Conny Haraldsson

Competition between iron- and carbon-based colloidal carriers for trace metals in a freshwater assessed using flow field-flow fractionation coupled to ICPMS

Abstract Flow field–flow fractionation (FlFFF) coupled to an inductively coupled plasma mass spectrometer (ICPMS) has been used to determine the chemical composition of colloids from a freshwater sample as a function of size. Organic carbon and iron are the most abundant colloidal components, and are considered as the major carrier phases for other chemical elements present. The size distribution of organic carbon colloids shows a single peak with an estimated hydrodynamic diameter between 1 and 1.5 nm, while the iron colloids show a more complex distribution centred at larger colloid sizes with estimated hydrodynamic diameters up to 5 nm. The association of 32 trace elements with these two carrier colloids has been quantified by deconvolution analysis, and the resulting distributions are shown to be chemically consistent. The observed distributions are also shown to be broadly consistent with predictions from speciation modelling for the subset of 8 elements for which appropriate stability constants are available.

Trace metals in the water columns of the Black Sea and Framvaren Fjord

Abstract The trace metals cadmium, copper, nickel, lead, zinc, cobalt, iron and manganese from the oxic and anoxic water columns of the Black Sea and Framvaren Fjord are reported. The importance of particulate metal analysis is shown by data for Framvaren Fjord, which acts as a trap for trace metals. The input of trace metals is calculated based on data on the inflowing water.

Determination of nickel and cobalt in natural waters and biological material by reductive chronopotentiometric stripping analysis in a flow system without sample deoxygenation

Abstract The instrumental set-up consists of a thin-layer cell with a glassy carbon working electrode and an inlet valve by means of which six different solutions can be sucked through the cell. The system is controlled by a microprocessor and suction is provided by means of a peristaltic pump. In the first step of the analytical cycle, a mercury film is plated onto the glassy carbon electrode and then the sample solution is allowed into the cell and nickel(II) and cobalt(II) are potentiostatically adsorbed onto the mercury film as their dimethylglyoxime complexes. Nickel(II) and cobalt(II) are then reduced in a medium of 5 M calcium chloride by means of constant current and simultaneously the microprocessor records the potential vs. time behaviour of the working electrode. Finally the mercury film is removed by mild oxidation in an iodine/iodide solution and the glassy carbon surface is cleaned with ethanol and sodium hydroxide prior to the next analytical cycle. The cobalt(II) and nickel(II) concentrations are evaluated by means of a standard addition procedure. The technique was applied to drinking, estuarine and sea water samples. The detection limits on the one sigma level after one minute of potentiostatic adsorption were 9 and 11 ng l−1 for nickel(II) and cobalt(II), respectively. Nickel(II) and cobalt(II) were determined in reference samples of bovine liver and sea-water sediments after acid digestion. In order to obtain correct cobalt values, it was necessary to reduce cobalt(III) species formed during the acid digestion with sodium tetrahydroborate.

Determination of mercury in natural samples at the sub-nanogram level using inductively coupled plasma/mass spectrometry after reduction to elemental mercury

Abstract Inductively coupled plasma/mass spectrometry was used to determine mercury. Sodium borohydride was used to reduce the mercury to its elemental form, which was purged directly to the plasma using the nebulizer gas. Applications to natural waters and reference sediment are demonstrated. The detection limit, defined as three times the standard deviation of the blank, is 8 pg. The precision at the 100-pg level is 3%. The ability to make isotope dilution measurements is demonstrated.

Complexation of aluminum with DNA.

The extent of complexation of aluminum(III) with DNA (Calf thymus, Sigma type I) was estimated by means of two experimental techniques: potentiometric titration with a fluoride selective indicator electrode and dialysis followed by aluminum determination by graphite furnace AAS. Both types of experiments indicate that aluminum(III) is bound to DNA. The data are treated by assuming an ion exchange reaction with the phosphate diester groups. Using Rt to denote the concentration of these groups the values of log [AlMn-3R]/(Rt-3[AlMn-3R])[Al3+] decrease from approx. 7.6 to 5.6 when the concentration of sodium chloride is increased from 1 to 100 mM. In the pH range 4.5-5.5 the ion exchange constant increases approximately 0.5 log units. Dialysis gives lower values for the complex formation constant than potentiometry.

Multi-element speciation of trace metals in fresh water adapted to plasma source mass spectrometry

A method for speciation of trace metals at natural concentration levels has been developed. The speciation is carried out in a cleanroom laboratory and the determination is performed with an ICP-MS. The method is based on fractionation of metal species on three adsorbents. Chelex-100, Sep-Pak C-18 and Fractogel DEAE. The method distinguishes between labile complexes, non-polar organic adsorbable matter and ion exchangeable substances. The filtered water samples are pumped through columns with the adsorbents. Following a prefraction, samples for determination of metal concentrations are taken. The adsorbents are not eluted. After extensive cleaning, the used adsorbents have blank values that are low enough for trace metal analysis in fresh water. Concentration and speciation data for Al, Cd, Co, Cu, Fe, Pb, Mn, Mo, Ni and Zn are obtained.

Total and Suspended Cadmium, Cobalt, Copper, Iron, Lead, Manganese, Nickel, and Zinc in the Water Column of the Black Sea

The trace metals cadmium, cobalt, copper, iron, manganese, nickel, lead and zinc were determined at eleven different stations in the Black Sea, in November 1984. Sampling from the surface down to 2100 m was carried out. Suspended matter was collected and analysed. It was found that elements which form strong sulphide complexes show significantly lower concentration in the anoxic zone. A simple scavenging mechanism based on adsorption of sulphides onto organic matter is proposed in order to explain this. The complex behaviour of particles in the oxic/anoxic interface is discussed.

Mobility and Methylation of Mercury in Forest Soils Development of an In-Situ Stable Isotope Tracer Technique and Initial Results

A method for investigating in-situmethylation and mobility of mercury has beendeveloped and applied to forest soil. The methodis based on additions of stable 199Hgisotopes to forest soil plots followed bysampling and analysis of isotope ratios of totalmercury and MeHg using ICP-MS. Initial resultsindicate that a fraction (30%) of the mercuryadded to the forest soils is immobilised over atime scale of 16 months. A small but significantfraction of the mercury is methylated during thesame time scale. Higher methylation rates werefound in wetland soil than in dry forest podzolsoil.

Gran linearization of potentiometric Winkler titration

Abstract A method for Gran linearization of a potentiometric Winkler titration curve is presented and compared with photometric detection and second-derivative evaluation of the potentiometric titration curve. Potentiometric and photometric data for the same titration were recorded simultaneously using a two-channel A/D converter. The equivalence value of the Gran linearization was found to agree very well with the two other methods (coefficient of variance 0.03%). For the Gran linearization only few titration points have to be collected and, in contrast to the two other methods, titration points after the equivalence volume are not needed at all. This makes the Gran method easier and faster than the other two. The Gran function values in the beginning of the titration can also be used as the basis of a reliable method of predicting the equivalence volume and adapting the volume increments during the rest of the titration accordingly. With this method it was possible to perform a series of titrations in 1 min 50 s each.

Indication of thiols in black sea deep water

Abstract Potentiometric titrations of deep Black Sea water give reasonably precise values of sulphide in the concentration range 30–300 μmol l −1 and a strong indication of thiols in the concentration range 10–30 μmol l −1 . Organic analysis of Black Sea water should therefore include the search for compounds containing SH groups. A simple stoichiometric model indicates that sulphur-containing proteins might be the main source of thiols after hydrolysis and deamination. The alkalinity and total sulphide are simply related by A t = 3287 ± 30 + (3.84 ± 0.10) [H 2 S] t μmol kg −1 . The slope of 3.84 instead of the stoichiometric slope of 2.31 indicates a lack of reduced sulphate in the form of hydrogen sulphide.