J.E Sánchez Urı́a

Inorganic and methylmercury speciation in environmental samples

The different strategies for mercury species analysis in environmentally-related samples are reviewed. After consideration of the main different steps involved in the speciation of mercury, such steps are discussed with more extension for mercuric ion and methylmercury. The different approaches for preservation of these mercury species during the storage of samples are considered. Different ways for the extraction of mercury species from the several possible environmental compartments and the possibilities for preconcentration of such species after previous derivatization reactions are discussed. Mercuric ions and methylmercury chromatographic and non-chromatographic separations along with different techniques used for sensitive and selective detection of mercury are also critically reviewed. Ranges of published detection limits achievable for such species determination, by using hyphenated techniques between a chromatographic separation and a specific atomic detector are also given.

Speciation of mercury by continuous flow liquid-liquid extraction and inductively coupled plasma atomic emission spectrometry detection

An accurate, precise, sensitive and automated non-chromatographic method for methylmercury speciation based on a selective continuous liquid-liquid extraction of methylmercury, into xylene, as bromide and cold mercury vapour generation directly from the organic phase and final ICP-AES mercury detection is proposed. Both separation steps, liquid-liquid and gas-liquid are accomplished in a continuous mode and on line with ICP-AES as detector. The detection limit attained for methylmercury was 4ng·ml−1 (as mercury). The precision of the determination at a concentration level around 20 times the detection limit was +-5%. The proposed methodology has been applied successfully to the speciation of methylmercury and inorganic mercury in spiked sea water and spiked urine samples.

Determination of bromide by low power surfatron microwave induced plasma after bromine continuous generation.

A simple continuous flow generation of volatile bromine is described for the determination of low concentrations of the elements by atmospheric-pressure argon microwave induced plasma (MIP) surfatron. Bromine is continuously generated by mixing the bromide with sulphuric acid and hypochlorite solutions. The bromine vapor is separated from the aqueous phase by a gas-liquid separator and is desiccated by passing it through concentrated sulphuric acid. The detection limit attained was 2 microg/l. and the precision was +/-0.7% (at the 80 microg/l. level). The proposed determination is very selective if oxidizing/reducing agents are absent. The procedure has been tested for bromide determination in two drug preparations. Good agreement between the experimental results and the certified values has been obtained.

Continuous flow and flow injection halogen generation for chloride, bromide and iodide determinations by microwave induced plasma atomic emission spectroscopy

Abstract Continuous flow generation of molecular, volatile halogens (I 2 , Br 2 , Cl 2 ), based on chemical oxidation, is a very useful sample introduction technique in microwave induced plasma atomic emission spectrometry (MIP-AES), which provides improved transport efficiency for sample to plasma, thus enhancing the sensitivity of the determinations. Optimum conditions for halogen generation/MIP detection (chemical oxidant system, type and size of gas-liquid separator, influence of halide concentration and MIP instrumental parameters) are discussed with an aim to improving both the intensity of the emission signal, and its stabilization time for I −1 , Br −1 and Cl −1 determinations. For continuous halogen generation, the influence on the MIP emission signal (and its stabilization time) of (i) the size and form of the gas-liquid separator, and (ii) the atomic weight and concentration of the halogen itself has been investigated in detail. Even for optimum conditions, iodine generation/transport to the plasma is rather slow (i.e. 4 min for signal stabilization). The use of flow injection analysis (FIA) however, allows an increase of the attainable sample throughput by up to 60 samples/h, but at the expense of a slight loss of sensitivity (20–30%) compared with continuous flow generation. The influence on the MIP signal that was observed with FIA parameters (such as the injected sample volume and flow rates of the different reagents) is discussed.

Determination of iodide by low power surfatron microwave induced plasma after iodine continuous generation

Abstract This paper describes an improvement of the detection capability of the surfatron-microwave induced plasma (MIP) for iodide determination based on the chemical generation of iodine. This element is continuously generated by on-line mixing of iodide-sulfuric acid and hydrogen peroxide solutions. The iodine vapour is separated from the aqueous phase by a gas-liquid separator and is desiccated by passing it through concentrated H2SO4 before feeding it into the plasma. The system was optimized for the continuous generation of iodine and for its final determination in the MIP. The detection limit attained was 20 μg l−1 and the precision was ± 0.75% (at the 200 μg l−1 level). An interference study showed that the proposed determination is very selective in the absence of oxidizing/reducing agents. The proposed procedure has been tested for iodide determination in real samples of table salt with very good agreement between the experimental results and the certified values.

Extraction and spectrophotometric determination of trace amounts of niobium with diphenylglioxal-bis-(2-hydroxybenzoylhydrazone)

Abstract A method is described for the direct spectrophotometric determination of microamounts of niobium based on its extraction into chloroform with dephenylglyoxal-bis-(2-hydroxy benzoyl) hydrazone (BSHB). This reagent builds up a chelate with Nb(V) in very acidic media, its chloroform solution being pink to reddish depending on niobium concentration (λ max = 495 nm). Optimum conditions for chelate extraction and niobium determination have been established. The precision of procedure proposed, expressed in terms of relative standard deviation, is ±1.0%. It is shown that the method is sensitive, the molar absorptivity being 1.95 ± 0.02 × 10 4 liter · mol −1 · cm −1 in the organic phase, and the interferences study demonstrates a high selectivity against common cations and the majority of those accompanying niobium in its natural sources and special alloys.