Ion Chromatography - Computer Acquisition And Data Processing

Computer Acquisition And Data Processing

The computer data acquisition and process equipment is virtually the same for all chromatographic systems although each technique will often require its own specific software. Electronically the signal from the detector normally passes initially to a scaling amplifier, then to an A/D converter where the detector output is digitized and thence to the computer. The software available from the manufacturer is usually highly proprietary but they all process the chromatographic data in more or less the same manner.

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Figure 26. The Metrohm Automatic Sample Collection System

The computer software provides as a minimum, retention data, peak widths, analysis by peak areas and by peak height with user selected response factors. The data is also formatted in an attractive manner with all the sample details including sample handling etc and presented in a well laid out report. Extra software can be provided that utilizes the data from the ion chromatograph for process control purposes

The report can be presented on a monitor or printed out. In preparative work the eluent, after passing through the detector, is sometimes collected in fractions using an automatic sampleing system. A photograph of a Metrohm automatic sampler is shown in figure 26,

The Ion Chromatograph

It should be recalled that liquid chromatography (LC) was the first type of chromatography to be discovered and, as liquid-solid chromatography (LSC) it was originally invented in the late 1890s by the Russian botanist, Tswett who employed the technique to isolate and separate a range of plant pigments. The colored bands that were produced in the adsorbent bed elicited the term chromatography (color writing) for this form of separation technique.

The work of Tswett was not initially accepted, as the original paper was presented in Russian and thus, was not readily available to western chemists at that time. Another reason was the condemnation of the method by Willstatter and Stoll in 1913 who repeated Tswett's experiments without taking note of his warning not to use too "aggressive " adsorbents as it would result in the decomposition of the chlorophylls. As a result, the experiments of Willstatter et al. failed and their publication rejecting the work of Tswett held up the development of chromatography for nearly 20 years.