Thermal Decomposition of Endrin as a Measure of Surface Activity of Gas Chromatographic Support Media Herbert L. MacDonell and David L. Eaton Research and Deoeloprnent Laboratories, Corning Glass W o r k s , Corning, N . Y . 14830
Surface active sites on support media promote the thermal-catalytic decomposition of certain moderately stable organic compounds. Endrin, a compound of this type, was chosen to demonstrate the relationship between decomposition as a function of column temperature using columns containing diatomaceous earth and soda-lime glass bead support media. Surface. textured glass bead columns were also evaluated and were found free of active sites by the testing procedure employed.
ficult to separate on conventional gas chromatographic support media because of its tendency to tail and/or decompose (8, 9). For this reason it was selected as the test compound to evaluate surface activities of three support media : refined diatomaceous earth, soda-lime glass beads, and surface-textured glass beads of optimized composition (IO). A solution containing 10 ,ug of endrin per pl was prepared using n-hexane as the solvent. All data were obtained on 0.25-pl injections, or 2.5 pg of endrin per run. EXPERIMENTAL
ONEOF THE MORE DESIRABLE PROPERTIES of a gas chromaSupport Material. Diatomaceous earth that had been tography support is inertness. Unfortunately, inertness is acid- and base-washed, silanized with dimethyldichlorosilane, difficult to achieve, as natural or manufactured materials and coated with 1.23% Dow Corning No. 710 silicone oil often have one or more types of active sites which are sources was used to pack column 1. Column 2 was filled with unof adsorption or catalytic activity. Such activity is generally textured soda-lime glass beads that had been silanized with caused by the presence of either acidic or basic groups on dimethyldichlorosilane and coated with 0.09 % Dow Corning the surfaces of the support materials. These sites can be in No. 710 silicone oil. Column 3 was filled with surfacethe form of silanol groups or metallic oxides ( I ) . textured glass beads that had been silanized with dimethylWhile many have observed the effects of these active groups, dichlorosilane (Corning Glass Works Code 0201 glass beads) which cause tailing, decomposition, or rearrangement of and coated with 0.14% No. 710 silicone oil. Although the weight per cent loadings differ considerably between these certain organic compounds, few have actually studied these columns, the per cent loadings per unit area are somewhat effects on the various types of gas chromatography support closer because of the difference in density and area between materials. Gottfried (2) investigated the decomposition of glass beads and diatomaceous earth. The surface area per corticosteroids, Hayashi (3) and Hesse ( 4 ) studied the catalytic unit volume in a packed column is about three to five times decomposition of terpene compounds, and Verzele ( 5 ) and greater for diatomaceous earth than for surface-textured Bens ( 6 ) utilized a gas-solid chromatographic technique to glass beads. Therefore, the partition phase is only two or study, respectively, the catalytic and adsorptive properties three times thicker on the diatomaceous earth support than of support media. Evans (7) reported on the relationship on glass beads. All support media were of 100/120-mesh between support activity and relative retention for several particle size. Partition phase coating was effected using the compounds on a variety of commercially available support fluidized bed procedure described earlier (11). Apparatus. Columns were ’/a-inch by 6-foot borosilicate materials. All found marked activity in so-called “inert” glass, rinsed with a 5 % dichlorodimethylsilane in toluene supports. This work should not be confused with actual solution, followed by acetone, and dried prior to packing. catalysis investigations or gas reaction studies, which have A Microtek MT-220 gas chromatograph, having dual-flame been the subject of considerable investigation. ionization detectors, was used with a I-mv Esterline Angus Our own studies of gas chromatography support materials recorder having a OS-second response. have shown that catalytic activity depends markedly on the choice of support medium, the type and amount of partition RESULTS phase loading, and the column temperature. Therefore, if The decomposition of endrin on column 1 became aptwo or more support media are loaded to approximately the parent at 175 “C and increased progressively as the column same degree with the same partition phase, it is evident that temperature was raised (Figure 1 and Table I). The detheir surface activity may be compared as a function of the composition products are not characterized but are believed decomposition of a specific test compound at various temto be the delta keto-1,3,5 and the delta aldehyde (12). peratures. This hypothesis is the basis for the present study. Endrin was far more stable.on the column containing unThe compound endrin (1,2,3,4,10,10-hexachloro-6,7-epoxy1,4,4a,5,6,7,8,8a-octahydro-l,4,5,8-endo-endo-dimethanonaph- textured soda-lime glass beads. No decomposition products were observed below 200 “C when this column was used. thalene), a pesticide of commercial importance, is difEven at 225 “C relatively little decomposition occurred. In contrast to the diatomaceous earth and untextured glass (1) M. L. Hair, “Infrared Spectroscopy in Surface Chemistry,” Marcel Dekker, New York, 1967. (2) H. Gottfried, Steroids, 5 , 385 (1965). (8) H. L. Reynolds, J. Gas Chromatog., 2 , 219 (1964). (3) S. Hayashi, K. Yano, N. Yokoyama, and T. Malsuura, Nippon (9) H. Shuman and J. R. Collie, J. Assoc. Ofic.Agr. Chemists, 46, Kagaku Zasslii, 85, 553 (1964). (4) G . Hesse, 2. Anal. Chem., 221,5 (1965). (5) M. Verzele, K. Van Canwenberghe, and J. Bouche, J . Gas Chromatog., 5 , 114 (1967). (6) E. M. Bens, ANAL.CHEM., 33, 178 (1961). (7) M. B. Evans and J. F. Smith, J . Chromatog., 30, 325 (1967).
922 (1963). (10) A. M. Filbert and M. L. Hair, J . Gas Chromatog., 6 , 150, 218 (1968). (11) H. L.MacDonell, ANAL.CHEM., 40,221 (1968). (12) Herbert Hughes, University of Toronto, private communication. VOL. 40, NO. 10, AUGUST 1968
1453
n j +'
BOTH ENDR I N
175'
I
DECOMPOSITION PRODUCT
Figure 1. Endrin on diatomaceous earth (column 1)at various temperatures Column. l/a-inch X 6-foot glass filled with 100/120-mesh diatomaceous earth support Coating. 1.23% DC-710 silicone oil Carrier gas. Nitrogen, 40 psi, 95 ml/minute Sample. 2.5 pg of endrin in 0.25 MI of hexane Carrier gas. Flow varied to maintain relatively consistent Rt for endrin. Rt = 6 to 13 minutes Attenuation. 1014 to 1011 to contain endrin peak Temperature. As indicated on curves
bead supports, the surface-textured glass bead column (column 3) produced no decomposition of endrin whatsoever at any temperature up to 225 "C. This temperature was taken as a limit, as it is the highest recommended operating temperature for DC-710. The results obtained on columns 2 and 3 are illustrated in Figure 2, which compares the two glass bead types. HETP calculations from endrin curves obtained on columns 2 and 3 at 170 " C demonstrate the su-
Table I.
P e r Cent Undecomposed Endrin Column 1 Column 2 Column 3
(diatomaceous Temp., "C 175 180 185 190 195 200 205 210 21 5 220 225
1454
earth) 65.9 64.4 45.7 42.6 41.4 31.6 28.1 20.7 19.2 13.8 11.7
ANALYTICAL CHEMISTRY
(soda-lime beads) 100 100
100 100 100 95.1 91.9 89.4 88.5 84.8 80.2
(textured beads) 100 100 100 100 100 100 100 100 100 100 100
0
6
4
2
Time i n minutes
Figure 2. Endrin response on untextured glass beads (column 2) and surface-textured glass beads (column 3) at high temperature Column 2. 114-inch X 6-foot glass filled with 100/120-mesh untextured soda-lime glass beads Coating. 0.09% DC-710 silicone oil Column 3. li4-inch X 6-foot glass filled with 100/120 mesh surface-textured glass beads Coating. 0.14% DC-710 silicone oil Carrier gas. Nitrogen, 40 psi, 3 ml/minute Samples. 2.5 fig of endrin in 0.25 pl of hexane Attentuation. 10/4 Temperature. 225 "C
periority of surface-textured glass beads over soda-lime glass beads. HETP values of 0.42 and 3.91 mrn were obtained, respectively. Asymmetry calculations of 0.98 and 1.11 also favor the surface-textured glass bead column. No determinations were made above 225 "C,although it is very probable that thermal decomposition of endrin will occur at some higher temperature because of thermal instability, whether catalyzed by active sites or not. Data in Table I represent a comparison between the peak areas of endrin and its first decomposition product. The second decomposition product was not considered because of its long retention time at lower temperatures. The percentages in Table I, therefore, list values that are relative to each other and not absolute.
Other columns were prepared to verify the above data. One column filled with a refined diatomaceous earth support, 80/100-mesh, acid-washed, DMCS-treated, and coated with 1.43% DC-710,gave identical results to column 1. All other columns, some 35 in number, were filled with surfacetextured glass beads. The DC-710 loading on these columns ranged from 0.008 to 1.52%. No decomposition of endrin was detected on any of these 35 glass bead columns. A mixture of six pesticides was prepared for a further comparison of diatomaceous earth and surface-textured glass bead supports. Lindane, heptachlor, aldrin, dieldrin, endrin, and DDT were dissolved in hexane, so the final solution contained 1 pg per pl of each pesticide. The appearance of
endrin decomposition peaks just before the DDT response, and the reduction of the endrin response itself, confirm the decomposition of this pesticide on diatomaceous earth support. Again, the surface-textured glass beads allowed a single, symmetrical response to endrin. This support material is ideally suited for the separation and analysis of biomedical, pharmaceutical, and lower-molecular-weight polymer compounds, because surface-textured glass beads permit shorter retention times and lower operating temperatures than conventional supports. RECEIVED for review March 4,1968. Accepted May 27, 1968.
Direct Gas Chromatographic Analysis of Isomeric Diaminotoluenes Friso Willeboordse, Quentin Quick, and E. T. Bishop Research and Development Department, Union Carbide Corporation, South Charleston, W . Va. 25303 A direct gas chromatographic method has been developed for the determination of isomer content in diaminotoluenes. Mixtures of 23-, 3,4-, 2,4-, 2,5-, and 2,6-diaminotoluenes can be readily and accurately determined. The method utilizes a mixed partitionihg agent of Carbowax 20M and Siponate DS-10 on baseloaded Chromosorb G, followed by Siponate DS-10 on the same solid support. The present method compares very favorably with the NMR method and the derivatives’ GC method which are generally employed. THEdiaminotoluenes (TDAs, tolylene diamines) are important as intermediates in the manufacture of tolylene diisocyanate (TDI) which is widely used in the preparation of polyurethane foam and elastomers. Commercial TDA consists of a mixture of the 2,4- and 2,6-isomers (about 7 9 z and 19%, respectively) together with smaller amounts of the 2,3-, 3,4(these are named the two ortho-isomers), and the 2,S-isomer (each about 0.5% by weight). A knowledge of the isomer ratio of a TDA mixture allows one to predict the ratio of isomers in the TDI. A previous paper by Brydia and Willeboordse ( I ) discussed the use of trifluoroacetic anhydride derivatives to effect the quantitative gas chromatographic determination of TDA isomers. Until recently, this was the only satisfactory single method available to us for a complete analysis of TDA mixtures. However, the use of the derivatives’ determination involves a conversion operation and the choice of one of two procedures: one which is fairly rapid but does not resolve the 2,4- and 2,5- isomers, the second one resolving all the isomers but consuming more time because of .an extra evaporation step. In addition, the 2,5-isomer (small amount) is exhibited in the tail-end of the 2,4-isomer (major component) which constitutes an inherently undesirable facet of this method. An NMR method for the analysis of mixtures of TDA has been described by Mathias (2). The NMR method has poor accuracy for the minor isomers and does not lend itself readily to control applications. (1) L. E. Brydia and F. Willeboordse, ANAL.CHEM., 40,110 (1968). (2) A. Mathias, ibid., 38, 1931 (1966).
The approach in the present study was to effect a complete direct gas chromatographic analysis of the five TDA isomers in a more simple manner than either of the derivatives’ procedures or the NMR method. EXPERIMENTAL
Apparatus. An F and M Model 500 gas chromatograph equipped with thermal conductivity detector was used. The detector was equipped with W-2 filaments. Detailed experimental parameters are summarized in Table I. Chemicals. The 2,4-, 2,6-, and 3,4-diaminotoluenes are available from commercial sources. The 2,5-isomer is available as the dihydrochloride which was converted to the free diamine by reaction with an equivalent amount of potassium hydroxide and extraction with ether. The sample of crude ortho-TDA is a product of the Union Carbide Corp. Siponate DS-10 (dodecyl benzene sodium sulfonate) was obtained from Alcolac Chemical Corp., Carbowax 20M is a product of the Union Carbide Corp., and Chromosorb G , NAW (non-acid washed), 60/80 mesh, was obtained from the Johns-Manville Corp. Preparation of Base-Loaded Support. To prepare a 1 % base-loaded solid support, 1 gram of KOH was dissolved in 175 ml of methanol and 99 grams of Chromosorb G were dispersed in this solution. The slurry was mixed well, and the methanol was evaporated on a rotating evaporator (Rinco) until the support appeared dry. Preparation of Columns. FOURTEEN-FOOT COLUMN.Four grams of Carbowax 20M and 2 grams of DS-10 were dissolved in a minimum quantity of methylene chloride, and then added to the solid support (94 grams). The methylene chloride was evaporated by stirring the slurry periodically under a stream of dry nitrogen until the loaded support appeared dry. This material was then transferred to a 14-foot, 0.25-inch-0.d. aluminum column with gentle vibration to assure a uniform packing. Exposure to the air should be minimized during the loading operation. SIX-FOOTCOLUMN.Five grams of DS-10 were dissolved in methylene chloride, added to the base-loaded support (95 grams), and then processed in much the same way as described for the 14-foot column. The two columns were connected with a union. The DS-10 column follows the mixed column. No glass wool VOL. 40, NO. 10, AUGUST 1968
1455
