Colorimetric determination of manganese(II) in natural and waste waters after preconcentration on a polymeric adsorbent

A combined procedure has been developed for the colorimetric determination of manganese(II) in natural and waste waters based on the selective preconcentration of metal ions on a polymer complexing adsorbent,—polystyrene-2-oxy-〈1-azo-1′〉-2′-oxy-3′-sulfo-5′-nitrobenzene, followed by the digital detection of the analytical signal. Manganese(II) is extracted (95–100%) in the batch mode in the pH range from 4.9 to 6.8. The determination is not interfered by n × 10⁵-fold excess (by weight) of K, Na; n × 10⁴-fold excess of Ca, Mg; n × 10³-fold excess of Ba, Sr, Al, Fe(III); n × 10²-fold excess of Ti(IV), Ni, Co, Zn, Pb, Cu. The accuracy of the procedure has been examined by the standard addition method. The relative standard deviation varies from 9 to 16%. The advantages of the procedure include simplicity, availability of the apparatus, rapidity, and the possibility of its application in field conditions.     

Fluorimetric determination of uranium(VI) in waters by flow-injection analysis after preconcentration on a silica gel microcolumn

A method was developed for the selective determination of trace concentrations of uranium(VI) by flow-injection analysis (FIA) with fluorimetric detection. Uranium(VI) is selectively separated and/or pre-concentrated from a volume up to 20 ml on an activated silica gel microcolumn (2 x 40 mm) from a medium of 0.03M EDTA, 0.06M tartrate, and/or 0.05M NaF at pH = 9.3. After washing the column the uranium is eluted with a mixture of 1.33M sulphuric and phosphoric acids and determined with a relative standard deviation not exceeding 6% for concentrations in the range 10-250 mug/l. The detection limit was estimated to be 0.1-0.2 mug of uranium. The method has been verified on artificial water samples with high content of the interfering elements and applied to analysis of waste and natural waters.     

Spectrophotometric determination of uranium in natural waters after preconcentration on TBP-plasticized dibenzoylmethane-loaded polyurethane foams

A method is presented for the spectrophotometric determination of uranium in natural waters after a preconcentration step involving percolation of a suitable aliquot of the water sample whose pH is adjusted to 6.0–6.5 through a TBP-plasticized dibenzoylmethane-loaded polyurethane foam bed. Uranium on the foam is eluted with 0.6M HCl solution and then determined spectrophotometrically using arsenazo III as a chromogenic reagent.     

Determination of uranium in natural waters after anion-exchange separation

A method is described for the determination of uranium by fluorimetry and spectrophotometry in samples of natural non-saline waters. After acidification with hydrochloric acid, the water sample is filtered and, following the addition of ascorbic acid and potassium thiocyanate, passed through a column of the strongly basic anion-exchange resin Dowex 1-X8 (thiocyanate form). On this exchanger uranium is adsorbed as an anionic thiocyanate complex. After removal of iron and other coadsorbed elements by washing first with a mixture consisting of 50 vol.% tetrahydrofuran, 40 vol.% methyl glycol and 10 vol.% 6 M hydrochloric acid, and then with pure aqueous 6 M hydrochloric acid, the uranium is eluted with 1 M hydrochloric acid. In the eluate, uranium is determined fluorimetrically or by means of the spectrophotometric arsenazo III method. The procedure was used for the routine determination of uranium in water samples collected in Austria.     

A portable fluorescence analyzer for determining uranium(VI) in natural waters

A portable fluorescence analyzer has been developed for determining 0.03–3000 ng/L of uranium(VI) in various types of waters; the relative standard deviation is 10%. The principle of time selection of the luminescence of analyte and the impurities has been used. In contrast to the previous apparatus with a bulky nitrogen laser or a low-power light diode, this apparatus involves a powerful pulse xenon lamp.     

Determination of methylmercury in natural waters at the sub-nanograms per litre level by capillary gas chromatography after adsorbent preconcentration

Methylmercury was preconcentrated from water on to a sulph-hydryl cotton fibre adsorbent, using the column technique or the batch-column two-stage technique. A small volume of 2 M HCl was used to elute methylmercury and to separate it from inorganic mercury; 0.4–0.6 ml of benzene was used to extract methylmercury from the eluate. Analysis was performed by capillary gas chromatography with electron-capture detection. The detection limit for methylmercury was <0.05 ng l^?1 in a 4-l water sample. Four surface waters were analysed to test the agreement of methylmercury concentration between the two preconcentration methods, and to test the interference of humic substances on the filtered and unfiltered surface water. The methylmercury concentrations found in different surface water samples ranged from 0.08 to 0.48 ng l^?1.     

On the spectrophotometric flow injection determination of chromium(VI) in natural waters after on-line preconcentration on activated alumina

The feasibility of chromium(VI) preconcentration on to activated alumina in a continuous flow system with spectrophotometric detection was investigated. Chemical and flow variables, and the influence of concomitant species were studied both with and without preconcentration systems. The best results were obtained by using a 2.5 cm long, 1.6 mm i.d. alumina minicolumn, and selecting 1 x 10(-4) M nitric acid as the preconcentrating medium and 0.1 M ammonium hydroxide as the eluent. The eluted chromium(VI) was mixed with diphenylcarbazide in acidic medium and the absorbance of the colored complex was measured at 540 nm. Linear calibrations for 5, 25 and 50 ml sample volumes were established over the concentration ranges 10-50 mug 1(-1), 2-10 mug 1(-1) and 1-5 mug 1(-1) with sensitivity enhancements of 44, 196 and 392 and detection limits (3sigma) of 3.0 mug 1(-1), 0.3 mug 1(-1) and 0.2 mug 1(-1), respectively. The methods is relatively fast and cheap. Natural waters were analyzed with use of the developed procedure.     

Determination of methylmercury in natural waters by headspace gas chromatography with microwave-induced plasma detection after preconcentration on a resin containing dithiocarbamate groups

A method for the determination of methylmercury at ng l^?1 levels in natural waters is described. Methylmercury present in a sample is first preconcentrated on a column of a resin containing dithiocarbamate groups and eluted quantitatively with acidic thiourea solution. Methylmercury in the effluent is then converted to the iodide by addition of sulphuric acid and iodoacetic acid and determined by headspace gas chromatography with microwave-induced plasma detection. The adsorption properties of the resin are discussed.     

Determination of uranium(VI) in monazite sand

The design and characterization of an argon segmented-solid phase extraction system is described. A 200 ul volume micro-column has been constructed for the preconcentration of rare earth elements (REEs) from salt matrices containing uranium. An inductively coupled plasma atomic emission spectrometer has been utilized for simultaneous detection of Sr, Y and the REEs (namely Ce, Eu, La, Nd, Pr, Sm) at levels ranging from 5- to 2000 ppm in LiC1/KCl samples containing U. Preconcentration factors of 100 fold have been demonstrated. The precision, linear dynamic range and column performance of the system will be presented.     

Automated determination of uranium(VI) in seawater using on-line preconcentration by coprecipitation

An automated method is developed for the spectrophotometric determination of nanoamounts of uranium(VI) with Arsenazo III using online preconcentration by the coprecipitation of the uranium complex of the reagent with organic coprecipitants. The collector was an Arsenazo III ion pair with organic cations poorly soluble in water. The concentrate was separated by filtration through a cellulose fiber membrane and dissolved in a flow of an organic solvent; the analytical signal was recorded as the output peak. The developed method is characterized by simplicity, sufficiently high sensitivity, high throughput and rapidity, and can be used for the selective determination of uranium(VI) in complex liquid matrices. The detection limit is ～0.01 ng/mL (3s, n = 5, P = 0.95). The throughput of the method is 150 samples per hour.     

Solid phase extractive preconcentration of uranium(VI) onto diarylazobisphenol modified activated carbon

Diarylazobisphenol (DAB) 1 and diarylazobisphenol modified carbon 2 were synthesized and characterised. The latter has been used for solid phase extractive preconcentration and separation of trace amounts of uranium(VI) from other inorganics. In this, a column mode preconcentration of uranium(VI) was carried out in the pH range 4.0-5.0, eluted with 1.0 mol l⁻¹ HCl and determined by an Arsenazo III spectrophotometric procedure. Calibration graphs were rectilinear over the uranium(VI) concentrations in the range 5-200 μg l⁻¹. Five replicate determinations of 25 μg of uranium(VI) present in 1 l solution gave a mean absorbance of 0.032 with a relative standard deviation of 2.52%. The detection limit corresponding to three times the standard deviation of the blank was found to be 5 μg l⁻¹. The accuracy of the developed preconcentration method in conjunction with the Arsenazo III procedure was tested by analysing MESS-3, a marine sediment certified reference material. Further, the above procedure has been successfully employed for analysis of uranium(VI) in soil and sediment samples.     

Determination of trace chromium(VI) and molybdenum(VI) in natural and bottled mineral waters using long pathlength absorbance spectroscopy (LPAS)

A flow-through solid phase spectrophotometric (SPS) sensing device is proposed for the determination of minoxidil. The analyte is concentrated on Sephadex SP-C25 ion-exchanger packed in a flow cell and it is monitored by UV-Vis spectrophotometry at 282 nm, without derivatization reaction. When a HCl (10(-2) mol l(-1))/NaCl (5x10 (-2) mol l (-1)) solution is used as carrier/desorbing solution, the sensor responds linearly in the measuring range of 0.2-7, 0.1-4 and 0.05-2 mug ml(-1) with detection limits of 60, 33 and 6 ng ml(-1) for 600, 1000 and 2000 mul of sample, respectively. The relative standard deviations (%) for these volumes are 0.38, 1.06 and 2.63, respectively. The method was satisfactorily applied to the determination of minoxidil in pharmaceutical preparations and the results were compared with those obtained by high performance liquid chromatography (HPLC).     

Determination of cadmium by flame atomic absorption spectrometry after preconcentration on naphthalene-methyltrioctylammonium chloride adsorbent as tetraiodocadmate (II) ions

A sensitive and simple solid-phase preconcentration procedure for enrichment of cadmium prior to analysis by flame atomic absorption spectrometry (FAAS) is described. The method is based on the adsorption of cadmium as CdI₄²⁻ on naphthalene-methyltrioctylammonium chloride adsorbent, elution by nitric acid and subsequent determination by FAAS. The effect of pH, iodide concentration, sample flow rate, volume of the sample and diverse ions on the recovery of the analyte was investigated and optimum conditions were established. A preconcentration factor of 40 was achieved using the optimum conditions. The calibration graph was linear in the range 1-100 ng ml⁻¹ cadmium in the initial solution. The detection limit based on the 3S_b criterion was 0.6 ng ml⁻¹ and the relative standard deviations (RSD) were 3.9 and 1.05% for 5 and 40 ng ml⁻¹, respectively (n=8). The method was successfully applied to the determination of cadmium added to river, tap and Persian Gulf water samples.     

Determination of seven trace elements in natural waters by neutron activation analysis after preconcentration with 1-(2-pyridylazo)-2-naphthol

A procedure is described for the preconcentration of Cd(I), Co(II), Cr(III), Cu(II), Mn(II), U(VI) and Zn(II) from 800 ml of water and sea-water samples by coprecipitation with 1-(2-pyridylazo)-2-naphthol (PAN) prior to neutron activation. Chromium is reduced to Cr(III) by hydroxylammonium chloride at pH 4 before the preconcentration step. Coprecipitation of 30 mg of PAN was most effective at pH 9 with final recoveries of 76–91% for six elements and 50% for uranium. The scheme is based on double irradiation of the same samples. Short (10 min) irradiation followed by γ-spectrometry counting for 10 min gives data for Cd (^111mCd), Co, Cu, Mn and U (²³⁹U). A second 16-h irradiation permits determination of zinc and uranium (²³⁹Np) after a waiting time of 6 h, cadmium (¹¹⁵Cd) after 24 h and chromium after a waiting period of 2 weeks followed by counting for 30 min. Detection limits are 0.04 ng g^?1 for Co, 0.8 ng g^?1 for Cd, 0.3 ng g^?1 for Cu, 0.2 ng g^?1 for Cr, 0.006 ng g^?1 for Mn, 0.006 ng g^?1 for U and 0.3 ng g^?1 for Zn. A further decrease of the detection limit for chromium to 0.05 ng g^?1 can be achieved by separation of interfering nuclides and scintillation counting of ⁵¹Cr with a NaI(Tl) well-type detector.     

Determination of uranium and thorium in natural waters by ICP-OES after on-line solid phase extraction and preconcentration in the presence of 2,3-dihydro-9,10-dihydroxy-1,4-antracenedion

An on-line solid phase extraction method, linked to inductively coupled plasma optical emission spectrometry (ICP-OES), has been examined using octadecyl-bonded silica cartridge for determination of low levels of uranium and thorium in aqueous samples. 2,3-dihydro-9,10-dihydroxy-1,4-anthracenedion forms a hydrophobic complex with cations and the resulted complex was retained on SPE. The retained complex was eluted using an acidic solution and introduced into ICP for determination. Various effective parameters and chemical variables such as sample pH, amount of ligand (as a complexing agent), sampling and eluting flow rates and concentration of the eluent were optimized. Under optimal conditions, calibration curves with dynamic linear ranges of 1–200 μg/L (r ₂ = 0.9999) and 1–500 μg/L (r ₂ = 0.9994) for U and Th were obtained, respectively. Detection limits based on three times of standard deviations of blank by 6 replicates were 0.69 μg/L and 0.84 μg/L for U and Th, respectively. Sample throughput was 10 samples/h. The interference effects of several metal ions on percentage of recovery of U and Th were also studied. The method was applied to the recovery and sequential determination of these actinide elements in different water samples.     

Determination of phenols by liquid chromatography after online adsorption preconcentration on the Strata-X adsorbent

An online adsorption-high-performance liquid chromatography (HPLC) method was developed for the determination of phenols (11 priority water pollutants) in waters, using polystyrene chemically modified with N-vinyl-2-pyrrolidone (Strata-X). The detection limits for phenols obtained using a preconcentration from 10 mL of water and calculated by different means vary from 0.3 to 2 μg/L. The accuracy of the determination of phenols in tap and river water samples was verified by the standard addition method.     

Epithermal neutron activation determination of uranium in environmental waters by neptunium-239 after preconcentration on activated carbon

A method for the analysis of uranium in natural waters based on preconcentration of uranium on activated carbon, irradiation with epithermal neutrons, and a high resolution gamma-spectrometry of²³⁹Np was developed. The chemical yield of uranium preconcentration is determined by treating a parallel sample to which a known uranium quantity is added. The lower limit of determination amounts to 1.4·10⁻⁸ g uranium per liter. The possible interfering in gamma-spectrometry of neptunium-239 was discussed too. The applicability of the proposed method is shown by the analysis of uranium in sea-, river-, geothermal-, drinking- and rain-water samples.     

Spectrophotometric determination of uranium in natural waters

A method for the spectrophotometric determination of uranium in samples of natural water is described. Ion exchange with Amberlite IR-120 (H⁺) to concentrate the metal was used. The absorption properties of the complex formed between uranium and the chromogenic reagent Arsenazo III, its stability over several hours, the effect of the pH on the ability of the resin to retain uranium, the reproducibility of the method and the effects of ionic interferences were considered. The sensitivity was 0.67 and 0.05 μg l^?1 of uranium for the direct and the addition methods, respectively. Uranium concentrations for the samples analysed were between 0.10 and 0.50 μg l^?1.     

Solid-phase extraction for the simultaneous preconcentration of organic (selenocystine) and inorganic [Se(IV), Se(VI)] selenium in natural waters

The recombinantly produced different forms of protein G, namely monofunctional immunoglobulin G (IgG) binding, monofunctional serum albumin (SA) binding and bifunctional IgG/SA binding proteins G, are compared with respect to their specific affinities to blood IgG and SA. The affinity mode of the recently developed high-performance monolithic disk chromatography has been used for fast quantitative investigations. Using single affinity disks as well as two discs stacked into one separation unit, one order of magnitude in adsorption capacities for IgG and SA were found both for monofunctional and bifunctional protein G forms used as specific affinity ligands. However, despite the adsorption difference observed, the measured dissociation constants of the affinity complexes seemed to be very close. The analytical procedure developed can be realized within a couple of minutes. Up-scaling of the developed technology was carried out using another type of monolithic materials, i.e. CIM affinity tubes.     

Determination of beryllium trace contents in mineral waters after preconcentration on a chelating ion-exchanger

Summary A separation-preconcentration procedure for the determination of Be traces in mineral waters is described. The precision and the accuracy of the procedure were checked by the use of artificial as well as of real samples by AAS-ETA and AES-ICP. On the basis of the results and of their statistical evaluation, the proposed procedure allows to obtain reliable results with the necessary limit of determination and can provide important, till now not accessible information on Be-concentration in waters.