Environmental Context. A new group of arsenic compounds, namely thio-arsenosugars, has recently been discovered in some marine samples, including seafood products. We do not yet understand how these arsenic compounds are produced by living organisms, nor do we know their implications for human health. Their unusual chromatographic properties are the reason that they are difficult to detect by existing methods. We present a new method for finding these thio-arsenosugars, and we also report two new thio-arsenosugars. Abstract. Two new thio-arsenosugars were identified in aqueous and methanol extracts from the gonad and the muscle of the great scallop by using high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICPMS) and HPLC–electrospray ionization mass spectrometry (ESMS). The gonad of the scallops contained thio-arsenosugar–sulfonate [0.067 mg (As) kg−1; dry mass ± 3.7%] and thio-arsenosugar–sulfate [0.267 mg (As) kg−1; dry mass ± 1.2%]. The muscle also contained both thio-arsenosugar–sulfonate [0.030 mg (As) kg−1; dry mass ± 2.6%] and thio-arsenosugar–sulfate [0.200 mg (As) kg−1; dry mass ± 2.6%]. Methanol increased the extraction efficiency threefold for the two thio-arsenosugars as compared to water. Fresh and freeze-dried samples from both parts of the scallop showed no significant difference with respect to the concentration of the two thio-arsenosugars. In order to confirm the presence of the thio-arsenosugars, a new method for their determination with HPLC–ESMS was developed. Under optimized conditions [Hamilton PRP-X100; 150 by 1.0 mm; 20 mM NH4HCO3 with 55% (v/v) methanol at pH 10.3] we succeeded in determining the pseudomolecular ions of thio-arsenosugar–glycerol, thio-arsenosugar–phosphate, thio-arsenosugar–sulfonate, and thio-arsenosugar–sulfate at concentrations less than 5 µg (As) dm−3 in standard solutions and real samples.

In contrast to the large body of data on naturally-occurring arsenic compounds in marine organisms, relatively little is known about arsenic speciation in freshwater biota. We report an investigation using HPLC-ICPMS into the arsenic compounds in five species of freshwater mussels collected from five sites from the Danube in Hungary. Total arsenic concentrations in the mussels ranged from 3.8-12.8 mg As kg(-1). The arsenic speciation patterns were broadly similar for mussels representing each of the five species and five sites, but quite different from those reported for marine mussels. The major extractable arsenicals were two oxo arsenosugars (glycerol sugar and phosphate sugar), and their thio analogues (thio glycerol sugar and thio phosphate sugar). Arsenobetaine, usually the major arsenical in marine organisms, was not a significant compound in the freshwater mussels and was detected in only three of the 11 samples. This is the first report of thio arsenosugars in freshwater biota and suggests that these compounds may be common and widespread naturally-occurring arsenicals.

No abstract

This contribution describes the development of nitrogen-doped diamond-like carbon (N-DLC) thin films for multi-reflection mid-infrared (MIR) attenuated total reflectance (IR-ATR) spectroelectrochemistry. N-DLC coatings were deposited using pulsed laser deposition (PLD) involving the ablation of a high purity graphite target. The DLC matrix was further modified by ablating the target in the presence of nitrogen gas. This technique offers the advantage of depositing thin films at room temperature, thereby enabling coating of temperature-sensitive substrates including e.g., MIR waveguides. The resulting films were analyzed with X-ray photoelectron spectroscopy (XPS), and determined to be composed of carbon, nitrogen, and adventitious oxygen. Raman spectroscopic studies indicate that the addition of nitrogen induces further clustering and ordering of the sp(2)-hybridized carbon phase. The electrochemical activity of PLD fabricated N-DLC films was verified using the Ru(NH(3))(3+/2+) redox couple, and was determined to be comparable with that of other carbon-based electrodes. In situ spectroelectrochemical studies involving N-DLC coated zinc selenide (ZnSe) MIR waveguides provided evidence concerning the oxidation of N-DLC at anodic potentials in 1 M HClO(4) solutions. Finally, the electropolymerization of polyaniline (PAni) was performed at N-DLC-modified waveguide surfaces, which enabled spectroscopic monitoring of the electropolymerization, as well as in situ studying the structural conversion of PAni at different potentials.

No abstract