Output, detection systems

A new cyanide dye for derivatizing thiols has been reported (65). This thiol label can be used with a visible diode laser and provide a detection limit of 8 X 10 M of the tested thiol. A highly sensitive laser-induced fluorescence detector for analysis of biogenic amines has been developed that employs a He—Cd laser (66). The amines are derivatized by naphthalenedicarboxaldehyde in the presence of cyanide ion to produce a cyanobenz[ isoindole which absorbs radiation at the output of He—Cd laser (441.6 nm). Optimization of the detection system yielded a detection limit of 2 x 10 M. 

Both the sensing device of the LC detector and the associated electronics can be temperature sensitive and cause the detector output to drift as the ambient temperature changes. Consequently, the detecting system should be designed to reduce this drift to a minimum. In practice the drift should be less than 1% of FSD at the maximum sensitivity for 1°C change in ambient temperature. 

The classic work of Dawson and Pritchard [264] on the determination of a-amino acids in seawater uses a standard amino acid analyser modified to incorporate a fluorometric detection system. In this method the seawater samples are desalinated on cation exchange resins and concentrated prior to analysis. The output of the fluorometer is fed through a potential divider and low-pass filter to a comparison recorder. 

The procedure is strictly analogous to that used for absorbance measurements in UV and visible molecular spectrometry (p. 355). To avoid interference from emission by excited atoms in the flame and from random background emission by the flame, the output of the lamp is modulated, usually at 50 Hz, and the detection system tuned to the same frequency. Alternatively, a mechanical chopper which physically interrupts the radiation beam, can be used to simulate modulation of the lamp output. 

Chromatogram the resultant electrical output of sample components passing through a detection system following chromatographic separation. A chromatogram may also be called a trace. 

The output trace from the laser end-point detection system for a typical resist development cycle is depicted in Figure 9. The temporal distance between maxima can be related to a change in resist thickness through Equation 11... 

Figure 8, Laser End-point Detection System. Light from the laser is reflected off of the resist-substrate and resist developer interfaces. The reflected light is collected on a photodiode, the output of which is monitored on a strip chart recorder as a function of time. The output of this device is provided in Figure 9.

Figure 9. Output of the Laser End-point Detection System.

One needs to deploy an outlier- or fault-detection system, based on the analyzer outputs... 

Where the need for fire detection is identified, the required performance of the fire detection system is already specified as part of the grading process. Fixed fire detection is typically installed to protect equipment that is high value, long lead time, or likely to be significant fire escalation hazards. The performance specification defines fire size and response time thresholds for alarm and action(s). Fire hazards are defined by radiant heat output (RHO). RHO gives a reasonable indication of the potential damage and the probability that the fire will escalate or cause loss. The RHO should not be used to determine fire thermal loading onto equipment and structures. Table 8-3 compares RHO and flame area for some typical hydrocarbon fires. 

The detection system consists of a monochromator and photomultipher, the latter wired for fast response, and able to support relatively high output currents... 

One aspect of CAD detection to be aware of is that analyte response is directly proportional to percentage of organic however, the magnitude of this effect is very similar for all compounds.69 Therefore, a shift in retention time will cause a difference in response. Because of the uniformity of response characteristics outlined above, CAD is a very interesting option as a universal detection system for HPLC. From the author s experience, it is a very simple detector to utilize and can be integrated with laboratory data collection system quite easily with the analog output. 

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