Peter Viberg

Continuous full filling capillary electrochromatography-electrospraying chromatographic nanoparticles

The influence of instrumental parameters affecting the ionization in continuous full filling capillary electrochromatography/electrospray ionization mass spectrometry (CFF‐CEC/ESI‐MS) was investigated. The investigated parameters were the BGE and sheath liquid ion strength and organic modifier content, the nebulizer gas pressure, and the concentration of nanoparticles in the BGE. It was found that the nebulizer pressure had the largest influence on the separation efficiency and apparent retention. It was shown that even the lowest pressure investigated was sufficient to guide the nanoparticle flow away from the mass spectrometer inlet. A nebulizer pressure of 5 psi was found to be optimal; increasing the pressure significantly decreased the separation efficiency due to the generation of a hydrodynamic flow. Generally, the ion strength of both the BGE and the sheath liquid were found to have very moderate effects on the separation of a homologous series of dialkyl phthalates, whereas the ionization efficiency was found to be unaffected by the nanoparticles and the separation efficiency was found to increase with increasing concentrations up to 3.8 mg/mL, whereafter it was observed to drop. The optimized method was linear over a wide concentration range and presented LOD and LOQ more than threefold lower than those previously reported using CFF‐CEC/ESI‐MS.

Airborne chemistry single cell level

A miniaturized analysis system for the studying of living cells and biochemical reactions in microdrops was developed. Cell studies were performed using single adipocytes in 250‐nL drops. Continuous flow‐through droplet dispensers, developed in‐house, were used for additions to the levitated droplet. Addition of b‐adrenergic agonists stimulates the lipolysis in the adipocytes, leading to free fatty acid release and a consequent pH decrease of the surrounding buffer, a change that can be easily followed using a pH‐dependent fluorophore continuously monitored by fluorescence imaging detection. An analytical method using capillary electrophoresis and nanospray mass spectrometry for measurement of the cAMP level in activated single adipocytes are now being developed for future use in combination with the levitation technique. The levitation approach was also employed for the screening of nucleation conditions for macromolecules. Here, the acoustic levitator offers a simplified way to determine the main featur...