Optical fiber silica

C. E. Arthur and J. Pawliszyn, Solid phase mia oextr action with thermal desorption using fused silica optical fibers . Awn/. Chem. 62 2145 - 2148 (1990). 

To monitor the brain tissue, the fiber optic sensor based on the immobilization of a pH-sensitive dye, seminaphthorhodamine-1 carboxylate (SNARF-1C), was designed66. The dye-doped sol-gel was deposited onto the end of a 12 pm-diameter silica optical fiber and in vivo studies were performed. 

In our earlier study, a pure fused silica optical fiber, SF-112UV (Sumitomo Co. Ltd., Japan), was chosen to serve as both delivery and collection fibers. The fiber has a core diameter of 114 pm, a total diameter of 125 pm, and an NA value of 0.20 [28]. Table 2.1 shows fibers with smaller i b values, and they would have been satisfactory, but we were also concerned about cost and continuing availability. There was no problem with using this fiber for both 720 and 785 nm excitation wavelengths. 

Author, C.L. and J. Pawliszyn (1990). Solid phase microextraction with thermal desorption fused silica optical fibers. Anal. Chem., 62(19) 2145-2148. 

Raman probes constructed from fused silica optical fibers have gained much attention recently. Typically, low-OH content fibers are utilized to reduce the fiber fluorescence. The probe design also includes filters at the distal end to suppress the fused silica Raman signal from the excitation fiber and suppress the elastically scattered fight entering the collection fibers.25 Commercial probes are now available and they offer ruggedness and easy access to samples with various special or geometrical constraints. 

Solid-phase microextraction (SPME) — is a procedure originally developed for sample preconcentration in gas chromatography (GC). In this procedure a small-diameter fused silica optical fiber, coated with a liquid polymer phase such as poly(dimethylsiloxane), is immersed in an aqueous sample solution. The -> analytes partition into the polymer phase and are then thermally desorbed in the GC injector on the column. The same polymer coating is used as a stationary phase of capillary GC columns. The extraction is a non-exhaustive liquid-liquid extraction with the convenience that the organic phase is attached to the fiber. This fiber is contained in a syringe, which protects it and simplifies introduction of the fiber into a GC injector. Both uncoated and coated fibers with films of different GC stationary phases can be used. SPME can be successfully applied to the analysis of volatile chlorinated organic compounds, such as chlorinated organic solvents and substituted benzenes as well as nonvolatile chlorinated biphenyls. 

The various probe beams can be coupled into the same singlewavelength, dual-channel pulse-probe transient optical absorption set-up. A one-meter-long optical delay line is used to control the variable time delay between the electron and the probe pulses. Approximately half of the probe beam is deflected onto a reference photodiode while the other half of the beam is slightly focused into the sample, which is placed in front of the output window of the accelerator. Subsequently, the probe beam is then transported to the sample photodiode. (Alternatively, in some laboratories the probe and reference beams are transported into the detection room by long, low-OH silica optical fibers in order to reduce electronic noise pickup on the detector signal cables.)... 

Silica optical fibers produced by the chemical vapor deposition of silicon intermediates are now revolutionizing communication networks. Photovoltaic cells based on silicon, again produced primarily by chemical vapor deposition processes are now important power generators for electrical and electronic devices. 

Figure 12.13. Raman spectrum of a typical silica optical fiber, showing eommon Raman features from siliea 514.5 nm exeitation. (Adapted from Referenee 17 with permission.)...

Solid-phase extraction devices and applications are evolving rapidly, and novel techniques that stretch the classical definition of SPE are becoming routine. Pawliszyn introduced solid-phase micro extraction (SPME) in 1989,5,14 and a commercial apparatus is available from Supelco (Bellefonte, PA). The SPME apparatus is merely a modified syringe that houses a fused silica optical fiber coated with an immobilized polymer film. The fiber can be exposed for extraction and then retracted for insertion or removal from the sample vial or instrument. Both manual and autosampler devices are available and each can be adjusted for proper fiber depth. Several coatings are available with varying thickness including polydimethylsiloxane, polyacrylate, polydimethylsiloxane/divinylbenzene, and carbowax/divinylben-zene. In contrast to SPE, which is an exhaustive extraction approach, SPME will extract only a fraction of an available analyte, hence it is not suitable for the isolation of impurities and degradants in most applications.15... 

Solid-phase microextraction (SPME) is a sampling and concentration technique used to increase the sensitivity of HS methods. This technique is utilized for arson analysis and environmental monitoring purposes and also for clinical and forensic procedures. Short, narrow diameter, fused-silica optical fibers coated with stationary phase polymers are either immersed in the sample or the HS and compounds are adsorbed or absorbed (depending on... 

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