Direct Solution Analysis Research Articles

A study of ion adsorption onto surface functionalized silica particles

Abstract The surface charging properties of silica micro-particles in aqueous solutions before and after surface chemical amination were measured and analysed using a new approach to the theoretical modelling of ion adsorption. The surface of aminated silica microspheres were further modified by chemical adsorption of l -cysteine groups to determine their ability to adsorb low levels of arsenic ions from aqueous solution. The adsorption of arsenic ions was observed both from changes in particle surface charge and from direct solution analysis, using ICP-OES. The results obtained indicate adsorption levels of about 2–5% of the cysteine surface density, from low-level arsenic solutions (i.e. less than 1 ppm). These initial results indicate that a suitable silica-based depth filter could be developed for the removal of low-level arsenic ions from contaminated water.

Cold-spray ionization mass spectrometry: principle and applications.

A direct solution analysis method, cold-spray ionization (CSI) mass spectrometry (MS), a variant of electrospray (ESI) MS operating at low temperature (ca -80 to 10 degrees C), allows the facile and precise characterization of labile organic species, especially those in which non-covalent bonding interactions are prominent. We applied this method to investigations of the solution structures of many labile organic species, including unstable reagents and reaction intermediates, asymmetric catalysts, supramolecules and even primary biomolecules. Remarkable analytical results were obtained for highly ordered supramolecules using the CSI method. Whereas conventional ESI is not applicable to these compounds because of their instability to heat and/or air, CSI affords multiply charged molecular ions with many solvent molecules attached. Investigation of the constitution of Grignard reagents in solution is extremely challenging, but CSI-MS allowed us to identify one of the key structures in THF solution. Recently, this method was adopted for investigations of the solution structures of primary biomolecules such as nucleosides, amino acids, sugars and lipids, revealing singly charged Na(+) adducts of large clusters (chain structures), presumably linked by non-covalent interactions, including hydrogen bonding and/or hydrophobic interactions. The principle of the CSI method and applications of the method to a wide variety of labile organic species and primary biomolecules in solution are described.

Alkali metal-mediated proline aggregation in solution observed by coldspray ionization mass spectrometry.

L-Proline aggregates to form cyclic clusters in the presence of alkali metal ions in solution, whereas a large-scale-aggregated chain structure was observed for several other amino acids. The major cyclic clusters are suggested to be constructed from trimeric and tetrameric subunits on the basis of direct solution analysis by coldspray ionization mass spectrometry.

Direct solution analysis by glow discharge: electrolyte-cathode discharge spectrometry

A new glow discharge atomic emission source was developed for the direct determination of metals in aqueous solutions by applying an atmospheric glow discharge in the air gap (2–6 mm) between an electrolyte solution cathode and a W-rod anode. Cathode sputtering of the solution surface and subsequent excitations occur when the pH of the solution is below 2.5. The spectrum emitted contains the basic atomic lines of the dissolved metals from K 769.9 to Zn 213.8 nm, ion lines of Mg and Ca and strong OH, NH and N2 bands. Boiling of the cathode pole can be avoided by use of a flow-through technique. The electron temperature was found to be around 5000 K. The calibration curves of line intensities versus metal concentrations were linear in the 1–50 ppm range and showed strong positive dependence on the discharge current and on the hydrogen ion concentration of the solution. Pulse modulated operation with time-resolved signal processing promises a substantial increase in the signal-to-background ratio. The flow-through electrolyte acts as a continuously renewed cathode pole, thereby enabling the continuous direct multi-metal assay of solutions. This report is the first discussion on the analytical characteristics of electrolyte-cathode discharge (ELCAD). spectrometry as a new technique for metal monitoring in aqueous solutions.

Direct solution analysis using an arc source incorporating two plasmas rotating in a graphite tube

As a continuation of earlier work on arc sources for the spectrochemical analysis of powdered samples, a source appropriate for multi-element analysis of trace elements in solution has been developed. The nebulized solution to be analysed is introduced into a horizontal graphite tube in the gap between two plasmas rotating in a magnetic field. Both water and ethanol have been used as solvents and the effect of lithium additions on the detection limits for certain elements has been studied. This source provides advantageous conditions for the determination of trace elements present at very low concentrations. Source parameters investigated include a study of the magnetically induced rotation of the plasmas by high speed cine photography, and the temperature distribution within the tube. Both aqueous and ethanol solutions were used and the effect of lithium additions was measured.