Routine maintenance detectors

Conductivity Detection. The use of a conductivity detector is the basic configuration scheme of any ion-chromatography system. The sensitivity is high and it needs practically no maintenance, an important cispect in routine analysis. The detector is so simple to use that it is — cf. above the case of the Karl Fischer determination — not recognized as an electrochemical detector. Latest developments with membrane suppressor systems allow the use of the gradient elution technique. Using this procedure it is possible to analyse in the same run ions of extremely different characteristics (cf. Fig.4) as demonstrated for the analysis of a protein based active principle. 

The AED would represent a useful tool for the simultaneous selective detection of a number of elements occurring in pesticide molecules however, its rather high cost and maintenance requirements virtually ruled this detector out of the routine practice. The PEPD is another detector that can be tuned to selectively detect more elements (up to two simultaneously) based on their time-delayed chemiluminescence emission versus carbon. Thus, in contrast to the FPD that can only be employed either in phosphorus or sulfur mode, the PEPD offers simultaneous detection of these (or other) two elements. However, no element selective detector, even if it detects several elements simultaneously, is confirmatory without additional information because structural isomers with the same molecular formula may exist. 

AES with a microwave-induced plasma has been a popular technique for organotin analysis allowing very selective detection by utilization of specific Sn emission wavelengths such as 326, 303, or 271 nm. However, the detector can require high maintenance, which can be a drawback for routine use. 

There are several kinds of detectors. There are detectors for heat, smoke, flame, and gas content. Each type works best for particular applications. Selection depends on the type of fire that can occur and the kind of flammable or combustible materials present. Placement of detectors is critical. Some require more maintenance than others. Routine testing is essential to assure reliable performance. 

The most important maintenance effort for IMS detectors is to maintain a dry drift flow. This effort requires routine checking and replacement of dryer cartridges. 

The price of a column ( 200 to 800) may be viewed as relatively small compared to the initial, routine, and preventive maintenance costs of the instrument. In fact, a laboratory may find that the cost of a set of air and hydrogen gas cylinders of research-grade purity for FID (flame ionization detector) operation is far greater than the price of a single conventional capillary colunm Consequently, to derive maximum performance from a gas chromatographic system, the colunm should be carefully selected for an application, handled with care following the suggestions of its manufacturer, and installed as recommended in the user s instrument manual. 

A fuel leak from the fuel supply pipework is foreseeable. It may arise following assembly, either when new or following maintenance, since the fuel pipework is routinely dismantled for turbine maintenance at intervals of one to three years. Gas turbines should operate without excessive vibration, and vibration detectors are often, but not always, fitted to larger units to detect bearing failmre. Such vibration could also cause fuel pipe joint failure. Catastrophic, sudden guillotine, pipe failure is very improbable, but a fuel leak from a control valve, flexible pipe, or flanged, screwed or welded pipe joint is a hazard against which appropriate precautions should be taken. 

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