Capillary isotachophoretic determinations of metal ions by use of complexation equilibria in acetone-water medium

The determination of metal ions by capillary isotachophoresis and the complexation equilibria between metal ions and polyaminopolycarboxylic acids has been investigated. A seven-component mixture of metal ions can be separated in 45% v/v acetone-water medium when EDTA or DCTA is used as the terminating ion. Linear calibration graphs are obtained for a standard mixture of Mn(+), Cu(2+), Zn(2+), Cd(2+), Pb(2+) and Fe(3+) in the range 0.5-5.0 nmole, with relative standard deviations of 1.0% or better. The effective mobilities of the Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes increase in parallel with the stability constants, except for the Cu(II) complexes. It is concluded that the abnormal behaviour of the Cu(II) complexes may be attributed to a difference in steric configuration.     

毛细管区带电泳技术快速分离检测爆炸残留物中的无机离子

利用间接紫外毛细管区带电泳方法完成了对爆炸残留物中7种无机离子(K+,NH+4,NO-2,NO-3,SO2-4,ClO-3,ClO-4)的分离检测。阳离子测定采用的缓冲体系为10 mmol/L吡啶（pH 4.5）-3 mmol/L冠醚,K+和NH+4在2.6 min内达到基线分离,检出限分别为0.25 mg/L和0.10 mg/L(S/N=3)。阴离子测定采用的缓冲体系为40 mmol/L硼酸-1.8 mmol/L重铬酸钾-2 mmol/L硼酸钠（pH 8.6）,氢氧化四甲铵为电渗流改性剂,5种阴离子在4.6 min内达到基线分离,检出限为0.10～1.85 mg/L。该方法已成功地应用于实际爆炸物样品种类的判定分析,取得了很好的结果。     

毛细管区带电泳技术快速分离检测爆炸残留物中的无机离子

利用间接紫外毛细管区带电泳方法完成了对爆炸残留物中7种无机离子(K+,NH+4,NO-2,NO-3,SO2-4,ClO-3,ClO-4)的分离检测。阳离子测定采用的缓冲体系为10 mmol/L吡啶（pH 4.5）-3 mmol/L冠醚,K+和NH+4在2.6 min内达到基线分离,检出限分别为0.25 mg/L和0.10 mg/L(S/N=3)。阴离子测定采用的缓冲体系为40 mmol/L硼酸-1.8 mmol/L重铬酸钾-2 mmol/L硼酸钠（pH 8.6）,氢氧化四甲铵为电渗流改性剂,5种阴离子在4.6 min内达到基线分离,检出限为0.10～1.85 mg/L。该方法已成功地应用于实际爆炸物样品种类的判定分析,取得了很好的结果。     

Separation of trans-1,2-cyclohexanediaminetetra-acetic acid chelates of bismuth(III), iron(III) and copper(II) by reversed-phase paired-ion chromatography

Trans-1,2-cyclohexanediaminetetra-acetic acid (DCTA) chelates of bismuth(III), iron(III) and copper(II) have been separated by two techniques using reversed-phase paired-ion chromatography. In one, the chelates in aqueous solution were separated within 20 min on a 6.0 × 300 mm ERC-ODS column with 10⁻²M tetrabutylammonium ion (TBA⁺) in methanoi-water mixture (45:55 v/v) as eluent. In the other, the metal ions in aqueous solution were separated within 10 min by direct injection into an ERC-ODS column with 10⁻²M TBA⁺/10⁻³M DCTA in methanoi-water mixture (40:60 v/v) as eluent.     

Simultaneous separation of inorganic anions and cations by capillary zone electrophoresis

A new capillary electrophoretic approach for simultaneous separation of fast anions and cations is demonstrated. Indirect UV detection at 214 nm in conjunction with electromigration sampling from both ends of the capillary was developed. Two electrolyte systems based on imidazole-nitrate and copper(II)-ethylenediamine-nitrate were investigated for the simultaneous separation of chloride, sulphate, hydrocarbonate, potassium, ammonium, calcium, sodium and magnesium ions. Experimental parameters that were evaluated included a nature of UV chromophore, pH of electrolyte, a nature of complexing agent. The method permits the excellent separation of three anions and five cations in only 4 min using electrolyte system containing 2.5 mmol l⁻¹ Cu(NO₃)₂, 5 mmol l⁻¹ ethylenediamine and 1 mmol l⁻¹ fumaric acid at pH 8.5 adjusted with tetraethylammonium hydroxide.     

Complexometric catalytic titrations using the indicator reaction periodate-triethanolamine

The possibility of applying a new indicator reaction, i.e., periodate-triethanolamine, as the indicator in titrations of ethylenediamine-N,N,N′,N′-tetracetic acid (EDTA), 1,2-diaminocyclohexanetetraacetic acid (DCTA), and diethylenetriaminepentaacetic acid (DTPA) with standard manganese(II) sulfate solution (phosphate buffer pH 6.84) has been investigated. The titration course was followed potentiometrically using a perchlorate ion-selective electrode. The optimum conditions for determinations in relation to concentration of the indicator reaction components have been established. Furthermore, the influence of some ions on the possibility of EDTA determination was considered and maximally tolerable concentrations under these conditions were established. The amounts of 0.170–18.00 mg of EDTA, 0.150–16.00 mg of DCTA, and 0.180–19.00 mg of DTPA were determined with a maximal relative standard deviation less than 1.0%. Results are in good agreement with those of comparable methods. Finally, the experimental catalytic titration curves obtained in this way are compared to the simulated ones.     

Simultane Ionen-Chromatographie von Kationen und Anionen mit Komplexonen als Elutionsmittel und selektiver UV-Detektion

Summary The complexones EDTA, DCTA and EGTA were investigated as eluting agents at various pH-values for the simultaneous separation of 9 cations and 6 anions using ion chromatography on a silica gel based anion exchanger (Nucleosil 10-Anion II). 1,2-Diaminocyclohexanetetraacetic acid (DCTA) proved to be the best eluting agent. UV spectrophotometry was used for both direct and indirect detection of the anions and anionic metal complexes and a detailed study was carried out with respect to selectivity of detection. This was facilitated by referring to the UV absorption spectra of the anions and metal complexes involved. By choice of a suitable wavelength between 203 and 270 nm and taking into account pH effects, a number of selective determinations were possible. Examples include Pb and Cu in the presence of excess of Ca and Mg as well as nitrate, nitrite and bromide in a large excess of chloride and sulphate. Some examples of detection limits are (g/l) nitrate 2, Fe(III) 3, Cu 9 and Pb 12 (sample volume 20 l, direct UV-detection). The Chromatographie behaviour of Fe(II) and Fe(III) was studied and discussed. Drinking water was analysed for chloride, nitrate and sulphate as well as Ca and Mg using DCTA in the eluent. Complete analyses can be carried out in less than 15 min.

---

---

Herrn Prof. Dr. R. Neeb zum 60. Geburtstag gewidmet     

Adsorption of radiocobalt on lead dioxide from aqueous solution

Adsorption of cobalt on lead dioxide from aqueous solutions has been studied in relation to shaking time, amount of adsorbent, pH, and concentration of the adsorbate. The data fitted very well Langmuir, Freundlich, and Dubinin-Radushkevich isotherms and their corresponding constants were calculated. In another set of experiments the influence of different anions and cations on the adsorption of cobalt under the optimum experimental conditions have been determined. EDTA, tartrate, citrate, thiocyanate, oxalate, U(VI), Al(III), Fe(III), Cr(III), and Th(IV), drastically reduced adsorption of cobalt. Therefore these anions and cations should be removed before adsorption of cobalt on lead dioxide. Adsorption of other metal ions on the oxide were measured under identical conditions. TheK _D values indicate that cobalt can be separated successfully from Hg(II), Ag(I), Ta(V), In(III) and Tc(VII).     

Rhodamine-based probes for metal ion-induced chromo-/fluorogenic dual signaling and their selectivity towards Hg(II) ion

The new signaling probes 2-6, rhodamine-B derivatives of various receptors which contain different donor atoms for effective metal ion coordination, were synthesized and their absorption as well as fluorescence spectral responses were evaluated in the presence of various metal ions. All these probes along with the reference probe 1 have exhibited optimal metal ion-induced absorption and fluorescence enhancement with Hg(II) ion in the longer wavelength region (>500 nm) in MeCN, exploiting the spectral characteristics of metal ion-induced structural transformation of rhodamine. The selectivity and sensitivity towards Hg(II) ion were better pronounced in MeCN-H(2)O (1 : 1 v/v) medium, implying the role of the solvent molecules, water in particular, in the preferential Hg(II) coordination environment. Complexation of Hg(II) to 1-6 not only enhanced the absorption at ~560 nm, which turned the colourless solution into pink to facilitate a naked eye detection, but also amplified the fluorescence intensity simultaneously to offer high sensitivity of detection at lower concentration. The Hg(II)-induced photo-physical spectral responses of 1-6 in presence of other competitive metal ions rendered their high selectivity towards Hg(II). Further, their reversible dual channel signaling pattern under the action of counter anions, exploiting coordination tendency of anions towards Hg(II), which compete with probe-metal interaction, implied the reversibility in their Hg(II) coordination. The selectivity, sensitivity and reversibility, in principle, establishes the potential of these probes as chemosensors for Hg(II) ion detection.     

化妆品中阴阳离子的快速测定及其用于化妆品鉴别的研究

用离子色谱电导检测器对黑泥类化妆品中的阴、阳离子(Na+,NH+4,K+,Mg 2+ ,Ca 2+ ,Cl-,Br-,NO-2,NO-3和SO 2- 4)进行了测定。阳离子分离条件: 阳离子交换柱ICS C25,均苯四甲酸淋洗液浓度2.0 mmol/L ,流速0.6 mL/min ;阴离子分离条件: 阴离子交换柱Shim pack IC A1,淋洗液为2.5 mmol/L 邻苯二甲酸和2.4 mmol/L 三羟基氨基甲烷,流速1.0 mL/min 。结果表明,上述10种离子在较宽浓度范围内有良好     

Speciation of V, Cr and Fe by capillary electrophoresis-bandpass reaction cell inductively coupled plasma mass spectrometry

Capillary electrophoresis-dynamic reaction cell inductively coupled plasma mass spectrometry (CE-DRC-ICP-MS) for the speciation of iron(III/II), vanadium(V/IV) and chromium(VI/III) is described. Two different CE migration modes were employed for separating the six metal ions using pre-capillary complexation. One is counter-electroosmotic mode in which iron(III/II) and vanadium(V/IV) ions were well separated using a 60 cm x 75 microm i.d. fused silica capillary. The voltage was set at +22 kV and a 15 mmol l(-1) tris(hydroxymethyl)aminomethane (Tris) buffer (pH 8.75) containing 0.5 mmol l(-1) ethylenediaminetetraacetic acid (EDTA) and 0.5 mmol l(-1) ortho-phenanthroline (phen) was used as the electrophoretic buffer. The other is co-electroosmotic mode in which chromium(VI/III) ions were well separated while the applied voltage was set at -22 kV and a 10 mmol l(-1) ammonium citrate buffer (pH 7.7) containing 0.5 mmol l(-1) diethylenetriaminepentaacetic acid (DTPA) and 0.01% polybrene was used as the electrophoretic buffer. The mass spectra were measured at m/z 51, 52 and 56 for V. Cr and Fe, respectively. The interfering polyatomic ions of 35Cl16O+, 40Ar12C+ and 40Ar16O+ on 51V+, 52Cr+ and 56Fe+ determination were reduced in intensity significantly by using NH3 as the reaction cell gas in the DRC. The detection limits were in the range of 0.1-0.5, 0.4-1.3 and 1.2-1.7 ng ml(-1) for V, Cr and Fe, respectively. Applications of the method for the speciation of V, Cr and Fe in wastewater were demonstrated. The recoveries were in the range of 92-120% for various species.     

离子色谱-紫外检测法同时分析碘酸根、碘离子、溴酸根和溴离子

建立了同时分析碘酸根、碘离子、溴酸根和溴离子的离子色谱-紫外检测分析方法。用季铵型阴离子交换柱,以柠檬酸-乙腈为流动相,采用紫外检测器实现了4种离子的同时分离和检测。研究了检测波长和流动相种类、浓度、pH值等因素对4种离子分离和测定的影响,探讨了保留规律,优化了色谱分析条件。在检测波长为210 nm、流动相为1.0 mmol/L柠檬酸-乙腈（85：15,v/v;pH 5.0）、流速为0.9 mL/min、柱温为40 ℃条件下,4种离子完全分离,且系统峰不干扰测定。4种离子的检出限（S/N=3）为0.07~0.16 mg/L,连续5次进样测定的峰面积和保留时间的相对标准偏差均在1%以下。将此方法用于离子液体样品及地下水样品的分析,结果准确、可靠。     

Voltammetric Sensing of Mercury and Copper Cations at Poly(EDTA‐like) Film Modified Electrode

Complexing polymer‐coated electrodes have been synthesized by oxidative electropolymerization of ethylenediamine tetra‐N‐(3‐pyrrole‐1‐yl)propylacetamide (monomer L ). The presence of four polymerizable pyrrole fragments on the same EDTA skeleton was thought to confer enhanced rigidity and controlled dimensionality to the resulting complexing materials, which were used for the electrochemical detection of Hg(II), Cu(II), Pb(II) and Cd(II) ions by means of the chemical preconcentration‐anodic stripping technique. The polyamide electrode material showed particularly a significant selectivity towards mercury ions, even in the presence of a large excess of other metal cations. Moreover, the use of imprinted polymer‐coated electrodes prepared by electropolymerization of L in the presence of metal cations turned out to significantly improve the detection limits, down to 5×10^?10 mol L^?1 for Hg(II) and Cu(II) species.     

Cloud point extraction and simultaneous spectrophotometric determination of V(V), Co(II) and Cu(II) ions in water samples by 5-Br-PADAP using partial least squares regression

In this work, a new method has been proposed to simultaneously determine V(V), Co(II) and Cu(II) ions from aqueous solution by spectrophotometry after cloud point extraction using partial least squares regression (PLS). The metal ions in 10 ml of aqueous solution (containing 0.2 M sodium acetate buffer solution, pH 3.5) were formed complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). Then, Triton X-114 (2 %, v/v) was added to the solution. By increasing the temperature of the solution up to 55 °C, a phase separation occurred. After centrifugation at 3,000 rpm for 10 min, the surfactant-rich phase was dissolved and diluted to 0.5 mL with ethanol. The metal ions were then determined using spectrophotometry. At these optimal extraction and operating conditions, linearity was obeyed in the range 7–300, 3–100 and 15–700 ng mL^?1 of V(V), Co(II) and Cu(II), with the detection limit of 2.2, 1.0 and 4.5 ng mL^?1, respectively. The relative predictive error for the simultaneous determination of 15 test samples of different concentrations of V(V), Co(II) and Cu(II) was 3.28, 3.64 and 4.04 %, respectively. The root mean square error of prediction for applying the PLS method to 15 synthetic samples in the linear ranges of these metal ions was 3.4, 1.6 and 18.1 ng mL^?1. The interference effect of some anions and cations was also tested. The proposed method has been applied successfully to the simultaneous determination of V(V), Co(II) and Cu(II) ions in real matrix samples with the recoveries of 96.75–104.80 %.     

Development of capillary electrophoresis for the determination of metal ions using mixed partial and complete complexation techniques

A new capillary electrophoretic (CE) method was developed for the selective and sensitive determination of common metal ions. The proposed method is based on conventional CE separation of metal cations followed by complete complexation of separated analytes with 1,10-phenanthroline using the zone-passing technique. This approach combines both partial and complete complexation modes and, thus, enables rapid, selective, efficient separation together with sensitive direct UV detection of metal species. The optimal conditions for the separation and derivatization reaction were established by varying type of electrolyte, electrolyte pH, introduction time and concentration of 1,10-phenanthroline. The optimized separations were carried out in 50 mmol l(-1) glycolic acid electrolyte (pH 6.0 with imidazole) using direct UV detection at 254 nm. Five common metal cations (Fe2+, Co2+, Ni2+, Cu2+ and Zn2+) were separated in less than 4 min. The proposed system was applied to the determination of Fe(II) and Zn(II) in snow samples. The recovery tests established for snow samples were within the range 100+/-12%.     

Spectrophotometric determination of vanadium(IV) with nitrilotriacetic acid

A new and convenient spectrophotometric method for the estimation of vanadium(IV) with NTA is described. The minimum ratio of metal ion to ligand, working pH, wavelength for maximum absorbance of the complex ion, and the effect of various cations and anions are described. The complex ion obeys Beer's law in the concentration range 1–32 mmol/liter of the vanadium(IV) ion. It is observed that iron(II), cobalt(II), nickel(II), copper(II), and oxidizing anions such as chromate and nitrite interfere in this determination, whereas managanese(II), chromium(III), iron(III), and anions like nitrate, chloride, bromide, iodide, thiocyanate, sulfate, and sulfite do not have any effect. Excessive amounts of acetate, phosphate, oxalate, tartrate and thiosulfate must also be avoided in this determination. Anions and cations which interfere in the determination of vanadium(IV) by NTA should not be present in the system.     

Determination of Sn(II) and Sn(IV) after mixed micelle-mediated cloud point extraction using alpha-polyoxometalate as a complexing agent by flame atomic absorption spectrometry

The cloud point extraction behavior of Sn(II) and Sn(IV) using alpha-polyoxometalate and mixed surfactants solution was investigated. The mixture of a nonionic surfactant (Triton X-100) and a cationic surfactant (CTAB) was utilized as a suitable micellar medium for preconcentration and extraction of tin complexes. Sn(II) in the presence of Sn(IV) was extracted with alpha-polyoxometalate, 0.3% (w/v) Triton X-100 and 3.5x10(-5) mol L(-1) CTAB at pH 1.2. Whereas the pH value of 3.7 were used for the individual determination of Sn(II) and Sn(IV) and also for total tin determination at the same conditions. Enrichment factors of 100 were obtained for the preconcentration of both metal ions. Under the optimal conditions, linearity was obeyed in the ranges of 55-670 microg L(-1) of Sn(II) and 46-750 microg L(-1) of Sn(IV) ion concentration. The detection limit of the method was also found to be 12.6 microg L(-1) for Sn(IV) and 8.4 microg L(-1) for Sn(II). The relative standard deviation of seven replicate determination of 100 microg L(-1) both metal ions were obtained about 2.4%. The diverse ion effect of some anions and cations on the extraction efficiency of target ions were tested. Finally, the optimized conditions developed were successfully utilized for the determination of each metal ion in various alloy, juice fruit, tape and waste water samples with satisfactory results.     

Square‐Wave Voltammetric Transfer of Silver Ions Across the Water|1,2‐Dichloroethane Interface

Recently reported studies on the transfer of silver ions across the aqueous|1,2‐dichloroethane interface using cyclic voltammetry (CV), facilitated by organic phase electrolyte anions, have been augmented by square‐wave voltammetry (SWV) and square‐wave stripping voltammetry (SWSV) studies and by consideration of the possible transfers of additional metal cations. Using SWV and SWSV, detection limits have been improved, from the 0.02 mM obtained by CV, to 1.4 μM (SWV) and 2 nM (SWSV). Additional studies show that mercury(I and II) ions, platinum(II) ions and gold(III) ions are also transferable across this interface, to differing extents. Of these three ions studied, highest sensitivity is achieved for the gold species.     

单一阴离子交换柱同时分离有机酸和无机阴阳离子

研究了用乙二胺四乙酸（ＥＤＴＡ）作淋洗液时，性质迥异的有机酸、无机阴离子和碱土金属离子（Ｃａ＾２＋、Ｍｇ＾２＋）在同一阴离子交换柱上的同时分离以及保留机理，结果表明，在离子交换机理之外，非离子交换机理对有机酸及钙镁的ＥＤＴＡ络阴郭的保留行为起一定的辅助作用，９种有机酸和无机阴阳离子在１０ｍｉｎ内得到了较好的分离。各离子的电导检测灵敏度在１０＾－９至１０＾－１１ｍｏｌ，能满足环境和食吕分析的要求。     

Ion exchange separation of strontium and rubidium on Dowex 50W-X8, using the complexation properties of EDTA and DCTA

A chromatographic method for separation of strontium from rubidium, using the unique alkaline-earth metal complexation ability of the carboxylic acids EDTA and DCTA is proposed. The method was developed in order to improve the effectiveness of (87)Sr/(86)Sr isotope studies with ICP-QMS. Due to the isobaric overlap of (87)Rb with (87)Sr, strontium needs to be separated from rubidium prior to sample analysis with ICP-QMS. The method involves the retention of strontium, calcium, magnesium, and rubidium on Dowex 50W-X8 resin in its NH(4)(+) form, followed by elution of the divalent cations as metal EDTA or DCTA complexes. Because divalent cations have different EDTA and DCTA complex formation constants, it is possible to separate them under the correct conditions. Neither EDTA nor DCTA form complexes with alkali metals, thus rubidium remains retained by the column and is later eluted using HNO(3). Both EDTA and DCTA elution methods were tested with different concentrations of the elements to determine the effect of increased concentration on separation efficiency. The EDTA elution procedure was proved to be effective in separating strontium from both calcium and rubidium, while the DCTA method was found to be even more effective, because strontium is separated from all the elements involved in this study.