Negative mode nanostructure-initiator mass spectrometry for detection of phosphorylated metabolites

The chemical complexity of the metabolome requires the development of new detection methods to enlarge the range of compounds detectable in a biological sample. Recently, a novel matrix-free laser desorption/ionization method called nanostructure-initiator mass spectrometry (NIMS) [Northen et al., Nature 449(7165):1033-1036, 2007] was reported. Here we investigate NIMS in negative ion mode for the detection of endogenous metabolites, namely small phosphorylated molecules. 3-Aminopropyldimethylethoxysilane was found to be suitable as initiator for the analytes studied and a limit of detection in the tens of femtomoles was reached. The detection of different endogenous cell metabolites in a yeast cell extract is demonstrate

Negative mode nanostructure-initiator mass spectrometry for detection of phosphorylated metabolites

ISSN:1573-3882ISSN:1573-389

Migration of silver from commercial plastic food containers and implications for consumer exposure assessment

<div><p>Food storage containers with embedded silver as an antibacterial agent promise longer durability of food. For risk assessment the release of this silver into the stored food and resulting human exposure need to be known. For the purpose of exposure assessment, silver migration from commercial plastic containers with declared content of ‘nano-’ or ‘micro-silver’ into different food simulants (water, 10% ethanol, 3% acetic acid, olive oil) was quantitatively determined by ICP-MS and the form of the released silver was investigated. The highest migration of silver was observed for the acidic food simulant with 30 ng silver cm⁻² contact surface within 10 days at 20°C. In a second and third use cycle, migration dropped by a factor of up to 10, so that the maximum cumulated release over three use cycles was 34 ng cm⁻². The silver release over time was described using a power function and a numerical model that simulates Fickian diffusion through the plastic material. The released silver was found to be in ionic form, but also in the form of silver nanoparticles (around 12%). Consumer exposure to the total amount of silver released from the food containers is low in comparison with the background silver exposure of the general population, but since natural background concentrations are only known for ionic silver, the exposure to silver nanoparticles is not directly comparable with a safe background level.</p> </div

Novel sampling techniques for trace element quantification in ancient copper artifacts using laser ablation inductively coupled plasma mass spectrometry

ISSN:0305-4403ISSN:1095-923

Characterization of an Airborne Laser-Spark Ion Source for Ambient Mass Spectrometry

An airborne laser plasma is suggested as an ambient ion source for mass spectrometry. Its fundamental physical properties, such as an excellent spatial and temporal definition, high electron and ion densities and a high effective cross section in maintaining the plasma, make it a promising candidate for future applications. For deeper insights into the plasma properties, the optical plasma emission is examined and compared to mass spectra. The results show a seemingly contradictory behavior, since the emitted light reports the plasma to almost entirely consist of hot elemental ions, while the corresponding mass spectra exhibit the formation of intact molecular species. Further experiments, including time-resolved shadowgraphy, spatially resolved mass spectrometry, as well as flow-dependent emission spectroscopy and mass spectrometry, suggest the analyte molecules to be formed in the cold plasma vicinity upon interaction with reactive species formed inside the hot plasma center. Spatial separation is maintained by concentrically expanding pressure waves, inducing a strong unidirectional diffusion. The accompanying rarefaction inside the plasma center can be compensated by a gas stream application. This replenishing results in a strong increase in emission brightness, in local reactive species concentration, and eventually in direct mass spectrometric sensitivity. To determine the analytical performance of the new technique, a comparison with an atmospheric pressure chemical ionization (APCI) source was conducted. Two kitchen herbs, namely, spearmint and basil, were analyzed without any sample pretreatment. The presented results demonstrate a considerably higher sensitivity of the presented laser-spark ionization technique