The chromatographic interaction and separation of metal ions with 8-Quinolinol stationary phases in several aqueous eluents

Several 8-quinolinol silica gel (QSG) columns were used, with metal-uptake capacities of 10–156 μmol g^?1. Various transition and heavy metal ions were used as analytes in nitrate, sulfate, phosphate, citrate, tartrate, oxalate, phthalate, and maleate mobile phases. Metal-ion retention increased with column capacity and pH. Optimum capacity factors were obtained on columns of intermediate capacity (27 and 46 μmol g^?1). Retention times decreased with an increase in eluent buffer concentration, typically by half with a doubling of buffer. Evidence is presented for the occurence of mobile-phase complexation of analyte ions by eluent buffer species. Multiple or split peaks were often observed when the analyte solvent differed from the mobile phase. Chromatographic separation of up to six metals on the QSG columns is demonstrated in tartrate and maleate mobile phases.     

Preconcentration of palladium(II) from water with thionalide loaded on silica gel

2-Mercapto-N-2-naphthylacetamide (thionalide) on silica gel is used for rapid preconcentration of μg l^?1 levels of palladium(II) from aqueous solution, followed by atomic absorption spectrometric measurement. In batch experiments, palladium was quantitatively retained on the gel from solutions 5 M in acid to pH 8; equilibrium was achieved within 10 s. The chelating capacity of the gel was 7.5 μmol Pd g^?1 at pH < 4. The effect of flow rate on retention was studied. Palladium retained on the column was completely eluted with 20 ml of 0.2 M thiourea in 0.1 M hydrochloric acid. The palladium concentration in sea water is shown to be < 0.3 μg l^?1.     

Single-column ion chromatography of weak inorganic acids for materials and process characterization

Single-column ion chromatography allows the separation and direct conductometric detection of anions of weak inorganic acids. Mixtures containing borate, silicate, germanate, fluoride and chloride can be resolved by using a resin-based anion-exchange column and a 0.06 g l^?1 sodium hydroxide/2.5 × 10^?5 M sodium benzoate eluent. Judicious selection of sample preparation and of eluent composition is important. Glasses are analyzed for boron and fluoride by fusion with sodium hydroxide, suitable dilution and use of a benzoate eluent. Results on standard glasses are in good agreement with certified values. The separation of arsenite and arsenate in a gold plating bath is outlined.     

Separation of proteins by consecutive sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and reversed phase high performance liquid chromatography

A procedure for the preparative separation of proteins was developed by using consecutively sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (SDS-PAGE) and reversed phase high performance liquid chromatography (HPLC). The proteins were separated by SDS-PAGE and afterwards extracted from the gel. The extracted proteins were separated from SDS and other small molecular weight contaminants on a Fractogel TSK HW-40 (F) column in acidic aqueous acetonitrile. The proteins eluted from the Fractogel column were fractionated by HPLC. The identity and purity of the recovered proteins was confirmed by SDS-PAGE analysis.     

Differential preconcentration of arsenic(III) and arsenic(V) with thionalide loaded on silica gel

2-Mercapto-N-2-naphtylacetamide (thionalide) on silica gel is used for differential preconcentration of μg l^?1 levels of arsenic(III) and arsenic(V) from aqueous solution. In batch experiments, arsenic(III) was quantitatively retained on the gel from solutions of pH 6.5–8.5, but arsenic(V) and organic arsenic compounds were not retained. The chelating capacity of the gel was 5.6 μmol g^?1 As(III) at pH 7.0. Arsenic retained on teh column was completely eluted with 25 ml of 0.01 M sodium borate in 0.01 M sodium hydroxide containing 10 mg l^?1 iodine (pH 10). The arsenic was determined by silver diethyldithiocarbamate spectrophotometry. Arsenic(V) was subsequently determined after reduction to arsenic(III) with sulphite and iodide. Arsenic(III) and arsenic(V) in sea water are shown to be < 0.12 and 1.6 μg l^?1, respectively.     

Ion chromatographic determination of trace amounts of aluminium with on-line preconcentration and spectrophotometric detection

Trace amounts of aluminium in aqueous samples can be determined by ion chromatography using ammonium sulphate-nitric acid as eluent and pyrocatechol violet as post-column chromogenic reagent. The detection limit for a 50-μl sample is 10 μg 1^?1. Preconcentration of the sample (obtained by replacing the sampling loop with a short ion-exchange column) allows larger amounts of sample to be loaded and lowers the detection limit below 1 μg 1^?1.     

Determination of hydrogen in stainless steels by spark-source mass spectrometry

A spark-source mass spectrometric (SSMS) method capable of determining traces of hydrogen in micro-volumes of metals was developed by using a pointed metal probe technique. The hydrogen background was decreased to μg g^?1 levels by the combination of a method in which the sample in the ion source is baked under vacuum at 323–343 K for more than 25 ks and a liquid nitrogen or liquid helium cryogenic pump method. This method was applied to the analysis of austenitic stainless steels at μg g^?1 hydrogen levels, and the relative standard deviation was within 20% for samples with hydrogen concentrations ranging from 2 to 4 μg g^?1. The relative sensitivity coefficent was 2.3 (Fe=1).     

Ion-chromatographic behavior of alkali metal cations and ammonium ion on zirconium-adsorbing silica gel

The preparation and evaluation of zirconium-adsorbing silica gel (Zr-Silica) as an ion-exchange stationary phase in ion chromatography for inorganic anions and cations was carried out. The Zr-Silica was prepared by the reaction of silanol groups on the surface of the silica gel with zirconium butoxide (Zr(OCH2CH2CH2CH3)4) in ethanol. The ion-exchange characteristics of the Zr-Silica were evaluated using 10 mM tartaric acid at pH 2.5 as eluent. The Zr-Silica was found to act as a cation-exchanger under the eluent conditions. The retention behavior of alkali and alkaline earth metal cations was then investigated. The Zr-Silica column was proved to be suitable for the simultaneous separation of alkali metal cations and ammonium ion. Excellent separation of the cations on a 15 cm Zr-Silica column was achieved in 25 min using 10 mM tartaric acid as eluent.     

A Simple Method for Determination of Homologue Imidazolium Cations in Ionic Liquids Using IC with Direct Conductivity Detection

An investigation was carried out into the fast determination of five homologue imidazolium cations in ionic liquids by ion chromatography using a cation-exchange column and direct conductivity detection. Ethylenediamine, complex organic acid (citric acid, oxalic acid and tartaric acid) and organic modifiers (acetonitrile) were used as mobile phase. The influences of the eluent types, eluent concentration, eluent pH and column temperature on separation of the cations were discussed. Simultaneous separation and determination of the five homologue imidazolium cations in ionic liquids were achieved under an optimum condition. The optimized mobile phase was consisted of 0.25 mmol L^?1 ethylenediamine + 0.5 mmol L^?1 citric acid + 3% acetonitrile (v/v) (pH 4.1), set at a flow rate of 1.0 mL min^?1. The column temperature was 40 °C and detection limits were obtained in the range of 1.1–45.6 mg L^?1. The relative standard deviations of the chromatographic peak areas for the cations were <3.0% (n = 5). This method was successfully applied to separate imidazolium cations in ionic liquids produced by organic synthesis. The recoveries of spiked components were 92.5–101.9%.     

高效阴离子交换-脉冲安培检测同时分析单糖和糖醛酸

建立了高效阴离子交换-脉冲安培检测(HPAE-PAD)同时分离测定8种单糖和2种糖醛酸的分析方法。以CarboPacPA20阴离子交换柱为分离柱,以2mmol/LNaOH溶液将8种单糖从分离柱上洗脱,而后用NaAc(50~200mmol/L)梯度淋洗2种糖醛酸,淋洗液流速为0.5mL/min,总分析时间为30min。在优化的分离测定条件下,8种单糖和2种糖醛酸的检出限为2.5~14.4μg/L(进样体积25μL,峰面积定量)。5mg/L的10种化合物的混合标准溶液连续7次进样,峰面积的相对标准偏差为0.3%~1.5%。用所建立的方法测定了多糖水解液和木材半纤维素水解液中的单糖和糖醛酸含量。     

Differential Pulse Polarographic Determination of Cd(II) and Pb(II) in Milk Samples after Solid‐Phase Extraction Using Amberlite XAD‐2 Resin Modified with 2,2′‐DPED3P

In the present paper novel column solid phase extraction procedure was developed for the determination of Cd(II) and Pb(II) in cows', goats', ewes', buffalos' and humans' milk samples using newly synthesized reagent 2,2′‐DPED₃P (2,2′‐{[1,2‐diphenylethane‐1,2‐diylidene]dinitrilo}diphenol) for preconcentration and separation prior to differential pulse polarography using amberlite XAD‐2 in the ranges of pH 4.0–5.0. The sorbed elements were subsequently eluted with 10 mL of 2 M HCl elutes were analysed by differential pulse polarography (DPP). The interference of foreign ions has also been studied. Effects of various instrumental parameters are investigated and received conditions are optimized. The total metal concentration of the milk samples in the study area were in the following ranges 0.030–0.090 μg L^?1 of Cd(II), 0.009–0.026 μg L^?1 of Pb(II) respectively. The limits of detections were found to be 0.020 and 0.024 μg L^?1 for Cd(II) and Pb(II) respectively by applying a preconcentration factor ～40. The proposed enrichment method was applied successfully for the determination of metal ions in cows', goats', ewes', buffalos' and humans' milk samples.     

Retention behavior of alkali, alkaline earth and transition metal cations in ion chromatography with an unmodified silica gel column

An unmodified silica gel (Develosil 30-5) column (150×4.6 mm I.D.) has been applied to the ion chromatographic separation of alkali, alkaline earth and transition metal cations. The retention behavior of the above cations on the bare substrate was investigated using a number of weak inorganic and organic acid eluents. During this investigation, several separations were achieved and the most suitable eluent conditions were identified. It was concluded that: (a) 1.5 mM HNO₃-0.5mM pyridine-2,6-dicar☐ylic acid eluent was the most effective for the simultaneous separation of common alkali and alkaline earth metal cations, (b) 1.5 mM oxalic acid eluent resulted in the best separation of alkali, alkaline earth, and transition metal cations, (c) 0.5 mM CuSO₄ eluent could be used for the separation of alkali metal cations alone and (d) 0.5 mM ethylenediamine-oxalic acid eluent at pH 5.5 resulted in themost efficient separation of both alkaline earth and transition metal cations.     

Determination of tungstate in soils and sludges by using single-column ion chromatography

A procedure has been developed for the determination of tungstate at trace levels in aqueous extracts of soil and sludge by single-column ion chromatography (SCIC). Chromatographic parameters based on ion selectivity, time of determination and signal response were optimized for tungstate with the simultaneous detection of nitrate and sulfate. Chloride, phosphate, chromate, molybdate and vanadate were found not to interfere in the determination. A low-capacity resin-based column was used for the separation with p-hydroxybenzoic acid (5 mM) at pH 8.5 as the eluent. The limit of detection defined as three times the signal-to-noise ratio was 170 μg l^?1 (2-ml sample). The resolution between tungstate and sulfate was R_s=2.84. The results for aqueous extracts agree closely with those obtained by an accepted spectrophotometric method.     

Simultaneous determination of zirconium and hafnium as ternary complexes with 5-Br-PADAP and fluoride using solid-phase extraction and reversed-phase liquid chromatography

Solid-phase extraction (SPE) along with reversed-phase liquid chromatography (RP-LC) was used for the simultaneous determination of Zr(IV) and Hf(IV) by means of their ternary chelates with fluoride and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). The conditions of SPE sorption were examined in detail: type of SPE column, volume of the sample, volume of the eluent, concentrations of metal ions, fluoride salt, chromogenic reagent, organic phase, and pH. It was established that the sorption of Zr(IV) and Hf(IV), as their ternary chelates, on SPE Zorbax SPE C18 (EC) cartridge was the most efficient, when the sample containing metal ion (Zr(IV), Hf(IV), both, up to 2 μg), 5-Br-PADAP 1.5×10⁻⁴, NaF 7.5×10⁻⁵ mol l⁻¹, methanol 40%, pH 4.5±1 was applied for the SPE sorption. The chelates were discarded from SPE cartridge using acetonitrile/water (99.75+0.25, v/v) eluent containing 3.8×10⁻⁴ mol l⁻¹ sodium fluoride and subsequently separated by RP-LC method. The RP-LC separation of both chelates was optimized and Zorbax SB-C18 analytical LC column along with acetonitrile/water (65+35, v/v) eluent containing the 1.5×10⁻⁴ mol l⁻¹ sodium fluoride was used. The established SPE/LC conditions allow Zr(IV) 0.08-2.0 μg and Hf(IV) 0.04-2.0 μg determination in a sample volume up to 150 ml. The detection limits, 0.03 μg Hf(IV) and 0.05 μg Zr(IV), were obtained. Recoveries, (94±2)% for Hf(IV) chelate and (106±2)% for Zr(IV) chelate were obtained, when 1 μg of Zr(IV) and Hf(IV) ions were determined by the present SPE/LC method from the sample volume of 100 ml. The established, pre-concentration SPE conditions, along with the LC separation and determination allow the assay of Zr(IV) and Hf(IV) in complicated matrix materials. The present SPE/LC method was applied to the determination of Zr(IV) and Hf(IV) in tap water and reference geological material (rock, NCS DC 73303; certified content: Zr, 27.7×10⁻³% (w/w) and Hf, 6.5×10⁻⁴% (w/w)).     

Determination of traces of inorganic anions by means of high-performance liquid chromatography on zipaxsax columns

Zipax-SAX pellicular beads are used as the anion-exchanger material ; a high-pressure packing technique is described. A Zipax-SAX column (200 × 4.5 mm) is used in a separation system with eluent suppression and conductivity detection as in ion-chromatography. Good separation of chloride, nitrite, bromide, nitrate and sulfate is obtained with 1.4 × 10^-3 M succinate or adipate eluents at pH 7. A complete separation takes about 6 min at a flow rate of 3 ml min^-1. Detection limits of 2 μg l^-1 chloride, 4 μg l^-1 nitrate and 10 μg l^-1 sulfate can be reached if 2 ml of sample is preconcentrated.     

Sensitive determination of traces of boron in waters,fertilizers na geological and biological materials by isotope-dilution mass spectrometry

A method is described for determining traces of boron in water, fertilizers, geological and biological (reference) materials by isotope-dilution mass spectrometry after separation on an Amberlite IRA-743 borate-selective ion-exchange column. Boron (–250 ng g^?1) in water can be determined with an accuracy of 5–20% (computed on a 2s basis). After correction for weighing errors and for moisture, content, which varied from 0 to 8% for the samples tested, 1–35 μg g^?1 boron in “dry” fertilizer, biological or geological sample can be assayed with an accuracy of 5–30% (2s). In an IAEA interlaboratory program on a simulated fresh water, the method yielded a value of 24.3 +? 2 μg l^?1, compared to the make-up value of 25 μg l^?1.     

Preconcentration of metal ions on silica gel modified with 3(1-imidazolyl)propyl groups

Silica gel functionalized with 3(1-imidazolyl)propyl groups and packed in a glass column is used to adsorb and preconcentrate metal ions from ethanol solution. Elution is done with 0.1 M hydrochloric acid in an ethanol/water mixture having a mole fraction of water of 0.85. The modified silica is applied to preconcentrate metal ions (Cu, Ni, Fe, Zn and Cd) from commercial ethanol, normally used as engine fuel. The method is suitable for quantifying these metals at low μg 1^?1 levels.     

On-line coupling of supercritical fluid extraction with high-performance liquid chromatography for the determination of explosives in vapour phases

An investigation into the selectivity of an iminodiacetic acid (IDA) modified silica gel column for transition and heavy metal ions using non-chelating inorganic eluents has been carried out. A number of eluent parameters were investigated to determine the exact retention mechanism taking place and to control selectivity. The parameters studied were eluent ionic strength and the nature of the inorganic salt used, eluent pH and eluent temperature. The results obtained showed how despite certain metal ions exhibiting similar stability constants with the bonded IDA groups, careful control of each of the above parameters, in particular eluent chloride ion concentration and eluent temperature, could result in large changes in selectivity. Optimal conditions for the isocratic and gradient separation of Mg(II), Ca(II), Mn(II), Cd(II), Co(II), Zn(II) and Pb(II) were determined. An isocratic method using a 0.035 M KCl, 0.065 M KNO3 (pH 2.5) eluent was successfully applied to the determination of Mn(II), Cd(II), Co(II) and Zn(II) at concentrations between 20 and 121 microg/l in a freshwater certified reference material (NIST 1640).     

Iminodiacetic acid/ethylcellulose as a chelating ion exchanger : Part 1. Determination of trace metals by atomic absorption spectrometry and collection of uranium

A chelate-forming ion exchanger, iminodiacetic acid/ethylcellulose, is used for the separation of trace metals from waters and different organic solvents. Added uranium was collected from sea waters with recoveries of about 97%. Graphite-furnace atomic absorption spectrometry and solution spectrophotometry were used to quantify the metals. For the direct determination of trace metals in waters by the graphite-furnace method, a simple matrix-matching method is described. The detection limit for cadmium was 0.1 μg l^?1 and for lead 1 μg^?1 in drinking water.     

Ion Chromatographic Determination of Traces of Sodium,Magnesium and Chlorine in Gadolinium Nitrate

Abstract

Two independent and sensitive ion chromatographic methods with suppressed conductivity were developed for determination of traces of Cl, Na, and Mg in gadolinium-nitrate. Na-Mg was determined by cation-exchange column after matrix separation, whereas Cl was analyzed without matrix separation by high capacity anion-exchange column. Detection limit for Cl was 0.01 µg mL^?1 in sample solution and 1 µg g^?1 in solid sample. The reproducibility (100 µL injected) was better than 3%, 3% and 4% at 50, 25 and 50 µg L^?1 level for Cl, Na, and Mg respectively. The overall precision was better than ±7% for Na-Mg and ±5% for Cl.