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High-throughput screening of catalysts could dramatically improve performance and reduce costs in the discovery and study of various catalysts. Here we report a cataluminescence-based array imaging as a high-throughput screening technique in the combinatorial discovery of active catalysts for CO oxidation. This strategy is based on the fact that the CO oxidation generates cataluminescence emission on the surface of nanomaterials, whose intensity is correlated to the activity of the catalyst. To demonstrate the feasibility of the cataluminescence-based array imaging for high-throughput screening of catalysts, different nanosized metal catalysts supported on TiO2 nanoparticles were prepared. These catalysts include monometallic Au, Pt, and the bimetallic Au-Pt heteroaggregate catalysts, at total metal loadings of 0.5%, 1.0%, and 2.5%, and with atomic ratios of 1:1, 1:2, and 2:1 (Au/Pt). A 4 × 4 array was integrated by depositing these nanosized catalysts onto the ceramic chip, and the brightness of each spot in the image was recorded. The catalytic activities of those catalysts for the CO oxidation were evaluated parallelly by both the cataluininescence imaging and the gas chromatography method. The correlation coefficient is 0.9 14 for the two techniques, indicating that the cataluminescence imaging technique can be applied for the evaluation of the catalytic activities. Moreover, fast evaluation of multiple catalysts at a series of working temperature can be achieved by this cataluininescene-based array imaging. With the development of nanotechnology as well as the catalyst industry, the cataluminescence-based array imaging will address its importance in the high-throughput screening of catalysts. [ABSTRACT FROM AUTHOR]

A low-temperature plasma (LTP) probe has been developed for ambient desorption ionization. An ac electric field is used to induce a dielectric barrier discharge through use of a specially designed electrode configuration. The low-temperature plasma is extracted from the probe where it interacts directly with the sample being analyzed, desorbing and ionizing surface molecules in the ambient environment This allows experiments to be performed without damage to the sample or underlying substrate and, in the case of biological analysis on skin surfaces, without electrical shock or perceptible healing. Positive or negative ions are produced from a wide range of chemical compounds in the pure state and as mixtures in the gaseous, solution, or condensed phases, using He, Ar, N2, or ambient air as the discharge gas. Limited fragmentation occurs, although it is greater in the cases of the molecular than the atomic discharge gases. The effectiveness of the LTP probe has been demonstrated by recording characteristic mass spectra and tandem mass spectra of samples containing hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6-trinitrotoluene (TNT) from poly(tetrafluoroethylene) (PTFE) surfaces where limits of detection are as low as 5 pg. Other performance characteristics, when using a commercial ion trap mass spectrometer, include 3-4 orders of magnitude linear dynamic range in favorable cases. Demonstration applications include direct analysis of cocaine from human skin, determination of active ingredients directly in drug tablets, and analysis of toxic and therapeutic compounds in complex biological samples. Ionization of chemicals directly from bulk aqueous solution has been demonstrated, where limits of detection are as low as 1 ppb. Large surface area sampling and control of fragmentation by a simple adjustment of the electrode configuration during operation are other demonstrated characteristics of the method. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including the scope of analytical chemistry, principles of chemical measurement science, and measurement of chemical compound and other elements.