On-column complexation of metal ions using 2,6-pyridinedicarboxylic acid and separation of their anionic complexes by capillary electrophoresis with direct UV detection

On-column complexation of metal ions with 2,6-pyridinedicarboxylate (2,6-PDC) to form anionic complexes enabled their separation by capillary zone electrophoresis with direct UV detection at 214 nm. Nine metal ions, Cu2+, Zn2+, Ni2+, Cd2+ Mn2+, Pb2+, Fe3+, Al3+ and Ca2+, were determined in less than 7 min using 10 mM 2.6-PDC solution containing 0.75 mM tetradecyltrimethylammonium bromide at pH 4.0. Satisfactory working ranges (20-300 microM), detection limits (3-10 microM) and good repeatability of the peak areas (RSD 2.1-4.2%, n=5) were obtained using hydrodynamic injection (30 s). The proposed method was used successfully for the determination of Mn2+, Fe3+, Al3+ and Ca2+ in groundwaters.     

低压离子分离-化学发光在线检测过渡金属离子

 研究了低压离子 (LPIC)分离 柱后鲁米诺化学发光 (CL)检测方法 ,并分离测定了Cu2 + ,Co2 + ,Cr3 + ,Fe2 + ,Mn2 + 等 5种过渡金属离子。以草酸 柠檬酸混合溶液作为洗脱液 ,Luminol H2 O2 Mn + 作为化学发光检测体系 ,对过渡金属离子进行在线检测。测定的线性范围分别为 (mg·L-1) :Co2 + ,0 0 0 1～ 0 .1;Cu2 + ,0 1～ 6 ;Mn2 + ,0 0 6～ 4 ;Fe2 + ,0 0 3～ 5 ;Cr3 + ,0 0 2 5～ 1。检测限分别为 (μg·L-1) :Co2 + ,0 85 ;Cu2 + ,85 ;Mn2 + ,4 2 ;Fe2 + ,2 1;Cr3 + ,2 0。     

High-voltage contactless conductivity detection of metal ions in capillary electrophoresis

The detection of alkali, alkaline earth and heavy metal ions with a high-voltage capacitively coupled contactless conductivity detector (HV-C(4)D) was investigated. Eight alkali, alkaline earth metal ions and ammonium could be separated in less than 4 min with detection limits in the order of 5 x 10(-8) M. The heavy metals Mn2+, Pb2+, Cd2+ Fe2+, Zn2+, Co2+, Cu2+ and Ni2+ could also be successfully resolved with a 10 mM 2-(N-morpholino)ethanesulfonic acid/DL-histidine (MES/His)-buffer. Zn2+, Co2+, Cu2+ and Ni2+ showed an indirect response. The detection limits for the heavy metals were determined to range from about 1 to 5 microM.     

2'-硼酸基苯甲醛-7-(8-羟基-5-磺酸基)喹啉腙衍生物的合成及对Pb2+的识别

合成了2', 3'和4'-硼酸基苯甲醛-7-(8-羟基-5-磺酸基)喹啉腙衍生物(化合物1~3), 研究了硼酸基团取代位置对主体分子识别金属离子客体性能的影响, 比较了不同主体分子与Pb2+结合能力的差异. 研究结果表明, 在pH=7.0的KH2PO4-NaOH缓冲溶液中, 3种腙衍生物对Pb2+均具有选择性识别作用, 主客体分子间形成1∶1型的发光配合物. 其中邻位取代的化合物1与Pb2+的结合能力比化合物2和3强, 配合物1-Pb2+的最大发射波长为477 nm, 稳定常数为1.1×103 L/mol. 其它金属离子如Cu2+, Mn2+, Mg2+, Fe2+, Ca2+, Co2+, Ni2+, Hg2+, Cd2+和Ag+ 等对主体分子荧光光谱的影响较小. 同时, 荧光强度的变化值与Pb2+浓度在0.36~10 μmol/L范围内呈现良好的线性关系, 相关系数R=0.9976(n=16), 检出限为0.23 μmol/L. 将此方法用于环境水样中Pb2+的测定, 回收率为92%~108%.     

Simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ by using second-derivative spectrophotometry method

A new method of simultaneous determination of Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ is proposed here by using the second-derivative spectrophotometry method. In pH=10.35 Borax-NaOH buffer, using meso-tetra (3-methoxyl-4-hydroxylphenyl) porphyrin ([T-(3-MO-4-HP)P]) as chromomeric reagent, micelle solution was formed after Tween-80 surfactant was added into the solution containing Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions. The original absorption spectrum of the above complexes was obtained after heating in the boiling water for 25 min. The second-derivative absorption peaks of five metal-porphyrin complexes can be separated from the original absorption spectrum by using chemometric tool. In this way, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ ions can be determined simultaneously. Under the optimal conditions, the linear ranges of the calibration curve were 0-0.60, 0-0.60, 0-0.40, 0-0.80 and 0-0.48 μg mL(-1) for Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+, respectively. The molar absorptivity of these color systems were 1.38×10(5), 1.01×10(5), 3.24×10(5), 1.07×10(5) and 1.29×10(5)Lmol(-1)cm(-1). The method developed in this paper has advantages in selectivity, sensitivity, operation and can effectively resolve spectra overlapping problem. This method has been applied to determine the real samples with satisfactory results.     

High-resolution determination of H+ by ion chromatography. Application to the simultaneous determination of H+, Na+, NH4+ and K+ in acid rain.

An ion chromatographic (IC) method was developed for the high-resolution determination of a sample's free hydrogen ion concentration (H+). Highly purified lithium dodecyl sulfate was used as the stationary phase, a slightly acidified aqueous LiCl solution was used as the mobile phase and conductivity was used for analyte detection. An electrical double layer (EDL) containing H+ was established on the stationary phase by using a slightly acidified electrolyte solution as the eluent. H+ in the EDL protonated any weak acid groups (i.e., silanols) on the stationary phase so that H+ from the sample could be retained/separated purely by dodecyl sulfate. The optimum molar ratio of H+:Li+ in the EDL for this IC system was obtained by using an aqueous solution containing 40.0 mM LiCl and 0.07 mM H2SO4 as the eluent. After separation, H+ was detected by direct conductimetric measurement. An H+ detection limit of better than 8.2 x 10(-6) M was obtained from the analysis of standard aqueous H2SO4 solutions. Other monovalent cations could also be separated with this method, giving detection limits of 7.4 x 10(-5), 4.3 x 10(-5) and 4.2 x 10(-5) M for Na+, NH4+ and K+, respectively. The method was applied to the simultaneous determination of H+, Na+, NH4+ and K+ in acid rain. The results obtained showed a significant improvement in reproducibility when compared with those from a conventional pH-meter. Acid rain samples with a pH < 5 could be analyzed with this IC system.     

Beta-silyl-substituted silaadamantyl,silabicyclo[2.2.2]octyl,silanorbornyl, and 1-silacyclohexyl cations. A theoretical (DFT and GIAO NMR) study

Parent 1-silaadamant-1-yl (1+) and a series of mono-beta-silyl-substituted- (2-Me+, 2-F+, 2-Cl+, 2-Br+), bis-beta-silyl-substituted- (3-Me+), and tris-beta-silyl-substituted (4-Me+)-1-silaadamant-1-yl cations were studied by the DFT method at the B3LYP/6-31G(d,p) level and by GIAO NMR at the B3LYP/ 6-31G(d,p)//B3LYP/6-31G(d,p) level. The geometries, relative energies, NMR chemical shifts, and charge distribution in the bridgehead silylium ions are discussed and compared. The magnitude of the beta-silyl effect (the Si-C-Si+ hyperconjugation) is gauged as a function of structure. Related model studies on the silabicyclo[2.2.2]octyl (5+, 6+, 5a+, and 6a+), silanorbornyl (7+ and 8+), and silacyclohexyl cations (9+ and 10+) were carried out in which the effect of beta-silyl substitution on geometry, stability, and NMR chemical shifts was probed. The acyclic model Me3Si-CH2-Si+(Me)2 (11+) was used to gauge the influence of the twist angle between the p-orbital at Si+ and the C-Si bond on relative stability and on the changes in the 29Si NMR chemical shifts. Finally, interaction of 1+ with H2O and MeOH and 2-Me+ with H2O was also examined. The resulting optimized structures (12+, 13+, and 14+) and the computed NMR chemical shifts are most compatible with the formation of silaoxonium ions.     

Use of miniaturised isotachophoresis on a planar polymer chip to analyse transition metal ions in solutions from metal processing plants

An electrolyte system, using malic acid as a complexing agent, has been developed to allow the determination of transition metal cations using miniaturised isotachophoresis. The method allowed the simultaneous determination of Mn2+, Cr3+, Fe2+, Co2+, Zn2+ and Ni2+ to be made without interference from other common ions. Limits of detection were calculated to be in the range 0.5-1.0mg l(-1) for Mn2+, Cr3+ Co2+ and Zn2+ and 2.0 mg l(-1) for Fe2+ and 4.7 mg l(-1) for Ni2+. The successful analysis of five industrial samples, containing a range of these metal ions, obtained from metal processing plants were achieved in under 13 min. The separations were performed on a poly(methyl methacrylate) chip with integrated platinum wire conductivity detection electrodes.     

Preparation of a fast-flow agarose-based chelating adsorbent with a novel dioxime derivative for selective column preconcentration of copper.

Fast-flow spherical homogeneous agarose beads were prepared by an emulsification method, and were cross-linked and activated by repeated treatment with allylbromide and bromine/water, followed by alkali. Bis(2-aminopyridyl)dioxime (APD) was synthesized by the reaction of 2-aminopyridine, and dichloroglyoxime and characterized by melting-point as well as IR, 1HNMR, 13CNMR and MS spectroscopies. APD was chemically linked to activated agarose beads to be employed for the column preconcentration of metal ions. Capacity measurements for eight metal ions indicated a high selectivity of the adsorbent towards Cu2+ with a capacity of 25.7 micromol per ml packed adsorbent. A factorial design was used for optimization of the effects of 5 different variables on the recovery of Cu2+. Under the optimized conditions, Cu2+ was quantitatively accumulated on a 0.25 ml packed column of the adsorbent in the pH range of 4 to 6, and simply eluted with 2 ml of a 1 mol 1(-1) hydrochloric acid solution. The column could tolerate salt concentrations up to 0.5 mol 1(-1), sample flow rates up to 15 ml min(-1), and sample volumes beyond 1000 ml. Matrix ions of Na+, Mg2+ and Ca2+ and potentially interfering ions of Ni2+, Cd2+, Zn2+, Fe3+ and Co2+ with relatively high concentrations did not show any significant effect on the analyte's signal. Preconcentration factors up to 500 and a detection limit of 0.16 microg 1(-1) were obtained for the determination of the analyte by flame AAS. Application of the method to the determination of natural and spiked copper in river water and seawater samples resulted in quantitative recoveries.     

Cu2+ colorimetric sensing and fluorescence enhancement and Hg2+ fluorescence diminution in "scorpionate"-like tetrathienyl-substituted boron-dipyrrins

Four novel tetrathienyl-substituted boron-dipyrrin-type (BODIPY-type) complexes, 3-(R')-4,4-di(R')-8-R-4-bora-3a,4a-diaza-s-indacene (4a, R = 2-T, R' = 2-T; 4b, R = 3-T, R' = 2-T; 5a, R = 2-T, R' = 3-T; 5b, R = 3-T, R' = 3-T; T = thienyl) have been prepared and fully characterized to explore patterns of stoichiometric Mn+ recognition in solution. Treatment of the respective parent BF2 dipyrrin with 2- or 3-thienyllithium gave the unexpected asymmetric tetrathienyl-substituted products in 8.5-35% yield. Compounds 4a and 4b bear a neutral "scorpionate"-like [SSS] tridentate binding pocket. Extensive NMR and UV-vis spectroscopic studies were performed on 4a-5b; 5a, 4b, and 5b were structurally characterized. The PhiF values for 4a-5b all decrease compared to the BF2-containing parent molecules (0.00058, 0.012, 0.00090, and 0.0051, respectively), with lambda(abs,max) values (epsilon, M(-1) cm(-1)) of 563 (44,000), 553 (29,000), 539 (33,000), and 531 (44,000) nm, respectively, and Stokes' shifts of 25-36 nm. Upon treatment with metal ion (Ca2+, Cs+, Mn2+, Co2+, Cu2+, Ag+, Zn2+, Cd2+, Hg2+, Pb2+) perchlorate salts, the solution of 4b undergoes rapid pink-to-clear switch-off behavior upon Cu2+ addition (10 microM scale) with smaller effects seen for 4a. Further, there were 2- to 19-fold Cu2+ fluorescence enhancements for these ligands. Cu2+- and Hg2+-L (L = 4a-5b) binding was modeled, and response patterns for Mn+-L 1:1 molar solutions upon Cu2+ addition were measured. Upon treatment with Hg2+, all ligand solutions show a significant fluorescence decrease accompanied by minor absorption increases. The UV-vis spectroscopic detection limit for Cu2+ and Hg2+ is approximately 270 ppb and approximately 1.7 ppm, respectively; the naked eye detection limit for Cu2+ with 4b (1.0 x 10(-5) M) is approximately 23 microM. DFT calculations gave HOMO-LUMO gaps of 478 (4a), 462 (4b), 448 (5a), and 442 nm (5b). Molecular orbital diagrams for 4a-5b revealed that the HOMO and LUMO electron density is distributed onto the 3-position-thienyl group and to a lesser degree the B(thienyl)2 moiety.     

Monolithic octadecylsilyl-silica gel column for the high-speed ion chromatographic determination of acidity

A monolithic ODS-silica gel column modified by saturating it with lithium dodecylsulfate (Li-DS) was used to demonstrate the high-speed separation of H+ from other mono- and divalent cations, such as Na+, NH4+, K+, Mg2+ and Ca2+ using ion chromatography (IC). Using a 5 mM EDTA-2K solution containing 0.10 mM Li-DS (pH 4.80) as eluent, H+ was eluted with a sharp and symmetrical peak within 1.0 min before other cations at a flow-rate of 1.5 ml min(-1). The rapid elution of H+ and its conductimetric detection could be attributed to the presence of EDTA (HY2-), which can convert H+ ions as anions. i.e. H(+) + H2Y(2-) --> H3Y(-). The acidity of rainwater and deionized water samples was determined using this IC system with satisfactory results.     

Novel chiral N4S2- and N6S3-donor macrocyclic ligands: synthesis,protonation constants,metal-ion binding and asymmetric catalysis in the Henry reaction

New hydrophobic chiral macrocyclic ligands L1-L3 with chiral diamino and thiophene moieties have been synthesized by the Schiff base condensation approach. Protonation constants of L1 and L2 were determined by potentiometry titration. Metal-ion binding experiments exhibited that L1 and L3 are pronounced in selective recognition, Ag+, Cu2+ and Ca2+ ions among the surveyed metal ions (Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+, Ag+, Li+, Na+, K+, and Ca2+). L1 was found to spectroscopically detect the presence of Cu2+ and Ca2+ to function as a multiple readout sensor. The detection limit for Ca2+ ions was found to be 9.8 x 10(-5) M in CH2Cl2-MeOH solution. The trimeric chiral ligand L3 has been shown to be an efficient auxiliary in a Zn(II)-mediated enantioselective Henry reaction.     

Interferences removal for cadmium determination in samples with complex matrices by hydride generation coupled with non-dispersive atomic fluorescence spectrometry.

An intermittent on-line concentration and separation system coupled with HG-AFS was developed to eliminate serious interferences from Cu2+, Pb2+ and Zn2+ on the determination of cadmium. In the present method, the interferences from common coexisting ions, such as Cu2+, Pb2+, Zn2+, Fe3+ and Ni2+, were greatly reduced. Under the optimized conditions, a detection limit of 3 pg ml(-1) (3sigma, n=11) and a precision of 1.9% RSD for 1 ng ml(-1) of Cd were obtained. The method was successfully applied to the determination of cadmium in a series of Chinese Geological Reference Materials (SRMs) and GBW01621 ferronickel alloy using simple aqueous standard calibration technique. The results obtained were in good agreement with the certified values.     

Simultaneous preconcentration of copper, nickel, cobalt and lead ions prior to their flame atomic absorption spectrometric determination

A sensitive and simple method for the simultaneous preconcentration of nutritionally important minerals in real samples has been reported. The method is based on the adsorption of Cu2+, Ni2+, Co2+ and Pb2+ on 4-propyl-2-thiouracil (PUT) loaded on activated carbon. The metals on the complexes are eluted using 5 mL 3 M HNO3 in acetone. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally higher than 95%. The detection limits for Cu2+, Ni2+, Co2+ and Pb2+ were 1.6, 1.3, 1.2, 2.3 ng ml(-1), respectively. The method has been successfully applied for these metals content evaluation in some real samples including natural water samples.     

A novel 5-mercapto triazole Schiff base as a selective chromogenic chemosensor for Cu2+

A novel colorimetric cation sensor bearing phenol, thiol and HCN groups was designed and synthesized. In a DMSO/H2O (9:1, v/v) solution, the sensor exhibited highly selective recognition of Cu2+ among a range of metal ions tested. In the presence of Cu2+, solutions of the sensor underwent a dramatic color change from colorless to yellow, while the presence of other metal cations such as Zn2+, Pb2+, Cd2+, Ni2+, Co2+, Fe3+, Hg2+, Ag+ and Ca2+ had no effect on the color. The detection limit of the sensor toward Cu2+ is 8.0×10(-7) M and an association constant Ka of 4.3×10(5) M(-1) was measured. The sensing of Cu2+ by this sensor was found to be reversible, with the Cu2+-induced color being lost upon addition of EDTA.     

Second chemiluminescence behavior of Fe2+, Fe3+ and Cr3+ in the luminal-KMnO4 system.

A novel flow injection chemiluminescence (CL) method has been developed for the determination of three metal ions, namely Fe2+, Fe3+ and Cr3+, based on the second CL (SCL) signal of the mixture of luminal with KMnO4 in a sodium hydroxide medium by the catalysis of Fe2+, Fe3+ or Cr3+. The possible CL mechanism of the systems, the influencing factors, and the optimum conditions for the reactions were investigated based upon the kinetic curve of the CL reaction, CL spectra, UV-visible spectra and some other experiments. Under the optimum conditions, the SCL intensity was directly proportional to the concentration of these metal ions in solution in the range of 0.10 - 100.00 mg l(-1) for Fe(2+), 0.50 - 7.50 and 7.50 - 200.00 mg l(-1) for Fe3+, 0.01 - 0.25 and 0.25 - 10.00 mg l(-1) for Cr3+. The detection limits (3 sigma/s) were 9.87 x 10(-6) g l(-1), 2.71 x 10(-6) g l(-1) and 5.25 x 10(-7) g l(-1) for Fe2+, Fe3+ and Cr3+, respectively.     

A novel wire-type lead-selective electrode based on bis (1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine

The preparation of a lead-selective electrode based on bis(1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine (L) as sensing material is reported. The plasticized PVC membrane containing 30% PVC, 67% ortho-nitrophenyloctylether (NPOE) and 3% ionophore L was directly coated on a graphite rod. This electrode exhibits a nearly Nernstian slope of 27.8+/-0.2 mV decade(-1) over a concentration range 10(-6)-10(-2) M with a detection limit of 4.0 x 10(-7) M. The response time of the electrode was found to be <20 s. The potential of the sensor was independent on pH variations in the range 5-7. The selectivity of the electrode towards lead ions over Na+, K+, Ag+, Ca2+, Sr2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, La3+, Sm3+ and Er3+ ions was investigated. The prepared electrode was successfully used as an indicator for titration of a lead solution with a standard solution of EDTA. The applicability of the sensor for Pb2+ measurement in various synthetic and real samples has been also demonstrated.     

Simultaneous ion-exclusion chromatography and cation-exchange chromatography of anions and cations in environmental water samples on a weakly acidic cation-exchange resin by elution with pyridine-2,6-dicarboxylic acid

A non-suppressed conductivity detection ion chromatographic method using a weakly acidic cation-exchange column (Tosoh TSKgel OApak-A) was developed for the simultaneous separation and determination of common inorganic anions (Cl-, NO3- and SO4(2-)) and cations (Na+, NH4+, K+, Mg2+ and Ca2+). A satisfactory separation of these anions and cations on the weakly acidic cation-exchange column was achieved in 25 min by elution with a mixture of 1.6 mmol L-1 pyridine-2,6-dicarboxylic acid and 8.0 mmol L-1 18-crown-6 at flow rate of 1.0 mL min-1. On this weakly acidic cation-exchange resin, anions were retained by an ion-exclusion mechanism and cations by a cation-exchange mechanism. The linear range of the peak area calibration curves for all analytes were up to two orders of magnitude. The detection limits calculated at S/N = 3 ranged from 0.25 to 1.9 mumol L-1 for anions and cations. The ion-exclusion chromatography-cation-exchange chromatography method developed in this work was successfully applied to the simultaneous determination of major inorganic anions and cations in rainwater, tap water and snow water samples.     

Progress in developing polymerized crystalline colloidal array sensors for point-of-care detection of myocardial ischemia

The difficulty of rapid, definitive diagnosis of myocardial ischemia leads to unnecessary hospital admissions and treatment delays. Previously, decreased metal binding affinity in human serum was investigated as a marker for myocardial ischemia. Polymerized Crystalline Colloidal Array (PCCA) sensors for Ni2+ may be useful in developing a point-of-care test to determine metal binding affinity in plasma and to help rule out myocardial ischemia. PCCA sensors for Ni2+, with 5-amino-8-hydroxyquinoline as a chelating agent, were tested in aqueous solutions and diluted human plasma. The peak wavelength diffracted by the sensors was monitored by reflectance spectrometry and correlated with Ni2+ concentration. The PCCA sensors show a linear response to aqueous Ni2+ concentrations between 0.2 and 1.0 mmol L(-1), and can detect changes in free Ni2+ concentration of <60 micromol L(-1). The sensors respond at physiologic pH and can be reversibly dehydrated. The PCCA sensors developed here can report on free Ni2+ concentration in the presence of human plasma. These sensors can be used to detect a decrease in the Ni2+ affinity of plasma proteins, which may indicate recent myocardial ischemia. PCCA sensors offer a practical approach to rapid, point-of-care detection of a proposed biochemical signature of myocardial ischemia.     

"Naked-eye" detection of histidine by regulation of Cu(II) coordination modes

The association of various alpha-amino acids with four new, coordinatively unsaturated metal complexes ([Cu(5)]2+, [Cu(6)]2+, [Cu(7)]2+, and [Zn(8)]2+) was examined. The receptors [Cu(5)]2+ and [Cu(7)]2+ were found to discriminate histidine (His) from other zwitterionic alpha-amino acids by means of indicator-displacement assays (IDAs) using 5(6)-carboxyfluorescein as an indicator in buffered methanol/water (3:1) solvent. The colorimetric detection of His was achieved by using this IDA method, which appears to owe its selectivity to a unique process involving disruption of the host complex to form a 2:1 His/Cu(II) complex rather than simple indicator displacement. The occurrence of distinct intermolecular coordination processes in response to the introduction of a different amino acid is observed. X-ray crystal structures of the host metal complexes were obtained and exhibit the adoption of a variety of coordination geometries about the metal center.