高纯氧化钆中14种稀土杂质元素的柱色谱分离ICP-AES法测定

用Ｐ５０７萃淋树脂柱色谱法分离高纯氧化钆基体与稀土杂质。用ＩＣＰ－ＡＥＳ法测定高纯氧化钆中微量稀土杂质。选择了柱色谱分离的合适条件。优化了仪器测定参数。使本方法测定稀土总量下限小于１×１０－５％。可以满足９９．９９９９％高纯氧化钆的测定。此方法回收率在８５％－１１０％之间。相对标准偏差小于１８％。     

利用天然斜发沸石从高离子强度的强碱性溶液中吸附和洗脱K+和Rb+的研究

在80℃下，用间歇法研究了NH4^ 型天然斜发沸石对某厂高离子 强碱性循环液中的K^ 和Rb^ 的吸附，得到不同粒度天然斜发沸石对K^ 和Rb^ 的交换吸附量，用不同浓度的NH4HCO3溶液对沸石进行洗脱再生，是到洗脱速率随着洗脱液浓度增大而增大。本文对沸石与钾含量很高的高离子强度强碱性溶液中碱金属的交换吸附和洗脱过程进行了初步探讨。     

Sequential optimisation of the separation of a complex mixture of plastics additives by HPLC with a quaternary gradient and a dual detection system

Summary The separation of two families of plastics additives (phenolic antioxidants and UV absorbers) has been achieved by high performance liquid chromatography with a quaternary gradient. A methodology of separation based on a sequential optimization is described. After a preliminary study of the effects of solvents on retention of compounds, the mobile phase is first chosen for each class of additives (Irganox and Tinuvin), then for the mixture of all the compounds and the separation is finally optimized. The importance of the column phase ratio is also reported. The use of two detectors, UV absorbance and light-scattering, enables all the compounds to be detected. The performance of the detectors has been compared and the effects of the nebulization temperature on the detection of low molecular mass compounds is reported.     

HPLC of synthetic polymers characterization of polystyrenes by high performance precipitation liquid chromatography (HPPLC)

Summary The advantages and disadvantages of high performance precipitation liquid chromatography have been demonstrated for polystyrene homopolymers. Depending on the mobile phase composition at the dissolution point of the polymeric sample and surface properties of the stationary phase, elution is governed either by a solution process or by adsorption. A contribution by adsorption was noticed on silica as well as on reversed phases based on silica with a normal phase gradient of increasing polarity (heptane to dichloromethane). Elution was solely governed by solubility of the polymers on both types of stationary phase for polystyrenes with a molecular weight above 35 000 and reversed phase gradient of decreasing polarity (methanol to dichloromethane). Under these conditions an identical dependence of elution solvent composition on sample size was found as for turbidity titrations. Due to differences in the velocity of the eluent front and the polymeric sample with porous stationary phases the polymers can be eluted as colloidal solutions Non-porous stationary phases are superior in this respect because the velocities of eluent and solutes are identical.     

Evaluation of the enantiomeric selectivity in the chiral ligand-exchange chromatography of amino acids by a computational model

The chromatographic resolution of enantiomeric amino acids is accomplished on a reversed phase column using aqueous mobile phase containing the chiral reagent N,N-dimethyl-S-phenylalanine-Cu(II). The separation is a result of the whole interaction between the diastereomeric complex surface and the mixed stationary phase realized by the dynamic coating of the RP-18 carbon chains layer. The elution order seems to be related to the different water coordination capability on copper ion in the formation of the mixed ternary complexes.     

Separation of polar and non-polar analytes using dimethyl sulfoxide-modified subcritical water

Separations using methanol–water or acetonitrile–water mixtures at different temperatures have been well investigated in reversed-phase liquid chromatography. However, reversed-phase separation with dimethyl sulfoxide (DMSO)–water mixtures is much less studied. In this work, separations of polyhydroxybenzenes, phenol derivatives, benzene, toluene, ethylbenzene, and xylenes (BTEX), and polycyclic aromatic hydrocarbons (PAHs) with DMSO-modified subcritical water were performed at several temperatures to evaluate the effect of temperature on the elution strength of DMSO–water mixtures. The column efficiency obtained by using DMSO-modified subcritical water was also studied. Finally, the resolution of ethylbenzene and p-xylene was investigated.     

Elution order in gas chromatography

The retention behavior of a heterogeneous group of solutes has been examined on seven different stationary phases under isothermal and temperature-programmed conditions. Both ΔH_v (enthalpy of solute vaporization from the stationary phase) and ΔS_v (entropy of solute vaporization from the stationary phase) values were determined for each solute – stationary phase combination under isothermal conditions. Both program rate and carrier gas velocity were shown to affect solute elution order. Unless these and other experimental factors discussed are controlled, column equivalency studies based on solute elution order have dubious value.     

Elution of Cationic Species with/without Ion Pair Reagents from Polar Stationary Phases via SFC

Traditionally, the application of supercritical fluid chromatography has been limited to compounds of relatively low polarity. Thus, we report here that one secondary amine and two quaternary amine salts were successfully eluted from a Deltabond Cyano-bonded silica column with the addition of sodium alkylsulfonate to the methanol-modified, carbon dioxide-based mobile phase. A possible ion-pairing interaction between the positively charged analytes and the anionic part of the sulfonate additive has been proposed. In another set of experiments, the three amine salts readily eluted from both Ethyl-pyridine-bonded silica and Amino-bonded silica phases without the need of additive although the peak shapes were less than desirable. The addition of sulfonate salt to the mobile phase again sharpened the peaks. In the presence of a mixture of methanol and CO₂, we suggest that these stationary phases are positively charged. We describe here also for the first time the employment of a strong silica-based anion exchange (SAX) column for supercritical fluid separation of cationic species. Two elution mechanisms were proposed for the three amine salts depending upon whether the ionic additive was incorporated into the mobile phase. Separation as the ion-pair was proposed with an ionic additive in the mobile phase; whereas separation of the intact amine salt from the positively charged basic stationary phases was suggested to be operational without the ionic additive.     

Effective biosorption of arsenic from water using La(III) loaded carboxyl functionalized watermelon rind

Arsenic is highly toxic and carcinogenic element that mainly enters into our body through drinking water and caused adverse effect even at low concentration. A new type of cation exchanger is developed from waste biomass of watermelon rind after increasing the carboxyl functional groups by saponification. Saponified Watermelon Rind (SWR) was further loaded with La(III) to attenuate the contamination of As(III) from water. Characterization of biosorbent was performed using Fourier Transform Infra-Red (FTIR) spectroscopy, Field emission Scanning Electron Microscopy (Fe-SEM,) Energy Dispersive X-ray (EDX) spectroscopy and zeta potential analysis. Arsenic speciation of sorption product through X-ray photoelectron spectroscopic (XPS) analysis revealed that As(III) is partially converted into As(V) during biosorption process. The biosorption tests for As(III) were explored under different operating conditions. La(III)-SWR towards As(III) biosorption was best described by Langmuir biosorption isotherm and pseudo second order kinetic model. At a pH of 12.08, the optimum biosorption capacity was found to be 37.73 ± 0.12, 48.78 ± 0.09, 62.50 ± 0.11 mg/g, respectively at temperatures 298 K, 303 K and 308 K. The existance of chloride and nitrate showed negligible interference whereas sulphate and phosphate significantly inhibits As(III) biosorption. Thermodynamic study showed spontaneous and endothermic nature As(III) biosorption onto La(III)-SWR. The sorbed As(III) was eluted almost completely using 2 M NaOH. The findings of this study insinuated that La(III)-SWR biosorbent investigated in this study can be a low cost, environmentally benign and eco-friendly material for the treatment of aqueous solution polluted with arsenic ions.     

Chromatographic study of four sesquiterpenoids in volatile oil of Curcumae Rhizoma on reverse phase stationary phase with methyl-β-cyclodextrin as mobile additive

Abstract

The elution behavior of four sesquiterpenoids in volatile oil of Curcumae Rhizoma on reverse-phase high-performance liquid chromatography with methyl-β-cyclodextrin as mobile phase additive was studied, including germacrone, curzerene, furanodiene, and β-elemene. Stoichiometric ratio and apparent formation constants of inclusion complex formed by methyl-β-cyclodextrin and each analyte were calculated by varying the concentration of the additive in the mobile phase composed of methanol and water (90:10, v/v), in which the association constant for inclusion complex formed by the organic modifier methanol and methyl-β-cyclodextrin was also determined. Results showed that the stoichiometric ratio of all the inclusion complex was 1:1 when 0–9?mmol L^?1 of methyl-β-cyclodextrin was added in the mobile phase. Unusual retention behavior of the analyte germacrone was found, which was further investigated by the calculation of thermodynamic parameters. Meanwhile, enthalpy and entropy of the inclusion complexes and solute-stationary phase interactions were determined by linear van’t Hoff plots.