Determination of trace lead, cadmium and mercury by on-line column enrichment followed by RP-HPLC as metal-tetra-(4-bromophenyl)-porphyrin chelates

This paper reports the utilization of tetra-(4-bromophenyl)-porphyrin (T(4)BPP) as a chelating reagent using Waters Xterratrade mark RP(18) column for the on-line column enrichment and the separation of trace lead, cadmium and mercury ions by reversed-phase high-performance liquid chromatography (RP-HPLC) with photodiode array detector. When the Hg-T(4)BPP, Pb-T(4)BPP and Cd-T(4)BPP chelates were injected into the injector and sent to the enrichment column with 0.05 mol l(-1) of pH 10.0 pyrrolidine-phosphoric acid buffer solution (containing 10% of tetrahydrofuran (THF)) as mobile phase. The chelates were retained on the top of the enrichment column. After the enrichment is finished, by switching the valve of six-ports switching valve, the retained metal-T(4)BPP chelates will be eluted by mobile phase in reverse direction and will travel towards analytical column. With THF (containing 0.05 mol l(-1), pH 10.0 pyrrolidine-phosphoric acid buffer salt) and 0.05 mol l(-1), pH 10.0 pyrrolidine-phosphoric acid buffer solution (containinging 10% THF) gradient elution as mobile phase, the chelates separation on the analytical column was satisfactory. The linearity ranges are 0.01-120 mug l(-1) for each metal ion. The detection limits (S/N=3) of lead, cadmium and mercury are 1.0, 0.5 and 1.0 ng l(-1), respectively. This method can be applied to the determination (mug l(-1)) level of lead, cadmium and mercury in drinking water with satisfactory results.     

Determination of lead, cadmium and mercury in microwave-digested foodstuffs by RP-HPLC with an on-line enrichment technique.

A new method for the simultaneous determination of lead, cadmium and mercury ions in microwave-digested foodstuffs by reversed-phase high-performance liquid chromatography combined with on-line enrichment technique has been developed. The foodstuff samples were digested by microwave digestion. The lead, cadmium and mercury ions can be precolumn derivatized with 5,10,15,20-tetrakis(3-aminophenyl)porphine (T3APP) to form color chelates; then, the Hg-T3APP, Cd-T3APP and Pb-T3APP chelates can be enriched and separated on a valve switching HPLC system combined with on-line enrichment technique. The linearity ranges are 0.01-120 microg/l for each metal ion. The detection limits (S/N = 3) of lead, cadmium and mercury are 1.2 ng/l, 0.5 ng/l and 0.8 ng/l, respectively. This method was applied to the determination of lead, cadmium and mercury in foodstuffs with good results.     

Determination of Lead, Cadmium, and Mercury by On-Line Enrichment Followed by RP-HPLC

A new method for the simultaneous determination of lead, cadmium, and mercury ions as metal tetra-(4-chlorophenyl)-porphyrin (T₄CPP) chelates was developed using reversed-phase-high performance liquid chromatography (RP-HPLC) and combined with on-line enrichment technique. When the Hg-T₄CPP, Pb-T₄CPP, and Cd-T₄CPP chelates were injected into the injector and sent to the enrichment column with 0.05 mol/L of pH = 10 pyrrolidine-acetic acid buffer solutions (containing 10% of THF) as mobile phase, they were absorbed onto the tip of the enrichment column. By switching the six ports switching valve, the retained chelates can be back-flushed by mobile phase and travel towards the analytical column. With 0.05 mol/L of pH = 10 pyrrolidine-acetic acid buffer solution (containing 10% of THF) and tetrahydrofuran (THF) (containing 0.05 mol/L pH = 10.0 pyrrolidine-acetic acid buffer salt) gradient elution as mobile phase, the separation of chelates on the analytical column was satisfactory. The linearity ranges are 0.01 ± 120 g/L for each metal chelate. The detection limits (S/N = 3) of lead, cadmium, and mercury are 2.0, 1.5, and 2.0 ng/L, respectively. This method was applied to the determination of the g/L level of lead, cadmium, and mercury ions in a water sample with good results.     

Simultaneous determination of four heavy metal ions in tobacco and tobacco additive by online enrichment followed by RP-HPLC and microwave digestion

A new method for the simultaneous determination of tin, lead, cadmium, and mercury in tobacco and tobacco additive by reversed-phase high-performance liquid chromatography combined with microwave digestion and an online enrichment technique is developed. The tin, lead, cadmium, and mercury ions are precolumn derivatized with tetra-(4-dimethylaminophenyl)-porphyrin (T(4)-DMAPP) to form color chelates. The Sn-T(4)-DMAPP, Hg-T(4)-DMAPP, Cd-T(4)-DMAPP, and Pb-T(4)-DMAPP chelates are absorbed onto the front of the enrichment column using a buffer solution of 0.05 mol/L pyrrolidine-acetic acid (pH = 10.0) as the mobile phase. After the concentration is finished (by switching the six-port switching valve) the retained chelates are back-flushed by the mobile phase and move to the analytical column. The chelate separation on the analytical column is satisfactory using gradient elution with methanol (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0) and tetrahydrofuran (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0). The linearity range is 0.01-120 micro g/L for each metal ion. The detection limits (S/N = 3) of tin, lead, cadmium, and mercury are 0.6, 0.8, 0.5, and 0.6 ng/L, respectively. This method is applied to the determination of tin, lead, cadmium, and mercury in tobacco and it's additive with good results.     

Simultaneous Determination of Tin,Nickel, Lead,Cadmium and Mercury in Tobacco and Tobacco Additives by Microwave Digestion and RP‐HPLC Followed by On‐Line Column Enrichment

A new method for the simultaneous determination of five heavy metal ions, tin, nickel, lead, cadmium and mercury ions as metal‐tetra‐(2‐aminophenyl)‐porphyrin (T₂APP) chelates was developed using reversed‐phase high performance liquid chromatography (RP‐HPLC) equipped with a photodiode array detector and combined with an on‐line enrichment technique. The tin, nickel, lead, cadmium and mercury ions were pre‐column derivatized with T₂APP to form color chelates. The Sn‐T₂APP, Ni‐T₂APP, Hg‐T₂APP, Cd‐T₂‐APP and Pb‐T₂APP chelates can be absorbed onto the front of the enrichment column when they are injected into the injector and sent to the enrichment column [Waters Xterra? RP₁₈(5μ, 3.9 × 20 mm)] with a buffer solution of 0.05 mol/L pyrrolidine‐acetic acid (pH = 10.0) as mobile phase. After the enrichment had finished, by switching the six‐port switching valves, the retained chelates were back‐flushed by mobile phase and traveling towards the analytical column. These chelates separation on the analytical column [Waters Xterra? RP₁₈ (5μ, 3.9 × 150 mm)] was satisfactory by gradient elution with methanol (containing 0.05 mol/L pyrrolidine‐acetic acid buffer salt, pH = 10.0) and acetone (containing 0.05 mol/L pyrrolidine‐acetic acid buffer salt, pH = 10.0) as mobile phase. The linearity range is 0.01?120 μg/L for each metal ion. The detection limits (S/N = 3) of tin, nickel, lead, cadmium and mercury are 4.0 ng/L, 3.5 ng/L, 2.5 ng/L, 3.0 ng/L and 3.0 ng/L, respectively. This method was applied to the determination of tin, nickel, lead, cadmium and mercury ions in tobacco and tobacco additives with good results.     

Determination of copper,nickel, cobalt,silver, lead,cadmium, and mercury ions in water by solid-phase extraction and the RP-HPLC with UV-Vis detection

A new method for the simultaneous determination of seven heavy metal ions in water by solid-phase extraction and reversed-phase high-performance liquid chromatography (RP-HPLC) was developed. The copper, nickel, cobalt, silver, lead, cadmium, and mercury ions were pre-column derivatized with tetra( m-aminophenyl)porphyrin (T m-APP) to form colored chelates. The metal-T m-APP chelates in 100 mL of sample were preconcentrated to 1 mL by solid-phase extraction with a C(18 )cartridge; an enrichment factor of 100 was achieved. The chelates were separated on a Waters Xterra()RP(18) column by gradient elution with methanol (containing 0.05 mol L(-1) pyrrolidine-acetic acid buffer salt, pH 10.0) and acetone (containing 0.05 mol L(-1) pyrrolidine-acetic acid buffer salt, pH 10.0) as mobile phase at a flow rate of 1.0 mL min(-1) and detected with a photodiode array detector. The detection limits of copper, cobalt, nickel, silver, lead, cadmium, and mercury are 2, 2, 3, 4, 3, 3, and 3 ng L(-1), respectively, in the original sample. The method was also applied to the determination of these metals in water with good results.     

Metallverbindungen Meso-alkylsubstituierter Thio-β-diketone

By Claisen type condensation of suitable ketones with dithiocarbonic esters meso-alkyl substituted thio-β-diketones were prepared and studied in their sensitivity towards metal ions. Real metal chelates could be obtained only with cobalt(III) and nickel(II). The compounds of lead(II), cadmium(II), zinc(II), copper(I), mercury(II), silver(I), palladium(II), platinum(II) and rhodium(III) show an unchelated carbonyl group in the IR spectrum and are therefore interpreted as mercaptides. From the IR spectra it is also concluded that the free ligands are predominantly existing in the enethiolic tautomeric form. The absence of visible absorption bands characteristic for usual thio-β-diketones and their metal chelates in the case of the meso-substituted derivates is discussed as a consequence of distortion of the molecule accompanied by a decrease of conjugation.     

Chelate von β-dicarbonylverbindungen und ihren derivaten: Teil XLVII. Dünnschichtchromatographisches verhalten von metallchelaten mit thiodibenzoylmethan und acetylthioacetaniliden

The thin-layer chromatographic behaviour of thiodibenzoylmethane chelates with cobalt(III), zinc(II), mercury(II), palladium(II), platinum(II) and rhodium(III), and also of acetylthioacetanilide chelates with cobalt(III), nickel(II), zinc(II) and cadmium(II) on alumina is described. Different binary mixtures of eluents are used. The influence of solvent parameters and of the layer material, possible separations and the influence of substituents in the acetylthioacetanilides are discussed.     

Reversed-phase partition high-pressure liquid chromatography of trace amounts of inorganic and organic mercury with silver diethyldithiocarbamate

Inorganic and organic mercury diethyldithiocarbamates have been separated by reversedphase partition high-pressure liquid chromatography. The mercury chelates were formed by an exchange reaction with silver diethyldithiocarbamate in chloroform, in the presence of acetate buffer (pH 5.0). The inorganic and organic mercury chelates in the extract were separated within 30 min on a 3.9 x 300 mm mu-Bondapak C(18) column. EDTA (10(-4)M) in methanol-water mixture (78:22 v v ) was used as eluent at a flow-rate of 0.5 ml min .     

Fluorescence polarization immunoassays for metal ions

Antibodies raised against a given metal ion complex of a polyaminopolycarboxylate chelating agent can display specificity for the immunizing chelate and, when used in conjunction with a fluorophore-labeled analog of that chelate, can form the basis for highly sensitive and specific methods for detecting that metal ion by competitive inhibition fluorescence polarization immunoassay (FPIA). Chelate complexes of ethylenediamine-N,N,N',N'- tetraacetic acid (EDTA) and of a hetrocyclic ring-substituted derivative of diethylenetriamine-N, N', N"-triacetic acid (DTTA) have been used to configure such assays for the heavy metal ions lead(II) and cadmium(II) respectively. Limits of detection for the 1:1 metal chelates under ideal conditions are 20 ppt for lead(II) and below 100 ppt for cadmium(II). Standard curves for 0 - 100 nM cadmium (II) chelate can be constructed in the presence of fixed 250 nM concentrations of the corresponding, potentially cross-reactive chelates of zinc(II), copper(II) and mercury(II). Cross-reactivity of the lead (II) FPIA with 15 non-target metals is below 0.2% in all cases except for mercury(II) (0.37%). These characteristics have allowed the development of FPIA methods for the quantitative analysis of lead in a variety of samples relevant to environmental monitoring, including soil, dust, solid wastes and drinking water. Although applied thus far to heavy metals that are of concern as toxic contaminants in the environment, anti-chelate FPIA methods are also in principle applicable to a wide variety of other metal ions, including precious metals and various transition and main group elements used or monitored in a range of industrial applications. As conventional methods for trace metal analysis based on atomic spectroscopy are relatively slow, expensive and cumbersome, anti-chelate FPIA methods have the potential to supplant many existing techniques and in so doing extend the use of immunoassay technology beyond the biomedical, veterinary and agricultural spheres in which it has historically found use.     

Solution behaviour in alcohols and phase transitions of cadmium(II), mercury(II) and lead(II) carboxylates

Data were obtained for the solution behaviour of cadmium(II) and mercury(II) carboxylates in alcohols. A brief survey of the arguments about the existence of micelles and the current models of surfactant aggregation in non-aqueous media is presented. The plots of solubility against the carboxylate or alcohol chain length are linear for both cadmium and mercury soaps with the solubility having values higher in secondary than primary alcohols. The solution behaviour of metal 9, 10-dihydroxyoctadecanoates shows the effect on solubility, of substitution of dihydroxyl groups at the middle of the carbon chain. Recrystallisation temperatures of the dihydroxyoctadecanoates suggest the loss of stereochemical configuration in solution and indicate similarity in the mode of aggregation. The solution temperatures of cadmium soaps are very close to the temperatures of their phase transitions while those of mercury and lead soaps are lower than their fusion or phase transition temperatures. This behaviour is interpreted to be due to differences in the energy required for the disruption of the crystal structure which dominates the solubility mechanism.     

Anodic stripping voltammetry at a nickel-based mercury film electrode

The electrochemical properties of the nickel-based mercury film electrode (Ni-MFE) were investigated with respect to application of the electrode in the anodic stripping voltammetry (a.s.v.) of heavy metal ions. The hydrogen overpotential at the Ni-MFE is higher than those at MFEs based on other metals, and high enough to get quantitative a.s.v. peaks of lead and cadmium. The mercury film of the Ni-MFE is stable both mechanically and chemically; a.s.v. peaks at a Ni-MFE which had been used fifty times within 300 h after its preparation were identical with those at the freshly prepared electrode. With the Ni-MFE, 5 × 10^?10–10^?7 M lead(II) and 2 × 10^?10–10^?7 M cadmium(II) in the solution can be determined with relative standard deviations of 11 and 12%, respectively. These results are comparable to those obtained by a.s.v. at an in situ mercury-plated g]assy carbon electrode.     

Preparation of Amberlite XAD resins coated with dithiosemicarbazone compounds and preconcentration of some metal ions

The Amberlite XAD resins coated with dithiosemicarbazones were prepared and their collection behavior of metal ions from aqueous solution was investigated. Among the resins used, the reagent-loaded Amberlite XAD-7 was found to be superior for the collection of metal ions to other reagent-loaded resins used. The quantitative collection of mercury(II), palladium(II) and copper(II) was obtained from acidic medium, while cadmium(II) and lead(II) was obtained from neutral medium by the Amberlite XAD-7 resin coated with dimethylglyoxal bis(4-phenyl-3-thiosemicarbazone) (DMBS). These metal ions collected on the resin were easily eluted with a small volume of N,N-dimethylformamide as their DMBS chelates. This collection-elution method was applied to the determination of their metal ions by reversed-phase high performance liquid chromatography with a spectrophotometric detection.     

Reversed-phase ion-pair partition liquid chromatography of chelates with 2-(3,5-dibromo-2-pyridylazo)-5-[N-ethyl-N-(3-sulphopropyl) amino] phenol and analogues

The ion-pair reversed-phase chromatography of some transition metal chelates with 2-(3,5-dibromo-2-pyridylazo)-5-[N-ethyl-N-(3-sulphopropyl)amino]phenol (3,5-diBr-PAESPAP) was studied. 3,5-DiBr-PAESPAP and its V(V), Cr(III), Fe(II), Co(III) and Ni(II) chelates were retained on and the copper (II), zinc(II) and cadmium(II) chelates dissociated in an ODS column using acetonitrile/water (37+63, v/v) (pH 7.0) containing 0.01 M acetate, 0.01 M 3-(N-morpholino)propanesulphonate buffer (pH 7.0) and 0.05 M Na⁺ as mobile phase. The chromatograms of 3,5-diBr-PAESPAP chelates were compared with those of the chelates with 2-(3,5-dibromo- 2-pyridylazo)-5-[N-(3-sulphopropyl)amino]phenol (3,5-diBr-PASPAP),2-(5-bromo-2- pyridylazo)-5-[N-(3-sulphopropyl)amino]phenol and 2-(5-bromo-2-pyridylazo)-5-[N-propyl-N- (3-sulphopropyl)amino] phenol. With 3,5-diBr-PAESPAP the Fe(II) and Ni(II) chelates were not resolved, but resolution was achieved with 3,5-diBr-PASPAP. The calibration graphs were linear over the ranges 2.0–10.0 ng (10-μl injection) of Fe, Ni and Co and for 20–100 ng (10-μl injection) for V with 3,5-diBr-PAESPAP and 3,5-diBr-PASPAP.     

Voltammetric analysis using a self-renewable non-mercury electrode

Galinstan is a new kind of electrode material and the galinstan electrode is a promising alternative to the commonly used mercury electrodes. The eutectic mixture of gallium, indium and tin is liquid at room temperature (m.p. −19°C) and its voltammetric behaviour is similar to that of mercury. The potential windows of use were determined for different pH values and are similar to those obtained with conventional mercury electrodes. Furthermore, the high hydrogen overpotential, which is characteristic for mercury, can be observed when galinstan is used as electrode material. Galinstan can be employed as a liquid electrode in the voltammetric analysis of different metal ions, such as lead and cadmium, in different supporting electrolytes. Our results indicate that the non-toxic liquid alloy galinstan could therefore become immensely important in electrochemical research as a potential surrogate material for mercury.     

Study on the Determination of Heavy-Metal Ions in Tobacco and Tobacco Additives by Microwave Digestion and HPLC with PAD Detection

A new method for the simultaneous determination of heavy-metal ions in tobacco and tobacco additive by microwave digestion and reversed-phase high-performance liquid chromatography (RP-HPLC) was developed. The tobacco and tobacco additive samples were digested by microwave digestion. The lead, cadmium, mercury, nickel, copper, and tin ions in the digested samples were precolumn derivated with tetra-(4-aminophenyl)-porphyrin (T₄-APP) to form color chelates; the Hg-T₄-APP, Cd-T₄-APP, Pb-T₄-APP, Ni-T₄-APP, Cu-T₄-APP, and Sn-T₄-APP chelates were then enriched by solid-phase extraction with C₁₈ disks and the retained chelates were eluted from the disks using tetrahydrofuran (THF). The chelates were separated on a Waters Xterra RP₁₈ column by gradient using methanol (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH 10.0) and acetone (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH 10.0) as a mobile phase at a flow rate of 0.5 mL/min and detected with a photodiode array detector in the range 350–600 nm. The detection limits of lead, cadmium, mercury, nickel, copper, and tin were 5, 4, 2.5, 5, 8, and 4 ng/L, respectively, in the original samples. The method was applied to the determination of lead, cadmium, mercury, nickel, copper, and tin in tobacco and tobacco additive with good results.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 5, 2005, pp. 542–548.Original English Text Copyright © 2005 by Yang, Li, Shi, Wang.This article was submitted by the authors in English.     

Determination of Cadmium(ii), Copper(ii), Mercury(ii), and Lead(ii) in Water Using Stochastic Sensors Based on Graphite and Diamond Paste Modified with 1H-Pyrrole-1-Hexanoic Acid

Graphite/diamond pastes modified with 1H-pyrrole-1-hexanoic acid were used for the design of stochastic sensors. The proposed stochastic sensors were used to determine four heavy metals, copper(II), cadmium(II), mercury(II), and lead(II), in water samples. The sensitivities of the stochastic sensors were high for all four metal ions, and their limits of determination were sufficiently low to enable detection at very minute concentrations; in some cases, unreachable using standard methods of analysis. The recoveries of copper(II), cadmium(II), mercury(II), and lead(II) in water samples were higher than 93.00%, with relative standard deviation values lower than 1.00%. The sensors were used to simultaneously determine copper(II), cadmium(II), mercury(II), and lead(II) in water samples. The obtained results were in agreement with those obtained using standard analytical methods.     

Liquid-liquid extraction of some lanthanide metal ions by polyoxyalkylene systems

Polyoxyalkylene systems, namely, polypropylene glycol (PPG-1025), polyethylene glycol (PEG-600) and polybutadieneoxide (PBDO-700) dissolved in either nitrobenzene or 1,2-dichloroethane have been tested as prospective extractants for some lanthanide metal ions (Eu(3+), Pr(3+) and Er(3+)) from their aqueous solutions in the presence of picrate anions. The metal ions were quantified before and after extraction using the inductively coupled plasma emission spectrophotometry technique. The percent extraction and the distribution coefficients have indicated that pH of the aqueous phase, picrate concentration and the organic solvent are the major parameters that affect the extraction efficiency of the metal ions. The optimum pH range was found to be 3.5-5.5 and the picrate concentration should be as high as possible; however, a picrate concentration of about 0.05 M proved to be adequate for a near quantitative extraction. In all cases, nitrobenzene enhanced a higher percent extraction compared to 1,2-dichloroethane. The efficiency of the polyoxyalkylene systems to extract certain lanthanide metal ions was in the order PBDO-700>PPG-1025>PEG-600 when nitrobenzene was the organic solvent and in the order PPG-1025>PBDO-700 approximately PEG-600 when 1,2-dichloroethane used as the solvent in the organic phase. The extractability of PPG-1025 towards the lanthanide metal ions was in the order Pr(3+)>Eu(3+)>Er(3+) irrespective of the organic solvent used. The stoichiometry of the extracted polyoxyalkylene ion-pairs with the lanthanide metal ions has been estimated. Each mole of metal ions is associated with three moles of picrate anions and 13 to 14 moles of propyleneoxide units in the case of PPG-1025, and about 9 to 10 moles of ethyleneoxide units in the case of PEG-600 and 10 moles of butadieneoxide units in the case of PBDO-700.     

Extraction and photometric determination of lead with diazacrown ether dye

N,N'-Bis(2-hydroxy-5-nitrobenzyl)cryptand-22 (22-Koshland) forms yellow complexes with bivalent metal ions, and these are extractable into 1,2-dichloroethane. The overall extraction constants have been estimated for lead (10(-5.4)), copper (10(-5.6)), mercury (10(-5.8)) and cadmium (10(-8.4)). The result obtained has been applied to extraction and photometric determination of lead. The molar absorptivity at the absorption maximum (406 nm) is 4.47 x 10(4) l.mole(-1).cm(-1). The interferences from copper and mercury can be eliminated by the addition of sodium thiosulphate and the interference from cadmium can be eliminated by calculation from the absorbances at 406 and 391 nm (the cadmium complex with 22-Koshland has its absorption maximum at 391 nm). The method has been successfully applied to the determination of lead in zinc powder.     

A rugged and transferable method for determining blood cadmium,mercury, and lead with inductively coupled plasma-mass spectrometry

A simple, high-throughput method for determining total cadmium, mercury, and lead in blood in cases of suspected exposure, using inductively coupled plasma-mass spectrometry (ICP-MS), has been developed and validated. One part matrix-matched standards, blanks, or aliquots of blood specimens were diluted with 49 parts of a solution containing 0.25% (w/w) tetramethylammonium hydroxide; 0.05% v/v Triton X-100 (blood cell membranes and protein solubilization); 0.01% (w/v) ammonium pyrolidinedithiocarbamate (mercury memory effect prevention and oxidation state stabilization, solubilization by complexation of all three metals); 1% v/v isopropanol (signal enhancement); and 10 μg/L iridium (internal standard). Thus the final dilution factor is 1 + 49. The method provides the basis for the determination of total cadmium, mercury, and lead for assessment of environmental, occupational, accidental ingestion or elevated exposures from other means. Approximately 80 specimens, including blanks, calibration standards, and quality control materials can be processed in an 8-h day. The method has been evaluated by examining reference materials from the National Institute of Standards and Technology, as well as by participation in six rounds of proficiency testing intercomparisons led by the Wadsworth Center of the New York State Department of Health. This method was developed for the purpose of increasing U.S. emergency response laboratory capacity. To this end, 33 U.S. state, and 1 district health department laboratories have validated this method in their own laboratories.