Paper chromatography is used to separate complex photochemical mixtures whose composition would be hard to determine by other means. For developer solutions, i t is important to determine concentration of developing agents, their oxidation products, and other components. When sample size is l imi ted, pa­per chromatography gives the necessary separation

on a sample size on the order of 0.1 ml . A f t e r sepa­ration, components on the chromatogram are located by use of appropr iate developing agents on a p i lo t chromatogram. These areas are then cut f rom unde­veloped chromatograms, eluted in solvents, and indi­vidual components determined by infrared or ultra­violet spectrometry, or by microt i t r imetr ic techniques

LABORATORY OF THE MONTH

Photographic Techniques Help Improve Photographic Products

L IFTING oneself by one's own boot­straps is a good characterization of

the analytical section of Eastman Kodak's Industrial Laboratory. The spacious new quarters of the Industrial Laboratory are located at Kodak Park, Rochester, Ν. Υ.

EK uses photographic techniques to improve its photographic products. Photographic spectra made with the spectrograph, for example, are used to test gelatin, silver nitrate, and other emulsion chemicals for the presence of trace metals. Thus there is a con­tinuing feedback of information used to improve the products.

The 70 chemists and technicians use a wide variety of modern analytical tools plus classical wet methods in their efforts to improve EK's product line. The research related directly to the manufacture of photographic ma­terials presents special problems asso­ciated with sensitized materials and has led to adaptation of standard analytical methods. The laboratory also does considerable analytical work on water, lubricants, and packaging materials. It has also set up a chemical microscopy section to work with minute quantities of compounds.

In controlling concentration levels of various constituents in photographic processing solutions, a combination of paper chromatography and microinfra-red technique has proved valuable.

Ultraviolet and visible spectropho­tometry are also used for this purpose in addition to their regular use in rinding absorption characteristics of photographic filters and emission char­acteristics of light sources.

Gas chromatography has become a major tool in working with the com­plex solvents used in manufacturing film base. Five types of gas chromato­graphy are currently in use. A time-of-fiight mass spectrometer is fre­quently used with the gas chromato-graphs to identify unknowns.

X-ray diffraction and fluorescence also play an important role in deter­mining trace contamination in photo­graphic materials. These techniques are also used to identify foreign mate­rials.

Many other tests in the laboratory include: physical tests on film, paper, and packaging materials; analyses of photographic-grade gelatin and tests of its jelly strength and viscosity un­der various conditions; analysis of dust in air filters; and even specification testing of the familiar "Kodak Yellow" paper and cardboard.

For the various sections of labora­tory and for expansion, the new quar­ters provide 21,000 square feet of air-conditioned floor space on two floors of a renovated building in the center of Kodak Park. The building contains, besides ample laboratory space, a ref­

erence library, offices, and well equipped darkrooms. The Industrial Laboratory operates under the Manu­facturing Sendees Division.

The chemical and physical propert ies of photographic-grade gelat in must be closely control led because of the v i ta l role this material plays in sen­sitized products. Here the je l ly strength of a sample is measured wi th the Bloom gelometer

VOL. 3 1 , NO. 9, SEPTEMBER 1959 · 8 7 A

Identif ication of very small de­fects, such as desensitized areas, streaks, and spots on photo­graphic f i lm form an important part of x-ray dif fract ion and fluorescence work. Micro tech­niques ident i fy particles 0.002 inch in diameter. When a par­t ic le has been ident i f ied, the trouble may be localized and its recurrence prevented. In one in­stance a series of cometlike desensitized streaks was found on processed f i lm. The head of the comet was microscopic. By po­sitioning the entire piece of f i lm in a microcamera on the x-ray dif fract ion unit and using long exposure through the comet's head, a characteristic pattern was obtained. The desensitizing agent was found to be a zinc compound which came from the surface of processing f i lm drums

>olarizing microscope (see photo) , ng used to separate a crystal mix-3, is also used to determine the action of orientation in crystall ine ymers and for identi f icat ion of jrs. A binocular stereomicroscope I a micromanipulator are used to arate crystals (often less than y) f rom mult icomponent systems h as photographic developers and ntif ied by infrared analysis. A ral lurgical microscope is used to mine photographic films for de-ts or spots on the surface. A se microscope detects foreign t ides in clear plastics or films ;n the refract ive index of the par-e is similar to that of the matrix

ruments measure the extent of radioactive contamination in various raw rerials. Accurate though these instruments may be, photographic f i lm itself t i l l the final monitor. The laboratory prepares samples which are tested :ontact with f i lm, which is then developed to check for fogging

Analyses of silver nitrate and silver bull ion for Kodak plants around the world are performed on a spectro­graph. The instrument has been par­t icular ly valuable in replacing chem­ical assay methods with actual iden­t i f icat ion and measurement of trace metal content. This provides a clear evaluation of the sensitivity of the materials for photographic use. Ai r ­borne d i r t levels are checked with the spectrograph in photographical ly cr i t ical areas, and tests made on many other materials such as water, developers, organic and inorganic chemicals, processing residues, plas­tics, photoconductors, and raw mate­rials for opt ical glass manufacture

Af te r separating a sample of the solvents used for f i lm manufacture by gas chromatography, the fractions are analyzed in this t ime-of- f l ight mass spec­trometer. Less than ICH ml . of sample are required. Impurities present at levels no greater than 0 . 0 1 % are routinely ident i f ied. When components of material are present at 1 % or greater levels, a port ion of the carrier gas is passed from the gas chromatograph to the mass spectrometer

A desired sample is eluted f rom a paper chromatograph, mixed with potassium bromide, made into a pel ­let on a laboratory press, and then identi f ied in an automatic-recording, double-beam spectrophotometer. This technique is valuable in working with photographic products which are extremely sensitive to trace amounts of contaminants, since only a few microgram samples are re­quired. A reference l ibrary of 24,-000 spectra and an IBM card sorting machine for ASTM spectral-data sorting cards also speed operations. Three infrared units are currently in use in the industrial laboratory •

Identi f icat ion of minor constitutents of solvents used in f i lm base manufacture is one of the important uses of gas chromatography. This technique, plus mass spectrometry, allows determination of structure and estimation of puri ty. Us­ing a recently developed technique, a 5- to 10-mg. sample of f i lm or plastic mater ia l , V 4 inch in diameter, is placed in a stainless steel loop, which is then immersed in a heated Wood's metal bath. The vaporized solvents plus a small amount of pyrolyzate are swept d i rect ly into the gas chromatograph column

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Circle No. 106 on Readers' Service Card VOL. 3 1 , N O . 9, SEPTEMBER 1959 · 8 9 A