Anal. Chem. 1988, 60, 212R-226R
Chemical Microscopy Peter M. Cooke McCrone Research Institute, 2820 South Michigan Avenue, Chicago, Illinois 60616
This review surveys the developments in chemical microscopy from approximately January 1986 to November 1987, primarily as documented in Chemical Abstracts. It is not intended to be a comprehensive bibliography of microscopy literature; rather, emphasis has been placed on advances in microscopical techniques and instrumentation relevant to present or potential analytical methods. Guidelines dictate that publications of a more theoretical nature be omitted, as are virtually all publications concerning scanning electron and transmission electron microscopy. The alphanumeric referencing scheme and major text divisions are the same as the last review ( B l . l 9 ) ,for the reader’s convenience: sections range from A1 through Z1, A2 through 22, etc., and citations are referenced within a section by the rightmost one or two digits as in A1.3 or L2.1. References were obtained from regularly abstracted major microscope journals and a computer search of Chemical Abstracts. Various books and articles of general interest to the amateur and professional microscopist are included. The listings are not complete, nor could they be; space restrictions alone do not permit it. The breadth of publications featuring the microscope as the primary investigative instrument suggests the increase in its popularity. I apologize for any omissions of important work. The reader is invited to send papers (or suggestions) to be included in future reviews. There are many methods, instruments, and techniques of “looking at” or imaging an object that are included in this microscopy review: infrared, ultraviolet, Raman, fluorescence, laser, holography, polarized light, interference, phase contrast, Nomarski differential interference contrast, schlieren, X-ray, and acoustic are a few. New texts featuring the polarized light microscopy (see: Al.1-A1.4, A1.6-A1.8, A3.1) have appeared and entire chapters (R2.13, R2.14, R2.17) in texts attest to its growing use. During 1986-1987 over 1800 students at the McCrone Research Institute alone have been introduced to the light microscope in courses such as applied polarized light microscopy, fusion methods, microchemical analysis, spindle stage principles and practice, polymer, fiber, and film microscopy, crystal morphology and optics, and photomicrography or have applied the microscope in the identification of small particles, contaminants, pigments, asbestiform minerals, fibers, hair, and pharmaceuticals. The Royal Microscopical Society also offers microscopy courses as does the Institute of Paper Chemistry, International Cement Microscopical Society, American Association of Feed Microscopists, New York Microscopical Society, State Microscopical Society of Illinois, The Institute for Scientific Microscopy at Tubingen University, National Institute of Occupational Safety and Health, and various colleges and universities. There are 22 registered (light) Microscopical Societies (B1.ll);some boast 120 years of existence. Yet, polarized light microscopy is still misunderstood and overlooked as a research instrument. Universities offer courses to a limited few geology students. Most chemists who would appreciate the instrument’s worth, have never had the opportunity t o have formal training in applying the microscope to solving chemical problems (B1.5). A few universities like Cornel1 University and New York University may be reversing this trend. No other instrument, other than the microscope, has as many (A1.6) and varied applications. Paul Robinson, (B1.18) in addressing the Royal Microscopical Society, asserted “... since there is a range of different imaging methods, there is a range of different images of any object. Some give more, some give less information about features in any object ...what features of a specimen does each contrast technique emphasize, and what does it suppress?” This is fundamentally important in that the application of nonmicroscopical instrumentation to microscopical problems may lead to incom212 R
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plete or erroneous conclusions: vermilion and iron earth and titanium white pigments (from the Turin Shroud and Vinland map, respectively) were identified as such in applying the microscope. Others, using less direct methods, have analyzed the areas containing the pigments and misinterpreted the results, largely because the individual particles were undetectable. This says something about the understanding of the microscopy and the frustration of the microscopist. Al. Books-General Interest. A Practical Introduction to Optical Mineralogy offered by Gribble and Hall (A1.1)is meant to be a stepping stone to the study of optical mineralogy. Their purpose was not to replace any of the classic optical mineralogy books; rather, they assert: “Microscopy is a servant of all the sciences and the microscopical examination of minerals is an important technique to be mastered by all students of geology early in their careers”. Ehler’s (Al.2)two-volume Optical Mineralogy: Theory and Technique and (A1.3) Optical Mineralogy: Mineral Descriptions will rightfully find its way into many college classrooms and home libraries. The lucid text is beautifully illustrated with many photographs, photomicrographs, and line drawings. Both volumes have received rave reviews. Milovsky’s (A1.4) Mineralogy and Petrography includes general data on chemical composition, properties, morphology, and conditions of mineral formation and outlines basic knowledge of igneous, sedimentary, and metamorphic rock formation. Descriptions of Russian mineral and rock formations, and the inclusion of interesting facts (the use of labradorite to face the lower part of the Lenin Mausoleum, buildings, and metro stations) make this college text unique to the western world. Professional and amateur diatomists will welcome Kramer’s Kieselalgen (A1.5). The text is rife with useful and practical information, and any language difficulties (German) are allayed by the beautiful illustrations, photomicrographs, and scanning electron micrographs, rendering this a “must” read for diatom study. Many have said that Ino6’s (A1.6) Video Microscopy is the definitive work on the subiect-a one-volume encvcloDedia packed with useful informaGon for the video microscopiat‘from the master in the field. The book is thoroughly illustrated and well organized. It includes reviews on state-of-the-art video, 3-D video, editing, and video transfer, chapters on image formation, many types of microscopy, and video presentation. Inoue also provides an explanation of the physiology and sensitivity of the human eye to help the microscopist when designing or using any optical or video systems. The detailed descriptions and technical sections are so very useful that all microscopists involved in video microscopy - - should have and study thh book. Pettijohn, Potter, and Siever (A1.7) have updated their comprehensive and authoritative volume on sandgrains and sandstones in Sand and Sandstone (2nd edition). Geologists and analytical microscopists will benefit from the descriptions and interpretations ranging from entire rock suites to individual sand grains. The authors present a perfect union of geology and microscopy to help all envision the “bigger picture” and begin to “visualize a continent from a single grain of sand”. Polymer Microscopy, by Sawyer and Grubb (A1.8), is a practical guide to the microscopical study of synthetic polymers. It is written primarily for the industrial microscopist, yet is a valuable reference for all who work with polymers. It has an easy-to-understand, illustrated format. It offers applications of microscopy relating to a wide ran e of polymers including fibers, films, resins, composites, PO ymer blends, emulsions, and liquid crystalline polymers-complete with optical properties. Various specimen preparation methods accompany a comprehensive listing of published polymer microscopy references. Optical microscopy of polymers is well
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c.covered, indicating its importance although much of the book is devoted to electron microscopy. Students of geology, amateur paleontologists,and biologists will welcome Murray’s An Atlas of Invertebrate Macrofossils (AI.9). Excellently illustrated, (over 1400 photographs), it features classifications of sponges, stromatoporoids, corals, bryozoans, brachiopods, gastropods, bivalves, cephalopods, echinoderms, graptolites, and arthropods. References to other monographs and treatises provide for more detailed study. The Historical Microscopes of the Hessian State Museum in Darmstadt has been recommended by microscopists who ‘appreciate not only the beauty which may be observed through the lenses of the microscope, but the workmanship of the stands which support these delicate optics”. The catalog is one of a series issued by the museum describing its various collections (A2.20). The Design, Sample Handling and Applications of Infrared Microscopes consists of published papers from an ASTM sponsored symposium (September 30,1985) intended as an introduction for the analytical community to the use of the Fourier transform infrared spectrometer (A1.11). Illustrated Guide to the Protozoa edited by Lee, Hunter, and Bovee (A2.22) is an exceptional reference and textbook. It contains identificationkeys, text, and over 3000 flustrations and is said to be the most comprehensive reference book on the protozoa ever published. B1. Articles of General Interest. The broad applications of the polarized light microscope were highlighted by McCrone (B2.2)through timely examples of the subject of this very review: Chemical Microscopy-how a microscope is applied routinely to the solution of chemical problems. Professional, novice, and student microscopists will be challenged by reading about some of the many applications, including: (1) environmental particles of all kinds can be characterized and identifed almost at sight by the trained chemical microscopist using shape, color, size, and a variety of optical properties, (2) criminalists use microscopical fiber identification to aid in criminal convictions, as in the Wayne Williams Atlanta case involving murders of young blacks, (3) textile microscopists identifying modern polyester fiber, proved an attempted forgery of “Adolph Hitler’s” jacket, (4) microscopists found on the Vinland map a yellow inked line whose presence could only be to simulate an ancient map and light and electron microscopes also found in this ink a crystalline form of titanium dioxide pigment unknown before 1917, (5)in the case of the Shroud of Turin McCrone microscopically identified iron-rich “blood image” areas as iron earth and vermilion pigments. Many great microscopists are self-taught through the reading of classic books, articles, and texts. Both novice and professional will appreciate the “core- library of applied and theoretical microscopy provided by Delly (B2.2). The listings alone reflect the resources available to the microscopist and the many uses of the instrument. Descriptions of the hooks are helpful and the annotated listings of 144 books pared down to 10 as absolutely essential to the serious microscopist providing an overview of the entire field of microscopy. The avid microscopist is indebted to Loveland and Centifanto (81.3) for their thorough review of mounting media for the light microscope. Characteristics of various mounting media are examined and evaluated. Topics covered include refractive index, resins, liquids, polymerization, permanence, formulas, fluid mounts, and specialized media. The preparation, cleaning, and care of reference slides is also discussed.
Applequist (81.4)provides an historical account of optical activity and its discovery by Jean Baptiste Biot. The work features illustrated experiments with Polaroid filters (similar to Biot’s in 1912). and bandcolored sketches from Biot‘s definitive treatise on the optical rotation of polarized light, offering insights into the physics of light. Also pictured and elucidated are Fresnel and wave theory, Pasteur and molecular dissymmetry, electromagnetism, optical rotation, and circular dichroism. This hiatorical and scientific account is a veritable ‘who’s who” in optics. McCrone (B2.5) relates the rise, fall, and restoration of the use of the polarized light microscope BS a major microanalytical instrument in the school, laboratory, and industry. He traces the evolution of microchemical analysis from its early days and suggests reasons for its undesenred demise. The forgotten analytical resources of the polarized light microscope and trained microscopist are given and compared with other Hi-Tech analytical instrumentation. A series of 16 information bulletins from Carl Zeiss, Inc. (B2.61,guides microscopists in choosing the most applicable microscope and photo documentation equipment for specific applications in materials testing and metallography. Transmitted-light brightfield, phase contrast and polarized light, reflected-light brightfield or darkfield, and differential interference contrast methods are covered and applied to the examination of glass, plastics, and ceramics, building and coustruction materials, pharmaceutical and chemical products, iron and steel, nonferrous metals, alloys, and light metals. Fourteen additional information bulletins from Zeiss (B2.7) guide the microscopist in selecting equipment for specific applications in geology, soil science, and mining. Zeiss (B2.8) also provides guidelines on the microscopical analysis of imperfections in plastics and materials. The minimum equipment necessary to set up a home microscopy laboratory was suggested by Delly (B2.9);included are particle manipulation tools and supplies, magnification ranges for the stereoscope and polarized light microscope, mounting media, and reference books. McLaughlin (82.10)recommends a beginning reference list for the microscopical study and identification of diatoms. lists and discusses resources for purchasing Delly (B2.22) and restoring used microscopes. Included are sources for second-hand microscopes and a complete register of microscopical societies. An improved (Leitz) spindle stage for conoscopic and orthoscopic measurements was offered by Hinsch (B2.12). Improvements over the detent spindle stage and Hartshorne rotation apparatus include, in part, an adjustable detent precision drum which permits 360° rotation in 5O increments or multiples thereof, and a miniature collet to make handling of crystal-bearing needles easier. The centering of the crystal and reference azimuth determination is also easier and more convenient due to alterations in the spindle-bearing block and mounting disk. The Swift FM-31 “pocket” microscope, with the capabilities of a full-sized microscope, was reviewed by Delly (B2.23). It is inexpensive, portable, and easily converted between brightfield, phase contrast, polarized light, and dispersion staining, making it ideal for field use. Delly (B2.24) also described and reviewed a Zeiss conversion base that can easily be converted to a stereomicroscope hy using a pair of pocket binoculars. A simple demonstration providing a permanent record and using light microscopy is suggested by Grave (B2.25) for elucidation of the complex mixture of condensable compounds found in cigarette smoke. Several real-time production problems a t Polaroid were solved by Coates (B2.26) using a number of microscopical techniques including biological staining, microchemical analysis, polarized light, and dispersion staining. Fletcher (B2.17) gives details and reveals some of the unusual features of Powell and Leeland ohjectives (catalogue: 1895). Robinson (B1.18) challenges all microscopists, by way of provocation, in presenting various photomicrographs of the same subject under different contrast methods and asking the microscooist to identifv the imaeineI . (and information) made. Cooke‘(Bl.19) reviewed chemical microscopy during the years 1984-1985. I
ANALYTICAL CHEMISTRY, VOL. 60. NO. 12, JUNE 15. 1988
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See also: U1.1, Vl.1, R2.14, R2.16, R2.17. C1. Optics. Martin (Cl.1)relates the disadvantages of using eyepoint phase plates in obtaining oblique phase contrast. He considers different ways of mounting phase plates and their effects on image formation. Boyde (C1.2) describes a method for the production of stereo-pair images in the tandem-scanning reflected light microscope that color codes depths within the imaged field. Several microscopical objective contact caps for fluorescence microscopy were developed, described and tested by Morosz (C1.3);suggested uses include ultraviolet microscopy of living organs with incident illumination, cryomicroscopy, and centrifugation microscopy. The principles, materials, methods, and uses of variable asymmetrical contrast microscopy were evaluated by Strange (C1.4). He found that the addition of a simple multisection polarizing filter placed in the substage condenser filter carrier and a rotatable polarizer between the condenser and the light source effectively produced variable contrast, pseudostereoscopic images of low contrast, transparent, translucent, and poorly stained specimens. A new scanning microscope with a fiber-optics light source permits optical probing with a narrow (
