Introduction

The packed columns used in the early days of GC were inefficient by modern standards and so selective detectors that only gave a response to particular elements or compounds had obvious advantages when analysing complex mixtures. There was also a big incentive to develop more sensitive detectors and the detection of an organic vapour in an inert gas lent itself to the development of a host of devices, the majority of which have failed to make any lasting impact. Even today when the mass spectrometer is the selective detector par excellence there are still a number of other, more limited, detectors commercially available and this situation seems likely to continue. This paper describes some of these detectors; it should be noted that they are described as 'selective' rather than 'specific' since although they may give a large signal for one type of analyte they will also invariably give a small signal for others.

In general, selective detectors usually have more operating parameters than the two common universal detectors, the thermal conductivity detector (TCD) and the flame ionization detector (FID), and are more sensitive to small changes in these parameters. Some selective detectors are so temperamental that, having needed several days to set them up, they are then best left in continuous standby even when not in use.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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