V O L U M E 2 5 , NO. 8, A U G U S T 1 9 5 3
1179
Table X. Comparison of Chemical and Spectrographic Analyses, in Per Cent, for Lead in Carnotite-Bearing Sandstones from Various Localities
Table XII. Comparison of Chemical and Spectrographic Analyses, in Per Cent, of Hyatt Pegmatite Samples, Larimer County, Colo.
(Cheiiiical results as oxides reduced t o elements) Method of Analysis ~Locality of Saiiiple Chem. Spec. Mine D. Montroae County Colo. Butterfly mine Montrose County Colo. Radium No. 5 'mine San Miguel County, Colo. Raven mine San bfiiiguel Countv Colo. Calamity Kb. 13 mine, Mesa Codnty, Colo. Vanadous No. 1 mine, San Rli uel County, Colo. Bear Creek mine, San Rliguel t o u n t y , Colo. Primus claim, S a n hliguel County, Colo. Dunning-Greysill mine, San J u a n County, Colo. Stone No. 1 claim, Montrose County, Colo. Bitter Creek mine, hlontrose County, Colo. Club mine, Montrose County Colo. Wild Steer mine Montrose Cbunty Colo. 0.1-1 Eastside mine, S a v a j o Indian Resekration, Ariz. 0.011 0.01-0.1
Chemical results aa oxidea reduced t o elements. Samples from Larimer County, Colo., from plagioclase-perthite-quartzwal! zone of the H y a t t pegmatite. Purpose of analyzing samples waa t o determine presence in wall zone of minor elements t h a t crystallized in relative abundance in the next inner zone. Sample and Method of Analysis Bfi090-A BfiO9O-B B6090-A a n d 6090-B Element Chem. Chem. spec. Si ... 33.8 10 1-10 -41 8.25 8.24 1-10 Ka 4.35 4.28 0.1-1 K 3.3 3.22 0.1-1 Fe 0.51 0.50 0.01-0.1 0.25 0.24 Ca 0.01-0.1 h lg 0. 08 0.07 0.01-0.1 1' 0.02 0.02 Ti 0.006 0.001-0.01 0.006 0.01-0.1 0.031 &In 0.031 0.01-0.1 0.045 0.045 Ba
Table XI. Comparison of Chemical and Spectrographic .inalyses, in Per Cent, of Red and Gray Clays from the Colorado Plateau Chemical results a6 oxides converted t o elements. Red and gray clays consisting chiefly of hydromica quartz and calcite from a zone underlying vanadium-bearing ore a t B i t t i r Creek' mine, llontrose County, Colo. Red Clay Gray Clay Element Chem. Spec. Chem. Spec. Ca 1.7 1-10 1.8 1-10 Si 28.0 IO+ 30.0 1Q+ Fe 3.84 1-10 1.7 1-10 5.6 1-10 4.7 1-10 .41 2.46 1-10 2.42 1-10 1.37 1-10 1.45 1-10 Na 0.03 0.1-1 0.07 0.1-1 K 5.0 1-10 4.6 1-10 Ti 0.35 0.1-1 0.36 0.1-1 v 0.04 0.01-0.1 0.04 0.01-0.1
E:
~
Noted in the chemical aiialyses were several disagreements, especially for the follolYing elements: lead, manganese, magnesium. TmadiUm. aluminum, iron, sodium, zirconium, and cal-
+
cium. Standard plates for these elements have been remade, has been Oband better agreement the served. ACKNOWLEDGMENT
The authors wish to express appreciation to their associates of the Geological Survey: to F. S. Grimaldi, A. M.Sherwood, and ot,hers for the chemical analyses, and to Helen Worthing for performing part of the spectrographic analyses. LITERATURE CITED
(1) Ahrens, L. H., T r a n s . Geol. SOC.S. A f r i c a , 49,133-54 (1946).
(2) Churchill, J. R., IND.ENG.CHEM.,AN.~L.ED.,17, 66-74 (1945). (3) Eeckhout, J., Verhandel. K o n i n k l . Vlaarn. Acad. Wetenschap. Belg., Kl. Wetenschap., 7, (13), 71 (1945). (4) Meggers, SV. F., BXAL. CHEM.,22, 18-23 (1950). RECEIVED for review February 11, 1953. Accepted >,lay 7, 1953. cation authorized b y the Director, U. S. Geological Survey.
Pul-li-
Determination of Methoxychlor on Insecticide-Treated Paperboard by UI t raviolet Spect ro photowetry EDW. C. JENKINGS, JR., AND DAVID G. EDWARDS Reseurrh and Development Division, Fibreboard Products, Inc., Antioch, Calif. ETHOXTCHLOR, 2,2-bis (p-niethoxyphenyl j-1,l-1-trichloroethane, an analog of DDT, is a possible agent for improving the resistance of paperboard containers t,o insect infestation. Methoxychlor loadings above 50 mg. per square foot are being considered for this treatment. In order t o correlate experimental cont>ainer performance properly ryith methoxychlor loading3 in this range, the conrentrations of' methoxychlor present mus: be det,ermined within a precision of 10%. Previously published methods (1- 4 , 6 , 1 1 ) for the spectrophotometric determination of methoxychlor have depended on a tnostep conrrrsion of t,he methoxyrhlor to a colored derivative which could be measured in the visible region and xere designed to hanclle microgram quantities such aa might be present in food products as residues from crop or animal sprays. 111the extraction of methoxychlor from foods, the interfering substances which are also carried d o m are considerably different from those encountered with paperboard. For these reasons a method designed to handle larger quantities of methoxychlor in the presence of interfering agents found in
paperboard was desired. Furthermore] consideration of the molecular structure of methoxychlor suggested that a characteristic absorption should be evidenced in the ultraviolet region ( 6 ) , so that a direct determination could be made which would avoid the laborious preparation of derivatives. The ultraviolet spectral transmittance of methoxychlor dissolved in cyclohexane was explored in the 200- to 300-mp region, The relationship of the logarithm of the molar absorbancy index, UM (sometimes called molar extinction coefficient, E ) , to the wave length in millimicrons is shown in Figure 1. I n this paper the recommendations of the National Bureau of Standards on nomenclature are followed (10) and all terms and symbols used are defined below. I n Figure 1 maxima appear a t 230, 238, 246, 270, and 275 mfi. In the procedure for the quantitative determination of methoxychlor the strong absorption maximum a t 230 mp was of primary interest. Beer's law was found to hold for solutions with transmittances of 20 to 60%. Correction for background interference was made by the method of the double impurity index (8).
ANALYTICAL CHEMISTRY
1180
In correlating the insect-resistant properties of experimental insecticide-treated paperboard containers with the loadings of methoxychlor applied to the board, a more rapid and direct method of analysis was desired. Using the absorption maximum at 230 mp, concentrations of methoxychlor extracted from the paperboard by cyclohexane were determined spectrophotometrically. The concentration of known amounts of methoxychlor added to board extract blanks has been determined with good theoretical agreement in the range of 0.04 to 0.14 gram
Briefly, the procedure for the spectrophotometric determination of methoxychlor on paperboard consisted of four steps: (1) extraction with cyclohexane, (2) dilution of the extract to proper concentration for spectrophotometric transmittance measurements, (3) transmittance measurements comparing the unknown methoxychlor solutions against a board extract blank, and (4) calculation of results. REAGENTS
Cyclohexane (Emtman Kodak 702, m.p. 4.0-5.5' C.). Methoxychlor, oil concentrate 90%, technical (E. I. du Pont de Nemours & Co., Inc.). APPARATUS
Soxhlet extraction apparatus with standard-taper glass joints, 50 X 250 mm. extractor tube, 500-ml. flask. Small hot plate or heating mantle. Vigreux column, 470-mm., condenser, T 24/40, for concentration of extracts. Volumetric flasks with standard-taper .~ glass stoppers, 200and 50-ml. Measuringpipets 10 X 0.1 ml. Transfer pipets 5- and 1-ml, Beckman Model DU quartz spectrophotometer with No. 4300 photomultiplier (IP28) attachment or equivalent. Quartz cells, 1.000-cm. Quartz cell spacers, 0.900-cm.
per liter, and recoveries of 92.6 i2.2% were obtained when known amounts of methoxychlor in the range of 50 to 1000 mg. per sq. foot were added to paperboard. By this procedure the more laborious preparation of colored derivatives with consequent handling losses and the necessity of further evaluation of the effect interfering by-products produced in these reactions is avoided. The nature of the methoxychlor absorption curve is such that the presence of background interference can be compensated for by the double impurity index method.
PROCEDURE
Fifty square inches of treated board were used for the extraction. The treated liner was removed from the bulk of untreated board to reduce the amount of extraneous board extractables. For corrugated paperboard a sample was cut in strip form in the cross-grain direction of the board, so that the shorter dimension of the strip was parallel to the grain direction. The treated liner was then separated by inserting a metal rod, inch in diameter and 6 inches long ( a screw driver of these dimensions is excellent for this operation), through alternate corrugations and pulling the rod up sharply through the glue line between liner and corrugations while holding the sample firmly on a flat surface. For solid paperboard the treated plies were peeled as a single layer from the rest of the board, taking care that as little filler stock, which may contain finely dispersed asphalt, as possible was removed with the treated plies. The separated treated board was cut into pieces of approximately 0.5 X 2.5 inches and placed in a Soxhlet extractor tube (50 X 250 mm.). A 500-ml. flask containing 250 ml. of cyclo-
PREPARATION OF STANDARDS
About 5.0 grams of commercial methoxychlor were recrystallized from ethyl ether until all colored material was removed. The methoxychlor was recrystallized finally from acetone, and the last traces of solvent were removed by passing a stream of filtered air over the crystals. The melting point of the purified product was 87.8" =t0.1' C. by the standard capillary method. These operations may be made using 50-ml. beakers. The purified methoxychlor was checked spectrophotometrically in a cyclohexane solution by determining the relationship of the absorbancy, A,, expressed as log A,, to wave length. A concentration of 0.01 gram per liter using 1.0-cm. cells is satisfactory for this determination. Further recrystallization from acetone showed no change in the shape of the curve of log A , versus wave length. Standard concentrations of methoxychlor in cyclohexane were then made ranging from 0.004 to 0.014 gram per liter, and the regions of 210 to 220 mp were measured by 5 mp increments (using 0.07- to 0.05mm. slit widths) and 220 to 240 mp by 2 mp increments (using 0.02-mm. slit width) for a t least three, and preferably five, concentrations which cover the optimum region of transmittanceLe., 20 to 60%. The absorbancy indices, uara t 215,230, and 238 nip were calculated from Equation 1.
3'41 3.3
Figure 1.
The absorbancy indices of the methoxychlor in pure solvent were used in the double impurity index equations by the method of Mellon (8).
t P,z-I~S(p-YLlnOXYPnENYL~~l,l,l~lRlC~LORO~l~AN€
(METHOXYCHLOR) H C F , O - Q - C - Q - OI C b I CI-c-CI
Ultraviolet Absorption Spectrum for Methoxychlor
Slit widths. 0.06 mm. a t 215 m p , 0.02 mm. a t 220 to 240, 0.015 mm. a t 240 t o 260, 0.0125 mm. a t 260 to 300 Beckman DU quartz spectrophotometer with photomultiplier
1181
V O L U M E 25, NO. 8, A U G U S T 1 9 5 3 hexane was connected to the extractor, and the extraction was conducted for a t least 2 hours for loadings estimated to be 50 to 100 mg. per sq. foot. This gave 90 to 94% recovery as shown by samples 1 to 4 in Table I. For loadings estimated a t 200 to 1000 mg. per sq. foot longer extraction times were necessary, as evidenced by samples 5 to 10 in Table I. After 6 hours' extraction of these loadings, 90 to 96% recovery was achieved. ilfter completion of the extraction, the extract was concentrated to 150 ml. by fractional distillation using a Vigreux column, and after cooling to room temperature, the concentrated extract was transferred to a 200-ml. volumetric flask and made up to volume. Using a 0.1-cm. cell thickness (1.0-cm. cell with a 0.9-em. quartz cell spacer) the initial extract, made up to 200 ml., was compared to a blank extract in the region of 210 to 240 mp, and the absorbancy coefficients, k,,,at 215, 230, and 238 mp were used to calculate the impurity indices and the corrected concentration The sample extracts were compared to blank eytracts from an equal area of board. They were diluted or concentrated as was necessary to approach more closely the visible color of the sample extract because this was found to be a convenient method of approximating the background absorbance of the Bample. When 1.0-cm. cells were used with a spectrophotometer employing the standard blue-sensitive phototube, dilutions of l/60 to '/loo were necessary to obtain 100% transmittance for a blank extract at 210 mp. This, of course, reduces the concentration of methoxychlor to such an extent that errors greater than 10% may be encountered. By using 0.1-cm. cells and a photomultiplier attachment the initial board extract made up to standard volume could be used, and dilutions were necessary only when the concentration of methoxychlor was too high to yield transmittances between 20 and 60%. In addition, the sharpness of the absorption maximum was increased by the latter method, since slit widths of 0.04 to 0.05 mm. could be used when the instrument was adjusted for maximum sensitivity.
where (Z.Z.)*IZ = impurity index a t 215 mp ( 1 . 1 . ) ~=~ impurity index a t 238 mp These equations were obtained by substituting the appropriate terms in Mellon's equation ( 7 ) . The correction, 01, to be applied for the calculation of the methoxychlor concentration, cc, is giren by 01
=
1.45 ( 1 . Z . h
+ 2.71 (1.1.)~~
14)
and 15)
where the coefficients 1.45 and 2.71 are calculated according t o Xellon (9). The data in Table I1 illustrate the steps in this calculation to obtain ce. The samples were prepared by adding known aliquots of a standard methoxychlor solution in cyclohexane to board extract blanks with background concentrations in the ratio of 1:2 : 4. By doing this the method was tested over the widest range of board backgrounds that would usually be encountered. DISCUSSION O F CALCULATIONS
Because the amount of extraneous board extractables may vary for each sample, comparison of extracts of treated board with the extract of untreated board will afford only a partial compensation for the difference in background absorption. The authors hare used the method of the double impurity index to make a more exact correction for this difference. In choosing the reference wave lengths 215 and 238 mp they have attempted to obtain nearly equal background absorbancies on either side of the absorption maximum of the methoxychlor. The method assumes a CALCULATIONS linear horizontal absorption for the background between the reference wave lengths when absorbancy is plotted versus wave The impurity index, Z.Z., a t each reference wave length is callength. By actual measurement of the absorbancy of blank culated from the following equations: board extracts, a plot of log A , versus wave length evidenced a slight upward slope in the region 215 to 238 mp. Therefore, the agreement of +5% over the range of 0.04 to 0.14 gram per liter, as shown by the data of column 9 in Table 11, between the calculated concentrations of methoxychlor in the presence of varying amounts of background and the known values is probablx as good as could be expected. Outside of this range errors up to 10% were found between the calculated concentration, c,. shown in Table I. Recovery of Methoxychlor from Board by , in colunin 8. column 7 and the true concentration, c ~ shonm Extraction with Cyclohexane Column 8 gives the known amounts of methoxychlor added to Added, Found, Extraction Saniple hlg./Sq. Tt. Mg./Sq. Ft. Recovery, c/o Time, Hours board extract blank solutions. Figure 2 shows graphically the 49 3 44.5 90.2 relation between cc and CT. 4 s it is only a matter of preparing the 98.6 89.3 90.5 98 6 93.3 94.4 proper dilution of the board extract sample to obtain a solution 98 6 92.5 93.8 that can he measured in the range of 0.04 to 0.14 gram per liter, 197 163 82.7 197 182 92.3 the authors have followed this practice in order to avoid the 197 186 94.4 8 197 182 92.3 6 necessity of further corrections. 9 216 194 89.8 6 After the accuracy of the spectrophotometric measurement had 10 1082 1040 96.1 6 been dptermined. the over-all accuracy of the method including the extraction was cdnsidered. _ _ _ _ . . _ _ _ ~ The recovery of methoxychlor from board samples to which known amounts of insect,icide n-ere Table 11. Calculation of Methoxychlor Concentrations for Known I. added is given in oohmn Of Solutions with Various Board Backgrounds by the Double ImpuritjSamples 1 to 8 of Table I were prepared hy piIndex Method pet,t,ing aliquot,s of a st,andard methoxychlor solu[b = optical path = 0.095 cm. (oa)zao = 56.4. 021'= 0.757. = 0.7601 tion in cyclohexane over blank samples which (oJzro (adaro Transmittancy T a (ka)lro were in place in the extractor tube. The volumes Sample 215 m p 230 mp 238 mp n (adzao cc CT % Diff. of solution used were sufficient to wet the sa.m1 0.953 0.904 0.931 -0.553 0.00817 0.0127 0.0116 + 9.4 pies thoroughly without leaving an excess of solu2 0.679 0.589 0.667 0.0429 -0.027 0.0441 0.0464 + 5.0 3.7 tion. Samples 9 and 10 were prepared by rare3 0.449 0.385 0.489 +0.083 0.0774 0.0710 0.0685 4 0.344 0.260 0.361 +-0.040 0.1090 0.1046 0.1027 + 1.9 + 0.3 fully adding purified methoxychlor crystals from 5 0.348 0.249 0.364 -0.032 0.1128 0.1164 0.1160 6 0.268 0.189 0.287 +0.015 0.135 0.1329 0.1369 --10.3 2.9 a weighed vial to areas of wet adhesive coat7 0.165 0.0878 0.162 -0,056 0.197 0.208 0,232 - 8.2 ing on board samples. After the coating had 8 0.197 0.1005 0.185 -0.141 0.186 0.232 0,213 .dried, the board samples were extracted. .4n
1182
A N A L Y T I C A L CHEMISTRY 025 I
NOMENCLATURE
A, M
= absorbancy of sample, A , = log l,’?”*
= gram molecular weight
where subscripts m and a refer t o the sample and the pure component, respectively, Xo refers to the wave length a t which the pure component is measured, and X i refers t o the wave lengths a t which the impurity indices are t o be calculated from ( 7 ) . = transmittancy of sample, T , = Tao~n. Tiolv. T..A~. = transmittance of a given cell containing a solution, of
T,
0
005
OK)
OM
a20
GRMwnm -m-mc, Figure 2. Determination of Methoxychlor in Presence of Board Background
azs
Dmta of Table XI
average value of 92.6 ==! 2.2% was found for samples 1 through 10, excluding 5 , which apparently was not extracted for a sufEciently long period of time. A standard deviation of 2.2% appears t o be sufficiently low to justify the conclusion that a systematic error of about -7% has occurred in the extraction procedure. In view of this, the method should not be used without comparing the results with known treated board stendards. SUMMARY
.I direct ultraviolet spectrophotometric method for the determination of methoxychlor on treated paperboard has been developed using the 230 mg absorption maximum. The methoxychlor was extracted from the paperboard with cyclohexane and compared t o a blank extraction, and the correction for background interference MTas made by calculation by the double impurity index method. A precision of 2 ~ 5 %was obtained for the determination of methoxychlor in cyclohexane solution in the presence of board background. and recoveries of 92.6 f 2.2% from paperboard were obtained.
YsOi,.
=
a~
=
a,
=
b
=
C
= = = =
CO
CT
k,
which the compound of interest is the solute or one constituent transmittance of the same cell containing pure solvent or blank extract A If molar absorbancy index, U M = L, 1OOOsq. cm. per bc mole 9 absorbancy index of pure component, a , = 2, IO00 bc sq. cm. per gram cell thickness, cm. concentrat,ion,grams per liter calculated concentration, grams per liter hrue concentration, grams per liter absorbancycoefficient, f:, = a.c, c m - : LITERATURE CITED
(1) Ciaborn. H. V . , J . Assoc. Ofic.Agl. Chemists, 29, 330 (1946). (2) Claborn, H. V., and Beckman, H. F., ANAL.CHEM.,24, 220
(1952). (3) Doble, J., and Thornburg, T., “Modified Procedure for the Determination of Methoxychlor [2,2-Bis-(p-methoxyphenyl) l,l,l-trichloroethane],”Exhibit 1247-8 at Food and Drug Administration Tolerance Hearings (1950) (FDC-57); reprinted in “Methoxychlor, A Summary of Analytical Ivfethode,” Wilmington, Del., E. I. du Pont de Nemours & Co., Inc., 1961. (4) Fairing, J. D., and Warrington, H. P., Jr., Advances in Chem. Ser., No. 1,260 (1950). ( 5 ) Friedel, R. H., and Orchin, &I., “Ultraviolet Spectra of Aromatic Compounds,” New York, John Wiley & Sons, 1951. (6) Jones, L. R., and Riddick, J. .4.,. 4 x a ~ CHEM., . 24, 569 (1952). (7) hlellon, AI. G., ”Analytical Absorption Spectroscopy,” p. 390, Equation 7.38, New Tork, John Wiley & Sons, 1950. (8) Ibid.,pp. 395-7. (9) Ibid.,p, 396, equation 7.43. (10) Satl. Bur. Standards, Letter Circ. LC-857 (1947). (11) Tressler, C. J., J . Assoc. Ofic.Agr. Chemists, 30, 140 (1947). RECEIVED for review March 16, 1953. Accepted M a y 1. !Y53. Presented before the Division of Agricultural and Food Chemistry, Pesticides Subdivision, a t the 123rd Meeting of the AMERICAXCHEMICAL SOCIETY,Los Anpeles, Calif.
Spectrophotometric Determination of Tin( IV) HARRY TEICHER’ AND LOUIS GORDON Department of Chemistry, Syracuse University, Syracuse, N . Y .
I
N T H E course of a study of the coprecipitation of manganese(11) on basic stannic sulfate precipitated from homogeneous solution, it was found necessary to have a sensitive and convenient method for the determination of small amounts of tin(1V). Relatively few methods have been proposed for the colorimetric determination of tin(1V). Various authorg (5, 15, 18) have recommended the use of dithiol and thioglycolic acid t o determine up to 80 micrograms of tin(1V) in a volume of 10 ml. Gentry and Sherrington ( 7 ) have recommended the extraction of stannic 8-hydroxyquinolinate with chloroform from a solution at pH 2.5 to 5.5 and subsequent photometric measurement of the 1
Present address, Mound Laboratory, Monaanto Chemical C o , Miarnis-
b c r g , Ohio.
chloroform layer. Morrison (IS) reported that stannic cupferrate can be extracted by chloroform from aqueous solution; if a color is developed in the chloroform phase it may be suitable for photometric determination, However, no work has appeared on this latter application. Tin(1V) has also been determined colorimetrically by reduction to tin(I1) and subsequent reaction with a number of heteropolymolybdates to produce a blue solution (1,10,16). Thionalide produces a turbidity with tin(1V) and has been proposed as the basis for a turbidimetric procedure ( 2 ) . Recently, another turbidimetric procedure using 3-nitro-4-hydroxybenzene arsonic acid (11)has been introduced for the determination of 0.1 t o 0.2 mg. of tin(1V) in a 20-ml. volume.
