Reproducibility of glass open tubular columns in a production environment — Two years of experience

Summary The problems associated with the preparation of glass open tubular (capillary) columns are well documented in the literature. These problems are even more evident if column production is done on a routine basis, in a production environment. On the other hand, from the point of the user who wants to rely on a supplier, the reproducible quality of the columns is crucial. Here quality does not only mean efficiency but also refers to the reproducibility of the average liquid film thickness (capacity ratio) and the relative retention, as well as the tube treatment influencing the polarity of the column tube. In a paper published one year ago [1] our investigation concerning the reproducibility of the column manufacturing process was reported. The present paper continues this investigation. Four different columns will be considered: two types of OV-101 columns with thin and thick liquid film as well as columns prepared with Carbowax 20M and DEGS liquid phases. The consistency of their characteristics and efficiency will be investigated. Column characteristics include the capacity ratio which is directly related to the thickness of the liquid phase film. Column efficiency is investigated with help of the HETP and peak resolution. The effective and theoretical plate numbers are compared and the incorrectness of the assumption that the former is better suited for column testing is demonstrated. Relative retention reproducibility of even difficult peak pairs shows the consistency of column wall treatment. Finally, the consistency and performance of shorter columns obtained by the breaking of long columns will be discussed.Paper presented at the Second International Symposium on Glass Capillary Chromatography, Hindelang, Allgäu, Federal Republic of Germany, May 2–6, 1977.     

Irradiated interfaces in the Ara OB1, Carina,Eagle Nebula,and Cyg OB2 massive star formation regions

Regions of massive star formation offer some of the best and most easily-observed examples of radiation hydrodynamics. Boundaries where fully-ionized H II regions transition to neutral/molecular photodissociation regions (PDRs) are of particular interest because marked temperature and density contrasts across the boundaries lead to evaporative flows and fluid dynamical instabilities that can evolve into spectacular pillar-like structures. When detached from their parent clouds, pillars become ionized globules that often harbor one or more young stars. H₂ molecules at the interface between a PDR and an H II region absorb ultraviolet light from massive stars, and the resulting fluoresced infrared emission lines are an ideal way to trace this boundary independent of obscuring dust. This paper presents H₂ images of four regions of massive star formation that illustrate different types of PDR boundaries. The Ara OB1 star formation region contains a striking long wall that has several wavy structures which are present in H₂, but the emission is not particularly bright because the ambient UV fluxes are relatively low. In contrast, the Carina star formation region shows strong H₂ fluorescence both along curved walls and at the edges of spectacular pillars that in some cases have become detached from their parent clouds. The less-spectacular but more well-known Eagle Nebula has two regions that have strong fluorescence in addition to its pillars. While somewhat older than the other regions, Cyg OB2 has the highest number of massive stars of the regions surveyed and contains many isolated, fluoresced globules that have head–tail morphologies which point towards the sources of ionizing radiation. These images provide a collection of potential astrophysical analogs that may relate to ablated interfaces observed in laser experiments of radiation hydrodynamics.