Photoelectron spectroscopy of ammonia via a fast predissociative state

We report a study on resonance enhanced multiphoton ionization photoelectron spectroscopy (REMPI-PES) involving the fast predissociative (A) over tilde state of ammonia, using nano- and femtosecond lasers. The multiphoton scheme involves (1 + 1), (2 + 2), (2 + 2) + 1 and (2 + 2) + 2 photon processes. We have found a progression of stretching vibrations nu(1) in the PE spectrum when pumping NH3 (A) over tilde upsilon(2) = 0, 1 and 3 as intermediate states. The stretching vibration intensity distributions in the photoelectron spectrum are calculated by using the Chebychev method of the wavepacket propagation. The femtosecond spectrum shows a similar feature to the nanosecond spectrum. However, high laser power also causes band broadening and shifting effect as well as above threshold multiphoton ionization.

Modeling of protein adsorption in membrane affinity chromatography

For the design of affinity membranes, protein adsorption in membrane affinity chromatography (MAC) was studied by frontal analysis. According to fast mass transfer, small thickness of affinity membranes and high affinity between the protein and the ligand, an ideal adsorption (IA) model was proposed for MAC and was used together with equilibrium-dispersive (E-D) model to describe the adsorption of bovine serum albumin (BSA) onto cellulose diacetate/polyethyleneimine (CA/PEI) blend membranes with and without Cu2+ chelating. E-D model was found to better describe the initial region of experimental breakthrough curves. The influence of axial dispersion was revealed and it showed the importance of design of the module to homogenously distribute feed solution. IA model was found to be better for the whole experimental breakthrough curve. According to it, the capacity of affinity membranes and the specificity of the interaction are of equal importance for the design of affinity membranes. An optimum feed concentration was also found in the operation of MAC. The discrepancy between experimental optimum feed concentrations and predicted ones from IA model may be due to the ignorance of some experimental effects such as axial dispersion.

A new method for determination of adsorption and desorption coefficients of pesticides with soil column liquid chromatography

The adsorption and desorption coefficients of atrazine, methiocarb and simazine on a sandy loam soil were measured in this study with soil column liquid chromatographic (SCLC) technique. The adsorption and desorption data of all the three pesticides followed Freundlich isotherms revealing the existence of hysteresis. In comparing with other methods, SCLC method showed some characteristics such as rapidity, online and accuracy.