6.1.2. Aqueous V(III) Chemistry 877 6.1.3. Oxidation State of Vanadium in Tunicates 878 6.1.4. Uptake of Vanadate into Tunicates 879 6.1.5. Vanadium Binding Proteins: Vanabins 879 6.1.6. Model Complexes and Their Chemistry 880 6.1.7. Catechol-Based Model Chemistry 880 6.1.8. Vanadium Sulfate Complexes 881 6.2. Fan Worm Pseudopotamilla occelata 883 7. Vanadium Nitrogenase 883 7.1. Nitrogenases 883 7.2. Biochemistry of Nitrogenase 884 7.3. Clusters in Nitrogenase and Model Systems: Structure and Reactivity 885

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The chemistry and biochemistry of vanadium and the biological activities exerted by vanadium compounds.

The reactivity of a number of p-methylphenyl thioglycoside (STol) donors which are either fully protected or have one hydroxyl group exposed has been quantitatively determined by HPLC in conjunction with the development of a broadly applicable approach for a facile one-pot synthesis of oligosaccharides. The influence on reactivity of the structural effects of different monosaccharide cores and different protecting groups on each glycoside donor is characterized and quantified. In addition, a correlation between glycosyl donor reactivity and the chemical shift of the anomeric proton by 1 H NMR has been established. A database of thioglycosides as glycosyl donors has been created using this reactivity data. The utility is demonstrated by the easy and rapid one-pot assembly of various linear and branched oligosaccharide structures. In addition, a computer program as been described for use as a database search tool and guide for the selection of building blocks for the one-pot assembly of a desired oligosaccharide or a library of individual oligosaccharides.

Programmable one-pot oligosaccharide synthesis

The widespread use of silver nanoparticles (Ag-NPs) in commercial products, especially textiles, will likely result in an unknown spread of Ag into the environment. The quantification and characterization of the Ag released from nano-Ag-products is an important parameter needed to predict the effect of Ag-NPs on the environment. The aim of this study was to determine the amount and the form of Ag released during washing from nine fabrics with different ways of silver incorporation into or onto the fibers. The effect of pH, surfactants, and oxidizing agents was evaluated. The results show that little dissolution of Ag-NPs occurs under conditions relevant to washing (pH 10) with dissolved concentrations 10 times lower than at pH 7. However, bleaching agents such as hydrogen peroxide or peracetic acid (formed by the perborate/TAED system) can greatly accelerate the dissolution of Ag. The amount and form of Ag released from the fabrics as ionic and particulate Ag depended on the type of Ag-incorporation into the textile. The percentage of the total silver emitted during one washing of the textiles varied considerably among products (from less than 1 to 45%). In the washing machine the majority of the Ag (at least 50% but mostly >75%) was released in the size fraction >450 nm, indicating the dominant role of mechanical stress. A conventional silver textile did not show any significant difference in the size distribution of the released silver compared to many of the textiles containing nano-Ag. These results have important implications for the risk assessment of Ag-textiles and also for environmental fate studies of nano-Ag, because they show that under conditions relevant to washing, primarily coarse Ag-containing particles are released.

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The behavior of silver nanotextiles during washing.

Principles of mononucleating and binucleating ligand design.

The first instrumental method for simultaneous determination of peroxyacetic acid (PAA) and hydrogen peroxide has been developed. The successive quantitative reaction of PAA with methyl p-tolyl sulfide (MTS) and hydrogen peroxide with triphenylphosphine (TPP) yields the corresponding sulfoxide MTSO and phosphine oxide TPPO. The reagents and their oxides are separated by HPLC on reversed-phase columns with acetonitrile/water gradient elution within 5 min. External calibration with the solid standards of MTSO and TPPO leads to a very accurate and reliable method. Samples are stable and can be stored after derivatization for several days prior to analysis. Real samples from brewery disinfection were analyzed in comparison to titration with excellent correlation.

Simultaneous HPLC Determination of Peroxyacetic Acid and Hydrogen Peroxide

A method for the determination of peroxyacetic acid (PAA) and related
peroxycarboxylic acids is presented.
2,2′-Azino-bis(3-ethylbenzothiazoline)-6-sulfonate (ABTS), one of
the most popular substrates for the enzyme peroxidase, is oxidized
selectively by PAA to an intensely green radical cation
(ABTS
 ·+
) in the presence of hydrogen peroxide.
Photometric detection of the product can be performed in four
characteristic regions of the visible and near infrared spectrum in the
range 405–815 nm. The reaction is accelerated considerably by the
addition of iodide without any loss of selectivity. A quantitative
reaction, a limit of detection of 1 ×
10
 -

 6
 mol l
 -

 1
 (76
µg l
 -

 1
) for PAA and linear calibration
graphs over three orders of magnitude are obtained under these conditions.
No interferences by several ions at their typical concentrations in tap
water could be observed under pH control. Comparative HPLC measurements
were used to demonstrate the reliability of the proposed method. The
recovery and standard deviation for PAA in real samples (n = 53)
using the proposed method was 98 ± 4% of the respective HPLC
measurements. Microplates were used as an alternative to cuvettes to
analyse a large number of samples per timescale. The method may become a
valuable tool for the determination of PAA in disinfection solutions,
because reliable analysis results are obtained using standard laboratory
equipment. Direct calibration for rapid on-site analysis is performed by
using the molar absorptivity of the reaction product.

Selective photometric determination of peroxycarboxylic acids in the presence of hydrogen peroxide

Peroxide analysis in laundry detergents using liquid chromatography

A new method for the determination of peroxyacetic acid (PAA) in aqueous solutions is described. Methyl p-tolyl sulfide (MTS) is oxidized by PAA, forming the corresponding methyl p-tolyl sulfoxide (MTSO), which can be separated easily by high-performance liquid chromatography on a reversed-phase column and detected by ultraviolet spectroscopy at a wavelength of 230 nm. MTSO is a commercially available solid substance which can be used as an external standard for calibration. Therefore, calibration with the unstable PAA can be avoided

Ulrich Pinkernell

Papers

Simultaneous HPLC Determination of Peroxyacetic Acid and Hydrogen Peroxide

Selective photometric determination of peroxycarboxylic acids in the presence of hydrogen peroxide

Peroxide analysis in laundry detergents using liquid chromatography

Determination of Peroxyacetic Acid Using High-Performance Liquid Chromatography with External Calibration

An Unsymmetrical Dinuclear Iron(III) Complex with Peroxidase Properties