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How to switch HPLC columns using valves. Different analyses sometimes use different columns. But even when the same column can handle more than one kind of sample, many chemists dedicate a column to each analysis. This prolongs column life, reduces interferences, and eliminates equilibration delays. Rheodyne's Technical Notes 4 tells how to use switching valves to connect as many as five columns to a chromatograph. Any column can be selected, while the off-line columns remain sealed at each end. The effect on resolution is shown to be negligible in most cases.
X100 X-Ray Detection and Imaging System integrates the company's two-dimensional imaging proportional counter with a programmable 68000-based data acquisition and analysis system. It is capable of counting and positioning individual photons with energies between 6 and 35 KeV, with ar X-ray detection efficiency of 80% at 8 KeV. Xentronics 405 Sample Transport
Electronic Microbalance
RT40 RotoTitrator is a sample changer accessory to the company's DL40RC MemoTitrator. It holds up to 16 samples of different volumes from 30 to 400 mL. Control, monitoring, and coordination of work steps are handled by a micropro cessor in the RT40. Mettler 404
Model 4503 offers readability of 1 μg with an electronic weighing range and display of 300 mg. An additional 2003800 mg may be conveniently dialed up to the capacity of 4100 mg. The bal ance features full range tare by sub traction. Sybron/Brinkmann 410
Air Mass Flow Calibrator Two-by-two Flow Calibrator's applica tions include personal air samplers, lab flows, process flows, and R&D. Four mass flow ranges (10-200 SCCM, Ο Ι 000 SCCM, 0 - 5 SLPM, and 0 - 5 0 SLPM) give a range of 5000:1. Sierra Instruments, Inc. 409
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Chemicals Ampholytes Isolytes are complex mixtures of rela tively small amphoteric mixtures with differing isoelectric points. Incorporated into electrophoresis gels, they serve to stabilize the pH gradient created be tween the anodic and cathodic cham bers. They are available as 4 0 % aque ous solutions and are suitable for agar ose or PAG electrophoresis. Isolab, Inc. 419
Send for Tech Note # 4 For the well-illustrated tech note, contact Rheodyne, Inc., PO. Box 996, Cotati, California 94928, U.S.A. Phone (707) 664-9050.
RHEODYNE
THF LC CONNECTION COMPANY CIRCLE 186 ON READER SERVICE CARD
ICP/5500 AA System is capable of determining up to 15 elements/min under optimum condi tions. The sample introduction system employs a nebulizer with a cross-flow design requiring no adjustment, a plastic mixing chamber, and a demountable torch. It is able to handle any acids used in the lab and also high-dissolved solids. Perkin-Elmer 403
818 A · ANALYTICAL CHEMISTRY, VOL. 54, NO. 7, JUNE 1982
