V O L U M E 26, NO. 5, M A Y I 9 5 4
921
can oxidizc ni:ingaiintc [tho first product formed on the reduction of pc’rmanganate by an organic compound ( 5 ) ] t o permanganate. This observation has led to the development of a useful olefinsplitting reagent ( 7 ) . Since manganate decomposes t o mangancse dioxide and permanganate in acid medium, the regeneration of the permanganate by the periodate come8 to a stop once the p l l of the system has dropped t o about 6 ( 7 ) . Thus, the fact that the periodate oxidation of carbohydrates other than cellulose usually liberates considerable amounts of formic acid also favors the action of the new spray reagent. The usefulness of the reagent for detecting substances which reduce periodate Flightly or slowly probably depends mainly on the unreactivity of thc insoluhlc cellulo~e compared to dissolved compounds.
to 3 y of glucose, sylose, ascorbic acid, sorbose, maltose, cellobiose, and olefins-such as crotonic acid-are readily detected. The reagent requires 5 t o 8 y of substances such as glucuronolactone, 3-methylglucose, mannitol, erythritol, ethylene glycol, xylonolactone, and tartaric acid for positive detection. Ten t o 15 y of substances which reduce periodate only slowly or to a small extent are required. Such materials are, for example, p-methyl glucopyranoside, sucrose, trehalose, pentaerythritol, 2,3,4,6 - tetramethylglucose, 2,3 butanediol, and lactic acid. The time required for the appearance of a spot varies with both the amount and chemical nature of the substance. Forty to 60 minutes may be required for the appearance of spots for small amounts of substances such as trehalose.
-
EXPERIMENTAL
LITERATURE CITED
The spray reagent is prepared freshly before use by mixing 4 parts of 2% aqueous sodium metaperiodate and 1 part of 1% potassium permanganate in 2% aqueous sodium carbonate solution. h b o u t 1 ml. of the reagent is applied to each 50 sq. cm. of Whatman Yo. 1 paper and the sprayed paper is left at room temperature. It, is advantageous to hang the sprayed paper in a covered jar for development if the atmosphere is either contaminated or arid. If the paper is washed under the water tap after the spots have finished appearing and before the cellulose has discolored the permanganate background, a permanent record of the chromatogram is obtained in the form of brown spots on an almost n-hite backgrountl. RESL-LTS AND DISCUSSION
The new reagcnt compares favorably in sensitivit,y with many of the reagents commonly used t o detect reducing sugars. Two
.lbdel-.\khet~. 31.. and Smith, F.. J . .4m. Cheni. Soc., 73, 5859 (1951).
Block, 11. J., Le Strange. R.. and Z a e i g , G., “Paper Chromatograuhv.” DD.i8-91. Sew Tork. Academic Press. Inc.. 1952. Rurothe photometer cell with the mercury. Because most organic substances have an appreciable absorption in the ultraviolet region of the spectrum, the presence of organic impurities in the prepared pad may result in a spurious reading for mercury. When heating of the pad is accompanied by the generation of smoke. the presence of a n organic impurity is apparent and the analysis is discarded. I n those cases where there ie no visible evidence of pad contamination, it has been
necessary to apply the procedure to a mercury-free sample if the photometer reading is to he attributed unequivocally to the presence of mercury. PROCEDURE
-4relatively simple procedure has been found useful in these laboratories for detecting the presence of interfering substances in the photometer cell. rlfter the reading using the mcrcury photometer has been obtained, the cell is immediately transferred t o a Beckman DU spectrophotometer, and a second reading of absorbance is made a t 2537 A. using a slit width of 0.8 mm. to give a spectral slit width of 32 ,4. A special cell compartment has been built for the spectrophotometer to accommodate the mercwy cell. RESULTS 4 Y D D l S C U S S I O h
JIercur) vapor has no appreciable absorbance under these conditions. since it abEorbs only a narrow line a t 2537 A., which represents a small fiaction of the total energy in the wave lengths represented in the effective band. Interfering organic suhstances. on the other hand. generally have rather broad a h s o r p tion bands and produce a substantial absorbance both in the photometer and as measured by the Beckman instrument. ilccordingly, the amount of extraneous absorbance at 2537 A. can he approximately measured in the Beckman instrument and applied as a correction to the mercury reading. The accuracy of such a correction obviously depends upon the nature of the absorption curve of the contaminant within the hand limits. and the correction becomes exact when the effective absorbance betn een the hand limits is equal to the absorbance at 2537 A.
ANALYTICAL CHEMISTRY
922
Quantitative measurements were made on benzene, pyridine, and acetone vapors to evaluate the validity of the correction factor. The data on these substances (Table I ) indicate fairly good agreement between the two photometer readings when the Bechman spectrophotometer is set a t 2537 A. Agreement generally is less satisfactory a t adjacent wave lengths. especially in the case of benzene vapor, which is known to have a sharp absorption peak in the vicinity of 2537 A. It is expected that actual pyrolysis mixtures would have relatively flat absorption spectra
Table I.
Comparison of Photometer Readings with \-arious Substances in the Cell
Substance 'denzene
Absorbance, Beckrnan Length, -1. Spectrophotoiiierer 253; 0 583 2500 0,275 2530 0,383
% \e-ai'
Pyridine
Ammo niri in chloride s m o k e
0.640
2511; 2500
0.4717 0.480 0.453
0.510
253; 2.500 2550
0.455 0 383
o
m n hcetone
Ab$orbance, Alercury Photometer
480
0.455
2337
0.373
0,400
0 . ono
0.235
n nno o nno n. oon
0.455
0 noo 0 000 hlercury
Table 11. Correction Procedure .ipplied to IIixtures of IIercury F-apor with Acetone and Benzene A b ~ o r b a n c e(mercury pbutoineter) Absorbance iBecktiiani Absorbance (corrected] Mercury found (uncorrected), 1 RIercury found (corrected), 7 AIercnry added, 7
Acetone 0 4i6 0 x _ _i n 255 0 445
0 276 0 1811 _ _ n 096 o 270 n 095 n 0%
nm n 215
Benzene 0 337 0 1-13 0 149 n 079 n 188 n 215 n 325 n 075 n 180 0 oqj o 215
0 222
- -
decrease of the absorbance with time when measured b>- either photometer. The data given in Table I1 were obtained by volatilizing known amounts of mercury into a cell containing enough acetone or benzene to produce a relatively high absorbance, Readings were taken with both photometers, and the Beckman reading was subtracted as a correction factor. From the usual calibration curve of the instrument, the corrected value for mercury found is in reasonably good agreement with the known amounts added. The chief value of the correction method is in demonstrating that organic interferences are absent in a particular determination. The absorbance determined in the mercury photometer may then be attributed solely to mercury, and the analysis may be accepted n-ith confidence. As the magnitude of the correction increases, confidence in the corrected value for mercury decreases proportionately. When serious interference is encountered, additional work on the chemical steps of the procedure is indicated. LITERATURE CITED
Table I also shows that mercury vapor produces essentially no absorption in the Beckman spectrophotometer. Ammonium chloride smoke produces an apparent absorption OR-ing to lightscattering. The correction in this case is fair]!. good, in Spite Of thc fact that the smoke is vrq- unetnble. a:: indicated by a rapid
(1) Ballard. A. E . , and Thornton, C . K. D., ISD. ESG. CHEX..- 1 x . k ~ . ED.,13, 893 (1941). (2) and Ballsrd. -1.E.. ; I ~ . \ L . C H E M . , 22, n x i . . Zuehlke. C. (1950).
m..
R~~~~~~~ forreview h-orember 18, 19:~. .iccepted ~ e b r l ~ a I!, r ? lt2~j4. COIIImiinicntion SO.1 F 2 i from the Iiodak Resesrcli Lnburstories.
Determination of Aldrin and Dieldrin in Formulations by Partition Ch romatography HERMAN F. BECKMAN' Bureau of Entomology and Plant Quarantine, U. S. Department o f Agriculture, Texas Agricultural Experiment Station, College Station, Tex.
S
I l I P L I F I E D laboratory methods are needed for the quantitative determination of aldrin and dieldrin in insecticide formulations. Aldrin is defined as an insecticidal chemical containing not less than 95% of the compound 1,2,3,4,10,10-hexachloro 1,4,4a,5,8,8a hexahydro 1,4,5,8 dimethanonaphthalene ( a ) and 5% of insecticidally active related chlorinated hydrocarbons. Dieldrin is defined as an insecticidal product containing not less than 85% of 1,2,3,4,10,10-hexachloro-6,7epoxy 1,4,4a,5,6,7,8,8a octahydro 1,4,5,8 - dimethanonaphthalene ( 3 ) and not more than 15% of insecticidally active related compounds. Insecticide formulations very often are combinations of two or more insecticides and a method is of much greater value and convenience t o the analyst if all the active ingredients in a formulation can be determined simultaneously on a single sample. Chromatographic methods described by other authors (1, 4, 5 ) make possible the determination of ?-benzene hexachloride, niethoxychlor, and DDT. Ramsey and Patterson ( 5 ) have
-
-
*
-
-
-
-
-
Present address, 1015 hfilner, College Station, Tex.
applied partition chromatography to analysis of insecticides and have separated and identified the constituents of commercial benzene hexachloride (1,2,3,4,5,6-hexachlorocyclohexane). This work was extended by Aepli et al. (I), providing a method for quantitatively estimating the gamma isomer content of benzene hexachloride. Harris ( 4 ) has shown that benzene hexachloride-DDT-sulfur formulations may be accurately separated using the partition chromatographic technique and that this procedure may be applied to the assay of I, 1,l-trichlor~2,2-bis(pmethoxyphenv1)-ethane in technical methoxychlor. -411 of these methods have employed silicic acid as the supporting medium with nitromethane and n-hexane as the partition solvent-. The present author has found that this procedure may also be adapted to determine dieldrin and aldrin, singly, and in combination with DDT, and aldrin in combination with sulfur. RE4GENTS
Silicic acid, IIallinckrodt's reagent grade ( Y o 2844' n-Hexane. Skellysolve B is satisfactory. Sitromethane, Commercial Solvents Corp. Redistill before use.
