<Superscript>137</Superscript>Cs/<Superscript>137m</Superscript>Ba radioisotope generator based on 6-tungstocerate(IV) column matrix

Summary Barium-137m radioisotope generator of the chromatographic column elution mode based on loading 1.5 g 6-tungstocerate(IV) gel matrix with ~54 kBq of fission-produced ¹³⁷Cs is described. The elution performance of the generated ^137mBa radionuclide was investigated as a function of chemical composition of the eluent, flow rate, elution frequency, and age of the generator system. At comparable conditions, ^137mBa eluates with 0.9% NaCl-0.1M HCl eluent had higher elution yields and radionuclidic purity than with 0.1M NH₄Cl-0.1M HCl eluent. The generator has been repeatedly eluted for 311 days by passing 4810 ml of the saline eluent (10 ml × 481 elution operations) at a flow rate of 3.0 ml/min. Barium-137m eluates of high and reproducible elution yields, chemical and radionuclidic purities of (≥ 99.99%) were obtained.     

Use of Microspherical Sulfonated Hypercrosslinked Polystyrene in Ion Chromatography

The possibility of applying sulfonated cation exchangers on the basis of hypercrosslinked polystyrene (HCPS) of different ion-exchange capacity for the ion-chromatographic separation of alkali metal and ammonium cations was demonstrated. The effect of the nature and concentration of the eluent, the temperature of the chromatographic column, additions of an organic solvent to the eluent, and the ion-exchange capacity of the sorbent on the retention of cations was examined. An unusual selectivity of the sorbent for lithium and ammonium cations was found; the elution order can change for the Li⁺/Na⁺ and Rb⁺/NH⁺ ₄ pairs depending on the nature of the eluent, the temperature, additions of an organic solvent, and the structural characteristics of the sorbent. When dilute solutions of nitric acid are used as the eluent, the following elution order of cations was obtained: Na⁺ < Li⁺ < K⁺ < NH⁺ ₄ < Rb⁺ < Cs⁺ Mg²⁺ < Sr²⁺ < Ca²⁺ < Ba²⁺. Under the optimum conditions of separation (1 mM solution of sulfuric acid, 20°C) on sulfonated HCPS with an ion-exchange capacity of 0.07 mequiv/g, the separation of ammonium and alkali metal cations was achieved within 17 min.     

Reduced sample recovery in liquid chromatography at critical adsorption point of high molar mass polystyrene

Low sample recovery may represent an important drawback in liquid chromatography at the critical adsorption point (LC-CAP) if the critical eluent is not carefully fitted to the system. So far, this problem was often overlooked and only few experimental examples can be found in literature. We showed that in the case of polystyrene (PS) in a tetrahydrofuran (THF)/n-hexane critical mixed eluent, PS with molar masses higher than 100 kg mol⁻¹ were not eluted from a tandem of two columns packed by bare silica gels with 30 nm and 100 nm pore size, respectively. The polymer trapped within the columns was well recovered after injection of a small volume of pure THF as demonstrated using 2D chromatography. We studied PS conformations by means of small angle neutron scattering and found that the THF/n-hexane critical eluent is in fact a theta solvent for PS. By replacing it by a CH₂Cl₂/n-hexane critical mixture, which is a good solvent for PS, the limits of reduced sample recovery was displaced towards far higher molar masses. Thus, thermodynamic quality of eluent - theta or good solvent - plays an important role on the phenomenon of sample recovery.     

流动注射在线吸附预富集-冷蒸气原子荧光法测定矿泉水中的痕量无机汞

研究了聚四氟乙烯管编结反应器(KR)在线吸附预富集技术与冷蒸气原子荧光联用测定矿泉水中痕量无机汞的方法.Hg2+与DDTC在线形成Hg2+-DDTC络合物并吸附在KR内壁上,采用电磁感应加热技术,用20% (V/V) HNO3在线加热洗脱并氧化预富集于KR内壁上的Hg2+-DDTC.洗脱液与KBH4溶液反应生成蒸气态汞,直接用冷蒸气原子荧光联用技术检测.20%(V/V)HNO3作为洗脱液的同时也为氢化发生提供了酸性介质.本方法未使用常用的有机洗脱液,具有操作简单和环保等优点.每小时可分析30个样品,最大吸附倍数为35倍,样品分析精密度RSD为2.2%(n=11),检出限(3σ)为2.0 ng/L.     

IC Determination of Halide Impurities in Ionic Liquids

An ion chromatographic (IC) method has been developed for determination of trace levels of halide impurities in various types of ionic liquids (ILs). The advantage of this method is that all relevant halide species can be measured in a single chromatographic analysis. Separation of halides was performed on a Dionex AS9-HC column using an eluent consisting of 20 mM NaOH and 10% (v/v) acetonitrile, delivered at 1.5 mL min⁻¹. Using this eluent, fluoride, chloride and bromide were well resolved from each other, but iodide was co-eluted with tetrafluoroborate (BF₄⁻) present as a counter-anion in tetrafluoroborate-based ILs. The same eluent was also used successfully for the determination of halides in highly hydrophobic ILs, such as those based on bis-(trifluoromethanesulfonyl)imide (TFSI⁻) and bis-perfluoroethylsulfonylimide (BETI⁻). In this case, 50% (v/v) acetonitrile aqueous was needed to dissolve the sample before injection, and this did not adversely affect the separation. Detection limits in the measured solution were 0.1, 0.2 and 1.0 ppm for chloride, bromide and iodide, respectively, by conductivity detection, and 0.02 ppm for iodide by UV detection.     

Use of zwitterionic micelles in the eluent: a new approach for ion chromatographic (IC) analysis of ions in biological fluids with direct sample injection

The problem of column performance degradation due to irreversible binding of proteins encountered in ion chromatographic (IC) analysis of ions in protein-containing samples was overcome by using zwitterionic micelles (e.g., Zwittergent-3–14) as a portion of the eluent. A zwitterionic micellar eluent showed high ability for solubilization of proteins, and, hence, the protein-containing samples could be analyzed without need for deproteinization. On the other hand, the zwitterionic micelle was insensitive to conductivity but interacted with the analyte ions, due mainly to its unique configuration of charges (namely, the zwitterionic micelle containing both positively and negatively charged groups but carrying no net charge). Using a zwitterionic micellar eluent, the analyte ions could be detected selectively and sensitively, and moreover, the selectivity for the analyte ions was unique. A conventional anion-exchange column conditioned with a Zwittergent-3-14 micellar eluent was applied for the analysis of real biological samples (serum and urine) with direct sample injection. The results of the successful detection of inorganic anions (Cl^–, SO₄ ^2–, NO₂ ^–, Br^–, and NO₃ ^–) have demonstrated the usefulness of this new IC approach for the analysis of biological samples.     

Portable,lightweight, low power,ion chromatographic system with open tubular capillary columns

Basic operation principles of a lightweight, low power, low cost, portable ion chromatograph utilizing open tubular ion chromatography in capillary columns coated with multi-layer polymeric stationary phases are demonstrated. A minimalistic configuration of a portable IC instrument was developed that does not require any chromatographic eluent delivery system, nor sample injection device as it uses gravity-based eluent flow and hydrodynamic sample injection adopted from capillary electrophoresis. As a detection device, an inexpensive commercially available capacitance sensor is used that has been shown to be a suitable substitute for contactless conductivity detection in capillary separation systems. The built-in temperature sensor allows for baseline drift correction typically encountered in conductivity/capacitance measurements without thermostating device. The whole instrument does not require any power supply for its operation, except the detection and data acquisition part that is provided by a USB port of a Netbook computer. It is extremely lightweight, its total weight including the Netbook computer is less than 2.5 kg and it can be continuously operated for more than 8 h. Several parameters of the instrument, such as detection cell design, eluent delivery systems and data treatment were optimized as well as the composition of eluent for non-suppressed ion chromatographic analysis of common inorganic cations (Na⁺, NH₄⁺, K⁺, Cs⁺, Ca²⁺, Mg²⁺, transition metals). Low conductivity eluents based on weakly complexing organic acids such as tartaric, oxalic or pyridine-2,6-dicarboxylic acids were used with contactless capacitance detection for simultaneous separation of mono- and divalent cations. Separation of Na⁺ and NH₄⁺ cations was optimized by addition of 18-crown-6 to the eluent. The best separation of 6 metal cations commonly present in various environmental samples was accomplished in less than 30 min using a 1.75 mM pyridine-2,6-dicarboxylic acid and 3 mM 18-crown-6 eluent with excellent repeatability (below 2%) and detection limits in the low micromolar range. The analysis of field samples is demonstrated; the concentrations of common inorganic cations in river water, mineral water and snow samples were determined.     

HPLC analysis of metal chelating agents in micronutrients

The separation and quantitative determination of organic chelating agents such as DTPA, EDDHA, EDDHMA, EDTA and HEDTA as their copper chelates using HPLC and UV detection is described. Analysis is performed on a Spherogel^TM TSK column. The eluent consists of methanol/water (50: 50, v/v) and 0.25 mmol/L Cu(NO₃)₂. The pH value, the composition of the eluent, the temperature, the sample concentration, the flow rate of the eluent and the influence of the detection wavelength were optimized. The linearity of the UV detector was in the range of 0.5 mmol/L to 2.5 mmol/L.     

Chelating resin preconcentration and Hg(II) assisted elution followed by differential-pulse anodic stripping voltammetry for the determination of Cd, Cu, and Pb in seawater

A new and efficient Hg(II) back-elution method for the desorption of Cd, Cu, and Pb from Chelex-100 chelating resin was developed. A smaller eluent volume and shorter elution time can be achieved using an Hg(II) containing eluent rather than pure nitric acid. Owing to the remaining Hg(II) ion in the effluent, a mercury thin-film electrode is formed in-situ during the anodic stripping voltammetric determination without any further addition of Hg(II). The results indicate that all the analytes in seawater matrix can be completely adsorbed on Chelex-100 resin from the sample at pH 6.5, and subsequently eluted from the resin with an acid solution of 5 × 10^–4 mol/L Hg²⁺ + 1 mol/L HClO₄. The detection limits obtained from the differential-pulse anodic (μg L^–1 to ng L^–1) stripping voltammetry are at sub-ppb to ppt (μg L^–1 to ng L^–1) levels permitting to determine Cd, Cu and Pb traces in seawater. The analytical reliability was confirmed by the analysis of the certified reference material CASS-II (open ocean seawater). Received: 22 April 1997 / Revised: 5 August 1997 / Accepted: 7 August 1997     

Peak parking technique for the simultaneous determination of anions and cations

An ion chromatography method is described for the simultaneous determination of anions (Cl^–, NO₃^–, and SO₄^2–) and cations (Na⁺, NH₄⁺, K⁺, Mg²⁺, and Ca²⁺) using a single pump, a single eluent and a single detector. An anion-exchange column modified with chondroitin sulfate C facilitated the elution of the above three anions using 5 mM tartaric acid as the eluent in isocratic mode, whereas the same eluent facilitated the separation of the above five cations on a commercially-available cation-exchange column. The separation columns were connected in series via two six-port switching valves, so the required cation-exchange or anion-exchange separation could be carried out by selecting the appropriate positions for the switching valves. The separations were completed in 30 min.     

Preconcentration of beryllium via octadecyl silica gel microparticles doped with aluminon, and its determination by flame atomic absorption spectrometry

A simple and sensitive method is presented for solid phase extraction (SPE) and preconcentration of trace quantities of beryllium using octadecyl silica gel modifed with aurin tricarboxylic acid (aluminon). Beryllium is then determined by flame atomic absorption spectroscopy. Parameters affecting SPE such as pH, sample solution and eluent flow rate, type, concentration and volume of eluent, interfering ions and breakthrough volume, were investigated. Under optimal conditions, the beryllium ions were retained on the sorbent at pH 6–6.7, while 3.0 mL of 0.05 mol L^?1 HNO₃ is sufficient to elute the ions. The limit of detection (LOD) based on 3σ was 0.8 µg L^?1 for 250 mL sample solution and 5 mL 0.05 mol L^?1 HNO₃ as eluent. The LOD can reach 0.1 µg L^?1 for 1 L sample solution and 3 mL of 0.05 mol L^?1 HNO₃. The accuracy and precision (RSD %) of the method is >90% and <10%, respectively. The method was applied to the determination of beryllium in aqueous samples.     

The Application of Cryptand 22 as a Bifunctional Stationary Phase for Ion Chromatography

Poly (styrene/divinyl benzene) with cryptand 22 as an anchoring group was synthesized and applied as a bifunctional packing material for the separation of both cations and anions. At pH < 2, the resin can be protonated and applied as an anion exchanger for the separation of anions; with water as eluent, inorganic anions such as F^?, Cl^?, Br^?, NO₃^?”, I^? were well separated. After deprotonation at pH> 10, the resin became a cation exchanger and successfully separated alkali metal ions such as Li⁺, K⁺ and Cs⁺ with methanol as eluent. The effects of solvents, flow rate and temperature on the separation of various ions were also investigated.     

Use of zwitterionic micelles in the eluent II: a new approach to ion chromatographic analysis of inorganic cations in biological fluids with direct sample injection

A new ion chromatographic (IC) technique has been developed for the determination of inorganic cations in biological fluids with direct sample injection. This involved the use of a mixed zwitterionic-micelle/electrolyte solution as an eluent. The proteins in the sample became bound to the zwitterionic micelles in the eluent and were thus eliminated from the column. The cations were separated by cation exchange. This method is ideal for the on-line, simultaneous determination of common inorganic cations (Na⁺, NH₄ ⁺, K⁺, Mg²⁺, and Ca²⁺) in urine and serum samples. Such an application was demonstrated experimentally. Non-suppressed conductivity was used for analyte detection. The detection limits obtained using this IC system were 2.94, 5.22, 34.9, 32.6, and 56.7 μg/L for Na⁺, NH₄ ⁺, K⁺, Mg²⁺, and Ca²⁺, respectively.     

Determination of anions by non-suppressed ion chromatography using an amine column

Summary The Synchropak AX300 column has been used to separate a wide range of anions. A standard solution containing F^–, Cl^–, NO ₂ ^– , NO ₃ ^– , HPO ₄ ^2– , SO ₄ ^2– ions can be analysed in 8–14 minutes using a phthalate or phthalate/citrate eluent at pH 6–7. Addition of citrate to a phthalate eluent has a pronounced effect on the times of analysis. Detection by direction and indirect UV absorption enables the analysis of a wide range of anions. Application of the technique range from rain water to ash pond liquor analysis.     

The study of applicability of dithiocarbamate-coated fullerene C60 for preconcentration of palladium for graphite furnace atomic absorption spectrometric determination in environmental samples

The present method comprises an off-line enrichment of Pd on the fullerene, C₆₀, coated with ammonium pyrrolidinedithiocarbamate (APDC), followed by the elution of formed Pd-chelate with ethanol and the subsequent determination of Pd from the eluate by graphite furnace atomic absorption spectrometry. By using fullerene loaded with 0.1% APDC, the analytical system is simplified as the sample can be directly preconcentrated on the column. The following parameters affecting the preconcentration of Pd on C₆₀ were optimized: amount of ligand used for the coating of fullerene, sample pH, kind of eluent, sample and eluent flow rates, volume and number of fractions of eluent used. The sorption efficiency for Pd on coated fullerene was 99.2±1.1%. The best elution efficiency for Pd from the column was obtained with 0.6 ml of ethanol at a flow rate of 0.2 ml min⁻¹. The limit of detection was 0.044 ng ml⁻¹. The effect of sample pretreatment procedure on the preconcentration of Pd by evaluated method is discussed. The content of Pd in road dust (179.2±17.4 ng g⁻¹) determined by proposed method was in agreement with the results obtained with a reference method. The low recovery of analyte (64%) was obtained for geological material CRM SARM-7 (platinum ore) due to the much higher concentration of interfering elements.     

Fast analysis of thiocyanate by ion-pair chromatography with direct conductivity detection on a monolithic column

Fast analysis of thiocyanate by ion-pair chromatography using a silica-based monolithic column and direct conductivity detection was carried out. Chromatographic separation was performed on a Chromolith Speed ROD RP-18e using tetrabutylammonium hydroxide （TBA）-phthalic acid-acetonitrile as eluent. The effects of eluent concentration, eluent pH value, column temperature and flow rate on retention time of thiocyanate were investigated. The optimized chromatographic conditions for the determination of thiocyanate were as follows： 0.25 mmol/L TBA-0.18 mmol/L phthalate-7% acetonitrile （pH 5.5） as eluent, column temperature of 30 ℃, and flow rate of 6.0 mL/min. Retention time of thiocyanate was less than 1 min under the conditions. Common anions （Cl^-, NO3 , SO42 and I^- ） did not interfere with the determination of thiocyanate. Detection limit （S/N = 3） of thiocyanate was 0.96 mg/L. Calibration graph between peak area and the concentration of thiocyanate was linear in the range of 2.0- 100.0 mg/L. Relative standard deviation （RSD） of chromatographic peak area was 1.4% （n = 5）. This method has been applied to the determination of thiocyanate in ionic liquids. Recoveries of thiocyanate after spiking were 100.5%.     

Determination of phenyltin compounds by reversed-phase liquid chromatography

An analytical procedure for the determination of phenyltin compounds in environmental sample waters was studied. Chromatography of mono-, di- tri-phenyltin (MPT, DPT and TPT) was performed on a reversed-phase C₁₈ column with the mobile phase comprising methanol/10⁻² M H₃PO₄ (80:20 v/v) at pH 3 and UV detection at 214 nm. To enhance the sensitivity of the detection system, the post-column reaction between morin or 3-hydroxyflavone and phenyltin compounds was formed before fluorescence detection. Several parameters affecting the fluorescence intensity were studied systematically, including the optimum condition for the post-column reagent that was also compatible with the eluent. The parameters concerned in this study were the pH, the percentage of Triton X-100, the ratio of fluorigenic reagent to phenyltin compounds and the amount of methanol in the eluent. Detection limits before the preconcentration process were in the region of 1.5 ppb for TPT and 150–250 ppb for MPT and DPT, respectively. Utilizing solid-phase extraction on a C₁₈ cartridge for sample clean-up as well as preconcentration successfully reduced the detection limit of TPT to the level of ng dm⁻³ and can be applied to seawater analysis. Recovery in the range 95.0–98.0% was obtained by developing the optimum elution profile in the preconcentration step. © 1998 John Wiley & Sons, Ltd.     

Experimental Design in Ion Chromatography: Effect of the Organic Modifier and Complexing Agent on the Retention of Alkaline and Alkaline Earth Ions

A Box–Behnken experimental design combined with response surface methodology was applied to investigate the effect of the eluent composition on the retention of common cations in ion chromatography. In particular, we modelled the retention factors of Na⁺, K⁺, NH₄ ⁺, Ca⁺⁺ and Mg⁺⁺ and the chromatogram resolution. Response surfaces were evaluated to assess interactive effects of nitric acid, pyridine-2,6-dicarboxylic acid and percentage of acetonitrile in the eluent on the above parameters. Nitric acid concentration and acetonitrile content appeared as the most and the least influential components of the eluent in determining the retention factors of individual ions or the global resolution of the chromatogram, while the concentration of the complexing agent exhibits an intermediate role. As expected, acidification of the mobile phase produces a decrease in the retention factors and a progressive worsening of resolution, and this effect can be modulated by the concentration of the complexing agent. The proposed approach seems suitable to investigate the retention phenomena in ion chromatography under application of complex eluent phases.     

A modified lead–matrix separation procedure shown for lead isotope analysis in Trojan silver artefacts as an example

A modified Pb–matrix separation procedure using NH₄HCO₃ solution as eluent has been developed and validated for determination of Pb isotope amount ratios by thermal ionization mass spectrometry. The procedure is based on chromatographic separation using the Pb·Spec resin and an in-house-prepared NH₄HCO₃ solution serving as eluent. The advantages of this eluent are low Pb blanks (<40 pg?mL^?1) and the property that NH₄HCO₃ can be easily removed by use of a heating step (>60 °C). Pb recovery is >95 % for water samples. For archaeological silver samples, however, the Pb recovery is reduced to approximately 50 %, but causes no bias in the determination of Pb isotope amount ratios. The validated procedure was used to determine lead isotope amount ratios in Trojan silver artefacts with expanded uncertainties (k?=?2) <0.09 %.