The Role of Column Switching in Analysing Complex Samplest

Abstract

Our objective in using column switching is primarily to achieve the desired separation in the minimum analysis time. Complimentary to this aim is the need for sample and column cleanup followed by column re-equilibration. Finally, all operations should be capable of automation. Fundamental to column switching methodology is the concept of Zone cutting, where part of the chromatogram is transferred to another column. This forms the basis of sample cleanup and is a very versatile and powerful method. Multiple zone cutting is also possible to further increase the scope of cleanup or to minimise analysis time. Zone cutting is also complimentary to the techniques of trace enrichment and recycling. Examples will be given involving the use of these techniques in the analysis of complex matrices such as urine, plant extracts, wine and serum. The latter will be used to propose a novel approach to the quantitative analysis of anti-convulsants in serum using hexobarbital as internal standard.     

The Radiation-Induced Polymerization and Copolymerization of Butadiene in Emulsion

Abstract

The polymerization of butadiene in emulsion initiated by ^{6 0}Co gamma radiation has been studied in some detail. Similar studies with styrene and styrene-butadiene comonomer mixtures were also conducted. The rates of polymerization were found to be much lower than anticipated from the reported k_p values for butadiene and for the comonomer mixtures. Styrene, on the other hand, polymerizes at normal rates. A number of possible explanations for this behavior is discussed.     

Radiation-Induced Graft Copolymerization of Styrene to Polyvinyl Chloride) Latex in a Pilot Plant System

A pilot plant study of the radiation grafting of styrene to polyvinyl chloride) (PVC) latex is described. When correct extraction conditions are used less than 3% grafting took place. This is shown to be due to the low total radiation doses needed to polymerize the styrene in an emulsion system. A parallel study with PVC film did, however, lead to substantial true grafting. The G (radical) value for PVC film as determined by ESR was found to be 4.6.     

Increased sample throughput in HPLC using sample switching

Summary Column switching methods are described which demonstrate an alternative approach to the reduction of analytical time in HPLC. Although most methods use a combination of techniques, it has been possible to group them into major categories involving column cleanup, sample cleanup, multicolumn methods and boxcar chromatography. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Monopole excitation of 4He in α-particle scattering from 12C, 13C,and 16O

The excitation of the O⁺ state in ⁴He at 20.1 MeV has been studied in α-scattering from ¹²C, ¹³C, and ¹⁶O at E_α=65MeV by measuring the decay $\text{α}{}^1\text{→}\text{p}\text{+}\text{t}$ with a coincidence method. DWBA calculations of this monopole transition using both microscopic and collective model transition densities are presented.     

Energy harvesting through arterial wall deformation: A FEM approach to fluid–structure interactions and magneto-hydrodynamics

Engineers are confronted with the energy demand of active medical implants in patients with increasing life expectancy. Scavenging energy from the patient’s body is envisioned as an alternative to conventional power sources. Joining in this effort towards human-powered implants, we propose an innovative concept that combines the deformation of an artery resulting from the arterial pressure pulse with a transduction mechanism based on magneto-hydrodynamics. To overcome certain limitations of a preliminary analytical study on this topic, we demonstrate here a more accurate model of our generator by implementing a three-dimensional multiphysics finite element method (FEM) simulation combining solid mechanics, fluid mechanics, electric and magnetic fields as well as the corresponding couplings. This simulation is used to optimize the generator with respect to several design parameters. A first validation is obtained by comparing the results of the FEM simulation with those of the analytical approach adopted in our previous study. With an expected overall conversion efficiency of 20% and an average output power of 30 μW, our generator outperforms previous devices based on arterial wall deformation by more than two orders of magnitude. Most importantly, our generator provides sufficient power to supply a cardiac pacemaker.     

Radiation-induced solution polymerization of styrene in an engineering flow system

Radiation induced solution polymerization of styrene in methylene chloride in a small scale pilot plant utilizing a flow reactor is reported. Both conventional free radical and ionic polymerization have been achieved. With rigorous drying accomplished over molecular sieves the ionic mechanism predominates. Conclusive kinetic evidence as well as polymer properties substantiate radiation induced ionic polymerization for the first time in an engineering pilot plant. The validity of Williams' model is reinforced by this study and a survey of over 100 literature observations.