Recent advances in the application of capillary electrophoresis for food analysis

This article reviews recent developments in the application of capillary electrophoresis (CE) for the analysis of foods and food components. CE has been applied to a number of important areas of food analysis and is fast becoming an established technique within food analytical and research laboratories. Papers are reviewed that were published during the two years to date following the previous review (Electrophoresis 2001, 22, 4197-4206).     

Enhanced separation of trivalent lanthanoids by solvent extraction with 18-crown-6 and EDTA complexonate

The selectivities during solvent extraction of lanthanoids with macrocycles can be modified with complexonates in the aqueous phase. In the case of solvent extraction of lanthanoids with 18-crown-6 and trichloroacetic acid (TCA), addition of EDTA to the aqueous phase enhances the selectivities of lanthanoids by 3-7 times compared to those without the complexonate. This is due to the fact that the stability of lanthanoid-EDTA complexes increases in the opposite direction to the crown-TCA complexes across the lanthanoid series. The selectivities observed in this system are among the largest reported for the light lanthanoids. The effect of the complexonate on lanthanoid extraction can be explained by a simple model presented in this paper.     

Determination of adriamycin in plasma and tissue biopsies.

A simple, rapid and sensitive method for the extraction and high-performance liquid chromatographic analysis of adriamycin in tissue and plasma is described. Tissue (5-100 mg) and plasma (1 ml) samples underwent a C18 Sep-Pak extraction into methanol. Chromatography was performed on a muBondapakphenyl column using a mobile phase of acetonitrile-0.1 M ammonium formate (pH 4.0) with a flow-rate of 2 ml/min. Fluorometric detection was used with an excitation of 480 nm and an emission of 550 nm. The procedure produced a linear curve for the concentration range 25-1000 ng/ml. The development of the assay produced rapid, repeatable and accurate results for both small tissue samples and plasma.     

Voices from the Front Lines: Exemplary Science Teachers on Education Reform

The purpose of this study is to gain insight into the experiences that nationally award‐winning, exemplary science teachers have had over their career and examine the alignment of their responses with calls for K‐12 science education reform from a selection of prominent commissioned government reports since 1980. From an assessment of the alignment of exemplary teachers, calls for reform have had a limited effect and highlight the weakness of using national reports as a wide‐scale, nationalized approach to science education reform. Findings are focused on seven different areas of teacher development: classroom issues, teaching scientific inquiry, use of technology, preservice experiences, professional development of in‐service teachers, vertical articulation, and science education reform over time. Among other issues, the teachers indicated one of the biggest barriers to inquiry teaching is the pressure to conform to high‐stakes testing and the lack of examples of inquiry teaching during teacher education experiences.     

Science Camp as a Transformative Experience for Students,Parents, and Teachers in the Urban Setting

This paper reports on creative partnerships to create learning communities to benefit students, parents, and teachers in the urban setting. Science Camp is a university day camp offering problem‐based science exploration for urban middle school students and an introduction to college life. For parents it is an opportunity to learn about college opportunities for their children and to gather information about funding sources. For middle school science teachers and preservice teachers it is a learning laboratory for conducting problem‐based learning in the urban setting. The findings describe the effects of the learning communities on the transformation of students, parents, preservice teachers, and in‐service teachers.     

Effect of wall heat transfer on shock-tube test temperature at long times

When performing chemical kinetics experiments behind reflected shock waves at conditions of lower temperature (<1,000 K), longer test times on the order of 10–20 ms may be required. The integrity of the test temperature during such experiments may be in question, because heat loss to the tube walls may play a larger role than is generally seen in shock-tube kinetics experiments that are over within a millisecond or two. A series of detailed calculations was performed to estimate the effect of longer test times on the temperature uniformity of the post-shock test gas. Assuming the main mode of heat transfer is conduction between the high-temperature gas and the colder shock-tube walls, a comprehensive set of calculations covering a range of conditions including test temperatures between 800 and 1,800 K, pressures between 1 and 50 atm, driven-tube inner diameters between 3 and 16.2 cm, and test gases of N₂ and Ar was performed. Based on the results, heat loss to the tube walls does not significantly reduce the area-averaged temperature behind the reflected shock wave for test conditions that are likely to be used in shock-tube studies for test times up to 20 ms (and higher), provided the shock-tube inner diameter is sufficiently large (>8cm). Smaller diameters on the order of 3 cm or less can experience significant temperature loss near the reflected-shock region. Although the area-averaged gas temperature decreases due to the heat loss, the main core region remains spatially uniform so that the zone of temperature change is limited to only the thermal layer adjacent to the walls. Although the heat conduction model assumes the gas and wall to behave as solid bodies, resulting in a core gas temperature that remains constant at the initial temperature, a two-zone gas model that accounts for density loss from the core to the colder thermal layer indicates that the core temperature and gas pressure both decrease slightly with time. A full CFD solution of the shock-tube flow field and heat transfer at long test times was also performed for one typical condition (800 K, 1 atm, Ar), the results of which indicate that the simpler analytical conduction model is realistic but somewhat conservative in that it over predicts the mean temperature loss by a few Kelvins. This paper presents the first comprehensive study on the effects of long test times on the average test gas temperature behind the reflected shock wave for conditions representative of chemical kinetics experiments.     

Intramolecular [4 + 1] pyrroline annulation approach to pyrrolizidine alkaloids. Formal total synthesis of (±)-supinidine.

Dienic azide $\text{7}$ was found to yield dehydropyrrolizidines $\text{10}$ and $\text{11}$ on thermolysis. The synthesis of these compounds is described and the mechanistic implications as well as synthetic utility of this new annulation sequence is discussed.