New test tools for determination of trace metals using polydentate cellulose

New test tools have been developed for the rapid determination of trace metals: Ag, Cd, Co, Cu(II), Fe(II,III), Hg(II), Pd and Zn, using polydentate irregular α-celluloses, containing in the 6 position the fragments heterylformazane or heterylhydrazone, with a pocket device for preconcentration. Received: 17 June 1997 / Revised: 1 November 1997 / Accepted: 6 November 1997     

New test tools: Benzidine on cellulose and silica gel

Chromogenic reagents based on covalent and non-covalent immobilization of benzidine on cellulose and silica gels have been developed and investigated. New test tools and test methods have been elaborated for the determination of chlorine in the concentration range of 0.05–120 mg/L. Received: 6 August 1997/Revised: 13 January 1998/ Accepted: 12 February 1998     

New test tools: Benzidine on cellulose and silica gel

Chromogenic reagents based on covalent and non-covalent immobilization of benzidine on cellulose and silica gels have been developed and investigated. New test tools and test methods have been elaborated for the determination of chlorine in the concentration range of 0.05–120 mg/L.     

Substoichiometric separation and determination of trace metals

Substoichiometric methods are eminently suitable for the determination of many elements. As a new application of substoichiometry, a substoichiometric speciation of the element in different chemical states is proposed. Substoichiometric speciation of As(III) and As(V) is demonstrated as an example. This is based on a highly selective substoichiometric extraction of As(III) with thionalide and As(V) with tetraphenylarsonium chloride in the presence of an excess amount of pyrogallol. Coexistence of other diverse arsenic species including methylarsenic compounds does not give any interference to the selective determination of As(III) and As(V). For substoichiometric radioactivation, a novel application of the synergistic extraction system in a combination of a substoichiometric amount of thenoyltrifluoroacetone with an excess amount of phenanthroline is demonstrated for Yb as an example. Substoichiometric speciation based on the selective speration and an application of synergistic extraction to substoichiometric separation have additional possibilities in substoichiometry.     

New sorbents and indicator powders for preconcentration and determination of trace metals in liquid samples

Two approaches to immobilize complex-forming analytical reagents (PAN, PAR, Xylenol orange, Brombenzothiazo, Crystal violet, Cadion, and Sulfochlorophenolazorhodanine) for the preparation of new sorbents and indicator powders are suggested: on-line coating of reversed-phase silica gel by reagents or doping of porous sol-gel silica with reagents. The retention of Ag, Cd, Cu(II), Co(II), Fe(III), Mn(II), Ni, Pb, and Zn on the sorbents developed was investigated. Quantitative sorption and desorption conditions were optimized. Procedures for the determination of Cd, Cu(II), Fe(III), Pb, and Zn with flame atomic absorption, spectrophotometric, and diffusion scattering spectrometric detection were elaborated. Detection limits for Cd, Cu(II), Fe(III), Pb, and Zn were 3 μg/L, 6 μg/L, 5 μg/L, 40 μg/L, and 1 μg/L, respectively. The procedures were used for the analysis of various real samples, e.g., natural and waste waters, and food.     

New sorbents and indicator powders for preconcentration and determination of trace metals in liquid samples

Two approaches to immobilize complex-forming analytical reagents (PAN, PAR, Xylenol orange, Brombenzothiazo, Crystal violet, Cadion, and Sulfochlorophenolazorhodanine) for the preparation of new sorbents and indicator powders are suggested: on-line coating of reversed-phase silica gel by reagents or doping of porous sol-gel silica with reagents. The retention of Ag, Cd, Cu(II), Co(II), Fe(III), Mn(II), Ni, Pb, and Zn on the sorbents developed was investigated. Quantitative sorption and desorption conditions were optimized. Procedures for the determination of Cd, Cu(II), Fe(III), Pb, and Zn with flame atomic absorption, spectrophotometric, and diffusion scattering spectrometric detection were elaborated. Detection limits for Cd, Cu(II), Fe(III), Pb, and Zn were 3 μg/L, 6 μg/L, 5 μg/L, 40 μg/L, and 1 μg/L, respectively. The procedures were used for the analysis of various real samples, e.g., natural and waste waters, and food. Received: 17 July 1997 / Revised: 20 January 1998 / Accepted: 5 February 1998     

New technique for the determination of trace elements using multiparameter coincidence spectrometry

Multiparameter coincidence g-ray spectrometry based on g-g coincidence is widely used in the field of nuclear structure studies, and has produced many succesful results. In this paper, feasibility of the method for neutron activation analysis of trace elements was studied. Particularly, a long-lived radioisotope ¹²⁹I (T_1/2 = 1.57^.10⁷ y) in algae samples and iridium in geological samples has been determined.     

New marine biological reference materials for trace metals

Summary A list of reference materials and certified reference materials (CRM's) useful to the marine analytical chemist for validation of trace element determinations is given. The preparation and certification for the trace element content of two new marine biological reference materials, dogfish flesh (DORM-1) and dogfish liver (DOLT-1), is described.     

Sequential voltammetric determination of trace metals in meals

An analytical procedure for the sequential determination of Zn(II), Cr(VI), Cu(II), Sb(III), Sn(II), Pb(II) by square wave anodic stripping voltammetry (SWASV) and Fe(III), Mn(II), Mo(VI) by square wave voltammetry (SWV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal is described.The digestion of each matrix was carried out using a concentrated HCl–HNO₃–H₂SO₄ attack mixture, employing dibasic ammonium citrate buffer solution (pH 6.9 and 8.7) as supporting electrolytes. The analytical procedure was verified by the analysis of the standard reference materials Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a.For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation (s_r) was of the order of 3–5%; the accuracy, expressed as relative error (e) was generally of the order of 3–6%.In presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique.Finally, the analytical procedure was transferred and applied to commercial meals sampled on market.A critical comparison with atomic absorption spectroscopic measurements is also discussed.     

Radionuclide X-ray fluorescence analysis of drinking water using preconcentration of trace metals on chelating cellulose exchanger OSTSORB-OXIN

Determination of Cr, Fe, Cu, Zn and Pb in drinking water preconcentrated on a chelating ion exchanger of Czechoslovak production is described. The analytical system consisted of a radionuclide source²³⁸Pu, a Si/Li semiconductor detector and a multichannel analyzer. Results are compared with trehshold limit values recommended for drinking water.     

Radiochemical determination of trace noble metals in silver artefacts

Radiochemical separations are essential for the determination of trace elements in silver artefacts by neutron activation analysis due to the high levels of both short and long-lived activities produced by the matrix, but the sensitivity of the technique permits the examination of small samples. The noble metals are considered most significant from a diagnostic standpoint, and radiochemical techniques have been developed for their determination in samples of a few milligrams. Methods have been investigated for the determination of Pd, Rh, Ir and Pt in samples removed from museum specimens of known provenance.     

Pre-concentration of trace metals from sea-water for determination by graphite-furnace atomic-absorption spectrometry

Determination of Cd, Zn, Pb, Cu, Fe, Mn, Co, Cr and Ni in coastal sea-water by graphite-furnace atomic-absorption spectrometry after preconcentration by solvent extraction and use of a chelating ion-exchange resin is described. Following the extraction of the pyrrolidine-N-carbodithioate and oxinate complexes into methyl isobutyl ketone, the trace metals are further preconcentrated by back-extraction into 1.5M nitric acid. Preconcentration on the chelating resin is effected by a combined column and batch technique, allowing greater preconcentration factors to be obtained. Provided samples are appropriately treated to release non-labile metal species prior to preconcentration, both methods yield comparable analytical results with respect to the mean concentrations determined as well as to mean relative standard deviations. Control and treatment of the analytical blank is also described.     

Intercomparison of five methods for the determination of trace metals in sea water

Trace elements (Mn, Fe, Co, Zn, Ni, Cu and Cr) were preconcentrated from sea water by retention on Chelex-100 resin, APDC/8-quinolinol complexation followed by extraction with 4-methyl-2-pentanon or Freon-113, or coprecipitation with Mg(OH)₂ or Fe(OH)₂. After consideratin of analytical blanks, extraction efficiency, precision preconcentration factor, and suitability for operation on board ship, the best results were obtained by preconcentrating Mn, Fe, Co, Zn, Ni and Cu on Chelex-100 resin and coprecipitation of chromium(III) and (VI) with Fe(OH)₂. Graphite-furnace atomic absorption spectrometry and inductively-coupled plasma atomic emission spectrometry were used for the final measurements. The accuracy of the method was tested by using the reference sea water sample NASS-1.     

On-line preconcentration and GFAAS determination of trace metals in waters

An on-line separation preconcentration system coupled to electrothermal (graphite furnace) atomic absorption spectrometry was developed. A miniature column packed with iminodiacetic acid ethyl cellulose (IDAEC) was inserted into the loop. A peristaltic pump was used to deliver solutions. A flow of air was driven into the packed column, evacuating it between sample loading, washing and elution. The retained analyte was introduced on-line to graphite furnace using countercurrent elution with HNO₃. The system was applied for the determination of V, Co and Pb in medicinal mineral water samples, and nickel in sea water samples. The detection limits (3σ) were 0.058, 0.022, 0.067, 0.062 μg/l for Co, Pb, V, and Ni, respectively. The R.S.D. (n=5) was <5% at 0.4–1.0 μg/l concentration range.     

Preconcentration and determination of trace metals by flow injection micelle-mediated extraction using flame atomic absorption spectrometry

Micelle-mediated extraction/preconcentration is incorporated on-line into a flow injection system used to determine low levels of Cd(II), Co(II), Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) present in various samples. The analyte is complexed with HBDAP (N,N′-bis(2-hydroxy-5-bromo-benzyl)1,2-diaminopropane). Under optimal conditions, a solution of 30% (m/v) NaCl and a sample solution containing 2.5 mL of 1% (m/v) sodium dodecyl sulfate (SDS), 0.5 mL of 1.8 × 10⁻³ M HBDAP and 2.5 mL of pH 8.5 borate buffer solution in 25 mL were pumped through the cotton filled mini-column; onto which the surfactant-rich phase containing the complex is collected. A solution of 0.5 M HNO₃ in 50% acetone is used as the eluent. The limits of detection are (ng mL⁻¹) Cd = 0.39, Cu = 3.2, Co = 7.5, Mn = 3.0, Ni = 3.4, Pb = 17.9 and Zn = 0.89 if the sample is allowed to flow for 30 s, but improved for extended preconcentration periods. Analysis of liquid and solid reference materials showed good agreement with the certified values. Complex formation constants between HBDAP and these metal ions were also determined potentiometrically.     

Use of a new type of 8-hydroxyquinoline-5-sulphonic acid cellulose (sulphoxine cellulose) for the preconcentration of trace metals from highly mineralised water prior their GFAAS determination

Sulphoxine cellulose microcolumn was used in an FI-GFAAS system for the preconcentration of trace metals, Cd, Co, Ni, Pb and V from water and from highly mineralised water and also in the presence of complexing agent, e.g. citrate. The recovery was quantitative at pH 5 for all of the elements from NIST 1643c trace elements in water SRM and from highly mineralised water samples. No significant difference was found in the sorption of V(IV) and V(V) during preconcentration. The preparation of the 8-hydroxyquinoline-5-sulphonic acid cellulose (sulphoxine-cellulose) by Mannich reaction from aminoethyl cellulose or via chlorodeoxy and ethylenediamine cellulose is also described.     

Novel disposable bismuth-sputtered electrodes for the determination of trace metals by stripping voltammetry

This work describes a novel type of bismuth electrode for stripping voltammetry based on coating a silicon substrate with a thin bismuth film by means of sputtering. The bismuth-based sensors were characterized by optical methods (scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD)) and as well as by linear sweep voltammetry. Subsequently, the electrodes were tested for the detection of low concentrations of trace metals (Cd(II), Pb(II) and Ni(II)) by stripping voltammetry. Well-formed stripping peaks were observed for trace concentrations of the target analytes demonstrating “proof-of-principle” for these sensors. This type of electrochemical device, utilizing thin-film technology for the formation of the bismuth film, holds promise for future applications in trace metal analysis.     

Accuracy of determination of trace metals in soil and sewage sludge

Errors in the analysis of liquid samples are often large enough to be important. For solid materials, additional potential complications arise in separating the determinand from the sample matrix and in controlling possible interferences from co-extracted species. These considerations have led to the development of a stepwise, co-ordinated approach by which a group of laboratories have achieved predefined standards of accuracy. Sample digestion has been examined. The analysis of digests has then been addressed; the control of analytical precision has been emphasised. Finally, a demonstration of overall comparability has been undertaken. The results are presented.