Preconcentration of cobalt with N-(dithiocarboxy)sarcosine and amberlite xad-4 resin

Cobalt reacts with N-(dithiocarboxy)sarcosine (DTCS) to form a 1:3 Co:DTCS complex which is so stable that after its formation no decomposition occurs even in 4M hydrochloric acid. The complex is sorbed on a column of Amberlite XAD-4 copolymer from an acidic solution and eluted with 10 ml of a 1:1:3 v v mixture of 1.0M ammonia solution (pH = 9), 0.1M EDTA and methanol. The absorbance of the eluted chelate is measured at 320 nm against water ( = 2.15 x 10(4) l.mole(-1).cm(-1)). The recovery of cobalt from 1 litre of tap-water or sea-water is quantitative. The effect of diverse ions can be eliminated by the addition of EDTA after chelation of the cobalt. The copper complex with DTCS is partly sorbed on the column because of its slow rate of decomposition by EDTA, but most of the copper chelate sorbed can be eluted with hydrochloric acid and any co-eluted with the cobalt chelate can be completely decomposed by heating the eluate. Cobalt enrichment factors of at least 100 are obtained, so the method is applicable to the determination of cobalt at the ng ml level.     

Ion chromatography of nitrite at the ppb level with photometric measurement of iodine formed by post-column reaction of nitrite with iodide

The difficulty in ion-chromatographic determination of nitrite in aqueous solutions containing a high concentration of chloride arises mainly from incomplete resolution of the peaks for these anions on the separation column whose efficiency is not high. A photometric measurement of iodine formed by a reaction of nitrite with iodide has been found to make it possible to determine, chromatographically, trace amounts of nitrite without any interference from chloride; chloride does not oxidize iodide to produce iodine. The proposed method was based on the separation of nitrite from matrix anions on a silica-based anion-exchange column with a 1.5·10⁻³ M phthalate eluent (pH 5.0), followed by photometric measurement of the iodine (as triiodide) formed via a post-column reaction of the separated nitrite with iodide. The optimal conditions for the post-column reaction were established by varying the concentrations of iodide, copper(II) and nitric acid in a post-column-reaction solution and the length of a reaction tube. A calibration graph for nitrite, plotted as peak heights versus concentrations, was linear up to 1.50·10⁻⁵ M (690 ppb). The detection limit, defined at S/N=3, was 1.00·10⁻⁷ M (4.60 ppb) nitrite. The presence of chloride ions up to 0.01 M did not give any interference to the determination of nitrite. This method was successfully applied to the determination of nitrite in lake water, river water, sewage works water and snow samples without any pretreatment.     

Extraction chromatography with bis(2-ethylhexyl)phosphoric acid for separation of tin(IV)

Tin is extracted from 0.01M hydrochloric acid on a silica-gel column impregnated with bis(2-ethylhexyl)phosphoric acid, stripped with 5M hydrochloric acid, and then determined spectrophotometrically as its Pyrocatechol Violet complex at 555 nm. Tin has been separated from several multicomponent mixtures containing arsenic, antimony, bismuth, lead and copper, and determined in various alloys.     

Synthesis and properties of a chelating resin containing triazolethiol groups

A macroreticular poly(acrylic acid)-based resin with triazolethiol as the functional group has been synthesized. The stability of the resin in acidic media and the behaviour in sorption and desorption of various metal ions have been investigated and compared with those of the acylthiosemicarbazide resin which is an intermediate in synthesis of the triazolethiol resin. Both resins show high affinity for copper(II) silver, cadmium and mercury(II), and high selectivity for silver and mercury(II) at low pH (1–2), and even at pH 7 if EDTA is present. The triazolethiol resin sorbs metal ions faster than the acylthiosemicarbazide resin does and sorbs mercury(II) from high concentrations of acids and neutral salt solutions. This resin has been applied to the concentration of silver and mercury(II) from sea-water samples by column operation.     

Separation and concentration of molybdenum(VI) and tungsten(VI) with chelating ion-exchange resins containing sulphur ligands

Three chelating ion-exchange resins based on macroreticular polyacrylonitrile-divinylbenzene copolymers with thioglycollic acid and cysteine as functional groups have been tested for separation of molybdenum(VI) and tungsten(VI). On a short column of the thioglycollic acid resin, molybdenum(VI) and tungsten(VI) can be selectively sorbed from pH-4.3 acetate buffer and eluted with 2M hydrochloric acid and a mixture of 0.1M sodium hydroxide and 0.1M sodium chloride, respectively, with quantitative recovery even at very low concentrations. Simulated sea-water samples have been analysed.     

Preparation and analytical properties of a chelating resin containing phenylalanine groups

A polystyrene-based macroreticular resin containing phenylalanine groups has been prepared and its analytical properties have been investigated and compared with Dowex A-1. The phenylalanine resin shows high selectivity for mercury(II) and copper(II) in the pH region 2-3. The sorption behaviour of copper has been examined in detail, with the intention of using the resin analytically. The important characteristics of the resin are fast equilibration, high selectivity and small volume change between its hydrogen form and metal forms. These enable it to be applied for the rapid concentration of trace amounts of copper in the presence of large amounts of diverse metals. It may be used for the determination of copper in sea-water and the separation of copper/cobalt and copper/nickel.     

Release of copper from commercial solid-state copper ion-selective electrodes

The release of copper from two commercial solid-state cupric ion-selective electrodes [Orion 94-29 Cupric Electrode (I) and Radiometer F1112 Selectrode (II)] was measured by immersion in the following media: 0.1M potassium nitrate (pH = 4.7), 0.5M sodium chloride (pH = 4.7) and 0.1M nitric acid. In the 0.1M potassium nitrate medium, the amount of copper released from both electrodes causes interference when they are used for the determination of cupric ion at the 10⁻⁷M level. In comparison with the 0.1M potassium nitrate medium, the copper release in the 0.5M sodium chloride and 0.1M nitric acid media was increased for electrode II but not for electrode I. The release of copper was not affected by removal of oxygen from the media but can be substantially lowered by coating the electrodes with a thin cation-exchange membrane (Nafion). The mechanism of copper dissolution is investigated.     

Indirect spectrophotometric determination of chloride by solvent extraction as tris(1,10-phenanthroline)iron(II) thiocyanate

An indirect spectrophotometric method for the determination of small amounts of chloride in fresh waters is described. Chloride ions react with mercury(II) thiocyanate to liberate thiocyanate ions, which can be selectively extracted into nitrobenzene with tris(1,10-phenanthroline)iron(II) chelate cations. The red color (516 nm) of the organic phase measured against a reagent blank is proportional to the initial concentration of chloride ions in the aqueous phase. At least an equimolar amount of tris(1,10-phenanthroline)iron(II) chelate and a 3-fold amount of mercury(II) thiocyanate are needed; the optimal pH range is 1.5–3.5. Beer's law is obeyed over the concentration range of 0.8–5.6 10^-5 M of chloride. The color stability and the apparent sensitivity are better than those of the mercury(II) thiocyanate-iron(III) method. Large amounts of sulphate, phosphate, fluoride, carbonate, acetate, potassium, sodium, and ammonium ions had negligible or no effect ; bromide, iodide, cyanide, sulphide, and thiocyanate interfere.     

The application of salicylaldoxime in solvent extraction : Part II. Spectrophotometric determination of copper with 2-(5-nitro-2-pyridylazo)-1-naphthol after separation with salicylaldoxime

A highly sensitive spectrophotometric method for the determination of traces of copper with 2-(5-nitro-2-pyridylazo)-l-naphthol (5N-α-PAN) has been developed. At a pH of 3–4copper(II) is selectively extracted into chloroform as its salicylaldoxime chelate and then stripped into an aqueous acid solution; the pH is adjusted to 9.3, and 5N-α-PAN is added. The 1:2 chelate between copper(II) and the reagent, which promptly precipitates, is extracted into chloroform and measured at 598 nm. The molar absorptivity is 86,000. The application of the method to the analysis of high-purity magnesium and cobalt is described.     

Electrochemical masking of large amounts of copper in dpasv and the determination of thallium in the presence of a large excess of copper

The influence of the following surfactants on the peak of copper in 0.2M EDTA at pH 4.5 was investigated: polyoxyethylated alkylphenols having an average of 3 and 9.5 ethylene oxide units; polyoxyethylene alcohols having 4 and 7 ethylene oxide units; poly(ethylene glycols) having M.W. 4000, 9000 and 20000; hexadecyltributylphosphonium bromide (HDTBPB), tetraphenylphosphonium bromide (TPPB),N,N,N,N,N',N',N-examethylhexamethylenediammonium bromide (HMB), benzyl(di-isobutylphenoxyethoxy) dimethylammonium chloride (Hyamine 1622), hexadecyltrimethylammonium bromide (HDTMAB), hexadecyldimethylbenzylammonium chloride (HDDMBAC) and tetrabutylammonium chloride (TBAC). HDDMBAC, as well as all the substances examined which contained an ethylene oxide chain, completely suppressed the copper peak. HDTBPB and TPPB partially suppressed the peak, whereas HDTMAB, HMB and Hyamine 1622 enhanced it. TBAC was without effect. In 0.2M EDTA at pH 4.5 containing TBAC at 0.01M concentration and 10 ppm of Rokafenol N-3, Cu(II), Pb(II) and Bi(III) can be tolerated at concentrations of up to 0.05M, the height of the thallium peak being unaffected. The precision of the determination (3–10%) and the recovery are satisfactory. A 10³-fold ratio of Fe(III) to Tl(I) does not interfere with the determination.     

Determination of mercury traces by differential-pulse stripping voltammetry after sorption of mercury vapour on a gold-plated electrode

Trace mercury is reduced with tin(II) to mercury metal, which is volatilised by bubbling air through the solution. A certain fraction of this mercury is sorbed on a rotating gold disk electrode and stripped in a thiocyanate solution. The detection limit is about 30 ng Hg(II) in solution; the relative standard deviation is 6% for 100 ng Hg(II) (n = 7). The detection limit for mercury in air is 1.7 ng l^?1 with a preconcentration time of 10 min.     

Anion-exchange enrichment and spectrophotometric determination of uranium in sea-water

A method is proposed for the determination of uranium in sea-water. The uranium is strongly sorbed on a strongly basic anion-exchange resin (Cl(-) form) from acidified sea-water containing sodium azide (0.3M) and is easily eluted with 1M hydrochloric acid. Uranium in the effluent can be determined spectrophotometrically with Arsenazo III. The combined method allows easy and selective determination of uranium in sea-water without using a sophisticated adsorbent. The overall recovery and precision are satisfactory at the 3 mug/1. level.     

Polarographic determination of copper, arsenic and arsenic in copper arsenite

A method is proposed in which Cu^II, As^III and As^v can be determined in copper arsenite without prior separation. It is based on the fact that Cu^II and As^III yield prominent, distinguishable, widely-separated cathodic polarographic waves in a 0.1M LiCl-0.01M EDTA—0.001M LiOH solution using a dropping mercury electrode, whereas As^v does not give a wave in this medium. The As^v is determined by difference after reduction with sulphurous acid.     

Separation and Removal of Mercury(II) from Water Samples Using (Acetylacetone)‐2‐Thiol‐Phenyleneimine Immobilized on Anion‐Exchange Resin Prior to Determination by Cold Vapor Inductively Coupled Plasma Atomic Emission Spectroscopy

Abstract

(Acetylacetone)‐2‐thiol‐phenyleneimine (H₂L) immobilized on an anion‐exchange resin (Dowex) was used for separation and removal of mercury from natural water samples and for preconcentration prior to its determination by cold vapor inductively coupled plasma atomic emission spectroscopy. The metal was eluted from the column using a solution of 10% thiourea in 0.1 M HCl. The modified resin is higly selective with an exchange capacity of 1.60 mmol g^?1. Various parameters like pH, column flow rate, and desorbing agents are optimized. The proposed method has a linear calibration range of 15–1000 ng/ml Hg(II), with a relative standard deviation at the 15 ng/ml level of 3.5%. The precision of the method (evaluated as the relative standard deviation obtained after analyzing six series of five replicates) was ±4.2% at the 50 ng/ml level of Hg(II). The method has been used for routine determination of trace levels of mercury species in natural waters. The potential application of modified resin for the removal of mercury(II) from two natural water samples (top water and lake water) spiked with 50 ng/ml of mercury (II) was studied by ICP‐AES, and the results proved that excellent percent extraction of mercury(II) from both natural water samples was obtained by column method using modified resin.     

A chelate-forming resin bearing mercapto and azo groups and its application to the recovery of mercury(II)

A new chelate-forming resin bearing mercapto and azo groups was prepared from a common anion-exchange resin by treatment with azothiopyrine disulphonic acid (ATPS). ATPS resin was very stable and highly effective for the collection of mercury(II) by the batch and column methods. In the column method, the amount of mercury(II) in solution could be reduced to below 0.5 mug/l. The mercury(II) adsorbed could be eluted with thiourea solution, and the resin could be used repeatedly.     

Preparation and properties of macroreticular resins containing thiazole and thiazoline groups

Three macroreticular polystyrene-based resins with amino- or imino-thiazole and thiazoline groups as the functional groups have been prepared. The resins are highly stable in acid and alkaline solutions and have high selectivity for mercury(II). In the presence of hydrochloric acid, sorption of mercury attains equilibrium fairly rapidly, the time for 50% uptake of mercury being 3-6 min. There are practically no interferences. In a column operation, mercury is quantitatively recovered by elution with 0.1M hydrochloric acid containing 5% thiourea. The thiazoline resin column can be used to concentrate mercury from sea-water.     

Determination of silver in ores, concentrates, zinc process solutions, copper metal and copper-base alloys by atomic-absorption spectrophotometry after separation by extraction of the tribenzylamine-silver bromide complex

A method for determining 0.1 μg/g or more of silver in ores and concentrates and 0.001 μg/ml or more of silver in zinc process solutions is described. Silver is separated from the matrix elements by chloroform extraction of the tribenzylamine—silver bromide ion-association complex from 0.08M potassium bromide—2M sulphuric acid and stripped with 9M hydrobromic acid. This solution is evaporated to dryness and organic material is destroyed with nitric and perchloric acids. Silver is determined by atomic-absorption spectrophotometry in an air—acetylene flame, at 328.1 nm, in a 10% v/v hydrochloric acid—1% v/v diethylenetriamine medium. Cadmium, bismuth and molybdenum are partly co-extracted but do not interfere. The method is also applicable to copper metal and copper-base alloys. Results obtained by this method are compared with those obtained by a fire-assay/atomic-absorption method.     

Extraction with long chain amines-VII polarographic determination of uranium

A polarographic determination of uranium is described, based on the highly selective extraction of uranium(VI) with a chloroform solution of trioctylammonium chloride, followed by re-extraction of uranium into an aqueous 0·5M KCl-0·5M HCl solution, which also serves as the polarographic supporting electrolyte. In this medium, uranium(VI) is reduced at the dropping mercury electrode to give two polarographic waves, the first of which is of analytical significance. In this way it is possible to determine 50–2400 μg of uranium in 1 ml of supporting electrolyte and in the presence of large amounts of accompanying elements.     

A selective lon-exchange separation and spectrophotometric determination of traces of copper in silicate rocks

Summary A combined cation-exchange separation-spectrophotometric procedure has been worked out for the accurate determination of traces of copper in silicate rocks. Silicates are opened up with sulfuric and hydrofluoric acids. The residue is taken up into a 0.5 M hydrochloric acid −0.05 M oxalic acid −1% hydrogen peroxide solution and loaded on a strongly acidic cation-exchange resin column. Polyvalent ions including ferric ions do not adsorb on the column, while copper (II) retains together with divalent metal ions as well as aluminum (III). Copper (II) can selectively be eluted by a small volume of 0.05 M thiosulfate solution. This fraction is sufficiently pure to allow a direct spectrophotometric determination of copper with Na-DDTC without the addition of tartrate and EDTA as masking agents. Quantitative results are quoted for the determination of copper in international standard rocks of the Geological Survey of Japan (GSJ) and the U.S. Geological Survey (USGS).     

Study on the Solid Phase Extraction of Hg(II)‐ABR Chelate with C18 Disks and its Application to the Determination of Mercury in Tobacco and Tobacco Additives

A highly sensitive, selective and rapid method for the determination of mercury based on the rapid reaction of mercury(II) with 5‐(p‐aminobenzylidene)‐rhodanine (ABR) and the solid phase extraction of the colored chelate with C₁₈ disks has been developed. In the presence of pH = 3.5 sodium acetate‐acetic acid buffer solution and Emulsifier‐OP medium, ABR reacts with mercury(II) to form a red chelate of a molar ratio 1:2 (mercury to ABR). This chelate was enriched by the solid phase extraction with C₁₈ disks and eluted the retained chelate from the disks with dimethyl formamide (DMF). The enrichment factor of 50 was achieved. In the DMF medium, the molar absorptivity of the chelate is 1.16 × 10⁵ L.mol^?1.cm^?1 at 540 nm. Beer's law is obeyed in the range of 0.01?3 μg/mL in the measured solution. The relative standard deviation for eleven replicated samples of 0.01 μg/mL level is 1.83%. This method was applied to the determination of mercury in tobacco and tobacco additives with good results.