A comprehensive automatic data analysis strategy for gas chromatography-mass spectrometry based untargeted metabolomics.

Automatic data analysis for gas chromatography-mass spectrometry (GC-MS) is a challenging task in untargeted metabolomics. In this work, we provide a novel comprehensive data analysis strategy for GC-MS-based untargeted metabolomics (autoGCMSDataAnal) by developing a new automatic strategy for performing TIC peak detection and resolution and proposing a novel time-shift correction and component registration algorithm. autoGCMSDataAnal uses original acquired GC-MS datafiles as input to automatically perform TIC peak detection, component resolution, time-shift correction and component registration, statistical analysis, and compound identification. We utilize standards and complex plant samples to comprehensively investigate the performance of autoGCMSDataAnal. The results suggest that the developed strategy is comparable with several state-of-the-art methods that are widely used in GC-MS-based untargeted metabolomics. Based on the proposed strategy, we develop a user-friendly MATLAB GUI for users who are unfamiliar with programming languages to facilitate their routine analysis, which can be freely downloaded at: http://software.tobaccodb.org/software/autogcmsdataanal.

Synthesis, characterization, and electrochemiluminescence of luminol-reduced gold nanoparticles and their application in a hydrogen peroxide sensor.

It was found that chloroauric acid (HAuCl(4)) could be directly reduced by the luminescent reagent luminol in aqueous solution to form gold nanoparticles (AuNPs), the size of which depended on the amount of luminol. The morphology and surface state of as-prepared AuNPs were characterized by transmission electron microscopy, UV/visible spectroscopy, X-ray photoelectron spectroscopy, FTIR spectroscopy, and thermogravimetric analysis. All results indicated that residual luminol and its oxidation product 3-aminophthalate coexisted on the surface of AuNPs through the weak covalent interaction between gold and nitrogen atoms in their amino groups. Subsequently, a luminol-capped AuNP-modified electrode was fabricated by the immobilization of AuNPs on a gold electrode by virtue of cysteine molecules and then immersion in a luminol solution. The modified electrode was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The as-prepared modified electrode exhibited an electrochemiluminescence (ECL) response in alkaline aqueous solution under a double-step potential. H2O2 was found to enhance the ECL. On this basis, an ECL sensor for the detection of H2O2 was developed. The method is simple, fast, and reagent free. It is applicable to the determination of H2O2 in the range of 3x10(-7)-1x10(-3) mol L(-1) with a detection limit of 1x10(-7) mol L(-1) (S/N=3).

Multi-channel electrochemiluminescence of luminol at a copper electrode.

Multi-channel electrochemiluminescence (ECL) of luminol at a copper electrode has been studied under conventional cyclic voltammetric (CV) conditions. Compared with the ECL of luminol at other electrodes, three ECL peaks were observed at 0.30, -0.24 and -0.65 V (vs. SCE), respectively, which was also imaged by a CCD camera. The effects of potential scan direction, anodic reverse potential, the presence of N2 and O2 of the solution, the pH of the solution, the NaNO3 concentration and the potential scan rate were examined. The effect of n-alkanethiol self-assembled monolayers on copper electrodes and 20 L-amino acids, dopamine, adrenaline and noradrenaline on the ECL of luminol were also investigated. The emission spectra of various ECL peaks at different potentials demonstrated that all ECL peaks were related to the luminol reaction. The results show that the oxygen dissolved in solution and copper oxide covered on the surface of the electrode play an important role in the luminol ECL process at a copper electrode. It has been proposed that three ECL channels of luminol at a copper electrode resulted from the reactions of luminol or luminol radical electrooxidized by luminol with various electrogenerated oxygen-containing species, such as O2, OOH- and copper oxides at different potentials.