Interface probe

Eisenthal K B 1996 Liquid interfaces probed by second-harmonic and sum-frequency spectroscopy Chem. Rev. 96 1343-60... 

Heinz T F, Himpsel F J, Palange E and Burstein E 1989 Electronic transitions at the CaF2/Si(111) interface probed by resonant three-wave-mixing spectroscopy Phys. Rev. Lett. 63 644-7... 

Yamakata, A., Uchida, T., Kubota, J. and Osawa, M. (2006) Laser-induced potential jump at the electrochemical interface probed by picosecond time-resolved surface-enhanced infrared absorption spectroscopy./. Phys. Chem. B, 110, 6423-6427. 

L. E. Morrison and G. Weber, Biological membrane modeling with a liquid/liquid interface. Probing mobility and environment with total internal reflection excited fluorescence, Biophys. J. 52, 367-379 (1987). 

In the AC impedance method, a modulation of potential causes a modulation of concentration at the interface. As a consequence there is a modulation of the concentration gradient and hence of the current density. The modulation of concentration decays with distance away from the interface. Thus there is a characteristic penetration depth into the solution phase of the concentration wave, SAC, where SAc = (2Dlw)m. The time scale for chemical processes, either in the solution or at the interface, probed by the perturbation, is simply / >. If the concentration boundary... 

Figure 4.9 First prototype CF-FAB interface probe, built by Caprioli et al. [83] (Reprinted with permission from [41], 1986, American Chemical Society).

The fiit-FAB interface consists of a 40-pm-lD fused-silica capillary, which ends at a porous stainless-steel frit with 2-pm porosity. A schematic diagram of the interface tip is shown in Figure 4.8. The frit-FAB interface is commercially available from Jeol. A frit-FAB interface, based on the use of a 8 pm thick stainless-steel screen (2 pm mesh) as FAB target, was described Hogge et al. [43], and subsequently commercialized by Micromass (currently Waters) as the screen-wick interface with a thin screen with 2 pm pores at the tip of the interface probe [44]. 

A quantitative bioassay for erythromycin 2 -ethylsuccinate (EM-ES, M, 861 Da), a prodrug of the macrolide antibiotic erythromycin, using Cf-FAB LC-MS was described by Kokkonen et al. [53-54]. Reversed-phase LC of extracted plasma samples was performed at a flow-rate of 1 ml/min. In order to meet the flow-rate requirements of the Cf-FAB interface, i.e., 15 pl/min, without splitting, the phase-system switching approach [53] was used. After post-column dilution of the column effluent with water, the eluent fraction of interest was enriched on a short precolumn, from which the compound of interest was desoibed and transferred to the Cf-FAB interface probe. A [ Hj]-analogue was used as internal standard. Good linearity was observed in the range of 0.1 to 10 pg/ml EM-ES in plasma. The within-ran precision was ca. 6%. The accuracy and inter-day precision, determined at 1.05 pg/ml in plasma, were 0.93 0.11 pg/ml and 12%, respectively (n=6). The determination limit was 0.1 pg/ml [54]. 

Figure 1 shows the LC/MS thermospray total ion chromatogram of 0.25 p.g standard mixture of the six sulfonylurea herbicides. Gradient HPLC conditions were used to separate the six compounds in less than 25 minutes total run time. The mobile phase composition was kept isocratic at 30% acetonitrile/.05M formic acid for the first 15 minutes to separate the four herbicides HARMONY, ALLY, OUST and GLEAN. A gradient from 30% acetonitrile to 60% in 10 minutes was then used to elute EXPRESS and CLASSIC. An acidified mobile phase is used with sulfonylureas to keep them in the undissociated form which is retained on the HPLC column (3). Organic acids are recommended for use with LC/MS to prevent the formation of deposits in the mass spectrometer source and to prevent clogging of the thermospray interface probe tip. In this work we used formic acid. 

Hildebrandt, P. and Stockburger, M. (1989) Cytochrome c at charged interfaces. 1. Conformational and redox equilibria at the electtode/electtolyte interface probed by surface-enhanced resonance Raman specttoscopy. Biochemistry, 28, 6710-6721. 

Tijana Rajh, Zoran Saponjic, Jianqin Liu, Nada M. Dimitrijevic, Norbert F. Scherer, Manuel Vega-Arroyo, Peter Zapol, Larry A. Curtiss, and Marion Thumauer, Charge transfer across the nanocrystal-DNA interface Probing DNA recognition. Nano Letters, 4,1017-1023 (2004). 

Sjoberg, J.R. Markides, K.E. New Supercritical Fluid Chromatography Interface Probe for Electrospray and Atmospheric Pressure Chemical Ionization Mass Spectrometry, J. Chromatogr. A 785,101-110 (1997). 

Stack, A.G., Higgins, S.R., and Eggleston, C.M., Point of zero charge of a corundum-water interface probed with optical second harmonic generation (SHG) and atomic force microscopy (AFM). New approaches to oxide surface charge, Geochim. Cosmochim. Acta, 65, 3055, 2001. 

MS Interface Probe. After separation on the capillary coltimn, analytes are introduced directly into the mass spectrometer source via the interface probe shown in Figure 2. The heart of the probe is a 60 cm length of uncoated, 25 urn i.d., fused-silica tubing (25VS-025ID, Scientific Glass Engineering, Inc., Austin, TX, USA). 

The outer diameter of the interface probe and the shape of its tip are dictated by the mass spectrometer s direct insertion port and source inlet. The probe s outer tube, OT, is a 40 cm length of 6.4 mm o.d. X 4.8 mm i.d. stainless steel tubing (Microgroup Inc.,... 

Several experimental variables have an important influence on the SFC-MS experiment using this equipment. These variables include the size of the restrictor orifice, the tuning of the mass spectrometer, the temperature of the MS-interface probe tip, and the pressure in the ion source manifold. All of these variables as well as the class and molecular weight of the analyte influence the sensitivity of the technique. 

SFC-MS Interface Tip Temperature. Figure 3 shows the effect of increasing MS interface probe-tip temperature on the separation of the oligomers in the surfactant Triton X-100. At probe tip temperatures below 300 0, the restrictor consistently... 

Thickness measurements of for example 0.5 mm composite materials within accuracies of 0.0. mm or less can be troublesome using conventional ultrasonic techniques. The u.se of a zero interface probe can provide accurate results, as such transducers are specifically... 

Finally, the liquid-vapor interface probes hydrophobic effects around solutes of infinite diameter, fn particular, the surface... 

Solid-Liquid Crystal Interfaces Probed by Optical Second-Harmonic Generation... 

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