the switching transient voltage pulses and the leakage current (dark noise). Although both are statistical (random) noise sources, their diode-to-diode variations create a coherent "fixed-pattern" noise that is nevertheless subtractable (66, 67).

In an alternative approach to I-SSID design, the necessary gain can be accomplished solely by image in­tensification, rather than by electron bombardment, even though either photon or electron detection can be utilized at the final stage. The SSID target serves merely as a temporary storage for the intensified image.

Photo-Detection Mode. Such a de­tector will consist of an image intensi­fier interfaced to a microchannel plate whose phosphor output is directly coupled to a SSID target through an optical-fiber faceplate. Since all three components are commercially avail­able in a ready-for-interfacing form, it should be relatively easy to assemble such a device. Unfortunately, this de­sign possesses some of the inherent disadvantages of a regular image in­tensifier tube, i.e., loss of resolution, especially if the intensifier is electro­statically focused, and a scan rate which is limited by the speed of the phosphor. Photo-detection mode I-SSID's of this type have already been

applied to astronomical (68) and X-ray (69) spectroscopy.

Electron-Detection Mode. An in­tensified detector operating in the electron-detection mode will consist of a photocathode as the photon-to-elec­tron image transducer, followed by a high-gain microchannel plate acting as an electron multiplier and a SSID tar­get directly attached to it. The target serves as a temporary storage medium for the intensified electron image. All components have to be "bottled" in an evacuated tube. This compact detec­tor should provide enough gain for single photon counting with adequate resolution, limited only by the micro-channel structure and high scan rates which are virtually limited by the scan rate of the SSID itself. At present, such a device is not commercially available. Finally, another interesting approach to I-SSID design, which is currently under investigation by NASA, involves a combination of a proximity-focused image intensifier (or converter) and a 500 X 500 CCD area array.

Summary

State-of-the-art TV-type multi­channel detectors have already broad­ened the scope of spectroscopy. Nev­ertheless, to become universally appli­

cable in the UV-VIS regime, their for­mat and number of pixels should be enlarged (1000 X 1000 pixels), their sensitivity improved to provide a sin­gle photon capability, their UV re­sponse extended to the vacuum UV, and their dynamic range extended to 103-105. There are very few detectors whose spectroscopic performance ap­proaches these requirements, and they are very complex and expensive. The technology required to manufacture solid-state imagers with such a perfor­mance is already available, but com­mercial production is slow because of lack of interest and financial support. Solid-state detectors that now cost $3800 are expected to go down to $50 in 1980 and thus should become wide­ly used. Either linear or area imagers should become useful for atomic spec­troscopy studies in which a spectral coverage of 200-800 nm and resolution of 0.02-0.05 nm are required. This will be accomplished by using a 15,000-pixel linear array or 500 X 500 area array coupled to a low-resolution éch­elle spectrograph. This last approach will be further simplified when a CID with x-y random access capability be­comes available. Finally, the construc­tion of intensified solid-state imagers or the commercial availability of low-noise imagers will allow for low-light

Perkin-Elmer's new 240A Auto Sampler System feeds, computes and prints CHN analyses for 60 samples...

Perkin-Elmer takes another giant step forward in the evolution of Automatic Elemental Analysis. The 240A is an automatic sampling and data handling system for Perkin-Elmer's Model 240 carbon, hydrogen, nitrogen, oxygen and sulphur analyzer. It feeds and computes up to 60 samples without operator

attention. There's really no limit to the number of sample containers that can be fed to the analyzer because each container is ejected after analysis. So a new magazine, even a rush sample, can be run without interruption.

The 240A's simplicity reduces chance of human error. It delivers greater efficiency because the

analyzer remains conditioned for a longer time. It reduces overhead by producing more data output per man-hour. Fail­safe features protect unanalyzed samples against practically all possible malfunctions.

The new system is completely adaptable to your requirements. You enter sample weight into the

Joyce-Loebl can do wonders for your image. The Joyce-Loebl Scandig 2 is a high speed digital microdensitometer ideally designed for computer analysis of photographic images. The Scandig 2 operates on a rotating drum principle, and can tape record data a t the rate of 20,000 readings per second • film scanning area from 1 m m square to a full 250 m m χ 250 m m ϋ select scan increment(orstepsize)froml2.5 to 200 microns U256(8bit) grey level output recorded on 9 track magnetic tape. Whether your interest is Radiography, X-ray Diffraction, Aerial Photography, Electron Micro­graphy, or standard photography, the Joyce-Loebl Scandig 2 can do wonders for your image. For complete details and specifications contact the microdensitometer experts.

I Joyce-Loebl Limited, Princesway, Team Valley, Gateshead, N E l l O U J . Tel: 0632-877891. Telex: 53257. It's here... it's now... it's made by Joyce-Loebl.

CIRCLE 128 O N READER SERVICE CARD

JOYCE LOEBL

while you do something else.

programmer at the push of a button. The 240A produces a complete analytical report — sample ID number, data, weight, gas responses, weight percent computations, simplest formula. You can add or change data in the programmer during runs.

Obviously, the Model 240A is the most accurate, most auto­

matic, most reliable means to determine the common organic elements. And with it you get Perkin-Elmer's system respon­sibility, installation and service.

The Model 240A System is described in a paper by R. F. Culmo. Ask for it. Instrument Div., Perkin-Elmer Corp., Norwalk, CT 06856. (203) 762-4705

PERKIN-ELMER CIRCLE 190 O N READER SERVICE CARD

Perkin-Elmer's new Model 460

AA Spectrophotometer comes with a friendly

microcomputer...

It's easy to talk to, does most of the work, and watches out for your mistakes.

The double-beam Model 460 talks your language, not computer language.

All you do is supply the standards and samples. To calibrate, simply push the but­tons. The microcomputer with its digital electronics does everything else, swiftly and accurately.

In fact, you'll find the Model 460 easier, faster, and more flexible than any other AA instrument you've ever worked with.

Calibration takes just two steps. First, enter the concentration of the standards. Then analyze the standards. You can use one, two, even three standards. The micro­computer automatically calculates the proper calibration curve for absorption or emission.

Model 460 flexibility lets you select in­tegration times from 0.2 to 60 seconds, or scale expansion from 0.01 to 100x at the touch of a button. Results are shown on a 6-digit electronic display (with connec­

tions for direct use of a laboratory record­er). The 460 can also be used with an accessory printer, or data logging devices compatible with its optional RS232C-type interface.

Besides all this, the460's proven double-beam optical system has been designed for both flame and flameless analyses, with double-beam background correction avail­able. The burner system and gas controls - with auto nitrous oxide switching, burner head interlock, and ignition interlock as standard equipment - are proven reliable, easy to use, and versatile.

Our nearest representative can give you more information on the Model 460, arrange a demonstration, or tell you about our full line of AA products and their unsurpassed technical back-up. Instrument Division, Perkin-Elmer Corporation, Main Avenue, Norwalk, CT 06856.

PERKIN-ELMER CIRCLE 192 ON READER SERVICE CARD

ANALYTICAL CHEMISTRY, VOL. 47, NO. 7, JUNE 1975 · 669 A

Good-bye to RI detection?

Ask the owners of Perkin-Elmer's Model LC-55 Detector. Or check these chromatograms now.

Corn syrup

Gradient : C H 3 C N - » H 2 0

Tr ig lycer ides

Gradient : Hexane to THF

HYDROCARBONS

Muscalure HC — (Cri2)l2 CH3 II

H C - ( C H 2 ) 7 C H 3

Isocrat ic 8 5 % C H 3 C N + 1 5 % H 2 0

A minute ago, you probably thought you needed refractive index detection for sugars, lipids, and hydrocarbons. With our Model LC-55 detector, though, the far ultraviolet lets you see almost all functional groups and, at the same time, run gradients. (About the only thing left is saturated hydrocarbons, but our gas chromatographs are handling them very well. )

Operating in the far UV is routine with Model LC-55, since a high energy beam condensing system - an exclusive - assures that maximum light passes through the cell and reaches the detector. You're also free of the effects of refractive index changes in the solvent. At last, a flat baseline other instruments can't dupl icate.

Is it linear in the far UV? Look at these graphs for sucrose. For quantitative work, linear range is better than 103 because the Model LC-55 is linear to three absorbance units. See for yourself. Call the nearest Perkin-Elmer sales office for literature and a demonstration of the new Model LC-55 in action. Or write Instru­ment Division, Perkin-Elmer Corporation, Main Avenue, Norwalk, CT 06856.

P E R K I N - E L M E R

LIPIDS SUGARS

LINEARITY FOR SUCROSE

CIRCLE 191 ON READER SERVICE CARD

ANALYTICAL CHEMISTRY, VOL. 47, NO. 7, JUNE 1975 · 671 A