Biomedical subjects

K D Zissis

Publications and source records attributed to K D Zissis.

3 recordsLinked to original sources

PubMed1999

Principal components scores and loadings plots for visualisation of the electrospray ionisation liquid chromatography mass spectra of a mixture of chlorophyll degradation products at different cone voltages.

Positive ion electrospray liquid chromatography mass spectrometry was performed on a mixture of allomers obtained from the degradation of chlorophyll a, at three cone voltages. An approach is described for obtaining principal components loadings and scores plots, involving mass selection, normalisation and standardisation of the data, principal components analysis and three dimensional projections. The loadings plots group ions which are assigned to five major compounds in the mixture by reference to the scores. At higher cone voltage fragmentation and differentiation between compounds with identical molecular weights is observed.

Chlorophyll↗

PubMed1998

Chemometric analysis of high performance liquid chromatography-diode array detection-electrospray mass spectrometry of 2- and 3-hydroxypyridine.

Triply coupled high performance liquid chromatography using diode array detection and positive ion electrospray mass spectrometry of 2- and 3-hydroxypyridine is presented. Considerations of the physical method for coupling the two detectors, the influence of pH on retention times, the cone voltage of the mass spectrometer and the linear concentration ranges are described. Data from both detectors are aligned and interpolated. The analyte mass spectra are reduced to 20 significant masses. Principal components plots on the raw, normalised and standardised data, derivatives to determine composition 1 regions, deconvolution and procrustes analysis to compare data from both detectors are discussed. Common trends in both mass spectral and diode array chromatograms are interpreted. This paper represents a new approach to common processing of chromatographic data from two detectors.

Antioxidants↗

PubMed1997

Monitoring of impurities using high-performance liquid chromatography with diode-array detection: eigenvalue plots of partially overlapping tailing peaks.

The chromatogram of ropinirole in the presence of about 5% of a closely eluting impurity, obtained by HPLC with diode-array detection, was analysed by chemometric procedures. Log eigenvalue plots were used to determine the relative composition of regions of the chromatogram. It is shown that since the peaks exhibit tailing, unusual behaviour is found in the plots. This is verified by performing simulations, in which it is demonstrated that peak asymmetry has a pronounced influence on this chemometric approach. In many cases of liquid chromatographic analysis, asymmetric peak shapes are encountered and methods for peak purity assessment should be re-evaluated in the light of these asymmetries.

Chromatography, High Pressure Liquid↗