for Safety and
Precision You
/ ,-JA
can't f beat the system
The MLA Pre cision Pipetting System, that is. Major hospital laboratories have standardized on the MLA Precision Pipetting System af ter competitive eval uation for precision and accuracy. The MLA Pipette displays outstanding repeat ability. Figure 8. CCD area array modes of operation their relative merits: the frame trans fer (vertical transfer), with separated photosensors and storage registers, and the interline transfer system, with alternate rows of photosensor ele ments and CCD shift registers. In the frame transfer mode, all charges col lected during the integration time are shifted into a shielded storage section each Υβο sec by simultaneously clock ing all the vertical registers in unison. The signal is then read out by sequen tially shifting in parallel one horizon tal line (storage) after the other into the output CCD register where it is read out as a linear CCD. In the inter line transfer process, sensing sites in tegrate for a V-so sec as "A" sites are shifted sideways at the end of the first integration and " B " sites are shifted in the opposite direction during the following integration time (Figure 8). With standard CCD's, only the light that falls in the gaps between the
And s a f e t y !
opaque electrodes (typically, 30-50% of the total illuminated area) is moni tored. Such light losses can be elimi nated if transparent (doped) polysilicon electrodes are used. Unfortunate ly, this design will not improve the UV response of the device. Alternatively, the light image can be monitored at the back surface of the CCD. The sili con substrate has to be substantially thinned (20-25 μηι) so that the deple tion region formed by the polysilicon gate potentials will reach the depth at which the photo-generated charge image is formed (back surface) (Figure 7). Essentially, all incident light is then effective in producing a signal charge. Another imaging problem, blooming, can be eliminated in linear CCD arrays (as well as photodiode ar rays) by the implementation of sink diodes, always reverse-biased, along the sensor to drain any excessive overspilled charge from oversaturated
Your hand need never touch the dis posable tip. Important for quality control before use because you don't contaminate the clean tip. Important for your own safety after use because you minimize your exposure to re sidual pathogenic material. Shouldn't you standardize on the MLA System? MLA Pipettes are available from selected Laboratory Supply Houses. The Pipetting Decision...is worth your time. Use the Reader Service Number to send for our Pipette In formation Pack.
Medical Laboratory Automation, Inc. 520 Nuber Ave., Mt. Vernon, N.Y. 10550 914/664-0366 CIRCLE 159 ON READER SERVICE CARD
ANALYTICAL CHEMISTRY, VOL. 47, NO. 7, JUNE 1975 · 707 A
