(2)—
An Infrared Spectrometer Interfaced to a Dedicated Microcomputer
The microcomputer should incorporate a VDU and have high-density colour graphics capability (up to
1760(x) × 1280(y)). This enables IR-spectra to be displayed on the screen of the VDU with excellent
definition so that comparisons, the results of scale expansions and other spectral manipulations can
immediately be seen. Parameters such as range, scan time, data point interval, etc., are set and
monitored under microprocessor control and stored along with the spectrum. During the scanning of a
sample, several thousand data points may be collected and stored in RAM which should be able to
accommodate and display at least three spectra simultaneously. There is a wide range of manipulations
that can be performed by the analyst on stored spectra, e.g.
- display of one or more spectra
- overlay of two spectra
- smoothing of a spectrum with a noisy baseline
- flattening of a sloping baseline
- conversion of a transmittance spectrum into absorbance and vice versa
- averaging repetitive scans of the same sample
- enhancing a weak spectrum by signal averaging
- addition or subtraction of two spectra
- ordinate and abscissa scale expansion
- transfer of a spectrum from RAM to disk and vice versa
- replotting a spectrum in RAM onto a chart recorder or VDU
- setting up and executing a command file consisting of a combination of the above operations
In addition to the above facilities which enable the analyst to save a considerable amount of time and to
improve the quality of spectra, there is also the ability to store thousands of spectra on disk in a library
of peak tables. Each table will consist of the wavenumbers of twenty or thirty of the most significant
peaks in the spectrum together with the corresponding peak transmittance values. Several thousand
tables can be stored on a single floppy disk and library searches can be conducted in a matter of
seconds. After recording the spectrum of an unknown sample, a preliminary search to indicate possible
structural features can be initiated. This may be followed by a complete search in which the peak table
for the unknown is matched with as many library tables as the analyst has available. The computer then
displays a list of ten to fifteen possible compounds in order of closeness of match using a graded scale,
e.g. 0 to 9.
(3)—
A Computing Integrator for Chromatographic Analysis
The automatic recording of retention times, peak heights and areas, the identification of unknowns and