Corne to Barnes for analytical accessories. You'll be in good company. Analytical accessories are a Barnes specialty, the only spectroscopy products we make. We deliver promptly, off the shelf, analytical accesories compatible with Beckman, Perkin-Elmer, and other IR spectrophotometers. Windows, liquid and solid sampling items, gas cells, reflectance units, and much more. Barnes quality, too, is compatible with the best. But the prices are a little lower. Because we have a special department that makes a big deal out of accessories, while for others it's only a sideline. Solve your accessory problem toll free (800) 243-3498. Or in Conn. (203) 348-5381 Barnes Engineering Company 30 Commerce Road, Stamford, Conn. 06904
BARNES CIRCLE 25 ON READER SERVICE CARD
A FAST, EFFICIENT ALTERNATIVE TO KJELDAHL...
The Microprocessor Controlled MODEL 707 Provides Nitrogen/ Protein Analysis... In as Little as 30 Seconds! Uses proven chemiluminescent detection principle Microprocessor controlled for greater stability and repeatability Programmed temperature parameters Handles from 5 to 120 samples per hour
MODEL 707 Accomodates up to 1g sample size 1 nanogram sensitivity with dynamic range of 106 Extended range accessory (Model 732) allows combined nitrogen in percentage range
A N T E K ®INSTRUMENTS,INC. 6005 North Freeway Houston, Texas 77076 TELEPHONE (713) 691-2265
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Perhaps one of the most unique fea-
CIRCLE 5 ON READER SERVICE CARD 536 A ·
ANALYTICAL CHEMISTRY, VOL. 5 1 , NO. 4, APRIL
graph and mass spectrometer and the other for the data system and computer/plotter. T h e G C - M S incorporates a number of features t h a t warr a n t further discussion. T h e gas chromatograph accommodates both packed and capillary columns and offers a separate flame ionization detector and an automatic sampler as accessories. For high-resolution capability, a special capillary column accessory (not shown) admits gas coaxially at the end of the column to minimize loss of capillary column liquid phase and to maintain maximum sample transmission and GC resolution through the jet separator. Conventional capillary inlets t h a t allow entry of sample directly into the ion source can lead to decreases in operating efficiency and to increased maintenance. As previously indicated, the DP-102 utilizes a jet separator to remove carrier gas. This system offers chemical ionization as well as electron impact ionization, and reagent gas for CI can be introduced automatically under computer control. T h e tip of the direct insertion probe forms an integral part of a novel rejuvenating ion source t h a t will be discussed in more detail later. T h e probe, which can be automatically inserted into the ion source under computer control, ensures t h a t all vacuum valves are operated in proper sequence and thereby prevents accidental loss of vacuum. T h e probe can also be temperature programmed to permit microdistillation and M S analysis of relatively unstable solid substances. T h e mass analyzer uses a 58° magnetic sector and scans with rapid accelerating voltage changes to achieve linear separation of masses. T h e magnetic analyzer is used because of its theoretically increased sensitivity and resolution at high mass. This system is capable of scan speeds approaching 1000 amu/s. A unique electron multiplier/ computer interface provides a dynamic range of 10 9 (significantly larger than even most research mass spectrometers). This makes it possible to detect small peaks accurately in the presence of major components without saturating the data system on the large peaks or sacrificing sensitivity on small peaks. Consequently, it is possible to use a single internal standard concentration for a very broad range of sample concentrations, thereby eliminating the need for sample dilution or repeat analyses at different instrumental settings. T h e data system consists of an interactive keyboard control center and cathode-ray tube (CRT) for display. T h e dedicated minicomputer has 64K words of direct memory and a high-capacity disc storage capability of 20 megabytes. A Tektronix hard-copy unit can reproduce images displayed on the C R T .
1979
