Two modes of liquid-phase microextraction (LPME) were developed for capillary gas chromatography. Both methodologies, i.e., static LPME and dynamic LPME, involve the use of very small amounts of organic solvent (<2 μL) in a conventional microsyringe. The performance of the two techniques is demonstrated in the determination of two chlorobenzenes extracted into a single drop of toluene by the use of a 10-μL syringe. Static LPME provided some enrichment (∼12-fold), good reproducibility (9.7%), and simplicity but suffered relatively long extraction time (15 min). Dynamic LPME provided higher (∼27-fold) enrichment within much shorter extraction time (∼3 min), and relatively poorer precision (12.8%), primarily due to repeated manual manipulation. Both methods allow the direct transfer of extracted analytes into a gas chromatograph.

The dynamics of nanoscale island growth, stability, and dissolution, accompanying the potential-induced phase transitions between the (22 × 3) and (1 × 1) structures of the Au(111) surface in 0.1 M HClO 4 solution, have been investigated by potential pulse perturbation time-resolved scanning tunneling microscopy (P 3 TR-STM). Starting from a potential at which the reconstructed (22 × 3) phase is stable, a short positive potential pulse briefly brings the electrode to a potential at which the (1 × 1) phase is stable. This pulse induces a perturbation that lifts the Au(111)-(22 × 3) reconstruction completely, resulting in nanoscale island formation on the surface. The nanoscale islands are metastable and dissolve with time. The initial average island area and the island decay rate are related to the pulse amplitude and duration. The higher and longer the pulse, the smaller the average size of the islands produced and the more slowly the islands decay. This result reveals a "voltammetric annealing" process that may be important in stable island formation at electrochemical interfaces. The dynamics of individual islands are quite heterogeneous and nonmonotonic. Small islands decay faster than large islands. Even under metastable conditions, large islands frequently grow before ultimately decaying, providing evidence for electrochemical Ostwald ripening in this system. A simple model, based on perimeter detachment as the rate-limiting step, provides a qualitative explanation for the observed decay dynamics.