Rall, H. T., Thompson, C. J., Coleman, H. J., Hopkins, R. L.. Roc. Am. Pet. lnst., 42, Sect. VIII, 19 (1962). Reid, E. M.. "Organic Chemistry of Bivalent Sulfur," Vol. I, p 1IO, Chemical Publishing Co., New York, N.Y.. 1958. Reid, E. M., "Organic Chemistry of Bivalent Sulfur," Vol. 11, p 60, Chemical Publishing Co., New York, N.Y., 1960a. Reid, E. M., "Organic Chemistry of Bivalent Sulfur," Vol. Ill, p 369, Chemical Publishing Co., New York, N.Y. 1960b. Rudenko, M. G., Gromova, V. N., Dokl. Akad. Nauk, SSSR, 81, 297 (1951). Sehon, A. H.,Darwent, B. de B., J. Am. Chem. SOC.,78, 4806 (1954). Taylor, W. F., J. AppI. Chem., 18, 251 (1968a). Taylor, W. F., SA€ Trans., 78, 281 1 (1968b). Taylor, W. F., J. Appl. Chem., 19, 222 (1969a). Taylor, W. F., Ind. Eng. Chem., Prod. Res. Dev., 8, 375 (1969b).
Taylor, W. F., Ind. Eng. Chem., Prod. Res. Dev., 13, 133 (1974). Taylor, W. F., Wallace, T. J., lnd. Eng. Chem., Prod. Res. Dev., 6, 258 (1967). Taylor, W. F., Wallace, T. J.. Ind. Eng. Chem.. Prod. Res. Dev.. 7, 198 (1968). Thompson, R. B., Druge, L. W., Chenicek, J. A,, lnd. fng. Chem., 41, 2715 ( 1949). Walker, H. E.,Kenney, E. B., Pet. Process., 11, 58 (1956).
Received for review June 5, 1975 Accepted August 14,1975 This work was sponsored by the Department of the Navy under Contracts N00019-71-C-0463and N00140-72-C-6892.
Analyzing Cetyldimethylbenzylammonium Chloride by Using Ultraviolet Absorbance Lawrence K. Wang,' Donald B. Aulenbach, and David F. Langley Department of Chemical and EnvironmentalEngineering, Rensselaer Polytechnic Institute, Troy, New York 72 78 7
The engineering significance of cetyldimethylbenzylammoniumchloride is described. The compound in distilled water in the range of 1.0 to 5.0 mg/l. can be rapidly measured by a uv method at 210 nm with less than 8 % relative standard deviation and relative error.
Introduction Quaternary ammonium compounds are widely used for: (a) fabric antistatics and softening (cationic quaternary ammonium compounds can eliminate the normal buildup of static electrical charges of plastics and synthetic fibers when dried in a mechanical drier, and the quaternary ammonium compounds with two long alkyl chains also have excellent softening properties when used in conjunction with common synthetic detergents for cleaning fabrics and clothes); (b) corrosion inhibition in flue gas scrubbers, acid pickling baths, and petroleum pipelines; (c) emulsion compounding (they have the special property of being substantive, that is, causing the oil phase of an emulsion to plate out on such surfaces as textile fabrics, metals, glass, plastic, wood, and foliage); (d) pigment treatment; and (e) ore flotation (separation of certain minerals from low grade ores can best be accomplished using quaternaries). For water pollution control, the release of such cationic surfactants to water resource systems should be monitored and controlled. Recently environmental engineers have been researching the use of quaternary ammonium compounds for water treatment (Grieves and Schwartz, 1966; Grieves and Conger, 1969; Grieves et al., 1970; Wilson, 1969; Wang, 1972; Wang and Peery, 1975),wastewater treatment (Wang e t al., 1974a; 1974b; Wang, 1973a, 1973b), and sludge treatment. Therefore, the development of effective analytical techniques for determining the initial and residual concentrations of quaternary ammonium compounds is necessary. For general analysis of quaternary ammonium compounds in aqueous solution, the presently accepted method is the two-phase titration method (Wang, 1973c; Wang et al., 1974b), which can measure the concentrations of quaternaries at a range of l to 30 mg/l. More recently, Wang and Langley (1975) developed a methyl orange method for more accurate determination of cationic surfactants (in68
Ind. Eng. Chem., Prod. Res. Dev., Vol. 15, No. 1, 1976
cluding quaternaries) a t the concentration range of 0.1 to 4.5 mg/l. Either the two-phase titration method (Wang 1973c; Wang et al., 1974b) or the methyl orange method (Wang and Langley, 1975) is applicable to the quantitative measurement of a single type of cationic surfactant in water. Neither method can differentiate between two quaternary ammonium compounds, between two amines, or between a quaternary ammonium compound and an amine compound. Nevertheless, the two methods are effective for chemical engineering processes control in which the specific cationic surfactant used is known, and for environmental water quality control in which only the residual concentration of a group of contaminants, such as cationic surfactants, is of particular concern. The objective of this paper is to introduce an ultraviolet spectrophotometric method for rapid analysis of a specific cationic surfactant (quaternary ammonium compound), cetyldimethylbenzylammonium chloride (CDBAC). Its molecular structure is shown in Figure l. Since CDBAC is an approved germicide (U.S.D.A. Regulation No. 1457-16), it may be used in throat lozenges, provided the individual lozenge contains not more than 5 mg of CDBAC and that the directions for use do not provide for consumption of more than 8 lozenges in 1 day. CDBAC is also generally used in mouth washes in a concentration of 1:4000. In the field of environmental engineering, CDBAC is a highly effective sanitizer (Ehlers and Steel, 1958; Fine Organics Inc., 1970), flotation agent (Wilson, 1969; Grieves and Conger, 1969; Grieves et al., 1970; Wang, 1972), and disinfectant (Wang and Peery, 1975). Many research projects are presently being conducted for the exploration of other applications and recovery techniques. The proposed uv method provides direct measurement ( 3 0 solvent extraction is involved), thereby significantly reducing the time for analysis and eliminating possible health hazards from toxic solvent vapors, such as chloroform.
Table I. Calibration Curve Preparation CDBAC concn, mg/l. 0
a
0.10 0.25 0.50 1.00 1.50 2.00 2.50 3.00 4.00 5.00 Light
0.308 0.342 0.335 0.358 (0.441 ) 0.500 0.572 0.670 0.782 0.945 (1.25) path = 10 cm.
0.317 0.318 0.316 0.360 0.407 0.485 0.564 0.650 0.780 0.955 1.15
Absorbance at 210 nma 0.292 0.331 0.332 0.312 0.387 0.475 0.562 0.650 0.765 0.940 1.10
0.285 0.305 0.334 0.320 0.392 0.474 0.548 0.665 0.760 0.920 1.15
Experimental Section In order to determine the optimum wavelength for detection, the wavelength of a uv spectrophotometer was varied in order to determine the wavelength a t which there was an absorbance peak for a solution of 2 mg/l. cetyldimethylbenzylammonium chloride (CDBAC) in distilled water. Both the scanning uv spectrophotometer (Microtech Unicam SPBOOA ultraviolet spectrophotometer) and the manually operated uv spectrophotometer (Beckman 109200 Model DU-2 ultraviolet spectrophotometer) were used for the determination of the optimum wavelength. Since both spectrophotometers generated almost the same absorbance data, only the data generated by the Beckman DU-2 spectrophotometer are documented in Figure 2 which shows that the optimum wavelength is 210 nm. A calibration curve was prepared using 10 replicate distilled water samples of 10 concentrations between 0.1 to 5.0 mg/l. of CDBAC. Experimental data are summarized in Table I. The functional relationship between the known surfactant concentration and the measured absorbance appeared to be a straight line in the CDBAC concentration range of 0.50 to 5.00 mg/l. Evaluation and Discussion The method of least squares was used to fit a straight line to the functional relationship between solute concentration and absorbance. The number of observations in the CDBAC concentration range of 0.50 mg/l. to 5.00 mg/l. was 80. The two bracketed values in Table I exceeded the standard deviation; thus they were not included in the calibration curve determination or the statistical analysis for the determination of precision and accuracy. Accordingly, the number of observations used was 78. The statistically determined calibration curve may be represented by a straight line as shown by eq 1 x = 5.55y
0.274 0.333 0.316 0.309 0.387 0.466 0.551 0.667 0.775 0.940 1.15
___
0.287 0.259 0.312 0.336 0.398 0.468 0.550 0.646 0.790 0.945 1.13
0.307 0.243 0.270 0.340 0.376 0.463 0.544 0.673 0.760 0.940 1.12
0.292 0.240 0.313 0.359 0.402 0.466 0.564 0.683 0.737 0.920 1.13
0.255 0.230 0.272 0.366 0.375 0.463 0.548 0.668 0.755 0.930 1.07
0.297 0.227 0.265 0.337 0.386 0.465 0.550 0.670 0.760 0.950 1.07
cn3
CF1,
Figure 1. Cetyldimethylbenzylammoniumchloride.
ZU2
i 21.
i:5
212
208 #A,LL!'IGTH,
220
UK
Figure 2. Absorbance vs. wavelength.
1.0 ~\ =
=:
0.8
$
0.4
+
-..:L
i.55i
- 1.20
(1) where x = the calculated concentration of CDBAC, mg/l., and y = the measured absorbance. I t should be noted that eq 1 (also shown in Figure 3) is valid only for the concentration range of 0.5 to 5.0 mg/l. of CDBAC. Outside this range the error is greater. The variance (S2), standard deviation (SD), relative standard deviation (RSD), range, error and relative error were then calculated for the data obtained in the range of 0.5-5.0 mg/l. CDBAC. Initially, the absorbance values indicated in Table I were converted to the measured concentration of CDBAC using eq 1. Comparing the accurately known CDBAC concentration with the experimentally measured CDBAC concentration in Table 11, one can then calculate the precision and accuracy of the uv method in terms of standard deviation, relative standard deviation,
WA V E L E V G T i = 113 NM L I G H T PR-'I
c'
0.2
=
1:
C4
0.0 0.0
1.3
2.0
3.0
4.0
5.0
6.0
CDBAC C O N C E H T R A T I O N , M G I L
Figure 3. Calibration curve of cetyldimethylbenzylammonium
chloride. range, error, and relative error, as indicated in Table 111. The relative standard deviation (RSD) and the relative error a t 0.5 mg/l. were determined to be 17.0 and 37.0%, respectively. In the CDBAC concentration range of 1.5 to 5.0 mg/l., both relative standard deviation and relative error Ind. Eng. Chem., Prod. Res. Dev., Vol. 15,No. 1, 1976
69
Table 11. Statistical Analysis Data Prepared CDBAC concn, mg/l.
Calculated CDBAC concn, mg/l.
0.785 1.245 1.573 1.973 2.517 3.138 4.043 5.736
0.50 1.00 1.50 2.00 2.50 3.00 4.00 5.00
0.796 1.057 1.490 1.928 2.406 3.127 4.099 5.181
0 529
Of946 1.434 1.917 2.406 3.044 4.015 4.904
0.574 0.973 1.429 1.839 2.489 3.016 3.904 5.181
0.663 1.007 1.395 1.850 2.383 3.183 4.043 5.070
0.513 0.946 1.384 1.856 2.500 3.099 4.015 5.181
0.790 1.029 1.384 1.928 2.589 2.889 3.904 5.070
0.685 0.885 1.368 1.817 2.533 3.016 4.015 5.015
0.668 0.940 1.379 1.850 2.517 3.016 4.071 4.737
0.829 0.879 1.368 1.839 2.505 2.988 3.960 4.737
Table 111. Precision and Accuracf CDBAC concn, mg/l.
0.50 1.00 1.50 2.00
2.50 3.00 4.00 5.00 a CDBAC = deviation.
S*
SD, mg/l.
Range, mg/l.
Error, mg/l.
Relative error, %
0.01346 0.01129 0.00432 0.00268 0.00430 0.00746 0.00429 0.08135
0.1160 16.98 0.316 -0.183 37 0.1062 10.72 0.366 0.009 1 0.0657 4.63 0.205 0.080 5 0.0518 2.76 0.155 0.120 6 0.0656 2.64 0.205 0.016 1 0.0864 2.83 0.294 -0.052 2 0.0655 1.63 0.194 -0.007 0 0.2852 5.61 0.999 -0.081 2 cetyldimethylbenzylammonium chloride. S2= variance; SD = standard deviation; RSD = relative standard
were below 6%. Assuming no sample dilution is needed, the required time to analyze a sample was less than 3 min.
Conclusion The uv method is a feasible analytical technique for measuring CDBAC in distilled water in the concentration range of 0.5-5.0 mg/l. It is simple and reproducible, saving time, and eliminating the solvent extraction hazards of other methods. The optimum wavelength was found to be 210 nm. L i t e r a t u r e Cited Ehlers, V. M., Steel, E. W., "Municipal and Rural Sanitatlon," 5th ed. pp 290-363, McGraw-Hill, New York. N.Y., 1958. Grieves, R. B.. Conger, W. L., Chem. Eng. Prog. Symp. Ser. Water, 200-206 (1969). Grikves.'R. B., Conger, W. L., Malone. D. P., J. Am. Water Works Assoc., 62 (5), 304-310 (1970). Grieves. R. B., Schwartz, S. M., J. Am. Water Works Assoc.. 58 (9), 11291136 (1966).
70
RSD, %
Ind. Eng. Chem., Prod. Res. Dev., Vol. 15, No. 1, 1976
"Product Index," pp 14-15, Fine Organics Inc., Lodi, N.H., 1970. Wang, L. K., Calspan Corporation, Buffalo, N.Y., Poject Report ND-5296-M2,-106 pp, 1973a. Wang. L. K.. Selected Water Resources Abstracts, 6 (21), W73-13648, 90-91 .. . (1973b). - --, Wang. L. K., Calspan Corporation, Buffalo, N.Y.. Project Report No. ND5296-M-3, 66 pp, 1973c. Wang, L. K., Langley, D. F., "Rapid Colorimetric Analyses of Catlonic and Anionic Surfactants," technical paper presented at the 1975 New England Water Works Associatlon, WaRham, Mass., Jan. 16, 1975. Wang, L. K., Peery, G. G., J. New England Water Works Assoc., 89 (2), 250-270 (1975). Wang, M. H., Ph.D. Thesis, Rutgers University, New Brunswick, N.J., 1972. Wang, M. H., Granstrom, M. L., Wilson, T. E., Wang, L. K., Water Resour. Bull., 10, (2), 283-294 (1974a). Wang, M. H., Granstrom, M. L., Wilson, T. E., Wang, L. K., J. Environ. Eng. Div., ASCE, 100 (EE3), 629-640 (1974b). Wilson, T. E., Ph.D. Thesis, Illinois Institute of Technology, Chicago, Ill., 1969. \
Receiued for reuiew July 11,1975 Accepted October 3, 1975 This research was partially supported by a Fellowship from Rensselaer Polytechnic Institute, Troy, N.Y.
