Cobalt In Biological Materials Research Articles

Determination of cobalt in biological materials by RNAA via induced short-lived 60mCo

A procedure is described for the determination of cobalt in biological materials, based on post-irradiation separation radiochemical neutron activation analysis (RNAA) using the short-lived induced radionuclide 60mCo. 60mCo has been rarely used as an indicator radionuclide in NAA due to low concentrations usually found in biological materials and due to its short-half life (t1/2=10.5 min). Using a procedure based on dissolution of the irradiated sample, precipitation of Co with sodium diethyldithiocarbamate, extraction of the complexes formed into toluene, purification and counting by gamma spectrometry, Co was determined in biological materials at ng g−1 levels. For evaluation of gamma spectra, the Hypermet-PC and HyperLab 2002 Gamma Spectroscopy systems were used. Differences between these software programs are discussed. The results of the analyzed biological materials (reference materials), together with the identified uncertainty sources, are presented. The RNAA method allows rapid, robust and simple separation of short-lived 60mCo from neutron irradiated biological samples in high and reproducible yield (83%), with adequate sensitivity for routine use, reducing the time necessary for the irradiation, processing and measurement in comparison to classical NAA using 60Co, thus retaining the important advantage of NAA as a blank free technique.

Metrological assessment of the high-accuracy RNAA method for determination of cobalt in biological materials.

The paper summarizes work on the development of the high-accuracy RNAA method for the determination of trace amounts of cobalt in biological materials. The method is based on a combination of neutron activation with selective and quantitative isolation of the analyte in a state of high radiochemical purity by use of column chromatography followed by gamma-ray spectrometric measurements. The method was devised according to a set of rules, which were formulated to obtain high accuracy of the method. The procedure has been also equipped with several criteria as key factors in quality assurance. Qualification of the high-accuracy RNAA method as a primary ratio method has been demonstrated and its usefulness in the certification of the candidate reference materials tea leaves and mixed Polish herbs is presented.

Electrothermal atomic absorption spectrometric determination of cobalt in biological samples and natural waters using a flow injection system with on-line preconcentration by ion-pair adsorption in a knotted reactor.

An on-line flow injection preconcentration-ETAAS method is developed for trace determination of cobalt in biological materials and natural samples by ion-pair sorption on the inner walls of a PTFE knotted reactor. The ion-pair is formed between the negatively charged cobalt-nitroso-R-salt complex and the tetrabutylammonium counter-ion. An enhancement factor of 15, a sampling frequency of 17 and a concentration efficiency of 4 are obtained for a preconcentration time of 60 s and a sample loading flow rate of 5 mL min(-1). The detection limit (3sigma) is 5 ng L(-1). The relative standard deviation at the 0.2 microg L(-1) level is 2.3%. The analytical results obtained for standard reference materials are in good agreement with the certified or indicated values and satisfactory recoveries of spiked cobalt in tap water are obtained.

Determination of Cobalt with a Tungsten Tube Atomizer by Electrothermal Atomic Absorption Spectrometry and its use for the Analysis of Biological Materials

The determination of cobalt by electrothermal atomic absorption spectrometry with a tungsten tube atomizer has been investigated. The absolute characteristic mass (the mass of element giving 0.0044 abs.) of cobalt by the atomizer was 5.8 pg and the detection limit was 0.65 ng/ml (3S/N). The interferences caused by large amounts of interferents like Al, Ca, Cu, Fe, K, Mg, Na, Pb and Zn were evaluated and most of these elements were found to interfere with the cobalt signal. Ammonium thiocyanate as a chemical modifier was found to be efficient to eliminate the severest interferences. The accuracies of the recommended method were found to be almost satisfactory for the determination of cobalt in biological materials, as shown by a comparison with the reported values of NIST materials at the 0.02–0.4 μg/g level.

Flame atomic absorption spectrometric determination of cobalt in biological materials using a flow-injection system with on-line preconcentration by ion-pair adsorption

Traces of cobalt in biological materials were determined by flow-injection flame atomic absorption spectrometry. The analyte was preconcentrated and separated from the bulk of the matrix by on-line ion-pair adsorption of the cobalt-nitroso-R salt complex in the presence of tetrabutylammonium bromide as a counter-ion reagent in a flow-injection system. The ion-pair was collected on an on-line C 18 micro-column and eluted by ethanol directly into the nebulizer-burner system of an atomic absorption spectrometer. The interference from iron was masked by merging a sodium citrate solution to the sample flow. An enhancement factor of 40 and a sampling frequency of 45 h −1 were obtained for a collecting time of 60 s. The detection limit (3σ) in the sample digest was 3 μg l −1. The relative standard deviation at the 50 μg l −1 cobalt level was 2.4%. The analytical results obtained for standard reference biological material were in good agreement with the certified or reference values.

Determination of cobalt in biological samples by radiochemical neutron activation analysis employing reverse-phase chromatography.

We report the final part of our "on-line yield" pilot program in this article. This last part deals with aspects of accuracy and precision of the determination of cobalt in biological materials by RNAA with on-line yield determination. To obtain an insight into the accuracy of the technique, certified reference materials were analyzed, and for selected materials, results obtained by INAA and RNAA of identical samples have been compared. It shows that the mineralization in our RNAA scheme may be a sample-related source of systematic errors that is not related to the presence or absence of HF. Finally, we present some critical notes on pros and cons of the practice of on-line yield concept and some ideas for further research.

Accurate determination of cobalt traces in several biological reference materials.

A newly devised, very accurate ("definitive") method for the determination of trace amounts of cobalt in biological materials was validated by the analysis of several certified reference materials. The method is based on a combination of neutron activation and selective and quantitative postirradiation isolation of radiocobalt from practically all other radionuclides by ion-exchange and extraction chromatography followed by gamma-ray spectrometric measurement. The significance of criteria that should be fulfilled in order to accept a given result as obtained by the "definitive method" is emphasized. In view of the demonstrated very good accuracy of the method, it is suggested that our values for cobalt content in those reference materials in which it was originally not certified (SRM 1570 spinach, SRM 1571 orchard leaves, SRM 1577 bovine liver, and Czechoslovak bovine liver 12-02-01) might be used as provisional certified values.

A definitive method for the determination of trace amounts of cobalt in biological materials by neutron activation analysis

A highly accurate and precise procedure deserving the name of “definitive method” has been devised for the determination of copper in biological materials. The method is based on combination of neutron activation and very selective and quantitative post-irradiation separation of copper from other radionuclides by extraction chromatography, using columns with LIX 70 on Bio-Beads SM-1, followed by gamma-ray spectrometric measurement. All potential sources of errors were carefully examined and eliminated or appropriate corrections were introduced into the procedure. The method contains several warning mechanisms safeguarding against making gross errors. Limit of detection for rather short irradiation time (tir≤1 h) (which enables radiochemical work without sophisticated shielding) amounts to 15 μg/kg. Results for copper concentration in several NBS, IAEA and other certified reference materials are presented and a new “recommended value” for IAEA's Milk Powder (A-11) is proposed.

Multi-element analysis of biological material by RNAA using HPLC with on-line yield determination

The idea to use high performance liquid chromatography with continuous UV detection for multi-element radiochemical separation and simultaneous multi-element “on-line” yield determination is introduced. The validity of the concept was evaluated by demonstrating the constancy of the ratio of the signals for a main isotope (60Co) and a carrier (59Co) as a function of the elemental mass processed in the separation. The suitability of the method for practical purposes is demonstrated by its application to the RNAA determination of cobalt in biological materials. It is concluded that the method, although not yet completely developed, bears the potential of improving both accuracy and precision of multi-element RNAA.

Determination of cobalt in urine by gas chromatography—mass spectrometry employing nickel as an internal standard

A gas chromatographic—mass spectrometric method for the determination of cobalt in biological materials employing stable enriched 62Ni as an internal standard and using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent is described. The method involves the addition of a known amount (1 μg) of 62Ni to the sample, the formation of the chelate and the determination by selected-ion monitoring of the m/z 571 574 ratio, which corresponds to 59Co 62Ni . No appreciable memory effect was observed, and an acceptable dynamic range of 100 was found. There was good agreement between the cobalt concentration values determined by gas chromatography—mass spectrometry and electrothermal atomic absorption spectrometry. The present method has high sensitivity and can be used for the quantitation of cobalt at concentrations as low as 1 μg/l. The use of enriched 62Ni circumvents the problem caused by endogenous nickel and simultaneously provides data on the nickel concentration in the biological sample without any additional experimental effort.

Determination of cobalt in biological materials by voltammetry and electrothermal atomic absorption spectrometry.

For industrial purposes cobalt is used to a large extent. About 2,300 persons are occupationally exposed to this carcinogenic metal in Western Germany. As reliable analytic methods for biological monitoring are not available we developed procedures for analyzing cobalt in whole blood and urine by using two independent methods, voltammetry and ETAAS. For ETAAS-analysis of urine the cobalt content is chelatized and extracted in an organic solvent. This clean-up step enables us to calibrate with aqueous standards.--Samples of whole blood are directly injected into the graphite tube after being diluted with a homogeniziser. For their gentle thermal decomposition we use a temperature/time programme containing six steps. Both kinds of sample treatments are uncomplicated and permit routine applications. For voltammetric determination of cobalt in urine and blood the biological material must be completely mineralized. The dry residue is dissolved in a NH4Cl/NH3 solution. Cobalt is chelatized with 2,3-butanedione-dioxime and preconcentrated by adsorption at the hanging mercury electrode. By scanning the potential into negative direction the cobalt complex is reduced. The resulting signal can be used for the quantitative determination. For comparison of both methods we have analyzed blood and urine samples of occupationally exposed persons. We found very good correlations with a statistical significance at the level of 0.01%.

Assessment of differential-pulse adsorption voltammetry for the simultaneous determination of nickel and cobalt in biological materials

An assessment of the voltammetric method based on chelate adsorption at the hanging mercury drop electrode is described for the simultaneous determination of nickel and cobalt in biological materials. The interfacial accumulation of the elements as metal dimethylglyoximates during the adsorption step, and the use of differential-pulse voltammetry during the reduction step, provide substantial gains in the sensitivity of their voltammetric responses. The decomposition of the sample material by direct dry ashing provides a blank-free approach for the accurate determination of the elements. Application of the method to the available certified biological reference materials for cobalt and nickel was successful. The limits of detection obtained under the conditions of this study were 0.01 μg g −1 and 0.02 μg g −1 for cobalt and nickel, respectively, in bovine liver.

Combined ion exchange - spectrophotometric method for the simultaneous determination of vanadium and cobalt in biological materials.

A combined anion exchange-spectrophotometric method has been developed for the determination of vanadium and cobalt in biological materials. A sample is dry ashed at 420 °C, the ash (ca. 0.5 g) is decomposed with a mixture of perchloric, nitric and hydrofluoric acids, and finally is taken up in hydrochloric acid. The metals are adsorbed by anion exchange on an Amberlite CG 400 (SCN–) column from a dilute ammonium thiocyanate-hydrochloric acid solution. The adsorbed vanadium and cobalt are separated chromatographically by elution with 12 M hydrochloric acid and 2 M perchloric acid, respectively. Both fractions of vanadium and cobalt are subsequently purified by anion exchange from 0.1 M hydrochloric acid-3%V/V hydrogen peroxide for vanadium and 6 M hydrochloric acid for cobalt. Vanadium and cobalt in the effluents are determined spectrophotometrically with 4-(2-pyridylazo)resorcinol. Results for the determination of vanadium and cobalt in various materials of biological origin and in NBS standard biological samples are given.

Determination of cobalt in biological materials by atomic absorption spectrometry

Determination of cobalt in biological materials by atomic absorption spectrometry

An improved method for the determination of cobalt in biological materials

A previously described method for the determination of microgram quantities of cobalt in biological material with diphenylthiocarbazone (dithizone) has been modified to allow the quantitative extraction of cobalt from other metals, with 1-nitroso-2-naphthol as the complexing agent. The effect of reagent concentration and the optimal pH range for the extraction are presented. The determination is completed spectrophotometrically by means of the cobalt-nitroso-R salt complex.

Microdetermination of Cobalt in Biological Materials

Microdetermination of Cobalt in Biological Materials

A test for cobalt

Dimethylglyoxime was used by Braley and Hobart 1 as an analytical reagent for cobalt following the researches of Tschugaeff 2 on metallic derivatives of dioximes. Compounds containing ammonia or pyridine were studied, and the brown colorations permitted to detect as little as 5 γ of cobalt. Using the same reagent combined with alkaline sulfides, Feigl and von Tustanowska 3 obtained a violet red coloration which allowed them to detect cobalt ion in a dilution of 1 to 830000. Bertrand and Machebeuf 4 developed a colorimetric method for the determination of cobalt in biological materials. Charottino 5 replaced ammonia by certain amines, chiefly aromatic ones (benzidine), and claimed to have thus increased the sensitivity of the test, which was confirmed by Braun 6. Finally, by the use of toluidine, Spacu and Macaronici 7 attained a still higher sensitivity.

Determination of Cobalt in Biological Materials with Nitrosocresol

Determination of Cobalt in Biological Materials with Nitrosocresol