Determination of elements in native and bypass human coronary artery plaque deposits from the same heart using inductively coupled plasma-mass spectrometry.

As part of an ongoing study on atherosclerotic arteries, the concentrations of 12 elements in a native and by-pass human coronary artery plaque deposits from five human hearts were determined using inductively coupled plasma-mass spectrometry (ICP-MS). These elements were Ca, P, Na, K, Mg, Zn, Cu, Pb, Fe, Al, Si, and S. For Zn, Ca, Pb, Fe, Al, and Si, the levels were at the fractional micromol/g levels and they probably played an unimportant role in plaque development. Sulfur levels varied from 23 to 140 micromols indicative of the possible presence of homocysteine, but there appeared to be no consistent relationship between by-pass and native concentrations. The calcium and phosphorus concentrations were relatively high in all cases, but the ratio of their molecular concentrations did not correspond to hydroxyapatite, which is conventionally considered to be the chemical form of calcium in heart plaque. In the mature native plaque, high calcium/phosphorus ratios indicated calcium in chemical forms other than hydroxyapatite. In undeveloped by-pass plaque, the phosphorus concentration was too high to be as hydroxyapatite but may be phospholipids. Because it is difficult to get suitable samples, only five heart samples were available. Therefore, these results should be treated as preliminary.

Open-tubular capillary electrochromatography/electrospray ionization-mass spectrometry using polymeric surfactant as a stationary phase coating.

We describe the use of the polymeric surfactant poly(sodium undecylenic sulfate) (poly-SUS) as a stationary phase coating in open-tubular capillary electrochromatography (OT-CEC) coupled with electrospray ionization-mass spectrometry (ESI-MS) for the analysis of beta-blocker and benzodiazepine analytes. The production of a polymeric surfactant coating on the capillary inner wall involves (i) adsorption of the cationic polymer poly(diallyldimethylammonium chloride) (PDADMAC) to the inner surface of capillary, and (ii) adsorption of the negatively charged poly-SUS onto the cationic polymer layer via strong physical interaction of the two polymer layers. As compared with micellar electrokinetic chromatography (MEKC) coupled with ESI-MS, the main advantage of this proposed method is minimization of introduction of the monomeric or polymeric surfactant into the mass spectrometer, thus avoiding the interference of the nonvolatile micelle in ESI-MS. The effects of buffer pH and applied voltage on the separation of the analytes are also discussed. Under optimum conditions, four of the five beta-blockers and four benzodiazepines are separated.

A colloidal graphite-coated emitter for sheathless capillary electrophoresis/nanoelectrospray ionization mass spectrometry.

A colloidal graphite-coated emitter is introduced for sheathless capillary electrophoresis/nanoelectrospray ionization time-of-flight mass spectrometry (CE/ESI-TOFMS). The conductive coating can be produced by brushing the capillary tip to construct a fine layer of 2-propanol-based colloidal graphite. The fabrication involves a single step and requires less than 2 min. Full cure properties develop in approximately 2 h at room temperature and then the tip is ready for use. The coated capillary tip is applied as a sheathless electrospray emitter. The emitter has proven to bear stable electrospray and excellent performance for 50 microm i.d. x 360 microm o.d. and 20 microm i.d. x 360 microm o.d. capillaries within the flow rate of 80-500 nL/min; continuous electrospray can last for over 200 h in positive mode. Baseline separation and structure elucidation of two clinically interesting basic drugs, risperidone and 9-hydroxyrisperidone, are achieved by coupling pressure-assisted CE to ESI-TOFMS using the described sheathless electrospray emitter with a bare fused-silica capillary at pH 6.7. It is found that the signal intensity of m/z in sheathless CE/ESI-TOFMS at pH 6.7 is approximately 50 times higher than that at pH 9.0 for the two analytes, although the electroosmotic flow (EOF) at pH 9.0 provides sufficient flow rate (approximately 150 nL/min) to maintain electrospray.

High resolution three-dimensional visualization and characterization of coronary atherosclerosis in vitro by synchrotron radiation x-ray microtomography and highly localized x-ray diffraction.

Human atherosclerotic plaques in both native and bypass arteries have been visualized using microtomography to provide additional information on the nature of coronary artery disease. Plaques contained within arteries removed from three white males aged 51, 55 and 70 are imaged in three-dimensions with monochromatic synchrotron x-ray radiation. Fields of view are 658 x 658 x 517 voxels. with cubic voxels ranging from 12 to 13 microm on a side. X-ray energies range from 11 to 15 keV (bandpass approximately 10 eV). At lower energies, high local absorption tends to generate reconstruction artefacts, while at higher energies the arterial wall is scarcely visible. At all energies, calcifications are clearly visible and differences are observed between plaques in native arteries (lifetime accumulations) versus bypass arteries (plaques developing in the interval between the heart bypass operation and the autopsy). In order to characterize coronary calcification, a microfocused, 50 microm2, 25 keV x-ray beam was used to acquire powder diffraction data from selected calcifications. Also, large calcifications were removed from the native arteries and imaged with 25 keV x-ray energy. Calcifications are composed of hydroxyapatite crystallites and an amorphous phase. In summary, native calcifications are larger and have a higher fraction of hydroxyapatite than calcifications from the bypass arteries.