determination of cationic surfactant in the presence of alcohol sulfate surfactant using orange ii...

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Short Communicatio, Determination of Cationic Surfactant in the Presence of Alcohol Sulfate Surfactant Using Orange II Dye During washing and conditioning treatments, both anionic and cationic surfactants may come in contact with human hair or textile fibers and attach to their surfaces. To study these interactions, an analytical procedure was required for the determination of cationic surfactant in the presence of fatty alcohol sulfate. A colorimetric met/hod, described by Few and 0ttewill (1) and recently modified by Scott (2), for the determination of cationic surfactants was selected for a study of the conditions which would make the method applicable to this problem of mixed surfactant analysis. The apparatus and reagents used in this study have been described previously (2). The recommended procedure is as follows: Weighed aliquots (0.1-0.6 g) of quaternary solution (approximately 2.4 mg quaternary/g) with an equivalent or less of sodium lauryl sulfate (SLS), are refluxed with 10 ml 4N HC1 for 1]fi2 hr. After the reaction mixture cools to room temperature, the pH is adjusted to 8.0 with 0.SN sodium hydroxide. The mixture is transferred to a 125 ml extraction cylinder, diluted to 100 ml volmne with deionized water and the remainder of the analysis performed as described by Scott (2). Tables I through IV summarize the results of the Orange II analysis of the two quaternaries dode- cy]trimethylammonium bromide (DTAB) and hexa- decyltrimethylammonium bromide (CTAB). Analyses were performed in the absence and in tile presence of SLS at different ratios of sulfate to quaternary. Analysis for quaternary in the presence of SLS is accomplished by acid hydrolysis of the alcohol sulfate, a technique which has been described previously to prevent fatty alcohol sulfate interference in mixed surfactant determinations (3). The data. show no significant differences between the ratios of quater- nary-absorbance in the absence of SLS and in the presence of SLS when hydrolysis is employed. From these data, assuming a 1:1 stoichiometry between alcohol sulfate and cationic, one may calculate the amount of alcohol sulfate. In sample 1, Table I, the amount of SLS is 0.59 ~moles by calculation and 0.71 ~,~moles by measurement. Thus, the agreement between calculated and measured values for cationic determination in the presence of SLS by this scheme is good; however, the method provides only for a rough estimation of fatty alcohol sulfate surfactant. In addition to hydrolysis, manipulations which are required to prevent SLS interference in this deter- mination include pH adjustment to neutralize excess acid, and dilution to a salt (sodimu chloride) con- centration of less than 0.5 M to avoid salting out of uncombined Orange II to the chloroform phase. Pre- sumably, fatty amines or amine oxides which are stable to acid hydrolysis, and capable of forming water-insoluble chloroform-soluble adducts with Orange II can be analyzed in the presence of alcohol sulfate surfactant by controlling the extraction pH (2) in this procedure. The technique as described should make the Orange II method a useful tool for studying the interactions of anionic and cationic surfaetants in solution. One TABLE I Analysis of DTAB in the Presence of SLS ~fg ])TAB Sample Absorbance ]~ig l~1olarSLS No. (DTAB) Absorbance Ratio ])TAB units 1 0,429 0.502 1,17 a 0.44 2 0,356 0.265 0.744 b 0.80 3 1.25 0.935 0.746 b 0.23 4 0.675 0.503 0,745 b 0.42 5 0,706 0.526 0.745b 0.40 a No hydrolysis was employed. b Hydrolysis was employed. The mean ratio of mg quaternary/A -~ x for samples 2-5 is 0.745. TABLE II Analysis of DTAB in ~e Absence of SLS ~gDTAB Sample Absorbance l~g (DTAB) No. Ahsorbancc units a 1 0.323 0.242 0.749 2 0,650 0.485 0,746 3 0,971 0,719 0.741 4 1,29 0.961 0.744 5 1.61 1.21 0,747 a NO hydrolysis was employed in the analysis of these samples which provided a ratio for x of 0.745. TABLE III Analysis of CTAB in the Presence of SLS I~igCTAB a ~olar SLS Sample Absorbance lV[g No. (CTAB ) Absvrbance ratioCTAB units 1 0.271 0.237 0.875 1.05 2 0.548 0.481 0.878 0.52 3 1.18 1.04 0.878 0,24 a Hydrolysis was employed in these determinations. ratio x for these samples is 0,877. TABLE IV Analysis of CTAB in the Absence of SLS The mean Sample Ahsorbance ~*1g (CTAB) No. Mg CTAB a Absorbance units 1 0.213 0.188 0.884 2 0.274 0.243 0.885 3 0,376 0.331 0.882 4 0.430 0.373 0.868 5 0.567 0.494 0.871 a No hydrolysis was employed in these analyses which provided a ratio for x of 0.878. instance of usefulness is demonstrated in a study of the interaction of these two surfactant types in the presence of keratin fibers (4). CLARENCE ROBBINS GEORGE V. SCOTT Colgate-Palmolive Research Center, Piscataway, New Jersey 08854 REFERENCES i. Few, A. V., and R. H. 0ttewill, Colloid Science 1I, 34 (1956). 2. Scott, G. V., Anal. Chem. 40, 768 (1968). 3. Schwartz, A., J, Perry and T. Berch, "Surface Active Agents and Detergents," Yol. 2, Interseience, New York, 1958, p. 348. 4. Robbins, C., G. V. Scott and ft. D. Barnhurst, Text. Res. J. 88, 1197-1199 (1968). [Received November 18, 1968] 272

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• Short Communicatio,

Determination of Cationic Surfactant in the Presence of Alcohol Sulfate Surfactant Using Orange II Dye D u r i n g wash ing and cond i t ion ing t rea tments , both

anionic a n d cat ionic su r f ac t an t s may come in contact wi th h u m a n ha i r or texti le fibers a n d a t t ach to the i r surfaces. To s t udy these in terac t ions , an ana ly t i ca l procedure was requ i red for the de t e rmina t i on of cat ionic s u r f a c t a n t i n the presence of f a t t y alcohol sulfate . A colorimetr ic met/hod, described by F e w a n d 0 t t ewi l l (1) a n d recen t ly modified by Scott (2) , for the de t e rmina t i on of cat ionic su r f ac t an t s was selected for a s tudy of the condi t ions which would make the method appl icable to this p roblem of mixed s u r f a c t a n t analysis .

The a p p a r a t u s and reagents used in this s t u d y have been described prev ious ly (2) . The recommended procedure is as follows: Weighed al iquots (0.1-0.6 g) of q u a t e r n a r y solut ion ( app rox ima te ly 2.4 mg q u a t e r n a r y / g ) with an equ iva len t or less of sodium l a u r y l sul fa te (SLS) , are refluxed wi th 10 ml 4N HC1 for 1]fi2 hr. A f t e r the react ion mix tu r e cools to room tempera tu re , the p H is ad jus t ed to 8.0 wi th 0.SN sodium hydroxide. The m i x t u r e is t r an s f e r r e d to a 125 ml ex t rac t ion cyl inder , d i lu ted to 100 ml volmne wi th deionized water a n d the r ema inde r of the analys is pe r fo rmed as described by Scott (2) .

Tables I t h rough IV summar ize the resul ts of the Orange I I ana lys is of the two qua te rna r i e s dode- c y ] t r i m e t h y l a m m o n i u m bromide ( D T A B ) and hexa- d e c y l t r i m e t h y l a m m o n i u m bromide ( C T A B ) . Analyses were pe r fo rmed in the absence a n d in tile presence of SLS a t d i f ferent rat ios of sul fa te to qua t e r na r y . Ana lys i s for q u a t e r n a r y in the presence of SLS is accomplished by acid hydrolys is of the alcohol sulfate, a t echnique which has been described prev ious ly to p reven t f a t t y alcohol su l fa te in te r fe rence in mixed s u r f a c t a n t de t e rmina t ions (3) . The data. show no s ignif icant differences between the rat ios of quater - na ry -absorbance in the absence of SLS a n d in the presence of SLS when hydro lys i s is employed. F r o m these data , a s suming a 1:1 s to ichiometry between alcohol su l fa te and cationic, one m a y calculate the a m o u n t of alcohol sulfate. I n sample 1, Table I, the a m o u n t of SLS is 0.59 ~moles by ca lcula t ion and 0.71 ~,~moles by measurement . Thus, the agreement between calcula ted and measured values for cationic de t e rmina t i on in the presence of SLS by this scheme is good; however, the method provides on ly for a rough es t imat ion of f a t t y alcohol su l fa te su r fac tan t .

I n add i t ion to hydrolysis , m a n i p u l a t i o n s which are requi red to p reven t SLS in te r fe rence in this deter- m i n a t i o n inc lude p H a d j u s t m e n t to neu t ra l i ze excess acid, a n d d i l u t i on to a sal t ( sodimu chloride) con- cen t ra t ion of less t h a n 0.5 M to avoid sa l t ing out of u n c o m b i n e d Orange I I to the chloroform phase. Pre- sumably , f a t t y amines or amine oxides which are stable to acid hydrolysis , and capable of f o r mi ng water - insoluble chloroform-soluble adduc t s wi th Orange I I can be analyzed in the presence of alcohol su l fa te s u r f a c t a n t by con t ro l l ing the ex t rac t ion p H (2) in this procedure.

The techn ique as described should make the Orange I I method a usefu l tool for s t u d y i n g the in te rac t ions of an ionic a n d cat ionic su r f ae t an t s in solution. One

TABLE I Analysis of DTAB in the Presence of SLS

~fg ])TAB Sample Absorbance ]~ig l~1olar SLS

No. (DTAB) Absorbance Ratio ])TAB units

1 0,429 0.502 1,17 a 0.44 2 0,356 0.265 0.744 b 0.80 3 1.25 0.935 0.746 b 0.23 4 0.675 0.503 0,745 b 0.42 5 0,706 0.526 0.745 b 0.40

a No hydrolysis was employed. b Hydrolysis was employed. The mean ratio of mg quaternary/A -~

x for samples 2-5 is 0.745.

TABLE II Analysis of DTAB in ~e Absence of SLS

~gDTAB Sample Absorbance l~g (DTAB) No. Ahsorbancc

units a

1 0.323 0.242 0.749 2 0,650 0.485 0,746 3 0,971 0,719 0.741 4 1,29 0.961 0.744 5 1.61 1.21 0,747

a NO hydrolysis was employed in the analysis of these samples which provided a ratio for x of 0.745.

TABLE III Analysis of CTAB in the Presence of SLS

I~ig CTAB a ~olar SLS Sample Absorbance lV[g No. ( CTAB ) Absvrbance ratio CTAB

units 1 0.271 0.237 0.875 1.05 2 0.548 0.481 0.878 0.52 3 1.18 1.04 0.878 0,24

a Hydrolysis was employed in these determinations. ratio x for these samples is 0,877.

TABLE IV Analysis of CTAB in the Absence of SLS

The mean

Sample Ahsorbance ~*1g (CTAB) No.

Mg CTAB a

Absorbance units

1 0.213 0.188 0.884 2 0.274 0.243 0.885 3 0,376 0.331 0.882 4 0.430 0.373 0.868 5 0.567 0.494 0.871

a No hydrolysis was employed in these analyses which provided a ratio for x of 0.878.

ins tance of usefu lness is demons t ra t ed in a s t u d y of the in t e rac t ion of these two s u r f a c t a n t types in the presence of k e r a t i n fibers (4).

CLARENCE ROBBINS GEORGE V. SCOTT Colgate-Palmol ive Research Center , P isca taway, New Jersey 08854

REFERENCES i. Few, A. V., and R. H. 0ttewill, Colloid Science 1I, 34 (1956). 2. Scott, G. V., Anal. Chem. 40, 768 (1968). 3. Schwartz, A., J, Perry and T. Berch, "Surface Active Agents

and Detergents," Yol. 2, Interseience, New York, 1958, p. 348. 4. Robbins, C., G. V. Scott and ft. D. Barnhurst, Text. Res. J. 88,

1197-1199 (1968).

[Received November 18, 1968]

272