Gas Chromatography - The Modern Gas Chromatograph > Page 2
The gas density balance, was the first detector with a truly catholic response that was linearly related to the vapor density of the solute and consequently its molecular weight. The gas density balance had a maximum sensitivity (minimum detectable concentration) of about 10-6 g/ml at a signal to noise ratio of two. This detector inspired the invention of a wide range of detectors over the next decade providing both higher sensitivity and selective response.
The Modern Gas Chromatograph
The modern gas chromatograph is a fairly complex instrument mostly computer controlled. The samples are mechanically injected, the analytical results are automatically calculated and the results printed out, together with the pertinent operating conditions in a standard format. However, the instrument has evolved over many years although the majority of the added devices and techniques were suggested or describe in the first three international symposia on gas chromatography held in 1956, 1958 and 1960. These symposia, initially organized by the 'British Institute of Petroleum' have been held every two years ever since 1956 and the meetings have remained the major stimulus for developing the technique and extending its capabilities. However, the majority of the techniques and devices that have been incorporated in the modern chromatograph, were described, reported, or discussed in the first triad of symposia.
The layout of the modern gas chromatograph is shown as a block diagram in figure 1.