STAINLESS STEEL ROTARY PUMPS
a I960 PRICES! That's
right.
Eco
ALL-CHEM®
r o t a r y p u m p s a r e still available a t 1960 prices. As a m a t t e r of fact, 1960 prices hold for E c o gear a n d centrifugal p u m p s as well. T h e s e self-priming r o t a r y p u m p s a r e available in 304, 316 a n d C a r p . 20 stainless steels, Hastelloy B a n d C, a n d n a v a l bronze. F e a t u r i n g t w i n Teflon or synthetic r u b b e r impellers, these E c o p u m p s a r e used for all t y p e s of liquids from missile fuels t o m e a t brines. A L L - C H E M r o t a r y p u m p s p u m p equally well in either direction a t capacities t o 10 g p m for low-viscosity liquids. T h e y c a n b e equipped with lip seals, packed stuffing boxes or mechanical seals. These are standard pumps stocked for i m m e d i a t e s h i p m e n t . T h e y a r e available with electric, air a n d variable speed drives. E c o A L L - C H E M p u m p designs
h a v e been standardized for 15 years a n d their prices h a v e n o t been increased in more t h a n five years. M a i l this coupon for complete data. •
Send data on rotary pumps
•
Have engineering representative call.
NameCorn pa nyCity State
i:,;2 ïZ3 rm Tri tm fm mm P U n l a
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ECO ENGINEERING COMPANY 12 New York Ave. · Newark, N. J. 07101 42
C&EN
O C T . 4, 1 9 6 5
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Uziel. This device multiplies the nucleotide analyzer's sensitivity 10-fold so that as little as 1 nanomole can be recorded quantitatively. By proper choice of ion exchange resin, temperature, eluent, and p H , it's now possible to speed the analysis of a mixture of nucleosides obtained from ribonucleic acid by alkaline hydrolysis and dephosphorylation, Dr. Cohn says. A complete base analysis, as far as the chromatography is concerned, can be done in less than an hour. Since the process regenerates the column, time between analyses is cut to a few minutes. One apparatus can handle one analysis, from loading to result, in an hour's time. In the nucleoside analysis, Dr. Cohn and Dr. Uziel use a fine-mesh cation exchange resin in the ammonium form. They load the column (20 cm. long with a cross section of 0.5 square cm.) with 5 to 500 nanomoles of the nucleoside mixture and elute with ammonium formate buffer (about 0.3M) at p H 4.6 to 4.7. The column is maintained at 40° to 60° C. Adequate resolution is possible at fast flow rates—up to 2 ml. per square centimeter per minute. The effluent stream passes through narrow-gage tubing through a flow cell in a Beckman DB spectrophotometer that takes alternate readings every few seconds at 260 mM. and 280 m^. The absorbances are plotted automatically by a recording potentiometer and form almost perfect Gaussian curves under appropriate conditions.
TLC Detects Amino Acid Derivatives A group of scientists at the Institute for Muscle Disease, in New York City, have developed a method for separating and detecting carbobenzoxy derivatives of amino acids by thin-layer (TL) chromatography. Key to the method is converting the compounds on the TL plate to hydrobromides with anhydrous hydrogen bromide before chromatographic separation, the institute's Dr. M. L. Maskaleris told the Division of Biological Chemistry during the 150th ACS National Meeting. The Institute for Muscle Disease workers encountered the problem of separating and detecting very small amounts of carbobenzoxy amino acids during their study of a radioactive synthesis of glycylprolylhydroxypro-
line. This substance has been isolated from human urine and may be a factor in the metabolism of collagen. Specifically, the need arose to detect the presence of carbobenzoxyglycine in carbobenzoxyglycyl-L-proline. The group, which includes Dr. A. C. Kibrick, Elisabeth S. Sevendal, and Dr. Maskaleris, initially tried both paper and TL chromatography on the carbobenzoxy derivatives but met with little success. They finally found a solution to the problem by hydrogen bromide treatment of the carbobenzoxy derivatives on German Instant Type-S TL chromatography plates. The treatment is done before chromatography with phenol-water and detection with ninhydrin. Method. In the chromatographic method, 20 micrograms of each component of the carbobenzoxy compound mixture are spotted on the instant plate. Next, the plate is treated with anhydrous hydrogen bromide, allowed to stand for 10 minutes, and washed in dry ether. After standing for 10 minutes, the plate is dried in an oven with circulating air at room temperature. Then chromatographic separation is accomplished with a solution of four parts by weight of phenol and one part of water in an ammonia atmosphere. The plate is then dried for 16 hours in the oven (again with circulating air at room temperature). Finally, the plate is sprayed with 0.3% ninhydrin and 1-butanol and heated at 110° C. for 15 minutes. Treating the plate with hydrogen bromide before chromatography gives good separation of carbobenzoxyglycylproline and carbobenzoxyglycine. With the free amino acids, omission of the hydrogen bromide treatment causes considerable blurring that masks the detection with ninhydrin. Dr. Maskaleris, Miss Sevendal, and Dr. Kibrick have applied their technique to a number of N-carbobenzoxy amino acids. Their laboratory studies indicate that carbobenzoxyglycine, carbobenzoxyhydroxyproline, and carbobenzoxyglycylproline can be separated and detected in a mixture. In a mixture of carbobenzoxyglycine, carbobenzoxyhydroxyproline, and carbobenzoxytryptophan, each compound is also identifiable, the studies show. In the hydrogen bromide treatment, the carbobenzoxy compounds are probably converted quantitatively to the hydrobromides. Therefore, other solvent systems that are more suitable for separating specific hydrobromides
from mixtures of carbobenzoxy com pounds may be substituted for the phenol-water developing system, Dr. Maskaleris says. The scientists at the Institute for Muscle Disease emphasize that their TL chromatographic method allows small amounts of radioactive com ponents to be separated and detected conveniently and accurately. And the method shows the desired synthetic intermediate to be pure. This con firms what the melting point determi nation indicates, but with greater cer tainty and with less material, they add.
Stripping Analysis Range Extended Spot electrolysis could extend the range of stripping analysis to include materials that cannot be formed by prior electrochemical reaction, accord ing to Dr. Dennis H. Evans of Harvard University. Appearing before the Di vision of Analytical Chemistry at the 150th ACS National Meeting, Dr. Evans explained that in stripping analysis, electroactive material is con centrated in or on an electrode by pre-electrolysis. In spot electrolysis, however, the sample is placed directly on the electrode and it need not be first deposited electro chemically. Dr. Evans uses a gold foil electrode supported by a platinum wire, which also serves as an electrical contact. The gold foil is etched lightly by dipping it in aqua regia. The Har vard chemist finds that it is easier to form sample spots of reproducible size on a slightly roughened surface. He applies a small volume (5 to 50 microliters) of sample solution to the surface of the gold foil with a cali brated microliter syringe, and allows the solvent to evaporate. This pro cedure leaves a spot of electroactive material adhering to the electrode. For solvents that evaporate slowly, he places the electrode on a hot plate at 60° to 85° C. depending on the sol vent used. It isn't convenient to duplicate the size of the spots exactly, though the average diameter is easily made to be within 10% of 3 mm., Dr. Evans says. With the reduction of iron ( I I I ) , he finds that doubling the spot size de creases the current by only 5 % . H e thus concludes that small variations in spot size can be tolerated. The electrode is then rigidly
mounted with the gold foil extending into an electrochemical cell. At first, only the lower part of the foil is sub merged in deaerated supporting elec trolyte with the spot above the electro lyte. The potential of the electrode is adjusted to a value that will reduce (or oxidize) the electroactive mate rial. Then the cell is raised rapidly with respect to the electrode and the spot is submerged in the supporting electro lyte. The resulting current is recorded and the current, at some time after the beginning of the electrolysis, is correlated with the quantity of sample on the electrode. Dr. Evans finds that measurement of the current at a given time is more reproducible than measurement of the current-time integral. Integration of the current-time curve shows, how ever, that up to 90% of the electro active material in the sample is re duced when the sample size is small. After the reduction is complete, the gold foil is rinsed with water and dried before application of another spot. Alternatively, two or more spots can be applied in a vertical row and each spot can be electrolyzed in turn with out removing the electrode from the cell. The cell is an ordinary polarographic H-cell. The reference elec trode is a mercury pool covered by either mercurous sulfate or chloride, depending on whether the supporting electrolyte contains sulfate or chloride ions. It seems to be necessary that the supporting electrolyte dissolve the sample spot very quickly to obtain reproductive results, Dr. Evans says. Thus various supporting electrolytes and solvent systems need to be tested for each electroactive material to be analyzed. In applying the spot elec trolysis method to the reduction of iron (III) and cadmium ( I I ) , and to the oxidation of hydroquinone, Dr. Evans uses 1M sulfuric acid as sup porting electrolyte for iron ( I I I ) , 0.2M potassium chloride for cad mium ( I I ) , and \M sulfuric acid in 50% ethanol for hydroquinone. Spot electrolysis has a high sensi tivity, Dr. Evans says. Less than one nanoequivalent of electroactive ma terial is detectable, and five to 20 nanoequivalents can b e detected to within 2 to 5%. Analyses require very little time, he notes—only about three minutes to prepare and electrolyze a sample spot.
Trial Balloons
Trial balloons, yes. But there's nothing ten tative about the offer of these high purity (99.9% typical analysis) intermediates. We've been making (and using) them right along. The coupon below will quickly get you data, samples and information about other organics we make or could make if need arises.
Dept. B-104
NATIONAL ANILINE DIVISION 4 0 Rector St., New York 1 0006
Please send data Π and sample Π of Π Diethylamide Π Dimethylaniline D Send a list of other organic intermediates you make. Specifically, we're interested in Name Title Company Address City
State
OCT.
4, 1965
Zip
C&EN
43
