Enrichment and determination of crotonaldehyde using magnetic multiwalled carbon nanotubes as an adsorbent and a matrix for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Nanomaterials as Assisted Matrix of Laser Desorption/Ionization Time-of-Flight Mass Spectrometry for the Analysis of Small Molecules

Matrix-assisted laser desorption/ionization (MALDI), a soft ionization method, coupling with time-of-flight mass spectrometry (TOF MS) has become an indispensible tool for analyzing macromolecules, such as peptides, proteins, nucleic acids and polymers. However, the application of MALDI for the analysis of small molecules (<700 Da) has become the great challenge because of the interference from the conventional matrix in low mass region. To overcome this drawback, more attention has been paid to explore interference-free methods in the past decade. The technique of applying nanomaterials as matrix of laser desorption/ionization (LDI), also called nanomaterial-assisted laser desorption/ionization (nanomaterial-assisted LDI), has attracted considerable attention in the analysis of low-molecular weight compounds in TOF MS. This review mainly summarized the applications of different types of nanomaterials including carbon-based, metal-based and metal-organic frameworks as assisted matrices for LDI in the analysis of small biological molecules, environmental pollutants and other low-molecular weight compounds.

Sensitive and fast beverage/fruit antioxidant evaluation by TiO2 -Au/graphene nanocomposites coupled with MALDI-MS

RATIONALE

Because the ratio of tripeptide glutathione (GSH) to glutathione disulphide (GSSG) is tightly associated with the oxidative stress and antioxidant level of an organism, it is often considered to be an indicator of the redox states of cells. Therefore, developing an integrated protocol for rapid, efficient, and low-cost detection of GSH to measure antioxidant ability is of significant importance for the diagnosis of oxidative stress-associated diseases.

METHODS

TiO2 -Au/graphene nanocomposites were synthesized to integrate the characteristics of graphene as matrix for MALDI-MS, gold NPs as selective probes for GSH and the photocatalytic property of TiO2 . Under UV-visible (UV-Vis) light irradiation, OH can be produced by the TiO2 -Au/G composites, which can oxidize GSH to form GSSG. When various antioxidants are introduced into the aforementioned system, OH can be scavenged, thereby leaving part of GSH in its reductive format. Based on the ratio of GSH/GSSG, the antioxidative capability of various beverages and fruits can be determined.

RESULTS

TiO2 -Au/G composites were employed to enrich GSH, where 0.01 mg/mL GSH can be efficiently extracted by the nanocomposites from aqueous solution and detected by MS with high signal-to-noise ratio. The proposed strategy was applied to evaluate three often-used antioxidants: Vitamin C, Vitamin E, and β-carotene; and demonstrated that the antioxidative ability of VC is the strongest. To further evaluate the feasibility of the proposed strategy for antioxidative ability evaluation of complex sample, commercial juices and fresh fruit were also studied.

CONCLUSIONS

A novel strategy for sensitive and fast characterization of the antioxidative ability of various beverages and fruits was developed based on TiO2 -Au/G nanocomposites coupled with MALDI-MS. Copyright © 2016 John Wiley & Sons, Ltd.

Simultaneous assessments of occurrence, ecological, human health, and organoleptic hazards for 77 VOCs in typical drinking water sources from 5 major river basins, China

Owing to the growing public awareness on the safety and aesthetics in water sources, more attention has been given to the adverse effects of volatile organic compounds (VOCs) on aquatic organisms and human beings. In this study, 77 target VOCs (including 54 common VOCs, 13 carbonyl compounds, and 10 taste and odor compounds) were detected in typical drinking water sources from 5 major river basins (the Yangtze, the Huaihe, the Yellow, the Haihe and the Liaohe River basins) and their occurrences were characterized. The ecological, human health, and olfactory assessments were performed to assess the major hazards in source water. The investigation showed that there existed potential ecological risks (1.30 × 10 ≤ RQtotals ≤ 8.99 × 10) but little human health risks (6.84 × 10(-7) ≤ RQtotals ≤ 4.24 × 10(-4)) by VOCs, while that odor problems occurred extensively. The priority contaminants in drinking water sources of China were also listed based on the present assessment criteria.