to the structure of the parent alcohol were made, although the small number of individuals in any class other than saturated aliphatic alcohols (1) made any generalization untenable. Within the same homologous series, separations were based on chain length; however, unsaturated alcohol derivatives had higher RJ values than saturated alcohol derivatives of the same chain length. For example, 3-hexen-1-yl o-nittophenylurethan could not he separated from n-pentauyl o-nitrophenylurethan, but was completely separated from the n-hexyl derivative (Figure 1). Phenol and aromatic alcohol derivatives had consistently higher RJ values (Table 111) than derivatives of other classes. The C,O terpene alcohol derivatives were difficult t o separate, although some separations were made. The separation of linalyl, dihydroliualyl, and tetrahydrolimdyl o-nitrophenyliiretham was apparently caused hy the differences in unsaturation. The separation of linalyl and terpinyl derivatives may have involved both the degree of unsaturation and a difference between an aliphatic and a n alicyclic molecular structure. The higher molecular weight sesquiterpene alcohol derivatives were lowest in R, value with apparent,ly some slight difference between the aliphatics, farnesol and nerolidol, as compared to the tricyclics, santalol and cedrol.
identified on paper chromatograms, even when the sample of alcohol was too small or too impure for the determination by infrared analysis. CONCLUSIONS
Both o-nitrophenyl- and p-phenylazophenylurethans give paper chromatographic separation of alcohols of various classes, with the o-nitrophenylurethans giving the best results. I n addition, o-nitrophenylisocyanate reacts well with microquantities of alcohols to give enough derivative for paper chromatographic analysis, making this technique a n effective supplement t o gas liquid chromatography, LITERATURE CITED
Figure 1. Typical separations of onitrophenylurethons (illuminated by ultraviolet light, 3600 A.) A. 8. C.
D.
Borneol, menthol, eedrol Carved, terpineol, demnol 3-Hexen-l-ol, linalool, terpineol. fornerol 3-Hexen-1 -01, hexonol, linolool, nanonol
tives of C, 'to C,, Saturated Aliphatic Alcohols." Submitted t o the Cohlentz
Society.
(3) Wolfprd, R. W., Attaway, J. A., Alberdmg, G. E., Atkins, C. D., presented at the 22nd Annual Meeting of the Institute of Food Technologists, Miami, Fla., June 10-14, 1962. Submitted for publication in J. Food Sei.
RECEIVEDfor review September 13,
Condensation of microliter quantities of alcohols and subsequent reaction with isocyanates gave quantities of urethans which could he detected and
Analysis of Polyester Resins
by Gas
1962. Accepted December 18, 1962. Cooperative research by the Florida Citrus Commission and Florida Citrua Experiment Station. Florida Agricult u r d Experiment Station Journal Series, No. 1502.
Chromatography
D. F. PERCIVAL California Research Corp., Richmond, Calif.
b The complexity of polyester resins has increosed in recent years because a greater number of acids and glycols have attained commercial significance. A method for the identification and semiquantitative determination of various constituents in these resins consists of isolation of resin from monomer solution by precipitation, then methanolysis and analysis of the resulting dimethyl esters and free glycols by g a s chromatography without prior separation. Analytical control can thus b e exercised on various formulations.
R
work in our laboratories required a general, semiquantitative analysis of unsaturated polyesters. Therefore, we developed a method involving methanolysis of the polyester followed by gas liquid chromatography that involves little contact time (but 236
,CENT
ANALYTICAL CHEMISTRY
long reaction t i e ) , is general for most unsaturated polyesters, and gives semiquantitative results for both dibasic acids and polyols. Methanolysis converts the polyester to a mixture of glycols and methyl esters of the acids, which without further manipulation can be easily separated and identified by gas chromatography. Temperature programming is useful in this separation but not essential. From the peak areas one can roughly calculate the molar concentration of each constituent in the polyester by using a simple conversion factor. Our method is similar to one recently published by Esposito and Swann (2)for the qualitative identificsr tion of carboxylic acids in alkyds and polyesters. The principal difference is in reaction time for transesterifteation. Our method does not require any separation prior to gas chromatography,
APPARATUS AND MATERIALS
A Willdns Aerograph A350 temperature-programmed gas chromatograph was used in this study. The recorder was a Leeds and Northrnp Speedomax Type G. .
OPERATINO CONDITIONS Detection cell, C. D.c. current, mah Injection temp.,o C. Column temp., C. (8" C./min for programmed runs)
Helium flow rate, ml./min.
200 200
200 110-1x0 50
COLUMNPREPARATION.Twelve feet by 1/4 inch 0.d. copper tubing packed with 10 grams of GE silicone SF-96 on 50 grams of Fluoropak 80. EXPERIMENTAL
Any solvent or monomer in the commercial resin is removed by precipitation, A 10-gram sample of the resin is weinhed into a tared beaker and 100
Table 1. Per Cent Nonvolatile by Petroleum Ether Precipitation"
Polyester,
%
60
Styrene, 5-G
40
- METHANOL - PROPYLENE GLYCOL C - DIPROPYLENE GLYCOL D - DIMETHYL METHOXY SUCCINATE E - DIMETHYL ISOPHTHALATE A
B
Polyester found, yo 61
30 TO 50 50 51 Double precipitated as described in experimental section. 50
ml. of petroleum etjher added with vigorous agitation. The mixture is allowed t o separate for 15 minutes and the supernatant liquid decanted or filtered from the residue. The residue is dissolved in the minimum amount of acetone and the petroleum ether precipitation repeated. After drying to constant weight in a yacuum oven at 50" C., the per cent nonvolatile is calculated as Jveight of sample after extraction and drying % NV = x 100 (Tveight of sample) The residue is then refluxed with 100 ml. of absolute methanol containing about 0.1 gram of sodium methoxide. (If undiluted resin is available, the analysis can be started at this stage.) Total refluxing is continued for about 18 hours. A 20- to 3O-pl. sample of the resulting solution is used for gas chromatography analysis. RESULTS AND DISCUSSION
Separation of styrene monomer from polyesters by precipitation with petroleum ether is fast and accurate (Table I). Nethanolysis of the resin using sodium methoxide as catalyst cleaves the ester linkages, yielding methyl esters and free glycols. For this reaction to approach completion, the solution must be basic to phenolphthalein. Therefore, if a resin of high acid number is being analyzed, enough sodium methoxide must be added to neutralize the free carboxyl groups and catalyze the methanolysis. Addition of sodium methoxide to the hot methanol mixture of polyester until bmic to phenolphthalein was sufficient in our analysis. Time for complete methanolysis is dependent on the polyester formulation and concentration. I n most cases 18 hours at a 95 to 5 methanol to resin dilution was sufficient; however, some resins required as much as 42 hours. Completion of reaction is easily determined by running chromatograms. If the reaction is complete, the relative peak areas from one sample will be the same as for another sample obtained after additional refluxing. At the start of methanolysis the resin is insoluble. Solution is complete after about 6 hours of reflux. The column used in our work gave
Figure 1
.
-
RETENTION TIME
Chromatogram of polyester after methanolysis
Programmed from 1 10' to 180' C. at 8' C. per minute
Table II. Retention Times
Sample
Boili:g point, C.
Dimethyl ester of Fumaric acid 192 Maleic acid 205 Itaconic acid 208 208 Methoxysuccinic acid 116c Adipic acid 284 Orthophthalic acid 284 Isophthalic acid Glycols 189 Propylene Ethylene 197 1,3-Butylene 207 Neopentyl Dipropylene Dimethylene Triethylene a Flow rate of 50 ml. He/minute. "rogrammed a t 8" C./minute.
Retention time," minutes 180" C. 110150°C. 110" C . 80" C.b 2.8 2.8 3.8 4.7 7.4 18.8
-
11.0 13.9 21.2 25.4
24.6
0.8 0.8 1.4
2.7 2.7
-
-
1 9
-
-
-
-
1.2 0.9
3.0 2.2
-
-
13 mm. Table 111.
Results for Dibasic Acids
Calcd. mole Resin ratio IP/MA/PGb 1/1/2,1 IP/MA/DEG ;$;$:.I IP/MA/PG IP/MA/PG/DPG 1/1/1.1/1.1 IP/FA/PG/DPG 1/1/1.1/1.1 PA/MA/PG 1/1/2.1 Moles of glycol found = molecular peak area weight X 1.4.
Mole ratio founda 110-80' c. 180" c. 0.9/1/2.1 1/1/2 w/2 1.1/2/3.1 1.1/2/3.3 1/1/0.9/0.9 -
-
l / l / O . 9/1
1.1/1p2.2
0
b
IP. Isophthalic acid PG. Propylene glycol DPG. Dipropylene glycol Ma. Maleic anhydride DEG. Diethylene glycol Mole ratios rationalized to give MA an integral value.
sufficient resolution in a reasonable time (Table 11)with little tailing. Retention times from air peak uncorrected for pressure drop for various constituents of polyesters are given in Table 11. Since commercial polyesters
rarely give rise to compounds other than glycols or dibasic acids, one can often estimate the boiling point of the constituent from the observed retention time. This makes qualitative identification simpler, since glycols or diVOL. 35, NO. 2, FEBRUARY 1963
237
methyl esters of the estimated boiling point can then be run for direct comparison with the unknown. I n this method fumaric acid is not distinguished from maleic acid, since under the methanolysis conditions employed both are converted t o dimethyl methoxysuccinate (3). It is expected that itaconic acid would also add methanol across the double bond, but this was not verified. Dibasic acids and polyols could also be quantitatively identified according t o the procedures of Esposito and Swann
ACKNOWLEDGMENT
(2) and Esposito ( I ) . These then could be followed by the quantitative method described in this paper. Quantitative results for the dibasic acids are in good agreement with the known composition of the resins (Table 111). Glycol content also agrees with the known composition using an empirical response factor of 1.4 (obtained by experiment). The total moles of glycol should equal the total moles of dibasic acid in a normal polyester, so errors in the determination are easily detected.
The author expresses appreciation t o the Oronite Division, California Chemical Co., for its interest and funds provided for this study. LITERATURE CITED
(1) Esposito, G. G., AXAL. CHEM. 34, 1173 (1962). (2) Esposito, G. G., Swann, hl. H., Ibid., 34, 1048 (1962). (3) Fyolka, Von P., Linz, J., Runge, F., Makromol. Chem. 26, 61 (1968). RECEIVEDfor review August 20, 1962. Accepted December 3, 1962.
Horizontal Chromatography Accelerating Apparatus Separation of Dyes and Indicators J. F. HERNDON, J. C. TOUCHSTONE, G. R. WHITE, and C. N. DAVIS The Malvern Institute, Malvern, Pa.
b
The Rf values for 22 dyes and indicators separated by a new centrifugally accelerated horizontal paper chromatography apparatus are given. Clear, reproducible separations can be effected in as little as 10 minutes. Amixture of seven dyes was separated by the tandem technique.
P
chromatography can be a valuable tool for the analysis and identification of commercial dyestuffs and indicators. Adsorption on various columns has also been widely used. APER
Table I.
Dye 1 L 3 O / O . 15b 0 1. Congo red 0 0.11 0.05 2. Toluidin blue 0 0.06 0.06 3. Eosin Y 0.04 0 0.17 4. Phloxine B 0.09 0.43 0.34 0.20 5. Fluorescein 0 0 0 6. Amido black 0.73 7. Bromocresol blue 0.57 0.56 0.08 0 ... 8. Saffarin 0.82 0.43 9. Bromocresol green 0.67 0 0 0 10. Janus green 0.60 O / O . 77 11. Bromocresol purple o/o. 73 0.42 0.22 0.48 12. Bromothymol 0.10 0.07 13. Indigo carmen o.ofi;o, 20 0 0 14. h'eutral red 0.09 0.13 0.05 15. Orange I1 0 0 16. Superchrome black 0 0 0 0 17. Erythrosin B 0.85 0.73 0.68 18. Cresol red 0.18 0.50 0.45 19. Methyl red 0/0.09 0 0 20. Bismarck brown 0.76 0.60 21. Thymol blue 0.53 0.38 0.17 22. Methyl orange 0.12 a Conditions for separation given in Table 11. b Two figures denote two bands separated. 0
238
ANALYTICAL CHEMISTRY
require temperature control and equilibration of solvent systems.
Hough, Jones, and Wadman (S), Lederer ( 5 ) , and Zahn (12) have described the separation of dyes by paper chromatography. Pagani (8) and Jungbeck (6) used ascending chromatograms. Sivarajan and Parikh (9) used circular horizont,al chromatograms developed with buffers for separation of reactive dyes. Maccio (6) and Verma and Dass (11) have described the use of reverse-phase systems t o separate fatsoluble dyes. Moloster (7') describes the separation of many different dyes. These methods in general have in common long development times and
0
The operation of the centrifugally accelerated horizontal chromatography apparatus has been described in detail (2). The apparatus was operated with an automatic solvent delivery systemzin the present studies. The dyes were divided into-:three groups according to solubility. In Table I dyes 1 to 12 are soluble in distilled water, 13 to 17 are soluble in 10%
Rf Values for 22 Dyes Solvents and conditions" 5 7 4 6
0 0
0.17 0.42 0.75 0
0.91
0
0.93 0
0.94 0.92
6"
0.16
0
0.12 0.93 0.74 0
EXPERIMENTAL
0.91 0.31
0
0
0.66 0.12 0.87 0.11 0.91 0 0.90 0.92 0.41 0.04 0.35
0.10 0.30 0.60 0.66 0.13 0.85 0.16 0.88 0.05 0.88 0.94 0.44 o/o. 09 0.35
0.24 0.93 0.68 O / O . 15 0.93 0.47
0.26 0.88 0.68 O / O . 13 0.91 0.45
0.07 0.28
0.55
0
0
0 0
...
0.54 0.79
...
0.87 0.06 0.86 0 0.90
0.87 *.. 0
8 0/0 .71 0
0.23 0.50 0.78 0.10 0.89 0
0.94 0
0.94 0.86 0.48
0
9 0/0.46b 0.34 0.21
O / O . 3gb
0.59 0.18 0.86 0.38 0.84 0.15 0.88 0.79 0 49 o/o, 29 0.45
0.48 0.13 0.77 0.29 0.77 0.15 0.83 0.76 0.44 O / O . 28 0.45
0
0.23
0.31
... 0.90 0.21/ O .63
0.18 0.93 0.23/0.81
0.91 0.54
0.78 0.35
0.91 0.42
0.86 0.70
...
0
0
0
0 ...
...
10 0.27
...
0
0
0.26 0.88 0.53 0/0 .38 0.86 0.60
