Magnetic carbon nanotube composite for the preconcentration of parabens from water and urine samples using dispersive solid phase extraction.

This study describes the use of a magnetic multi-walled carbon nanotube composite for the preconcentration of nine parabens (methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, phenyl and benzylparaben) from water and urine samples after in situ acetylation. The enriched extracts were obtained by dispersive magnetic solid phase extraction (DMSPE) and analysed by gas chromatography with mass spectrometry (GC-MS). Several parameters affecting the adsorption (extraction time, magnetic material mass and ionic strength) and desorption (desorption solvent nature and volume, and desorption time) DMSPE steps were investigated. Matrix-matched calibration was recommended for quantification of the samples. Linearities in the 0.5-150 ng mL-1 range were obtained, depending on the compound. Under the optimal experimental conditions, the limits of detection ranged between 0.03 and 2.0 ng mL-1, depending on the sample matrix and the paraben congener. None of the samples analysed contained the above mentioned parabens. The method was validated with two water samples (harbour and wastewater treatment plant) and two urine samples spiked at two concentration levels. Recoveries in the 81-119% range were obtained.

Potential applications of lipid peroxidation products - F4-neuroprostanes, F3-neuroprostanesn-6 DPA, F2-dihomo-isoprostanes and F2-isoprostanes - in the evaluation of the allograft function in renal transplantation.

F4-neuroprostanes, F3-neuroprostanesn-6 DPA, and F2-dihomo-isoprostanes, metabolites of non-enzymatic lipid peroxidation of polyunsaturated fatty acids [docosahexaenoic acid, n-6 docosapentanoic acid, and adrenic acid respectively], have become important biomarkers for oxidative stress in several diseases like epilepsy and alzheimer. These biomarkers and the 15-F2t-isoprostane (also known as 8-iso-PGF2α), a F2-isoprostane isomer measured as reference oxidative marker at systemic level, were analyzed by UHPLC-QqQ-MS/MS in the urine of 60 renal recipients from cadaveric donors of the Nephrology Unit of the University Hospital Virgen de la Arrixaca, at six different times during the first six months after renal transplantation, and were compared with a control group of 60 healthy subjects from the same hospital. A total of 11 metabolites were analyzed and different patterns were observed. A tendency to decrease was observed in three metabolites (4-epi-4-F3t- NeuroPn-6 DPA, ent-7(RS)-7-F2t-dihomo-IsoP, and ent-7(S)-7-F2t-dihomo-IsoP) and in our reference oxidative marker (15-F2t-IsoP) when kidney function improved and the excretion of urine proteins decreased. These results suggest that these three biomarkers of oxidative stress could be useful to assess renal function in the postransplant phase. Unfortunately, little is known about this kind of biomarker in this cohort of patients, so further investigation would be required in the clinical field to clarify the relationship between oxidative stress and the graft function, as well as the usefulness of these biomarkers as rejection markers.