Transition metal oxide ZnO nanoparticles as inorganic matrix was adopted in the matrix assisted laser desorption ionization time-of-flight mass spectrometry ( MALDI-TOF-MS ) analysis of small molecule compounds including sugars and stearic acid and its performances were investigated. In addition, the feasibility of metal ion selective ionization of L-arginine by using NiO and CuO nanoparticles as matrix directly was explored initially. In the experiment, the analyte and nanoparticle suspension were mixed on the sample plate. The crystal of analyte and matrix was excited by 337 nm laser after the solvent was evaporated, and then detected under reflection mode of TOF-MS. The results indicated that ZnO nanoparticles with high UV absorption could eliminate the interference of conventional matrix, simplify the mass spectra, and enhance the peak intensity of stearic acid under negative mode. Moreover, Cu+ ion selective ionization of L-arginine was achieved in comparison of CuO and NiO as matrix for MALDI-TOF-MS analysis of L-arginine.

A rapid and convenient ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS / MS) method for analysis of ribavirin and its two main kinds of metabolites, 1,2,4-triazole-3-carboxamide (TCONH2 ) and 1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxylic acid (RTCOOH), in fresh eggs has been developed and validated. The sample was extracted with acetonitrile water (9 ∶ 1, V/ V), added N-hexane to move liposoluble substances, after centrifugation, the upper solvent was cleaned-up by C18 and GCB, then determined by UPLC-MS / MS coupled with Agilent ZORBAX SB-Aq column (100 mm×3. 0 mm, 1. 8 μm). Over the concentration range of 2. 0-200. 0 μg / L (0. 5-200. 0 μg / L and 5. 0-200. 0 μg / L) for ribavirin (TCONH2 and RTCOOH) in fresh egg matrix, the correlation coefficients (R2 ) of the calibration curves were above 0. 99, and the limits of detection (LODs) were 0. 54 μg / L (0. 09 and 1. 54 μg / L). The limits of quantitation (LOQs) were 1. 79, 0. 31 and 5. 13 μg / L, respectively. At three spiked concentration levels of 5. 0, 10. 0 and 50. 0 μg / L, the recoveries of ribavirin and RTCOOH ranged from 96. 1% to 99. 6%and 42. 9% to 58. 3% . And at three spiked concentration levels of 0. 5, 2. 0 and 5. 0 μg / L, the recoveries of TCONH2 ranged from 75. 9% to 106. 7% . The results of the determination in various real samples showed that the method is simple, accurate, rapid and suitable determination of ribavirin and its two main kinds of metabolites in fresh eggs.