Background Subtraction Control

Most EDS systems are controlled by minicomputers or microcomputers and are easy to use for the basic operations of spectrum collection and peak identification, even for the computer illiterate. However, the use of advanced analysis techniques, including deconvolution of overlapped peaks, background subtraction, and quantitative analysis will require some extra training, which usually is provided at installation or available at special schools. 

Finally, the absorbances should be read in a an eight-channel computer-controlled Titertek Microplate Reader and Stacker at two wavelengths (540 and 690 nm). Subtract the absorbance measured at 690 nm from the absorbance at 540 nm, to eliminate the effects of cell debris scattering. Use the first column wells for background subtraction because they contain all reagents except MT-4 cells, virus, and compounds. 

Display Unit. The Radiacmeter Control Units have digital readout, automatically recognize the attached probes, and show rate information in the appropriate units. One can program alarm set points and background subtraction. The power supply is three 9-volt batteries, BA3090, or vehicular power systems. 

The computer owns the capacity for controlling the GC/MS-functions and for storage large numbers of data points. Programs like reconstructed ion chromatogram, background subtraction, comparison and subtraction of different sample runs help and facilitate the evaluation of the acquisitated data and identification of unknown compounds. 

A microprocessor controlled instrument, Sargent Welch Model 7001, also performs pulse techniques. A 20-character alphanumeric display and a 30-touch button keypad allow the user to specify the experiment. After recording a voltammogram, smoothing, averaging, and background subtraction are options. The price in 1980 was 8800. Pulse widths from 1 to 1000 ms may be chosen, with sampling from 100 x3 after pulse initiation to 500 ps before the end of each pulse. 

Inexpensive analog instruments as well as microprocessor-controlled units are commercially available. The equipment can include useful features such as IR compensation, data smoothing, background subtraction, and automated display capabilities. Commercial instruments offer scan rates of up to several hundred volts per second. However, units that have very high scan rate capability (to 10 V/s) can be constructed at relatively low cost. 

Another algorithm very often used is the background subtraction and noise reduction algorithm. To apply background subtraction, LC-MS analysis is performed on a sample of interest (analyte file) and on a control sample (blank). The software surveys each ion in the analyte file against that in the control file within the mass tolerance and retention-time-shift window. If such an ion is detected in the... 

A number of different computers with various capabilities have been used with a preference for the on-line variety. The common fundamental features required are 1. Collection and storing of the data. 2. Calculations such as background subtraction and normalization, and of the concentration level. 3. Control of operation. 4. Presentation of data. (See also Table 12). 

---