The application of single-drop microextraction (SDME) followed by gas chromatography/chemical ionization mass spectrometry (GC/CI-MS) was investigated for the determination of anisaldehyde isomers in human urine and blood serum. The effects of extraction solvent, sample agitation rate, salt addition, sampling time and temperature on the extraction efficiency were examined and optimized. Analytical parameters such as linearity, reproducibility, detection limit and relative recovery were evaluated under the optimized experimental conditions. Good reproducibilities of replicate extractions (n = 5) were obtained, with relative standard deviation (RSD) values below 6%. The limits of detection (LOD) using an extraction time of 5 min were found to be in the range 2-5 ng/mL under the selected ion monitoring (SIM) mode of GC/MS. Recoveries of 82-98% were achieved after 5 min extraction.

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For the first time, we observed a stable and intense ion (m/z 376) of the oxygenated water cluster ion ((H(2)O)(20)O(+)) produced from simply spraying an aqueous solution of iron nanoparticles (Fe NPs) into an electrospray mass spectrometry (ESI-MS) system. Tandem mass spectrometric (MS/MS and MS/MS/MS) results were applied to identify the assignments of the fragment ions of m/z 376 in order to explore the possible structures of this cluster ion. The possible structures of the (H(2)O)(20)O(+) ions are proposed as pentagonal dodecahedron water clathrate cages from the results of tandem mass spectrometry since eliminations of five water molecules were frequently observed in the MS/MS results for many subsequent fragment ions of m/z 376. The formation of this oxygenated water cluster ion ((H(2)O)(20)O(+)) in ESI-MS is attributed to the high surface reactivity and surface energy of Fe NPs during ESI processes (under high temperature and high voltage (5 kV) of ESI spray environment). We believe that the observation of self-assembly formation of oxygenated water clusters is an important issue in nanoscience as well as in the fields of water clusters.