Bulk index sensing

Using the method described in Sect. 8.3.3.1 to obtain the electric field in a microtube resonator, the device sensitivity can be calculated with the perturbation theory for different modes. This provides more systematic insight into the operation of microtube resonators. First, bulk index sensing is considered. The sensitivity is proportional to the integrated optical field inside the liquid core region over that of the entire space, and can be expressed as72 ... 

Fig. 8.33 Calculated sensitivity in bulk index sensing for different radial mode numbers with the same azimuthal number m 700...

Early chemical indexing did not approach the 67 words of index per 100 words of text which is approximately the present level for Chemical Abstracts. But gradually indexers sensed more of the searcher s needs as chemical literature grew in bulk and complexity, subject indexes made halting but persistent efforts to keep... 

The sensors in this section can also be utilized to detect chemicals in liquid through the bulk solution refractive index change induced by the presence of target chemicals. Since no recognition molecules are used, this type of chemical sensing may usually have low specificity. However, these sensors may perform excellently in conjunction with other technologies such as capillary electrophoresis, mass spectrometer, and liquid chromatography in chemical detection. 

The microphysics in the field generation and particle acceleration described here is clearly beyond the reach of the magneto hydrodynamic approximation. A parameter study utilizing a PIC code working from first principles is necessary to fully understand the interdependence between the relative bulk Lorentz factors of the colliding plasma shells, the power law index of the non-thermal electron population, eb and in a broader sense the detailed evolution and structure in collisionless shocks. 

Nonselective detectors react to the bulk property of the solution passing through. A refractive index detector monitors the refractive index of the eluate. The pure mobile phase has a specific refractive index which changes when any compound is eluted. The detector senses this difference and records all peaks hence the term nonselective or bulk-property detector. This is why the refractive index as well as the conductivity detector is not suited for gradient elution. 

Here, m is the refractive-index sensitivity of the sensor Uadsorbate and Ubiank are the refractive indices of the adsorbate (i.e., analyte) and the bulk environment prior to the sensing event, respectively (iadsorbate is the effective thickness of the adsorbate layer and k is the characteristic electromagnetic field decay length associated with the sensor. 

The second alternative classification is to define detectors as specific and non-specific detectors. In this sense a specific detector would be exemplified by the fluorescence detector as it detects only those substances that fluoresce. An example of a non-specific detector would be the refractive index detector that detects all substances that have a refractive index different from that of the mobile phase. The classification of detectors as specific and non-specific is acceptable, but in this book detectors will be classified as bulk property detectors and solute property detectors as it more closely associates the detector with its basic method of measurement. 

Multi-functional detectors monitor the column eluent by the measurement of more than one physical or chemical property simultaneously, employing a single sensing cell. To date, three bifunctional detectors and one trifunctional detector have been described. The three bifunctional detectors have combined UV absorption and fluorescent detection, UV absorption and electrical conductivity detection and UV absorption and refractive index detection. The latter uniquely combines a bulk property detector with a solute property detector producing, at least in theory, the nearest approach to a universal detector. The trifunctional detector incorporates UV absorption, electrical conductivity and fluorescence functions. Multi-functional detection provides detector versatility and a means of confirmir solute identity. Such detectors have to be designed, so that the performance specifications are not seriously compromised, and the cell and eluent conduits do not contribute significantly to peak dispersion. 

The refractive index detector, being a bulk property detector, has a significantly lower sensitivity than the UV detector but more nearly approaches the universal detector in the sense that it will detect any solute that has a refractive index different from that of the mobile phase. The presence of... 

---