Document YGYQJ8z4Q7JBg7wB25mQjdanD

FILE NAME: CTFA (CTFA) DATE: 1974 April DOC#: CTFA025 DOCUMENT DESCRIPTION: Article from Trade Journal -American Laboratory ' r: V : / Contents DEPARTMENTS COMING COVER 4 : APRIL 1974 Asbestos, 13 BY WALTER C. MC CRONE AND IAN M . STEWART Optical information processing in the characterization of microscope images, 23 BY B. H. KAYE AND A. G. NAYLOR Nutrition for chemists, 29 BY ROGER J . W ILLIA M S Humans, the mammalian mutants, 32 BY IRW IN STONE A high intensity transmitted light base for dark-field stereomicroscopy, 40 BY GENE E . SCHLUETER Aspiration and dispensing system for hand-held pipets, 47 BY JA M E S F. HOLSINGER Desk-top scanning electron microscopes, 51 BY DONALD J . EVINS AND ROBERT J . ENGLE Physics of the cell membrane: part one, the role of double-bond energy states, 59 BY A. KEITH BREW ER AND RICHARD A. PASSWATER Consultation microscopy, a review, 77 BY BERNARD FRIEDMAN Analytical scanning electron microscopy, 83 BY B. W . GRIFFITHS Toward automating radioimmunoassay, 91 BY D. J . MARSHALL The research marketplace, 1974-1980,103 BY W ILLIA M N. W HAM AND KENNETH S. HALABY Editor's page, 8 Computer interfacing: the view from the transmission line, 45 BY DAVID G. LARSEN AND PET ER R. RONY Laboratory profile: Walter C. McCrone Associates, Inc., 97 Scientific economics, 109 New products, 111 Available literature, 129 Advertising index, 136 Author's format, RSC The Delaware State College drug analysis program Differential light scattering analyses Determination of organic vapors in industrial atmospheres Gas-liquid chromatography of nucleic acid constituents High speed gel permeation chromatography Vapor phase pyrolysis and gas chromatographic analysis of fire retardant materials containing polyvinyl chloride Design concepts of a processor-based gas chromatograph Photomicrograph of vitamin C as seen through a polarized microscope. Courtesy of Sidney Braginsky. VOLUME 6, NUMBER 4 Published monthly by International Scientific Communications, Inc., Greens Farms, Connecticut 06436, U.S.A. Phone 203 255-2645. Controlled circulation postage paid at Dallas, Texas. Subscriptions available: $18.00 per year, add $3.60 for postage to all foreign countries; $1.75 for single copies, add $0.40 extra to all foreign countries. International Scientific Communications, Inc. assumes no responsibility for the state ments and opinions advanced by the contributors. Copyright 1374 by International Scientific Communications, Inc. All rights reserved. Reproduction in whole or in part without written permission from International Scientific Communications, Inc. is prohibited. a l b y b l 6 (4) i- i 3 8 (1974) fH S S l Am erican Laboratory Asbestos By Walter C. McCrone and Ian M. Stewart In m a y 1968, Dr. Irving J. Selikofi of the Mount Sinai Hos pital in New York established his position as the Rachel Carson of the industrial hygiene world. A series of New Yorker articles at that time was based largely on Dr. Selikoff's experiences in the study of asbestosis, lung and stomach cancer, mesothelioma, and other causes of death related to ex posure to asbestos. His careful analyses of mortality of industrial workers in known asbestos fiber contaminated areas are convinc ing arguments that asbestos is one of the most deadly industrial hygiene hazards. The reputation of large indus trial concerns has not always been good when faced with evidence that their plant environments may be contributing to worker disabil ities, if not death. However, large ly through Dr. Selikoffs effort, Dr. McCrone is Scientific Adviser and Mr. Stewart is Manager, Electron Optics Group, McCrone Associates, Inc. followed up by the FDA, Depart ment of Labor, and other inter ested parties, most responsible companies are now doing their best to minimize, if not eliminate, asbestos as a health hazard. The microscopist has an im portant role in this program to control asbestos as a contaminant in the air we breathe, the fluids we drink, and the food we eat. He must be able to identify asbestos fibers and quantify their size and number. There are problems be cause there are other fibrous sub stances confusingly similar to as bestos, and there are several dif ferent types of asbestos (Table 1), differing in optical properties and composition and possibly in the degree of their hazard to humans. Analytical methods must be sensitive enough for the identifica tion of single fibers. Of course, only a microscope and a trained microscopist can do this. There are methods, e.g., x-ray diffrac tion and DTA. that identify min ute percentages of asbestos in Chrysotile fiber bundle. Table 1 Composition Specific gravity Crystal system Refractive indices Serpentine CHRYSOTILE 3 M g O 2 S i0 2' 2H20 2.36-2.5 monoclinic 1.49-1.57 ACTINOTE 2CaO*4MgO* F e 0 * 8 S i0 2*H20 Asbestos Amphiboles TREMOLITE 2CaO*5MgO* SSiOj^HjO ANTHOPHYLLITE 7M g0*8Si02* H20 3.03-3.5 monoclinic 1.62-1.68 2.9-3.2 monoclinic 1.60-1.65 2.85-3.5 orthorhombic 1.60-1.66 AMOSITE 5*5FeO* 1*5MgO 8Si02'H 20 2.6-3.0 monoclinic 1.66-1.70 CROCIDOLITE Na20*Fe20 2* 3FeO*8SiOj H20 3.0-3.45 monoclinic 1.69-1.71 AMERICAN LABORATORY : 13 ASBESTOS continued Table 2 Asbestos type Chrysotile Anthophyllte Amosite Crocidolite Dispersion staining colors for asbestos Refractive index liquid Dispersion staining color Parallel Perpendicular 1.560 1.610 1.670 1.700 light blue blue-green red magenta magenta magenta golden yellow golden yellow blue magenta small samples, but only the microscopist can hope to identify in dividual fibers. Fortunately, the crystallographic properties of the different types of asbestos are suf ficiently distinct to enable certain identification. If the fibers are thicker than about 0.5 fim, light microscopy suffices; smaller fibers require the electron microscope. Identification of the larger fi bers by light microscopy is based on refractive index measurement using a polarizing microscope. The easiest way to apply refrac tive index measurement to asbes tos fiber identification is by use of dispersion staining, an optical staining procedure. This is based on annular or central screening of the objective aperture in common with specific refractive index me dia, such as the Cargille liquids. Under these conditions each type of asbestos shows two character istic dispersion staining colors, one for the light vibration direc tion parallel, and another perpen dicular, to the fiber length (but only in one particular refractive index liquid). Table 2 shows the colors obtained with several kinds of asbestos when mounted in ap propriate Cargille refractive index liquids. Different colors or no colors are observed if other than the specified liquids are used for each particular asbestos sample. Finding small percentages of very fine asbestos fibers requires care ful application of the method. In particular, intense Kohler illumi nation with carefully centered substage and objective apertures is essential. A careful microscopist should, however, be able to detect 0.01% of >0.5 fimthick fibers by this technique. Light microscopy is ideal for rapid identification of asbestos in most powdered samples: dust, mortar, insulation or wallboard, mineral samples such as talc, etc. When the presence of asbestos in a liquid medium, such as a water supply, soft drink, beer, or pa renteral solution is suspected, one must assume most of the fibers, if not all, will be too fine to ob serve by light microscopy. One turns, then, to the transmission electron microscope (Figure 1). The transmission electron micro scope (TEM) is superior to the scanning electron microscope for two reasons. Smaller fibers can be observed and identified by TEM, and selected area electron diffraction (SAED) is more de pendable for identification of as bestos than the elemental analysis capability of the SEM. Figure 1 Model 200KV transmission electron microscope. EXTENDING MANS VISION IN THE SEAS The seas are our new frontier. Scientists are exploring the vast resources of the oceans, not only for links to our origins, but for new sources of food. Many scientists believe that our beleagured planet cannot forever support the popula tion explosion. The warning voices of these men are at last being heard. Mankind is slowly awakening to the frightening realization that even our seas cannot withstand the absorption of man's waste without dire consequences. From an underwater Nikonos camera to the compact Model H microscope, we are produc ing instrum ents used by our scientist/conservationists to insure the continuation of the species, man. Producing the finest instru ments available for science and industry' is a constant challenge. Wherever essential research is being conducted; on land, beneath the seas, or in space-- we are meeting that challenge. Extending your vision is our main concern. Nikon is in the forefront of undersea research technology. The finest optics in the world. Nikon Instrument Division, Ehrenreich Photo-Optical Industries, (**22) d (523Stewart Ave.. Garden City, N.Y. Tel. (5161248-5200. In Canada. Anglophoto Ltd., Ontario. Nikon SMZ Stereo Zoom Microscope Total magnification range. 4X to I20X. Provides 5time zoom range without change in focus. Excep tional wide range of accessories. Reader Card ft 107 Nikon Epi-IHwninalor Fits any standard Nikon microscope. Designed for observation of opaque specimens. Provides colli mated on-axis illumination w'ith field and aperture control. Dark field reflected light systems available. Reader Card P *08 Nikon Kt Compact Versatile laboratory microscope with built-in transformer, continuously variable light intensity control, and inbase volt meter. Features brilliant Koehler type illumination and full range of Nikon accessories. Reader Card 3 109 AMERICAN LABORATORY : 15 BAUSCH & LOMB BaIdIaim MICROSCOPE O n eofak in d LOOK INTO BALPLAN. No other microscope system offers so much for so little . . . a premium quality microscope at up to half the price of another brand of comparable quality. See for yourself in a live demonstration in your lab with vour own specimens. Send for new 24-page full color catalog 31-2411 and our free demonstration offer. Optical Architecture . . . so outstanding in Bausch & Lomb's new Balplan Mi croscope, makes using this research quality instrument a delightful experience. Interchanging modules, attaching accessories, so quick and uncomplicated; focusing, so fine--so smooth; your most vital investigations become pleasanter, less fatiguing, most rewarding. Balplan's modular system of integrated components is mounted on a stand that features an exclusive, suspended inner arm. Pile as many accessories on the stand as you need, the optics, as part of the vibration-free inner arm, will still maintain drift-free, accurate focus. Focusing is controlled by concentric, comfortably lowpositioned knobs. Fine focus is graduated in single mi crons, allowing you to dissect visually each layer of the specimen with ease. A complete revolution of the focus ing knob moves the stage 100 microns. With the transformer housed in the base and with front push-button controls all circuitry is enclosed. The line cord plugs into the base at the rear while accessory cords plug into the upper back area of the stand. Hazardous, bothersome dan gling wires are eliminated. Notably improving performance, the patented slide holder on the mechanical stage is spring mounted downwards to hold the slide in con stant contact with the stage surface. Nosepieces for 2, 3, 4 or 5 objectives are reversible, interchangeable, parcentered and accurately position ob jectives with a ball detent. Accessories for visual and photographic use are all de signed to be compatible within the Balplan system. To top it off--There's a choice of interchangeable heads, including a dual-viewing adapter with illuminated pointer. That, in brief, is the architecture of Balplan, the oneof-a-kind new concept in a competitively priced micro scope with models for clinical, research and educational applications. TM. Batplan is a Bausch & to m b Tradanam BAUSCH & LO M B. SC IEN TIFIC O P TIC A L PRO DU CTS DIVISIO N . 38804 BAU SC H STREET. R O C H ESTER N Y 14602 Circle Reader Service Card No. 13 for information; No. 14 for demonstration. i.i Figure 2 Chrysotile fibers filtered from a water supply, 30,O00X. Figure 3 Selected area electron diffraction pattern for a single chrysotile fiber. A sample of water of known volume is filtered through the fin est membrane filter. A section of filter approximately 2-3 mm2 is then placed particle side down on a previously carbon-coated elec tron microscope grid, and the membrane filter is dissolved using acetone in a Soxhlet extractor. The sample grids are examined in our laboratory with a JEM 200 electron microscope, using an ac celerating voltage of 150 kv at a magnification of 17.000X on the M3 range of the instrument. This magnification is chosen to focus the intermediate lens aperture in line with the specimen plane; thus, a SAED pattern of the fiber is ob tained with no other adjustments to the microscope. In this way it is possible to spot check the dif fraction pattern of individual fi bers rapidly (Figures 2 and 3 ). The total number of asbestos fibers is related to a definite area of the filter, and hence a definite volume of sample, by counting fi bers over a known number of TEM grid squares (having known areas). The length and width of each asbestos fiber is recorded. Interpolation from the screen scribed at half-centimeter intervals allows an accuracy of measure ment on the screen of approxi mately + 0.05 cm, or about 3 4 nm. Measurements of the indi vidual fibers are read into a tape recorder; this permits the operator to devote full attention to the screen, precludes duplicate count ing of single fibers, prevents miss ing fibers, and maintains the op erator's dark accommodation. The recorded data are trans cribed onto punch-tape and com puter processed to give listings of the length, width, and aspect ratio of the fibers, together with a com puted mass of each fiber calcu lated on the basis of density D and dimensions L and W (D X L X W*). Density values for the different asbestos types are given in Table 1. Also presented in the computer print-out is the num ber of fibers per liter of water, the size distribution of the fibers based on length and width, and the distribution of fibers by aspect ratio. The program automatically assigns the longest dimension to the fiber length and excludes all fibers with an aspect ratio below three. This procedure, designed by Ian Stewart of our laboratory, has been applied with excellent suc cess to a number of water samples containing large numbers of amphiboles per liter but very low weight percentages. Most of these samples show no asbestos fibers by light microscopy. It is there fore important to specify the method of analysis when stating analytical results. The same sam ple of talc could be analyzed by different methods with very dif ferent results, e.g.: 1. X-ray diffraction shows no chrysotile or amphiboles. 2. A phase-contrast method (similar to the NIOSH procedure to determine the number of fibers per milliliter of air) shows 1500 fibers greater than 5wn/m3 of sample. 3. The scanning electron mi croscope with energy dispersive x-ray analyzer shows about 104 AMERICAN LABORATORY : 17 ASBESTOS continued fibers/liter suspected of being ara- phibole asbestos. 4. Dispersion staining shows 150 anthophyllite fibers/gram of sample. 5. Transmission electron mi croscopy shows 5 X 10e antho phyllite fibers/liter of sample. The AEI Scientific Apparatus, Ltd. EMMA-4 (Figure 4) only recently installed in our labora tory will undoubtedly be the ideal instrument for the detection and identification of very fine asbestos fibers. A combination transmis sion electron microscope and electron microprobe analyzer (EM A), it enables the microscopist to see the smallest fiber and to identify it by diffraction pattern and elemental analysis. Although a given sample mounted on a TEM grid can be examined successively by TEM and EMA, the advantage of being able to examine many particles in a sam ple with assurance of one-to-one correspondence of particle size, shape, diffraction pattern, and elemental analysis is obvious. We have already applied this instru ment to some asbestos samples with excellent results, and expect it will be the instrument of choice for such samples in our labora tory. The monitoring of asbestos as a contaminant in our environment is an excellent example of one important problem solved by microscopy. The importance of choosing the proper analytical tool and having a well-trained op erator is also emphasized by this application to asbestos detection and identification. Figure 4 EMMA-4, a combined transmission electron microscope and electron microprobe analyzer. Circle Reader Service Card No. 69 18 : APRIL 1974