Analysis of various classes of drugs by capillary supercritical fluid chromatography

Three classes of drugs were screened for analysis feasibility by capillary column supercritical fluid chromatography. These included steroids, therapeutic antibiotic drugs, and drugs of abuse, such as cannabinoids. Supercritical fluid carbon dioxide was used as the mobile phase in conjunction with a methylpolysiloxane stationary phase capillary column and a flame ionization detector. All compounds considered were analyzed either as single component solutions, simple mixtures, or in actual complex mixtures.     

Evaluation of contributions to the uncertainty of cholesterol determination in human serum by means of gas chromatography/(quadrupole-) mass spectrometry

 The uncertainty budget of the determination of cholesterol in a reference material (freeze-dried human serum) by isotope dilution mass spectrometry (IDMS) was evaluated. Measurements were run on a GC/quadrupole MS. A nested experimental design combined with a corresponding model for the analysis of variance (ANOVA) revealed the components making up the total uncertainty of the determinations. The coefficient of variation (CV) of the sole GC/MS-step was 0.47%, while that of the sample preparation including hydrolyzation, extraction and derivatization was 0.84%. This made the in-laboratory (overall) CV 0.96%. In addition, there was a vial-to-vial effect of 1.00% probably due to both inhomogeneity of the pooled material and lack of reproducibility of the filling procedure (including freeze drying) of the supplier as well as the reconstitution prior to use in the laboratory. These contributions sum up to an overall CV of a single determination of about 1.4%. Received: 17 October 1996/Revised: 14 November 1996/Accepted: 18 November 1996     

Zur Struktur von N-Benzoylthiobenzamid

Structure of N-Benzoylthiobenzamide N-Benzoylthiobenzamide forms two polymorphic modifications of which the crystal and molecular structures have been determined by X-ray structure analysis. In both modifications the molecules exist as NH tautomeres, but there are differences with regard to their rotameric configurations. In the monoclinic modification both symmetry independent molecules have a Z,Z′ configuration. The triclinic modification also contains two symmetry independent molecules, but now a Z,Z′ and an E,Z′ configuration exist. All four molecules deviate appreciably from planarity. The results of both structure determinations are compared with each other and with the structure of monothiodibenzoylmethane.     

Über Spurenelementbestimmungen in Leberproben Mittels Protoneninduzierter Röntgenfluoreszenz (Pixe)

Multi-element-analysis by PIXE in respect to medical applications is discussed. Examples of trace-element determinations in liver tissues are given, demonstrating the applicability and usefulness of this rather new analytical technique.      

On-line multidimensional chromatography using packed capillary liquid chromatography and capillary gas chromatography

The introduction of selected fractions from a liquid chromatograph into a gas chromatograph has been described; however, analyses were performed by off-line experiments requiring collection and reinjection of the separate fractions or by on-line procedures where disadvantageously, only a fraction of the separated peak or a well resolved component in a mixture could be introduced into a gas chromatograph. This disadvantage is overcome by the apparatus and method described in this paper, which utilizes a multidimensional chromatography system employing a high efficiency, packed capillary LC column coupled on-line to a capillary gas chromatograph. The liquid chromatograph (so designed) can act as a highly efficient clean-up or chemical class fractionation step prior to introduction into the gas chromatograph, significantly reducing sample preparation times in many applications. Thus minor components in a complex matrix can be determined without prior sample clean-up, an example of which is the determination of polychlorinated biphenyls in a complex hydrocarbon matrix.