The work described in this paper is integrated in an analytical programme organised by the Community Bureau of Reference with the aim of developing reference materials certified for sterol content. Preliminary inter-comparison of methods showed that the level of agreement of the results was insufficient for certification purposes. Errors could occur in the different steps before the final determination by gas-liquid chromatography. It was, therefore, decided to validate a quantitative procedure for the isolation of sterols. A well defined saponification-extraction method was tested using labelled sterols ([3H]cholesterol and [3H]cholesteryl oleate) and radiochemical measurements. The study has shown that total cholesterol recovery reached 100.5 +/- 1.4%, that cholesteryl ester was saponified quantitatively and that there were no appreciable amounts of degradation products. The procedure has been used as the basis for the certification of three reference materials and it has been shown that the saponification and extraction procedure leads to the quantitative recovery of sterols regardless of the nature of the fatty material tested.
SUMMARYDexamethasone phosphate (DXM-PHO) is an ester which is quickly hydrolysed by the bovine and the dexamethasone (DXM) plasma half-life was 5.16 h. It has been demonstrated that 54 h after DXM-PHO injection, DXM concentrations were lower than 0.1 mglml.Tritiated dexamethasone was also administered twice to an another young bull for metabolite investigation. The elapsed time required to recover, in plasma, half of the radioactivity injected was 8.8 h. Radioactivity recovery in the urine reached 36.4% and 22.6% for the first and the second injections respectively.
Summary.A method for the isotope dilution-mass spectrometric (ID-MS) determination of butyric acid C4 in butter fat (RM164) was developed in order to support the data gathered from nine experienced European laboratories within the final certification exercise. The ID-MS results (3,46 _+ 0,06 g C4/100 g fat) were in very good agreement with those obtained by "classical" GLC and HPLC techniques. (RM164 was finally certified at 3,49 + 0,06 g C4/100 g fat). This paper reports briefly on a previous preliminary study undertaken to validate a procedure (agreed by the BCRsterol group) for the isolation of the sterol from fats and oils. By use of labelled sterols and radiometric measurements it was shown that sterol recoveries were superior to 96%.The procedure was applied during the 3rd Intercomparison exercise for sterol determination in RM162 (Blend of Soya-Maize oil), for the GLC measurements of cholesterol in RM380 (Whole milk powder) and RM384 (Lyophilized pork muscle) and to the ID-MS determination of cholesterol in RM163 (blend of animal fats) and RM164 (anhydrous milk fat).
CHROMATOGRAPHIA is a peer-reviewed international journal dedicated to the latest advances in separation sciences. Its goal is to monitor state-of-the-art research and to promote study, research and improvement within its various application areas, including archaeology, biotechnology, clinical, environmental, food, medical, petroleum, pharmaceutical, polymer and biopolymer research, as well as preparative and processscale applications. The journal focuses on papers that show the scope and power of separation sciences when combined with spectroscopic methods, in particular with mass spectrometry. In addition to exciting new areas in chromatography, such as ultrahigh pressure and high-temperature approaches, CHROMATOGRAHIA focuses on hyphenated systems that combine several unit operations with chromatography and electro-based separations, especially on the micro-and nanoscale. Integrated biological procedures (e.g., enzymatic, immunological, receptor-based assays) can also be part of the overall analytical process. Developments in separation-related sampling and samplingpreparation approaches, and in particular the combination of these techniques with the above methodologies, are also comprehensively covered.
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