A microprocessor based multiwavelength-detector system for liquid chromatography

A multiwavelength-detector system for liquid chromatography was constructed using a state-of-the-art microprocessor and silicon linear photodiode array. By using a microprocessor, the control, data acquisition and data manipulation functions were alterable and flexible towards the optimization of a separation. The computer was used to digitize the analog output of the linear array, subtract the dark current and then correct the data for the non-linear response of the detector and the non-linear emissivity of the light source. These last functions were required due to the single beam nature of the instrument. The entire (200 nm) spectrum could be displayed on a CRT display, the transmittance values of the user selected wavelengths punched on paper tape and plotted as a multi-trace recording on an X-Y plotter. Up to eight wavelengths could be monitored in this manner. The wavelengths that the computer monitors are user selectable, as is the time between successive spectra (O to 99 seconds) and the integration time of the array (the time the light "strikes" the array, typically one to ten msec). The integration time selected depends on the intensity of the light source, a 55 W quartz-halogen lamp, the slit size used in the spectrometer and the sweep frequency, 500 or 50 KHz. To test the utility of the detector, the reduction of nitrobenzene to azoxybenzene and azobenzene was monitored with the standard single wavelength (254 run) detector and the computer detector. The results were comparable, but the 254 nm detector was more sensitive. A mixture of commercially available dyes was also separated with a low pressure column with the column effluent routed to the multiwavelength detector. This work demonstrated that a multiwavelength-detector system could be employed for analytical work. However, due to the low sensitivity of the detector, it will not find as many applications or be met with as much acceptance as the single wavelength 254 nm detector.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Chemistry

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1976

Author dc:creator

• Titus, Christopher A.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/10919/87322

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/87322