Interface spectrophotometer-computer

When used as a recirculating batch reactor, the spectrophotometer-computer interface can monitor but not record the "% trans-... 

Obtain an absorption spectrum of each of your standards, the unknown, and the control sample on a scanning UV-VIS spectrophotometer interfaced to a computer for data acquisition. Follow the instructions provided for your instrument and software. 

D Commercial COTS controlled by external computer Hybrid systems such as automated dissolution workstation with high-performance liquid chromatography (HPLC) or ultraviolet-visible (UV-Vis) interface Liquid chromatographs, gas chromatographs, UV/Vis spectrophotometers, Fourier transform infrared (FTIR) spectrophotometers, near-infrared (NIR) spectrophotometers, mass spectrometers, atomic absorption spectrometers, thermal gravimetric analyzers, COTS automation workstations... 

The general equipment used can range from very simple columns and test tubes to elaborate pumps, columns, detectors, and fraction collectors automatically controlled by a computer with an appropriate human interface. Minimal equipment is sufficient for exploratory work or one-time development cycles more sophisticated equipment is beneficial for laboratories engaged in more intensive development. A modest set of useful equipment includes 1) peristaltic pump 2) end-over-end tube rotator 3) fraction collector and 4) spectrophotometer (UV visible). 

All ground state diffuse reflectance spectra were recorded using a Phillips PU8800 UV-Visible spectrophotometer equipped with an integrating sphere, interfaced to an Elonex PC-386SX computer. These ground state diffuse reflectance spectra were measured relative to a BaSC>4 white reflectance standard (Eastman Kodak Ltd.). 

Spectrophotometry. Infrared spectra were obtained with a Perkin Elmer Model 281B Spectrophotometer interfaced with a computer data station. Films were encased in sample holders in the reference beam, and spectra were obtained with air as reference. The spectra were scanned from 1900 - 1500 cm-l at a scanning time of 60 minutes with a response setting of 2. The slit program was set at N. All spectra were recorded on computer disks. 

Advantages This assay in conjunction with the use of Multiwell plates, multichannel pipettes, microplate washer and shaker, together with a plate reading spectrophotometer, enables a large number of samples to be processed quickly. Interfacing the plate reader with a computer would provide an obvious additional advantage. 

Instrumental Color Measurements. When treated samples showed AATCC ratings of 4 or less, they were measured against the untreated samples on the Sargent-Welch SP8-200 UV-vis spectrophotometer with a diffuse reflectance sphere attachment. The instrument is interfaced with a Hewlett-Packard HP-85 computer and run by color measurement software. Spectral reflectance data at 10-nm intervals, tristimulus values, chromaticity coordinates, and CIELAB color difference were determined for these samples (21). 

T8. Toren, E. C., Eggert, A. A., Sherry, A. E., and Hicks, G. P., Interface instrumentation between computer and spectrophotometer for reaction-rate measurements. Clin. Chem. 16, 215-221 (1970). 

Once the electrical signal leaves the photomultiplier tube, it is fed to a recorder if a printout is required, or, more usually, to a screen where the absorption spectrum can be displayed. Most modern spectrophotometers are now interfaced to a personal computer to allow storage of large amounts of data, or to allow access to a library of stored spectra on the hard drive of the machine. This allows comparison of stored spectra with the experimentally derived results from the laboratory and aids in the identification of unknown compounds. 

Instrumentation. Absorption spectra for the pyrenyl dye were obtained by using a Perkin-Elmer Lambda 2 UVA is/NIR spectrophotometer. The spectrophotometer is interface to a 286 computer to store spectra and control the instrument. Each spectrum was recorded using a PECSS program (Perkin-Elmer). Fluorescence spectra were recorded on an SLM 8000 spectrofluorometer interfaced to an IBM PS/2 computer. 

Actinomycin D dissociation kinetics were measured on a Cary 219 spectrophotometer equipped with a magnetic stirrer and thermostated cell holders. Sodium dodecyl sulfate (SDS) was used to sequester dissociating actinomycin D, and the resulting Increase In absorbance was monitored at 452 nm as a function of time. Stop-flow studies (daunorubicin and daunorubicin/ actinomycin D) were conducted with a Durrum-Glbson Model 110 stopped-flow spectrophotometer equipped with a dual detector accessory and a Tektronix storage oscilloscope Interfaced with a PDF 11/34 computer. Experiments were done In a 0.01M Na phosphate buffer, 0.1M NaCl, 0.001M NaEDTA, pH=7. Dissociation time constants were computed with a multlexponentlal analysis computer program. 

Most absorption and emission spectrophotometers are interfaced to a computer, allowing for digital recording of the spectra. If the spectra change in time, for example when a photoreaction is monitored intermittently by absorption spectroscopy, one obtains a series of spectra such as that shown in Figure 3.18, where the absorbance data are stored in a... 

The spectrophotometer shown in Figure 13-2,s is designed to interface with most personal computer systems. T he instrument (without the computer) sells for about 10,(XK) the exact price depends on accessories and options. 

The instructor will describe how to operate the infrared spectrophotometer, because the controls vary considerably, depending on the manufacturer, model of the instrument, and type. For example, some instruments involve pushing only a few buttons, whereas others use a more complicated computer interface system. 

The AD-interface connecting the analyser and the data unit is an 8-channel serial AD-interface with 12-bit resolution. The ADC is based on a Linear Technology chip (LTC1290) and requires only a few additional components (a print board, complete with all components can be purchased for about 50 US from Conrad Electronic, D-92240 Hirschau). This interface is connected to a maximum of 8 spectrophotometer analogue outputs (or other instruments, e.g., an attached conductivity sensor) and to a serial port of the PC. One of the analogue inputs reads the sampler status. A serial ADC allows longer distance between wet analysis and dry data treatment (about 15 m). If parallel ADC interface cards mounted in the computer are used, the wet-analyser and computer have to be close together (less than 5 m). No additional hardware is required. 

D. R. Massie. A high-intensity spectrophotometer interfaced with a computer for food quaUty measurement. In Quality Detection in Foods, J. J. Gaffney, ed, 1 12-15. St. Joseph, MI American Society of Agricultural Engineers, 1976. 

Figure 2 describes the information flow between the IR spectrophotometer and an IBM/1800 computer system which are interfaced. The spectral data are monitored at wave number intervals as low as 0.2 cm over the complete spectral scan range of the spectrophotometer (about 700 to AOOO cm , corresponding to a maximum of about 16,000 data points). The "% transmission" versus "wave number" points are transmitted in digitized form to the computer from absolute encoders. At present, the complete spectral scan may be monitored and stored in a disk file and retrieved at a later time. The coupled Model 621 spectrophotometer with IBM/1800-compatlble Interface was purchased some time ago from Perkin-Elmer. 

The usefulness of a combined IR-kinetlcs study in establishing a more reliable kinetic model is apparent. The processing of such data to ascertain which spectral bands are significant is usually a very tedious chore. By interfacing the IR spectrophotometer to a digital computer, a number of data processing simplifications are evident. Full use of this situation has not yet been attained in this program. Whether or not Improved resolution of minor spectral bands results from an online computer facility still remains to be demonstrated for this reaction system. 

SpectrosooDy Absorption and fluorescence spectra were measured with a Cary spectrophotometer and Perkin Elmer fluorometer at 77 K with computer Interfacing as described In [Brown, Schoch 1982]. 

---