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Browsing by Author "Zheng, Qiao"

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  • Solid phase extraction based on nanomaterials for isolation of urinary volatile metabolites
    Publication . Zheng, Qiao; Câmara, José de Sousa; Rodrigues, João Manuel Cunha
    Testing of urinary volatile organic metabolites (VOMs) is recognized as a useful medical approach since they are the end-products of metabolic processes and non-invasively sampling. Among the various techniques conventionally used for metabolic profiling, gas chromatography-quadrupole mass spectrometry (GC-qMS) is viewed as an effective approach for the testing of VOMs in urine due to its high sensitivity, peak resolution and reproducibility. Solid phase extraction (SPE), one of the sample preparation methods, has been proven to be a robust tool for the application in target VOMs concentration and separation from complex matrix. The aims of this study are to explore new nanomaterials (NMs), such as inorganic and carbon-based nanoparticles magnetic NPs (MNPs), combined with GC-qMS in order to isolate and pre-concentrate the target urinary VOMs, reported as possible cancer biomarkers. Concerning to the nanosorbent, the best efficiency of extraction is achieved with nanohydroxyapatite (NHA) and magnetic Fe3O4@SiO2-C18 NPs. Some experimental parameters such as, sorbent amount, adsorption and elution time, as nature of elution solvent, were investigated and compared. Under optimal conditions for nanohydroxyapatite (NHA) and magnetic Fe3O4@SiO2-C18 NPs, the obtained results revealed a good linearity (r2 ≥ 0.988) within the linear dynamic range, for all urinary volatile metabolites under study. The projected strategy showed low limits of detection (LODs), ranging from 9.7 to 69.5 ng/L, and low limits of quantification (LOQs) from 32.4 to 231.6 ng/L. The methodology also afforded suitable results in terms of matrix effect (62.8–96.1%) and accuracy, higher than 70 % for the majority of the investigated VOMs. The precision, expressed as intra- and inter-day repeatability, was lower than 3 and 13 %, respectively. Together, the NHA and Fe3O4@SiO2-C18 NPs-based sorbent extraction combined with GC-qMS in the current study provides a new, reliable and high throughput strategy for the determination of VOMs in human urine.
    2014-07-30Master thesis Open access Show more