous ion-exchange systems. The heavier isotope, ⁷Li, was preferentially fractionated into the resin phase in every experiment conducted, and this result is consistent with the results of previous work. The value of the separation factor was 1.00089–1.00171 at 25°C. A comparison of lithium isotope effect with those of potassium and rubidium indicated that the isotope effect originating from hydration is larger than the effect due to phase change for lithium, while the opposite is the case with potassium and rubidium.     

Fractionation of Strontium Isotopes in Cation-Exchange Chromatography

Abstract

Strontium isotope fractionation has been observed in cation-exchange chromatography of strontium salts. The heavier isotopes have been found enriched at the front parts of displacement-type chromatograms, which means that the heavier isotopes are preferentially fractionated into the solution phase. The average values of the single-stage separation factor (S) minus one per unit mass difference between isotopes have been 1.0 × 10^?6 for the strontium chloride system, 2.9 × 10^?6 for the strontium acetate system, and 3.1 × 10^?6 for the strontium lactate system at 25°C. No evidence of the odd-even anomalous isotope effects has been observed. The isotopic reduced partition function ratios (RPFRs) of the strontium species involved in the present study have been estimated; the RPFRs of the complex species have been found to be larger than that of the simple hydrated strontium ion, which accounts for the experimental results that the S values of the strontium lactate and strontium acetate systems are larger than that of the strontium chloride system.     

Magnesium Isotope Fractionation in Cation-Exchange Chromatography

Abstract

Band displacement chromatography of magnesium has been carried out successfully for the purpose of magnesium isotope separation by using a strongly acidic cation-exchange resin and the strontium ion as the replacement ion. A small but definite accumulation of the heavier isotopes (²⁵Mg, ²⁶Mg) has been observed at the front parts of the magnesium chromatograms. The heavier isotopes have been fractionated preferentially into the solution phase. The single-stage separation factors have been calculated for the ²⁵Mg/²⁴Mg and ²⁶Mg/²⁴Mg isotopic pairs at 25[ddot]C. The reduced partition function ratios of magnesium species involved in the present study have been estimated.     

Separation of Nitrogen Isotopes by Displacement Band Chromatography

Abstract

A study of the separation of ¹⁴N and ¹⁵N isotopes via displacement band chronatography was conducted using sulfonated styrene-divinylbenzene resins. Starting with a feed solution of 0.5 N NH₄OH (containing 51% ¹⁵N), a band was developed that generated a concentration profile ranging from 11 to 85 % ¹⁵N. The separative power and HETP (height equivalent to a theoretical plate) were found to be dependent on the resin characteristics (size, crosslinkage) and operating parameters (superficial velocity, concentration). The use of a 7/10-microneter-size, high performance resin increased the separative power by a factor of 17 and decreased the HETP by a factor of 10, when compared to a 100/200 mesh Dowex 50W-X12 resin under similar process conditions. The HETP could further be reduced by lowering the superficial velocity and/or eluant concentration.     

Chromatographic Separation of Calcium Isotopes with Polymer-Bound Ligands

Abstract

Calcium isotopes were enriched in chromatography columns containing the polymer-bound ligands cryptand [2_B22], cryptand [2_B21], and 18-Crown-6. The largest equilibrium single stage separation factor, 1.0039 ± 0.0002 for the calcium 40/44 isotope pair, was found in calcium exchange with cryptand [2_B22]. The largest separation factor found for 18-Crown-6 was 1.0025 ± 0.0003 for the 40/44 isotope pair. The size of the isotope effect was found to be highly dependent on the solvent composition. An iminodiacetate resin ion exchange column yielded small enrichments of calcium isotopes. Calcium 40/44 exchange with the chelating functional group iminodiacetate yielded a small equilibrium separation factor of 1.00011 ± 0.00003, which was more typical of calcium ion exchange isotope effects.

Comparisons of the above chemical systems based on separative power showed crown chemical exchange to be an improvement over cryptand and iminodiacetate exchange. The cryptand system was rendered impractical as a consequence of a slow exchange rate and a resulting large stage residence time contribution to the separative power, on the order of 45 min. The separation factor for the iminodiacetate system was too small for practical applicability.     

Fractionation of Residuals by Gel Permeation Chromatography

Abstract

Gel permeation chromatography has been effectively used for the fraction-ation of residuals. The preparative-scale gel permeation chromatograph employed for these studies is described along with selected operating parameters. The instrument has been used to fractionate a shale oil residue, 50% reduced crude, and 25% reduced crude, into fairly narrow molecular weight fractions. The individual cuts from each residual have been analyzed and the elemental distribution established. The trends of heteroatom distribution, i.e., nitrogen, sulfur, nickel, and vanadium, as a function of molecular weight for the various residuals are discussed.     

Preliminary Experimental Survey of Hollow-Fiber Electropolarization Chromatography (Electrical Field-Flow Fractionation) for Protein Fractionation

Abstract

The operating characteristics of hollow-fiber electropolarization chromato-graphy (or electrical field-flow fractionation) of proteins are surveyed. Particular attention is given to the dependence of protein retardation and electroretention on field strength, protein loading, buffer concentration, and pH. Both mixtures of human serum albumin with Cohn fraction II (γG) and pure human serum albumin were studied. The results confirmed earlier findings that this process is highly efficient for separation of these two dissimilar proteins, but process dependence on the parameters studied is unexpectedly complex. Available models for predicting column performance are found adequate only as a rough guide, and strong interactions are shown between the effects of the above parameters. Much more work is needed to characterize this deceptively simple process, and it is particularly important to study the physics and chemistry of concentrated protein solutions.     

Displacement Band Chromatography of Hydrogen Sulfites for Enrichment of Sulfur Isotopes

Abstract

Experimental studies were conducted on the enrichment of sulfur isotopes by displacement band chromatography. In these studies, a band of hydrogen sulfite (bisulfite) ions from a sulfurous acid or bisulfite-salt solution was continuously displaced by bisulfate ions from a sulfuric acid or bisulfate-salt solution in a column packed with aminated polystyrene-divinyl benzene resin under varied process conditions. The sulfur isotopes were enriched through isotopic exchange between the bisulfite ions on the resin and the sulfurous acid and/or bisulfite-salt solution in contact with the resin within the moving band. During the isotopic exchange, S-34 isotope was favored in the resin phase and S-32 isotope in the liquid phase. As a result, the S-34 isotope was gradually enriched at the rear of the band, and S-32 isotope at the front. The effects of the various process conditions were evaluated on separative power, height equivalent to a theoretical plate, and operational simplicity. The highest separative power, 3.05 g S-34/cm³/yr, was achieved with an ammonium bisulfite feed displaced by a sulfuric acid displacer at 65°c operating temperature.     

Fractionation of Linear Polyethylene with Gel Permeation Chromatography. Part III

Abstract

Many commercial linear polyethylenes have very broad distributions of molecular weight. The high molecular weight fractions often extend beyond the highest molecular weight calibration standard of GPC. For this reason the reliability of information obtainable from GPC has been examined with attention to the average molecular weights. Calibration range is a serious limitation for the accurate determination of the - weight-average and the higher averages of molecular weight. Uncertainty in the baseline at the high molecular weight region, however, does not produce a significant error. With a four-column GPC having 10³ to 10⁷ A nominal capacity, improved resolution is needed in the high molecular weight range. In order to examine the resolution and to improve the calibration, a polyethylene standard of ca. 3–4 million molecular weight is required. With the present limitation of GPC the greatest amount of information can be obtained by examining and intercomparing the cumulative distribution curves. With this representation ca. 95% or more of the cumulative weight range is free from uncertainty in calibration and resolution. A question is raised as to whether melt index is precisely a function of the weight-average molecular weight. This question is pertinent when significantly different molecular weight distributions are involved. GPC offers an opportunity to resolve the question.     

The Effects of Operating Parameters on Nitrogen Isotopes Separation by Displacement Band Chromatography

Abstract

The separation of nitrogen isotopes by displacement band chromatography was studied under various operating conditions, using columns packed with sulfonated polystyrene-divinyl benzene, cation exchange resins. Average resin size was varied from 10 to 113 μm, operating temperature from 23 to 70°C, displacing solution concentration from 0.3 to 0.9 N, and superficial velocity from 1.0 to 2.0 cm/min. The maximum separative power for nitrogen isotopes was directly proportional to stage velocity (band velocity/height equivalent to a theoretical stage). The effects of operating parameters on the separative power were therefore evaluated in terms of stage velocity. The results indicate that operating temperature and resin particle size have greater effects on the maximum separative power than do displacing solution concentration and flow rate.     

Fractionation of D/H and 18O/16O Water Isotopes in a Packed Distillation Column

Theoretical Foundations of Chemical Engineering - An experimental packed fractionating column was designed to study the process of separation of water hydrogen and oxygen isotopes, including the...     

Boron Isotope Fractionation in Liquid Chromatography with Boron-Specific Resins as Column Packing Material

Abstract

Boron-specific resins with n-methyl glucamine as the functional group were used as column packing material of liquid chromatography for boron isotope separation. The shapes of chromatograms in reverse breakthrough experiments were heavily dependent on the pH of the eluents, and there existed a pH value at which a chromatogram of the displacement type was realized nearly ideally. The value of the single-stage separation factor for the boron isotopes varied between 1.010 and 1.022, depending on the temperature and the form of the resins. The existence of the three-coordinate boron species in addition to the four-coordinate species in the resin phase is suggested.     

Preliminary Results of the Studies on Fractionation of Ytterbium Isotopes in Yb(III)-Acetate/Yb-Amalgam System

ABSTRACT

Preliminary data on the fractionation of ytterbium isotopes in a Yb(III)-acetate/Yb-amalgam exchange system were obtained. The light isotope was preferentially fractionated to the amalgam phase. The values of the unit separation gain per mass difference, ?, were found to be ?00054 for ^176/71Yb and ?00069 for ^176/174Yb. The difference, which amounted to 00015, may be taken as evidence for the occurrence of the so-called “even-odd” effect. It was also found that the chemical isotope shift of ytterbium was mirrored by the optical isotope shift in its atomic spectra.     

阳离子交换型连续床用超大孔晶胶的制备

采用原位接枝法,将3-烯丙氧基-2-羟基-1-丙磺酸钠(AHPSA)接枝到聚丙烯酰胺基晶胶基质孔隙内表面,制备得到了阳离子交换型连续床用的带磺酸基超大孔晶胶介质.通过脉冲示踪法测量停留时间分布(RTD),得到了晶胶介质的理论等板高度(HETP).通过测量一定压差下流经晶胶床柱的液量,得到晶胶介质的渗透率.用溶菌酶作为模型蛋白测量晶胶介质的吸附容量.考察了单体浓度、接枝反应时间等反应条件对晶胶介质的HETP、渗透率、蛋白质吸附容量等性能的影响.结果表明:接枝AHPSA的阳离子交换晶胶介质的HETP基本不受接枝反应时间和单体浓度的影响,其渗透率随接枝反应时间增大略有减小,其对溶菌酶的吸附容量与接枝单体的浓度成正比,受接枝反应时间的影响较小.     

高效液相色谱法测定D-泛酸钙的含量

介绍了利用高效液相色谱法测定D-泛酸钙含量,采用ODS柱为分离柱,乙腈和0.02mol/L磷酸二氢钾水溶液比例为10:90(体积比)。方法简便、快速、分离条件好,回收率高、重现性良好。     

顶空毛细管气相色谱法测定瑞舒伐他汀钙的残留溶剂

目的:建立瑞舒伐他汀钙残留有机溶剂的检测方法。方法:采用顶空毛细管气相色谱法;色谱柱为DB-624(30 m×0.53 mm×3μm),FID检测器,测定瑞舒伐他汀钙中残留的甲醇、乙醚和丙酮。结果:各被测溶剂均能良好分离,各溶剂线性关系良好,精密度RSD均小于10%,平均回收率为95%~105%之间。结论:该法适用于瑞舒伐他汀钙原料药的残留溶剂测定。     

离子色谱法测定粘土矿微生物浸出液中钙离子含量不确定度评估

依据JJF 1059.1—2012《测量不确定度评定与表示》对离子色谱法测定粘土矿微生物浸出液中钙离子含量不确定度来源进行了分析和评估,最终确定了测定钙离子含量不确定度的主要影响因素和次要因素,得到相对不确定度和扩展不确定度。     

Separate Determination of Aluminum and of Lithium, Sodium, and Potassium in Fire-Clay and Silica Raw Materials and Refractories by Cation-Exchange Chromatography

Plant control dictates a need for a rapid accurate method for the determination of alumina in silica and fire-clay materials. The determination of the alkali oxide impurities is also important. Given a finely ground sample representative of the lot of material in question, the chemist has two basic problems. He needs (1) an acceptable method for complete solubilization of the sample and (2) a simple and accurate method for the determination of the constituent sought. Ion-exchange analysis permits both to be carried out with ease and precision in regard to alumina. For the alkalis the complete solubilization of all types of samples presents some problems, but ion-exchange analysis is applicable to the second requirement. Solubilized samples are passed down through an ion-exchange column of Dowex-50 cation-exchange resin perfused with the proper strength of HC1. The fractions are collected and the separated constituents are determined. Data are presented showing the results of various procedures as compared with accepted values for National Bureau of Standards samples.     

Fractionation of the Triacylglycerols of Evening Primrose Oil by High-Performance Liquid Chromatography in the Silver Ion Mode

Triacylglycerols from evening primrose oil have been resolved by HPLC in the silver ion mode on a stationary phase consisted of an ion exchange medium, i.e. a silica gel matrix with boned sulphonic acid moieties, loaded with silver ions. The mobile phase was a gradient of acetone into 1,2-dichloroethane-dichloromethane initially, before acetonitrile was introduced. A mass detector was employed to monitor separations. Fractions were collected via a stream-splitter for identification and quantification by gas chromatography as methyl esters. Excellent resolution was obtained, and species differing in saturation from disaturated- monoenoic to monodienoic-ditrienoic were resolved and quantified.     

离子色谱测定水溶性染料中的微量钙镁离子

本文采用离子色谱外标法,对水溶性染料中的微量钙镁离子进行了定量分析。测定结果表明该方法具有很高的精密度和数据重现性,不会对色谱柱造成污染。