Gas Chromatography - Data Acquisition and Processing > Data Processing > Page 51

Data Processing

In the early days of gas chromatography, the associated computers used core storage which was bulky, expensive and had a very limited capacity (e.g., 8 kilobytes was a large memory). The limited memory meant that the programming was limited and had to be written extremely economically (i.e. employing the minimum of memory) and much of the data processing was done 'on-the-fly'. This meant that after each peak was eluted, it retention time and height was noted and its area calculated and then the raw data was discarded and only the retention time, peak height and peak area were stored. This economic processing package could not recalculate the data after the separation was complete, it could not reconstitute the chromatogram and it could not employ an alternative algorithm for area measurement if the one used was not appropriate. These restrictions were entirely a result of the cost and size limitation of computer memory at that time. With the introduction of cheap, compact solid state memory and the high capacity disk memory, the situation has completely changed. 8 megabytes is now a small memory and disk capacities are now measured in gigabytes. All the chromatography data can now be stored and reprocessed after the separation as many times as required, chromatograms can be reconstituted (with modified axes if necessary) and quantitative data manipulated as necessary. In addition, because the computer speeds have also increased greatly, on the fly processing can be carried out in parallel with normal data processing if required. The processing can include a variety of fairly sophisticated mathamatical procedures such as base-line correction, peak skimming, and multi-peak deconvolution.