Determination of mercury in seawater by cold vapour atomic absorption spectrophotometry

Summary To avoid systematic errors in the sampling and determination of mercury in seawater an integrated sampling-analyzing system has been developed. A 500 ml PTFE-bottle attached to a sampling gear is used as sampling vessel for the cold vapour atomic absorption Spectrophotometry, using nitrogen aeration, SnCl₂ reduction, and preenrichment/ purification by amalgamation on finely dispersed gold. The detection limit of this procedure was found to be 0.5 ng·l^–1 and the coefficient of variation 4% for 1.5 ng·l^–1.

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Bestimmung von Quecksilber im Meerwasser durch Kaltdampf-Atomabsorptionsspektralphotometrie

Zusammenfassung Zur Vermeidung von systematischen Fehlern bei der Ultraspurenanalyse von Quecksilber im Meerwasser wurde ein integriertes Probenahme-Analysensystem entwickelt. Eine 500 ml PTFE-Flasche dient in Verbindung mit einem Greifarm als Probenahmegefäß für Oberflächenwasser und wird anschließend als Reaktionsgefäß in die Analysenapparatur gesetzt. Die Bestimmung erfolgt mit der Kaltdampf-Atomabsorptionsspektralphotometrie nach Reduktion des Quecksilbers durch SnCl₂ und Anreicherung sowie Reinigung mittels Amalgamierung an feinverteiltem Gold. Die Nachweisgrenze dieses Verfahrens beträgt 0,5 ng·l^–1, der Variationskoeffizient 4% bei 1,5 ng·l^–1.

     

Determination of particle-bound trace metals in high purity hydrogen chloride

Summary Two analytical procedures for the determination of particle-bound trace metals in high purity hydrogen chloride are described. Polycarbonate membrane filters with a pore diameter of 0.05 m were used for sampling. Membrane filtration with subsequent instrumental neutron activation analysis (using irradiation with a thermal neutron flux of 10¹³ n cm^–2 s^–1 and irradiation and measurement times of either 20 min) has made it possible to determine the elements Br, Mg, Mn, Na, Sb, Sn, Te, Ti and Zn. For a gas sample volume of 500 l the detection limits determined are in the range of 0.86 ng l^–1 for Zn to 0.30 pg l^–1 for Mn.The elements Cr, Cu, Fe, Mn and Ni were determined by membrane filtration with subsequent graphite tube furnace atomic absorption spectrometry. In this case the detection limits achieved are (for a gas sample volume of 500 l and 4 ml digestion solution) between 8.4 pg l^–1 for Fe and 2.1 pg l^–1 for Cu. The analytical procedures were applied for the characterisation of high purity hydrogen chloride, which is used in the manufacture of highly integrated semiconductor components, by trace analysis, both directly on the gas cylinder and at the 'point of use after passing through the supply system. A review of the status of element determination in high purity process gases is given.

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Bestimmung von partikelgebundenen Metallspuren in hochreinem Chlorwasserstoff

     

Determination of trace metals in sea waters of the Albanian coast by energy-dispersive X-ray fluorescence

Preconcentration of trace transition and heavy metal ions by precipitation with APDC has been combined with energy-dispersive X-ray fluorescence for environmental sea water analysis. The preconcentration procedure implies adding of 500 g Mo ion and 10 ml of 1% water solution of APDC to a 500 ml water sample at pH 4, filtering off on a Millipore filter and analyzing after drying. Realistic detection limits are at 1 g·l^–1 level and precision varies between 10–25% at about 5 g·l^–1 level, depending on the element. Eleven sea water samples, covering Albanian Adriatic and Ionian coast, are analyzed for trace metal ions.     

Flow-injection hydride generation atomic absorption spectrometric study of the automated on-line pre-reduction of arsenate, methylarsonate and dimethylarsinate and high-performance liquid chromatographic separation of their -cysteine complexes

An automated on-line pre-reduction of arsenate, monomethylarsonate (MMA) and dimethylarsinate (DMA) using flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) is feasible. The kinetics of pre-reduction and complexation depend strongly on the concentration of -cysteine and on the temperature in the following increasing order: inorganic As(V)<DMA<MMA. Arsenate is pre-reduced/complexed within less than 50 s at 70–100°C compared to 1 h at room temperature, while MMA and DMA require 1.5–2 min at 70–100°C and up to 1–2 h at room temperature. The characteristic masses and concentrations for 100 μl injections are 0.01 ng and 0.1 μg l⁻¹ in integrated absorbance and 0.2 ng and 2 μg l⁻¹ in peak height measurements, and the limits of detection are ca. 0.5 ng and 5 μg l⁻¹, respectively. In a high-performance liquid chromatography (HPLC)–HGAAS system, the -cysteine complexes of inorganic As(III), MMA and DMA are best separated within 7 min by HPLC on a strongly acidic cation exchange column such as Spherisorb S SCX 120×4 mm (5 μm) with a mobile phase containing 12 mmol l⁻¹ phosphate buffer (KH₂PO₄/H₃PO₄)–2.5 mmol l⁻¹ -cysteine, pH 3.3–3.5. Upon dilution to -cysteine levels below 10 mmol l⁻¹, which are compatible with HPLC separations, the DMA–cysteine complex is unstable on storage. No baseline separations are possible with anion exchange and reverse phase C₁₈ HPLC columns. The limits of detection with 50 μl injections in peak area mode are ca. 0.5 ng and 10 μg l⁻¹, respectively.     

Extraction and spectrophotometric determination of uranium in phosphate fertilizers

An extraction and spectrophotometric method for determination of trace amounts of uranium in phosphate fertilizers is described. It is based on the extraction of uranium with trioctylphosphine oxide in benzene and the spectrophotometric determination of uranium with Arsenazo III in buffer-alcoholic medium. The maximum absorbance occurs at 655 nm with a molar absorptivity of 1.2·10⁴ l·mol^–1·cm^–1. Beer's law is obeyed over the range 0.6–15.0 g·ml^–1 of uranium(VI). The proposed method has been applied successfully to the analysis of phosphate fertilizers with phosphate concentrations of 45% P₂O₅.     

Separation of 99mTc from 99Mo by Using TOPO — Kerosene Supported Liquid Membrane

Transport of ^99mTcO₄ ^– ions across TOPO-kerosene based supported liquid membrane was investigated at different concentrations of phosphoric acid as a feed solution and different concentrations of TOPO in the membrane, where 0.9% NaCl aqueous solution was used as a stripping solution. The flux of TcO₄ ^– ions across this liquid membrane varied with the concentration of both H₃PO₄ and TOPO. The best permeability coefficient was obtained at concentrations, [H₃PO₄] = 3 mole·l^–1 and [TOPO] = 0.5 mole·l^–1 (P = 2.08·10^–9 m²·s^–1). The results were utilized for the separation of ^99mTc from ⁹⁹Mo, where a selective and effective separation was obtained since no ⁹⁹Mo transport across this liquid membrane was noticed while a high rate of ^99mTc transport took place.     

Analysis of mercury(II), methylmercury and phenylmercury by RPHPLC with micellized dithizone post-column derivatization photometric detection

Post-column derivatization detection system based on dithizone solubilized in cetyltrimethyl-ammonium hydrogenesulfate micellar media at pH 2.0 was devised and evaluated for selective detection of mercury(II), methylmercury and phenylmercury in reversed-phase HPLC system with photometric detection at 500 nm. This reagent solution is fully compatible with acidic organo-aqueous mobile phases generally used in RPHPLC. With the aid of the detection systematic study of the retention behaviour of three mercury species on octadecylsilica sorbent was carried out. Influence of pH, acetonitrile volume fraction, complex forming additives was investigated in detail. In mobile phase consisting of 5–30% of acetonitrile in water at pH 2.0 and 2·10^–4 mol·I^–1 DCTA linear calibration curves were measured in range 20–1000 ppb with correlation coefficient better than 0.99. Detection limits were 1–5 ng for this three mercury species. Interferences of copper(II) and silver(I) are negligible.     

Selective Sorption–Spectrometric Determination of Nanogram Amounts of Vanadium(IV) and Vanadium(V)

Conditions of the selective sorption–spectrometric determination of vanadium(IV) and vanadium(V) using sulfonitrophenol M were found. The determination of vanadium (visual test (RSD = 30%) using a reference color scale or quantitative determination (RSD < 10%) by diffuse reflectance spectra is performed immediately after the dynamic-mode sorption of its colored complexes with sulfonitrophenol M at pH 3.5 (vanadium(IV)) or with sulfonitrophenol M and hydroxylamine at pH 1.5 (vanadium(V), 650 nm) at the surface of polyamide membrane disks (d= 1 cm, l= 0.1 mm, m= 2.7 mg). The flow rate is 10–20 mL/min. The detection limit is 5–7 ng of vanadium in the support zone or 0.2–0.5 ng/mL. The determination of 0.5–5 ng/mL vanadium(V) at pH 1.5 does not interfere with 20-fold amounts of V(IV) and 1000-fold amounts of Ni, Zn, Cd, Mg, Co, Cr(III), Mn, PO^3- ₄, and F^–.     

Atomic absorption spectroscopic determination of molybdenum in aqueous tetrathiomolybdate solutions

The flame atomic absorption spectroscopic determination of molybdenum, in aqueous solutions of tetrathiomolybdate (MoS ₄ ^2– , TTM) and paramolybdate species (Mo₇O ₂₄ ^2– , PM) has been investigated. A serious signal decrease occurred, if molybdenum has been present as tetrathiomolybdate species, and the sensitivity loss has been 85%. To improve the sensitivity, the solutions of TTM have been digested by wet-acid treatment, and made 0.14 mol·l^–1 ammonia. Finally, Mo has been determined by AAS using a nitrous oxide-acetylene flame. The range of the calibration was 0–100 mg·l^–1 and the relative standard deviation of the slope was less than 1%.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Determination of 3-amino-1,2,4-triazole (amitrole) in environmental waters by capillary electrophoresis

3-Amino-1,2,4-triazole (amitrole) is a widely used pesticide, with many difficulties to be analyzed at the regulatory level in drinking water, because its high solubility in water. This paper describes a simple and fast method for the simultaneous determination of amitrole and atrazin-2-hydroxy, principal degradation product of s-triazines, by capillary zone electrophoresis. Separation and determination of these herbicides in water samples was performed in 0.02 mol l⁻¹ phosphate buffer at pH 3.2. The method allows determination of the amitrole and atrazin-2-hydroxy in water samples in concentration lower than 100 μg l⁻¹. The detection limits using a previous preconcentration step of amitrole in Alberche River (Comunidad Autónoma de Madrid, Spain) and drinking water spiked samples was of 4 μg l⁻¹.     

Titrimetry in a continuous flow system

Summary Sulphate in the range of 5–2000 mol · l^–1 is automatically titrated with Ba(II) in a device with an optical detection which is able to correct automatically for dilution and turbidities. The flow-through system contains 80% v/v ethanol; the indicator is dimethyl sulfonazo(III). Above a concentration level of about 20 mol · l^–1 SO ₄ ^2– the standard deviation is less than 5% rel. The titration time is negligibly small as compared to the sampling time.

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Titrimetrie im DurchflußsystemI. Apparatur und Sulfatbestimmung

Zusammenfassung Sulfat wird im Bereich von 5–2000 mol · l^–1 automatisch mit Ba(II) mit einem Gerät mit optischer Detektion titriert, das automatisch für Verdünnung und Trübung korrigieren kann. Das Durchflußsystem enthält 80% v/v Äthanol; Indicator ist Dimethylsulfonazo(III). Die Standardabweichung für Proben mit einem Sulfatgehalt höher als 20 mol · l^–1 ist niedriger als 5% rel. Die Titrationsdauer ist vernachlässigbar im Vergleich mit der Zeit für die Probennahme.

     

Zur inversvoltammetrischen Bestimmung von Eisen(III)-dimethyldithiocarbamat (Ferbam)

The influence of important conditions for the determination of Ferbam by the anodic stripping technique has been studied: composition of base electrolyte, dependence on concentration, size of mercury drop, pre-electrolysis time and potential, speed of potential shift, temperature, and effect of stirring. The results are compared with those of determinations by classical polarography, and the electrode process is discussed. The smallest concentration of Ferbam for determination is 2.5 ng per ml (about 6×10^–9 M) and for qualitative detection 0.5 ng per ml (about 1×10^–9 M). The relative standard deviation of the method is about ±15%.In der Arbeit wird der Einfluß der bei der voltammetrischen Bestimmung von Ferbam [Eisen(III)-dimethyl-dithiocarbamat] bedeutsamen Versuchsparameter untersucht: Leitelektrolytzusammensetzung, Konzentrationsabhängigkeit, Größe des Quecksilbertropfens, Wartezeit und -potential, Potentialänderungsgeschwindigkeit, Temperatur und Rührwirkung. Die dabei erhaltenen Resultate werden mit den bei der klassisch-polaro-graphischen Bestimmung gemachten Beobachtungen verglichen und der Elektrodenvorgang diskutiert. Bei der Ferbambestimmung beträgt die Grenzkonzentration 2,5 ng/ml (etwa 6·10^–9M) und für die qualitative Erkennung 0,5 ng/ml (etwa 1·10^–9M). Der relative mittlere Fehler beträgt etwa ± 15%.     

Spectrophotometric determination of uranium with 5-(2′-carboxyphenyl)azo-8-quinolinol in the non-ionic micellar medium of Triton X-100

Triton X-100, a non-ionic surfactant, has been used to sensitize the reaction of 5-(2-carboxyphenyl)azo-8-quinolinol with uranium in aqueous medium at pH 5.2–6.1 to form a wine red coloured complex. The micellar sensitization results in two and a half-times enhanced molar absorptivity enabling the determination of uranium in rock samples at ppm level, stability of the complex enhanced from 4 hours to at least 72 hours. Extraction of the complex is avoided making the procedure simple, rapid and easy in operation. The molar absorptivity and Sandell's sensitivity of the complex are 1.50·10⁴l·mol^–1·cm^–1 and 15.9 ng·cm^–2, respectively, at _max=568 nm. Beer's law is obeyed over the range 0–3.3 g·ml^–1 of uranium. An amount as low as 0.19 g·ml^–1 of uranium could be determined satisfactorily within a relative standard deviation of ±1.3%. The limits of determination and practical quantitation are 0.29 and 1.80 ppm, respectively. The method was applied to the determination of uranium in soil, stream sediment and rock samples.     

Determination of decabromodiphenyl ether in sediments using selective pressurized liquid extraction followed by GC–NCI-MS

A method based on selective pressurized liquid extraction (SPLE) followed by gas chromatography–negative ion chemical ionization-mass spectrometry (GC–NCI-MS) has been evaluated for analysis of decabromodiphenyl ether (PBDE-209) in sediment samples. Instrumental operating conditions such as source temperature and system pressure were optimized in the NCI-MS system, giving an instrumental detection limit of 2 pg. The limit of determination of the entire SPLE–GC–NCI-MS procedure was around 50 pg g^–1 dry weight (dw), with repeatability of replicates between 4 and 21% relative standard deviation. Application of the method to 13 different river and marine sediment samples collected in Spain revealed that levels of decabromodiphenyl ether ranged between 2 and 132 ng g^–1 dry weight.     

Determination of some selected polycyclic aromatic hydrocarbons in environmental samples by high-performance liquid chromatography with fluorescence detection

Summary Analytical methods for the determination in environmental samples, of some selected Polycyclic Aromatic Hydrocarbons (PAH's), which are included on the EPA Priority Pollutant list, have been developed and evaluated. The methodology involves the extraction of PAH's from water samples by solvent extraction with dichloromethane. Solid samples were ultrasonically extracted with acetone/hexane and the extract was cleaned up on a silica gel/alumina column. The concentrated and cleaned up extracts were analysed by HPLC on a polymeric C₁₈ column using a gradient of acetonitrile/water as the mobile phase and fluorescence detection. Typical detection limits lie in the range of 1–30 ng ml^–1 of the analytes, but after sample pretreatment detection limits of 10–300 ng l^–1 were obtained. The extraction, clean-up and HPLC methodology was applied to the determination of selected PAH's in coal washings samples and the method was validated by the quantification of PAH's in a natural contaminated and a spiked sediment.     

Microcolumn preconcentration and gas chromatography-microwave induced plasma-atomic emission spectrometry (GC-MIP-AES) for mercury speciation in waters

A novel method for the direct determination of mercury species at the ng l^–1 level in natural waters is described. Methyl-, ethyl- and inorganic mercury are preconcentrated on a sulphhydryl cotton microcolumn incorporated in a flow injection system. Retained mercury species are then eluted with hydrochloric acid solution (3 mol/l) and subjected to phenylation before determination by gas chromatography-microwave induced plasma-atomic emission spectrometry. Limits of detection for mercury species are 10 ng l^–1 for methyl- and ethyl-mercury and 16 ng l^–1 for inorganic mercury based on processing 200 ml of sample. Application of the methodology to waters of the Manchester Ship Canal revealed elevated levels of methylmercury and inorganic mercury.     

Determination of total chlorine in waste oil

Summary A simple method has been developed to determine the concentration of organic chlorine in waste oil. The determination is based on the conversion of organic chlorine to inorganic chloride by reaction with sodium biphenyl followed by extraction with nitric acid and a mixture of nitric acid and water. The concentration of chloride is determined by direct potentiometry with an ion-selective electrode. The limit of determination amounts to 3·10^–5 mol·l^–1 chloride ions with a standard deviation of 3.5%. Different samples of waste oil have been analyzed and the results have been compared to those obtained by combustion in a H₂/O₂ flame followed by potentiometric titration with silver nitrate.     

Determination of aluminium, scandium and rare earth elements by emission flame spectrometry

Summary Emission spectrometry in nitrous oxide-acetylene flames in combination with a highly resolving double monochromator and sensitive detecting system enables simple, sensitive and selective determinations of aluminium, scandium and all rare earth elements with exception of cerium in complicated matrices. Calibration plots are linear for a large concentration interval ( 100 g·ml^–1), detection limits are in ng · ml^–1 level and RSD does not exceed 3% on the optimal concentration level of the particular element. The determination of Al, Sc, Eu and Yb showed particular advantages as to methods using ICP-spectrometry.

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Bestimmung von Aluminium, Scandium und Seltenen Erden durch Emissions-Flammenspektrometrie

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Flow-injection determination of HMF in honey by the Winkler method

Summary A new method for the semiautomatic determination of 5-hydroxymethylfurfural (HMF) by photometric flow injection analysis on the basis of the Winkler's reaction is proposed. The derivative FIA-gram signals were also obtained and detection limit was decreased. The linear range of determination is 2.3–98 g·ml^–1. The presence of sugars is well tolerated. The proposed method can be employed to determine HMF in honey samples with a sampling frequency of 35 h^–1.     

Determination of selenium in human milk by electrothermal atomic absorption spectrometry and chemical modification

A method was developed for the determination of selenium in human milk using electrothermal atomic absorption spectrometry. The use of chemical modifiers as well as their implications during the pyrolysis step was examined. The chemical modifiers that were studied were Zr, Ir as well as the mixed modifier Zr-Ir. The Ir modifier stabilized selenium at 1000 °C, Zr at 800 °C, while the mixed modifier at 1200 °C. The effect of modifier mass was studied and was found that better results are achieved with addition of 2 μg Zr and 2 μg Ir. The characteristic masses of selenium in the presence of Zr, Ir and the mixed modifier were found to be 73.3, 18.0 and 14.7 pg, respectively, while the corresponding limits of detection were found 2.0, 0.50 and 0.41 μg l⁻¹. Consequently better results were obtained with the mixed modifier. The developed method was applied for the determination of selenium in human milk, which was digested with a HNO₃ + H₂O₂ mixture in a microwave oven. The limit of detection of the method was 1.37 μg l⁻¹, the characteristic mass, m₀, was 48.8 pg and the repeatability was less than 5% as R.S.D.(%). Matrix matched calibration was used. Recoveries were estimated to be 93-105%. The method was applied to breast milk of Greek women (n = 9) and the Se content was found to be in the range 16.7-42.6 μg l⁻¹ with mean value 27.4 ± 5.5 μg l⁻¹.