Wolfgang Bertsch

Temperature and pressure effects in supercritical-fluid chromatography

Abstract In the search for a suitable programming technique, the effects of pressure and temperature in superficial-fluid chromatography were studied. Both pressure and inverse temperature programming can be used to influence the retention characteristics. The selectivity of separation can further be controlled by a “moderator”. Values of height equivalent to a theoretical plate for model compounds were measured within a wide range of operating conditions and correlated with pressure drop measurements. The results suggest that a compromise between the particle size and pressure drop is necessary.

Preparation of high resolution nickel open tubular columns

SummaryA detailed description of the production of nickel open tubular columns is given and the important steps are discussed. Two types of surface modification, etching and introduction of a suspended silanized silica, which result in conventional open tubular (COT) and in support coated open tubular (SCOT) columns are described. Properties of these columns are presented for one phase, Emulphor ON 870 and several examples of applications are given.

Concentration and anlalysis of organic volatiles in skylab 4

Abstract The volatile components in the cabin atomosphere of Skylab 4 at various times during the mission were concentrated and analysed. More than 300 compounds could be detected by high-resolution gas chromatography with differences in concentration of as much as six orders of magnitude. 107 substances were identified by mass spectromety, covering a molecular-weight range of approximately 60 to more than 500. The concetration of 80 compounds were determined for three samples taken on days 11·47 and 77 of the mission. The compositionof the volatiles in the spacecrafts atmosphere differs significantly from other environments. A wide variety of various silicon compounds, mostly methylated siloxanes of molecular weight up to 584, was detected. Fluorocarbons (Freons) were also present.

Analysis of trace volatile metabolites in serum and plasma

Abstract A method is described for analyzing volatile constituents in 5- to 10-ml samples of human serum and plasma. A headspace sampling technique was employed by which volatile sample constituents are carried in a stream of ultra-pure nitrogen and adsorbed onto a porous polymer with subsequent heat desorption. The concentrated volatiles were separated on highly efficient capillary columns. Mass spectrometric identifications were made with 55 ml of serum. Characteristic components in normal serum are: ethanol, 4-methyl-2-pentanone, hexanal, 1-butanol, 2-hexanol, 2-heptanone, and benzaldehyde.

Resolution of isomeric monosubstituted dimethyldiphenylmethanes

SummaryA high resolution open tubular column, 180 m×0.25 mm ID, using Emulphor 0 as the stationary phase was found necessary to resolve all six isomers of dimethyldiphenylmethane. For complete separation, two isothermal runs are required since one of the isomeric pairs loses resolution by a decrease in temperature.