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ANALYTICAL CHEMISTRY, VOL. 59. NO. 4. FEBRUARY 15. 1987
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IC LM183O overcomes this residual current. Commercial solenoids need modification on their tips. The device is simple in design and inexpensive to set up. The cost of all the components together was less than $200. It allowed us to incresse our efficiency significantly by enabling us to handle a greater number of columns a t any one time. We increased the number of columns from four to ten, and in addition, we can expand the system to 24 columns or more if needed. The device has a simple purpose, which to our knowledge is not being used in any other laboratory for ionexchange columns or column chromatography. It can a h be used in gel filtration.
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ACKNOWLEDGMENT The authors are greatly indebted to B. K. Lee, for designing and assembling dl of the electronic circuitry and for his many valuable suggestions. LITERATURE CITED
Figure 2. Assembled ctcuI1.
voltage, and 500-#A threshold current. Since the signal used is ac, the ac ripple cumponent should be minimized before the signal reaches the solenoid driver stage; therefore a filter capacitor was connected between pin 9 of IC LM1830 and common ground. DISCUSSION The IC L M l W prevents the deposits of electrolytes or any charged organic compounds on the platinum probes because of the ac current. When a strong electrolytic solution is used, traces of the solution on the walls act as a conductor, but the
(1) Glaun. C.: 8.htb22. J. J. Urn. J. Bo(. 1980 58. 40-54. (2) ZwebJ. 0.; Yarma. J. &n&c& of Unmetogaphy; CRC Rsrs: Cleveland. OH. 1972 Vd. 2. D 70. (3) zweb. 0.; shsnna. J. 01 ~ ( o g s p h y CRC ; ~ssa: CIevelaBnd. OH. 1972 Vd. 2. pp 195-254. (4) Blackbum. S. H a of Chromatcqaphy: Amho Adds and Amims: Zwsh?. G.. Slwma. J.. E*.: CRC Pres% Boca Raton. FL.
HanaDorr
1983: VoI. 1.
6 201.
(5) Dickson. R. E. phyrlol. mnt. 1979. 45, 400-400.
RECEIVED for review August 25,1986. Accepted October 27, 1986.
CORRECTION
Elemental Characterization of the National Bureau of Standards Milk Powder Standard Reference Material by Instrumental and Radiochemical Neutron Activation Analysis Robert R. Greenberg (Anal. Chem. 1986,58, 1986). An error was introduced into this paper in the final stages of the production cycle, after author review of the galley proof. On page 2511 the correct spelling of the name of the author is Robert R. Greenberg.
