Use of an in vitro digestion model to study the bioaccessibility of 4-hydroxy-2-nonenal and related aldehydes present in oxidized oils rich in omega-6 acyl groups.

Mixtures of either sunflower oil or thermodegraded sunflower oil and a standard meal were submitted to an in vitro digestion model. The same experiment was carried out with fluid deep-frying fat and thermodegraded fluid deep-frying fat. The thermodegradation of the oil and fat was provoked by submitting them to 190 degrees C with aeration in a convection oven, and the presence in the headspace of the thermodegraded oil and fat of oxygenated alpha,beta-unsaturated aldehydes (OalphabetaUAs), such as 4-hydroxy-2-nonenal (HNE), 4-oxo-2-nonenal (ONE), and 4,5-epoxy-2-decenal (EDE), was monitored by solid phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS).

Multi-residue screening of a minimum package of anabolic steroids in urine with GC-MS.

The method comprises the screening of two groups of anabolic compounds, the stilbenes and several steroids. All compounds, inclusive their metabolites when possible, for which gas chromatography-mass spectrometry (GC-MS) currently is the preferred analytical technique, are included. Two different derivatives are prepared.

Determination of acetyl gestagenic steroids in kidney fat by automated supercritical fluid extraction and liquid chromatography ion-trap mass spectrometry.

Acetyl gestagenic steroids are isolated from animal tissues such as bovine kidney fat by automated supercritical fluid extraction (SFE). After the addition of internal standards and sample pretreatment, the analytes are extracted from the matrix by supercritical CO2 and trapped directly in-line on alumina placed in the extraction vessel. The samples are analysed by liquid chromatography combined with ion-trap mass selective detection (LC-MSn).

Thyroid peroxidase: kinetics, pH optima and substrate dependency.

The oxidation of iodide, guaiacol and 2,2'-azino-di[3-ethyl-benzthiazoline-(6)-sulphonic acid] and the iodination of tyrosyl residues in bovine serum albumin, catalysed by partly purified thyroid peroxidase, were studied. The enzyme showed pH optima with all electron donors. With the exception of guaiacol, the position of the pH optima depended upon both the electron donor and hydrogen peroxide concentrations.