Computer monitoring, capture and analysis of gas/liquid chromatograph traces

The work described here is effectively the computerization of a gas/liquid chromatograph of the pen recorder type using a BBC microcomputer. The output from the g.l.c. can be captured by the computer in accordance with a series of parameters. The sampling rate can be altered, as can an averaging facility to reduce noise, and a threshold level to eliminate the storage of irrelevant and space-consuming data. The unprocessed readings are initially stored on the computer's floppy disk, then later retrieved and cut into smaller sections to allow maximum resolution for on-screen analysis. In the main analysis stage of the system all processing is shown graphically on the computer monitor at all stages. The principal steps in analysis involve the mathematical modelling and elimination of the solvent peak, the fixing of the retention time for each subsequent peak and its disentangling from any following peaks, and finally the calculation of the area under each individual peak. Several alternative methods are made available for disentangling peaks, which can be tried successively on a single peak then each printed out with comments for comparison later. All readings and results in table form and screen dumps of all trace images are available via a dot matrix printer.