Detection/Detectors

Detector Detection in FIA may be accomplished using many of the electrochemical and optical detectors used in ITPLC. These detectors were discussed in Chapter 12 and are not considered further in this section. In addition, FIA detectors also have been designed around the use of ion-selective electrodes and atomic absorption spectroscopy. 

Break-glass detectors detect the high frequencies produced when glass is broken or cut with a glasscutter. These are the most cost-effective methods of glass protection in most cases and are especially suited to areas accessible to the public. 

Thus, the region 2100-1830 cm 1 can be covered. This allows us to monitor CO(v,J) by resonance absorption and various M(CO)n [n = 3-6] as a result of near coincidences between the CO laser lines and the carbonyl stretching vibrations of these species. The temporal response of the detection system is ca. 100 ns and is limited by the risetime of the InSb detector. Detection limits are approximately 10 5 torr for CO and M(CO)n. The principal limitation of our instrumentation is associated with the use of a molecular, gas discharge laser as an infrared source. The CO laser is line tuneable laser lines have widths of ca. lO cm 1 and are spaced 3-4 cm 1 apart. Thus, spectra can only be recorded point-by-point, with an effective resolution of ca. 4 cm 1. As a result, band maxima (e.g. in the carbonyl stretching... 

The accuracy with which a system can measure lifetimes depends on a number of different factors including calibration of the instrument, the number of detected photons and also the efficiency of the analysis routines. In addition, sources of background and scattered light should be eliminated. Emission filters should be chosen with great care to make sure that no scattered laser light reaches the detector. Detection of scattered excitation light results in a spurious fast component in the decay and complicates the interpretation of the data. The choice of emission filters is much more critical in FLIM than in conventional fluorescence intensity imaging methods. 

In a method described by Bates and Carpenter [8] for the characterization of organosulphur compounds in the lipophilic extracts of marine sediments these workers showed that the main interference is elemental sulphur (S8). Techniques for its elimination are discussed. Saponification of the initial extract is shown to create organosulphur compounds. Activated copper removes S8 from an extract and appears neither to create nor to alter organosulphur compounds. However, mercaptans and most disulphides are removed by the copper column. The extraction efficiency of several other classes of sulphur compounds is 80-90%. Extracts are analyzed with a glass capillary gas chromatograph equipped with a flame photometric detector. Detection limit is lg S and precision 10%. 

An electron capture detector detects electrophilic compounds. 

Dead volume (VM), 4 Degassing, 17 Detector (detection), 19, 80 Detector sensitivity, 23 Dissociation constant (K), 113... 

UN Economic Commission for Europe UN Environmental Programme UVV detector/detection ultraviolet-visible very low density lipoprotein volatile organic compounds... 

This performance can, in fact, be measured, since magnetic field detectors detect little or no magnetic field surrounding the flux path (or even around the magnet in the flux path at an inch or two away from it), and yet coils placed in the spatial flux path outside the core interact with the field-free A potential that is still there. A coil placed around the flux path so that the flux path constitutes its core, interacts with both the field-free A potential outside the material flux path core, and simultaneously—via the magnetic field inside the coil—with the magnetic field flux energy inside the core. 

Sensitivity of Detector What types of radiation will the detector detect For example, solid scintillation detectors are normally not used to detect a particles from radioactive decay because the a particles cannot penetrate the detector covering. 

Since chlorophylls have distinct spectroscopic properties, absorption or fluorescence spectrophotometry can be employed for their identification and quantification (118). Usually wavelengths between 430 and 440 nm and 645 and 660 nm, respectively (93,115), are used for spec-trophotometric detection. With spectrophotometric detectors, detection limits of approximately 80 ng chlorophyll (119) and 1 ng chlorophyll (120), respectively, can be achieved. Fluorescence... 

The deformation of the cell (i.e. the warp of the cell) is measured using a laser beam. The picture of the configuration of the measurement is shown in Figure 10.48. A sample is set on an X-Y stage and a spot of laser beam is irradiated to the surface of the sample. A detector detects the reflection of the beam and the distance between the detector and the spot using the Doppler effect. The sample stage can move in a horizontal direction and the laser spot trace the surface of the sample. The relative vertical distance from the reference point to the sample surface is measured and the sample surface shape can be imaged. 

The eluate is nebulized and the aerosol passes through a heated tube where the mobile phase is vaporized. The remaining microparticles are then passed through a beam of light. The incident light is scattered by the particles [125]. This detector detects any sample less volatile than the mobile phase, such as lipids, carbohydrates, surfactants, and polymers. Unlike RI and low-wavelength UV, gradient conditions can be used. 

Material Ester Method Carrier gas Detector Detection limit Ref. 

Goodwin et al. [82] determined trace sulphides in turbid waters by a gas dialysis-ion chromatographic method. The sulphide is converted to hydrogen sulphide which is then isolated from the sample matrix by diffusion through a gas dialysis membrane and trapped in a dilute sodium hydroxide solution. A 200pL portion of this solution is injected into an ion chromatograph for determination with an electrochemical detector. Detection limits were >1.9ng/mL... 

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