Development, validation, and application of a novel LC-MS/MS trace analysis method for the simultaneous quantification of seven iodinated X-ray contrast media and three artificial sweeteners in surface, ground, and drinking water

A new method for the simultaneous determination of iodated X-ray contrast media (ICM) and artificial sweeteners (AS) by liquid chromatography-tandem mass spectrometry (LC-MS/MS) operated in positive and negative ionization switching mode was developed. The method was validated for surface, ground, and drinking water samples. In order to gain higher sensitivities, a 10-fold sample enrichment step using a Genevac EZ-2 plus centrifugal vacuum evaporator that provided excellent recoveries (90 ± 6%) was selected for sample preparation. Limits of quantification below 10ng/L were obtained for all compounds. Furthermore, sample preparation recoveries and matrix effects were investigated thoroughly for all matrix types. Considerable matrix effects were observed in surface water and could be compensated by the use of four stable isotope-labeled internal standards. Due to their persistence, fractions of diatrizoic acid, iopamidol, and acesulfame could pass the whole drinking water production process and were observed also in drinking water. To monitor the fate and occurrence of these compounds, the validated method was applied to samples from different stages of the drinking water production process of the Industrial Works of Basel (IWB). Diatrizoic acid was found as the most persistent compound which was eliminated by just 40% during the whole drinking water treatment process, followed by iopamidol (80% elimination) and acesulfame (85% elimination). All other compounds were completely restrained and/or degraded by the soil and thus were not detected in groundwater. Additionally, a direct injection method without sample preparation achieving 3-20ng/L limits of quantification was compared to the developed method

Shedding Light on Selenium Biomineralization: Proteins Associated with Bionanominerals ▿

Selenium-reducing microorganisms produce elemental selenium nanoparticles with particular physicochemical properties due to an associated organic fraction. This study identified high-affinity proteins associated with such bionanominerals and with nonbiogenic elemental selenium. Proteins with an anticipated functional role in selenium reduction, such as a metalloid reductase, were found to be associated with nanoparticles formed by one selenium respirer, Sulfurospirillum barnesii

In Vitro Assessment of the Formation of Ceftriaxone-Calcium Precipitates in Human Plasma

Ceftriaxone is a third-generation cephalosporin antibiotic, which has a broad spectrum of bactericidal activity. Ceftriaxone is highly soluble as a sodium salt, but far less soluble as a calcium salt. Incompatibility of ceftriaxone with calcium and the possible formation of precipitates have been stated in the product label from early on. It was the objective of the present in vitro study to further assess the risk of precipitation of calcium-ceftriaxone in human plasma. Analytical methods were developed (high-performance liquid chromatography and flame atomic absorption spectroscopy) to quantitate calcium and ceftriaxone in human plasma supernatants and human plasma precipitates. Using high concentrations of ceftriaxone (10 mmol/l) and calcium (4.2 mmol/l) did not result in any precipitation after a 2-h incubation in human plasma at 37°C. Under conditions of forced precipitations only formation of precipitation was observed. The identity of the precipitated material was confirmed by Energy Dispersive X-Ray Analysis and Fourier Transform Infrared Spectroscopy. We conclude that calcium-ceftriaxone in human plasma has an apparent kinetic solubility product constant of greater than 0.42 x 10-4 (mol/l)2, which exceeds the normal thermodynamic solubility product in water by a factor of 26. Under these conditions, formation of plasma precipitates is unlikely