Determination of Aromatic Diamines and Other Compounds in Hair

25 Determination of Aromatic Diamines and Other Compounds in Hair Dyes Using Liquid Chromatography KENNETH JOHANSSON and WALTER LINDBERG Downloaded by NORTH CAROLINA STATE UNIV on January 7, 2013 | http://pubs.acs.org Publication Date: April 2, 1981 | doi: 10.1021/bk-1981-0149.ch025

Department of Analytical Chemistry, University ofUmeå,S-901 87 Umeå, Sweden CHRISTOFFER RAPPE and MARTIN NYGREN Department of Organic Chemistry, University of Umeå, S-901 87 Umeå, Sweden

The use of permanent hair dyes or the occupational exposure to these cosmetic products has recently been discussed because of a possible l i n k to adverse long term effects l i k e genetic effects or carcinogenic effects (1, 2, 3). Epidemiological studies seem to indicate an overrepresentation of lung and breast cancer among occupationally exposed people ( 3). Previously, 2,4-diaminotoluene (TDA), a very common product in hair dyes, has been proven to be an animal carcinogen after oral administration and subcutaneous injection (4). The hair dyes consist of quite complex mixtures of a variety of ingredients, and are usually sold as two-component systems. One component is an oxidation agent, usually hydrogen peroxide. The other component is a mixture of vegetable and animal fats, detergents and aromatics holding oxidizable amino- and hydroxyl groups, which produce coloured pigments on oxidation. From a toxicological point of view much interest has been focused on a number of aromatic diamines used in most permanent hair dyes. S e v e r a l methods have been used f o r the a n a l y s i s o f aromatic diamines, i n c l u d i n g t h i n - l a y e r chromatography (TLC) (5., 6_, χ, 8.), paper chromatography (£) and gas chromatography (GC) (7.). Diaminotoluene isomers have been separated by GC (10, 11,12). T h i n - l a y e r chromatography w i t h f l u o r o m e t r i c d e t e c t i o n has been reported as a s e n s i t i v e method f o r 2 , 6 - and 2,U-TDA i n urethane foams (13). Unger and Friedman (ik) were s u c c e s s f u l i n s e p a r a t i n g t h e 2 , 6 - and 2 , U TDA by adsorption chromatography on a s i l i c a column. The lengthy rééquilibrâtion and d i f f i c u l t i e s i n c o n t r o l l i n g the amount o f water i n the eluent are wellknown w i t h t h i s mode o f chromatography. Turchetto et al. (15.) had some success w i t h the separation o f v a r i o u s diamines employing p o l a r bonded phases and gradient e l u t i o n . From the p u b l i s h e d chromatograms i t i s seen t h a t one o f t h e i r systems showed very low e f f i c i e n c y . The n e c e s s i t y o f rééquilibrâting the column a f t e r each gradient run makes t h i s approach time-consuming. 0097-6156/81/0149-0401 $05.00/ 0 © 1981 American Chemical Society

In Chemical Hazards in the Workplace; Choudhary, G.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.

402

C H E M I C A L HAZARDS IN T H E W O R K P L A C E

Recently Choudhary ( l 6 ) has d e s c r i b e d a GC-method f o r t h e determination o f l,i+-diaminobenzene, 2,5~diaminotoluene and 2 , U diaminoanisole i n h a i r dyes a f t e r e t h y l acetate e x t r a c t i o n . In t h i s work we d e s c r i b e a method based on modern LC which avoids an e x t r a c t i o n step. This technique i s r a p i d and s e l e c t i v e and g i v e s , w i t h multiwavelength d e t e c t i o n , good q u a l i t a t i v e and quantitative information. The standard compounds considered t o be o f i n t e r e s t and/or l i k e l y t o be found were 2 k - , 2 , 5 - and 2,6-diaminotoluene, 2 , U d i a m i n o a n i s o l e , r e s o r c i n o l (l,3~dihydroxybenzene), hydroquinone (l,U-dihydroxybenzene) and a-naphthol. Downloaded by NORTH CAROLINA STATE UNIV on January 7, 2013 | http://pubs.acs.org Publication Date: April 2, 1981 | doi: 10.1021/bk-1981-0149.ch025

9

Experimental Reagents and Chemicals. Ethanol was o f spectrograde o r absol u t e q u a l i t y , 99-5 % Kemetyl AB, Sweden, hexanes and methylene c h l o r i d e were HPLC grade, F i s o n s , Loughborough, England. P o l y g o s i l 10 ym CN m o d i f i e d s i l i c a , pore diameter 60 Â, pore volume 0.75 ml/g, Batch 9031 and P o l y g o s i l 10 urn N0 s i l i c a , Batch 8121 was obtained from Machery-Nagel, Duren, German F e d e r a l R e p u b l i c . 2 , U Diaminoanisole, 98 % 2,6-diaminotoluene 97 % and 2,U-diaminot o l u e n e , 98-99 % were obtained from EGA-Chemie, German F e d e r a l R e p u b l i c , and 2,5-diaminotoluenesulphate, p r a c t . , F l u k a AG, S w i t z e r l a n d , a-naphthol, pro a n a l y s i ( p . a . ) , J.T. Baker, r e s o r c i n o l , p.a., Merck AG, hydroquinone, l a b . grade, Baker, acetone, p.a., Merck, and chloroform, p.a., Merck, were a l s o used. Samples o f h a i r dyes were k i n d l y s u p p l i e d by the h a i r d r e s s e r s school i n Umeâ, Sweden. These dyes were commercially a v a i l a b l e o n l y t o h a i r - d r e s sers and not d i r e c t l y t o the p u b l i c . 9

2

9

9

9

P r e p a r a t i o n s o f the Free Amine. Since 2,5-TDA was s u p p l i e d as t h e sulphate s a l t i t was necessary t o prepare the f r e e amine. This was done by d i s s o l v i n g the diamine s a l t i n sodium c h l o r i d e s a t u r a t e d d i s t i l l e d water a c i d i f i e d w i t h a few drops o f s u l p h u r i c a c i d . Methylene c h l o r i d e was added t o t h i s s o l u t i o n i n a separat i n g f u n n e l . Sodium hydroxide was added t o adjust the pH t o 10-11 to t r a n s f e r the amine t o the organic phase, the methylene c h l o r i d e now c o n t a i n i n g the diamine was washed once w i t h s a t u r a t e d sodium c h l o r i d e and then evaporated i n a r o t a t i n g evaporator. Red c r y s t a l s o f 2,5-TDA r e s u l t e d from the evaporation. The p u r i t y was checked chromatographically. Equipment. A LDC (Laboratory Data C o n t r o l ) Constametric I I I pump was used together w i t h a Rheodyne 7120 20 y l loop i n j e c t i o n v a l v e and two LDC Spectromonitor I I I , v a r i a b l e wavelength UVd e t e c t o r s . A Stanstead constant pressure pump was used f o r packing the columns. P r e p a r a t i o n o f the Columns. Columns were manufactured from 316 SS s t e e l tubes l / U " χ h mm diam. Swagelok 1/8" χ 1/k" 3 l 6 SS s t e e l reducers were m o d i f i e d t o zero dead volume and were used w i t h 2 urn A l l t e c h s t e e l f r i t s as column ends. One 250 χ k mm


25.

JOHANSSON E T A L .

Aromatic

Diamines

in Hair

Dyes

403

column was prepared w i t h P o l y g o s i l CN s i l i c a as f o l l o w s . A s l u r r y of 1.55 g s i l i c a i n 75 ml acetone was u l t r a s o n i f i e d f o r 3 min and r a p i d l y poured i n t o the s l u r r y c o n t a i n e r . The column was subse quently packed by p r e s s u r i z i n g t o 300 atm. About 300 ml hexanes was pumped through. One 195 x k mm column was packed w i t h P o l y g o s i l N0 s i l i c a by the same method except t h a t t h e s l u r r y medium was U0/60 acetone/ chloroform and the p r e s s u r i z i n g s o l v e n t was acetone. The e f f i c i e n c y o f both columns was t e s t e d by e l u t i n g 1 , 2 dinitrobenzene w i t h a k^ o f a t l e a s t 3. The same columns were used throughout t h i s i n v e s t i g a t i o n . The dead volume was determined by i n j e c t i n g pentane and measuring by the c r o s s i n g o f base l i n e . Hexanes/ethanol m i x t u r e s , used as t h e mobile phase, were prepared by weighing. The columns were run w i t h a f l o w r a t e o f 2 ml m i n . The CN-column had 8100 t h e o r e t i c a l p l a t e s and a peak skew o f l.k (back/front c a l c u l a t e d a t 10 % peak h e i g h t ) , the N0 -column had 27ΟΟ p l a t e s and peak skew 2.1. A l l measurements were made a t ambient temperature but the temperature v a r i a t i o n s i n t h e eluent b o t t l e were measured c o n t i nuously and were constant w i t h i n 3~h °C.

Downloaded by NORTH CAROLINA STATE UNIV on January 7, 2013 | http://pubs.acs.org Publication Date: April 2, 1981 | doi: 10.1021/bk-1981-0149.ch025

2

- 1

2

Procedure. A sample o f 0.5 - 1 g o f h a i r dye was added w i t h 50/50 v/v hexanes/ethanol u n t i l i t d i s s o l v e d , a c l e a r s o l u t i o n was obtained and no s o l i d s remained. I t was then d i l u t e d t o known volume. F i l t r a t i o n was made through a Fluoropore 0.2 ym f i l t e r w i t h a g l a s s syringe and a swinny f i l t e r adaptor. This was neces sary t o a v o i d c l o g g i n g o f the column i n l e t f r i t . A f t e r p r e p a r a t i o n , t h e samples as w e l l as t h e standards were t r a n s f e r r e d and kept i n brown b o t t l e s i n a r e f r i g e r a t o r . Analyses were c a r r i e d out on the same day as t h e p r e p a r a t i o n i n order t o a v o i d problems w i t h diamine o x i d a t i o n . R e s u l t s and D i s c u s s i o n The Chromatographic Systems. Bonded phases caused the break through o f modern l i q u i d chromatography as an a n a l y t i c a l method due t o t h e i r s t a b i l i t y , f a s t rééquilibrâtion and ease o f o p e r a t i o n . In the i n i t i a l p a r t o f the work presented i n t h i s paper two d i f f e rent p o l a r bonded phases w i t h CN and N0 groups r e s p e c t i v e l y were i n v e s t i g a t e d . The parent s i l i c a was i n both cases P o l y g o s i l 10 ym i r r e g u l a r p a r t i c l e s . Hexanes and e t h a n o l mixtures were chosen as the mobile phase due t o ready a v a i l a b i l i t y and low t o x i c i t y . F i g u res 1 and 2 show k^-values measured f o r t h e standard substances on the two columns. The N0 -column g i v e s more r e t e n t i o n than the CN-column f o r the same mobile phase composition. I t i s a l s o i n t e r e s t i n g t o note t h e d i f f e r e n c e s i n s e l e c t i v i t y ; i t can be seen t h a t N02-column cannot d i f f e r e n t i a t e between t h e 1,3- and 1,U-0H p o s i t i o n s i n r e s o r c i n o l and hydroquinone. On both columns t h e r e i s s u f f i c i e n t s e l e c t i v i t y t o separate t h e 2,U-TDA from t h e 2,U-DAA. 2

2


404

IN

THE

WORKPLACE


C H E M I C A L HAZARDS

Figure 2.


25.

JOHANSSON

ET AL.

Aromatic

Diamines

in Hair Dyes

405


For the f u r t h e r work the CN-column was chosen w i t h a mobile phase composition o f 86.Î+/13.6 w/w % hexanes/ethanol, since t h i s system could r e s o l v e a l l the standards without g i v i n g excessive r e t e n t i o n times. Figure 3 shows the separation o f the standard substances. More t a i l i n g i s noted f o r the 2,5~TDA than w i t h the column t e s t procedure d e s c r i b e d e a r l i e r and i t i s l i k e l y t h a t the chemical matching column vs eluent composition and sample can be improved. The p r o p e r t i e s of p o l a r bonded phases have not yet been f u l l y i n v e s t i g a t e d and are beyond the aim of t h i s study, but work i s i n progress i n t h i s l a b o r a t o r y which i n c l u d e s a more extensive i n v e s t i g a t i o n on the chromatography o f diamines (17). Detection and L i n e a r i t y . Since the UV-detector measures 3c/9t, q u a n t i t a t i o n by use o f peak height measurements puts l e s s s t r i n g e n t demands on the constancy o f the flow r a t e . A fundamental requirement f o r adequate e v a l u a t i o n o f data i s t h a t the chromatography i s l i n e a r . I n v e s t i g a t i o n o f the UV-spectra o f the eluent and standards revealed t h a t a wavelength o f 235 nm should be the best compromise w i t h respect t o s e n s i t i v i t y and s t a b i l i t y (noise l e v e l ) . Moreover, the s e n s i t i v i t y can be i n c r e a s e d by u s i n g a wavelength i n the lower UV-range. However, one should be aware o f the f a c t , t h a t when measuring on an edge of the UV-spectrum the broad s p e c t r a l bandpass o f these instruments might cause d e v i a t i o n s from l i n e a r i t y already at low absorbance values. Figure k shows c a l i b r a t i o n curves measured as the peak absorbance at 235 nm. This shows good l i n e a r i t y and h i g h s e n s i t i v i t y f o r a l l substances. The d e t e c t i o n l i m i t i s w e l l below 10 ng f o r a l l substances and thus competes favourably w i t h flame i o n i z a t i o n d e t e c t o r - GC. The r e t e n t i o n times were a l s o measured at a l l conc e n t r a t i o n s since i t was suspected, due t o the apparent t a i l i n g , t h a t the chromatography might be n o n - l i n e a r . This d i d not prove t o be so. Peak I d e n t i t y Confirmation by Measurement of Absorbance R a t i o s . I t i s known t h a t peak absorbance r a t i o measurements provide an a l t e r n a t i v e method o f peak i d e n t i t y c o n f i r m a t i o n t o r u n n i n g the sample on two d i f f e r e n t columns, f r a c t i o n c o l l e c t i o n f o r MS and so on. I f Beer's law i s obeyed A = c · 1 · ε e

χ

e

one can o b t a i n \ / \ by measuring the peak height at two wave lengths and c a l c u l a t i n g the (peak height A.u. ^ / ( p e a k height A.u.)x "ti°« This should be constant f o r a c e r t a i n molecule i n a c e r t a i n s o l v e n t . As v a r i a b l e wavelength d e t e c t o r s f o r LC have l a r g e s p e c t r a l bandwidths one cannot determine t r u e ^ - v a l u e s . This means t h a t the absorbance r a t i o measured w i l l be s p e c i f i c f o r the bandwidth o f the d e t e c t o r used. When u s i n g one v a r i a b l e d e t e c t o r and performing successive l

2

ra

2

e


CHEMICAL

406

HAZARDS

IN

THE

WORKPLACE

X »235 nm 6

Figure 3. Separation of 1, a-naphthol; 2, resorcinol; 3, hydroquinone; 4, 2,6-diaminotoluene; 5, 2,4-diaminotoluene; 6, 2,4-diaminoanisole; and 7, 2,5-diaminotoluene. Mobile phase, 86.4/13.6 w/w % hexanes/ethanol; linear How velocity, 2.66 mm s' ; pressure drop, 380 ρsi; λ = 235 nm; column, 250 χ 4 mm Polygosil 10 μ/nCN.

7


1

0

4

8

ml

12


16

20

25.

JOHANSSON E T A L .

Diamines

in Hair Dyes

407

runs a t d i f f e r e n t wavelengths, the r e p r o d u c i b i l i t y o f the wavel e n g t h s e t t i n g w i l l prove t o be e s s e n t i a l . To overcome t h i s source of e r r o r we used two LDC Spectromonitor I I I d e t e c t o r s coupled i n s e r i e s t o o b t a i n two chromâtograms a t the same time on a twochannel r e c o r d e r . According t o the manufacturer, the s p e c i a l bandwidth o f t h i s d e t e c t o r i s 8 nm and the f l o w c e l l o f 10 y l volume. N e g l i g i b l e e x t r a bandbroadening was caused by the e x t r a d e t e c t o r due t o the l a r g e volume h a l f - w i d t h o f the e l u t i n g peaks. A l l the diamines have a UV-maximum i n the 290-310 nm r e g i o n and t h e r e f o r e 290 nm was the second d e t e c t i o n wavelength chosen. The r a t i o s 2 3 5 / 2 9 ο were c a l c u l a t e d f o r each standard substance and these values are found i n Table I . The v a r i a t i o n o f the absor bance r a t i o w i t h c o n c e n t r a t i o n i s a l s o i n c l u d e d i n the standard d e v i a t i o n shown i n the t a b l e . ε


Aromatic

ε

TABLE I . Peak Height Absorbance R a t i o s

ε

Substance 2,6-diaminotoluene 2,5-diaminotoluene 2,h-diaminotoluene 2,U-diaminoanisole Resorcinol Hydroquinone a-Naphthol

/ε 290

S.d.

η

6.39 6.ία

0.010 0.039

k.Ol k.3k

O.OkQ

1U 8 1U 11 1U 11* lU

235

2.37 0.88 7.3

0.028 0.037 0.022 0.31

When running the samples i t was considered t h a t i f absor bance r a t i o s and r e t e n t i o n volumes c o i n c i d e as s t a t i s t i c a l l y t e s t e d ( t - t e s t ) , the p r o b a b i l i t y o f p o s i t i v e i d e n t i f i c a t i o n i s high. I f r e t e n t i o n volumes c o i n c i d e but absorbance r a t i o s do n o t , t h i s i n d i c a t e s e i t h e r t h a t the peak i s not pure o r t h a t i t o r i g i n a t e s from a d i f f e r e n t substance. I t i s the o p i n i o n o f the authors t h a t a more e x t e n s i v e i n v e s t i g a t i o n o f multiwavelength d e t e c t i o n i n LC i s d e s i r a b l e . M a n i p u l a t i n g the d e t e c t i o n wavelength can provide a means o f changing the r e s o l u t i o n o f the chromâtogram when necessary i n s t e a d o f i n c r e a s i n g o r t r y i n g t o f i n d proper selectivity. A n a l y t i c a l R e s u l t s . F i g u r e s 5 and 6 show the chromât ο grams obtained from samples ( i ) and (IV) as measured at 235 nm. The f l o w r a t e was 2 ml min"" which means t h a t one run takes about 10 minutes. With the chromatographic system employed, nonpolar f a t s and detergents present i n the dyes can be expected t o have l i t t l e o r no r e t e n t i o n and t h e r e f o r e should e l u t e w i t h the solvent f r o n t . Peak 1 i n F i g u r e 6 might p a r t l y c o n s i s t o f such substances. Most 1


CHEMICAL


408

Figure 5. Chromatogram of hair dye I: mobile phase, 86.4/13.6 w/w % hex anes/ethanol; flow rate, 2 mL min (2.66 mm s' ); pressure drop, 380 psi; λ = 235 nm; column, 250 χ 4 mm Polygosil 10 prnCN.

HAZARDS IN T H E

WORKPLACE

1

1

r.0.02

r«0X)5 8

12

16

ml

X=235nm

Figure 6. Chromatogram of air dye IV: same chromatographic conditions as in r=Q02 Figure 5. Peaks: 1, unknowns eluting with solvent front; 2, resorcinol; 3, un 0 known; 4, 2,5-diaminotoluene.

r»Q01 4

r=0.1 8

12

16

ml


20


k

0.000U8 0.0008 0.00057

0.0098 0.0330 0.0195 0.0536 0.00258 O.O7O

resorcinol 2,5-TDA resorcinol 2,5-TDA resorcinol 2,5-TDA

dark ash blonde

l i g h t brown

mahogany

bordeaux r e d

black

medium brown

II

III

IV

V

VI

VII

0.0UU0 0.0155 0.0095

recorcinol 2,5-TDA 2,5-TDA

a-naphthol (?)

3

0.000U2

0.018U

0.000U7

0.0011

0.0016

0.0010

0.0000U2

3

3

5

k

3

3

3

3

3

2,5-TDA

0.000068

0.00727

resorcinol

η

medium matt blonde

S t d . dev.

I

A.u. peak height λ = 235

Substance found

Colour developi n g according t o manufacturer

H a i r dye analysed

TABLE I I . A n a l y t i c a l R e s u l t s


0.63

0.98

3.52

Ο.56

0.05

Ο.65

0.33

0.U0

1.66

1.17

0.50

Substance w/w % i n h a i r dye


410

C H E M I C A L HAZARDS IN

THE

WORKPLACE

f a t s and detergents have l i t t l e or no UV-absorbance at t h i s wavel e n g t h and are thus not detected. In Figure 5 the chromatogram i s r a t h e r clean i n the solvent f r o n t and t h i s might be e x p l a i n e d as above. In both dyes ( i ) and (IV) r e s o r c i n o l and 2,5- IDA c o u l d be i d e n t i f i e d , and these e l u t e as peaks 2 and k i n both chromâtοgrams. Peak 3 i n both F i g u r e 5 and Figure 6 i s the same substance s i n c e a b s o r p t i o n r a t i o s and r e t e n t i o n volumes c o i n c i d e . The unknown peak 1 i n Figure 5 i s not found i n dye (IV) but i t was found i n seve r a l other dyes. Table I I shows the substances i d e n t i f i e d and amounts d e t e r mined i n the v a r i o u s dye samples. R e s o r c i n o l and 2,5-TDA were found i n most samples. The i d e n t i f i c a t i o n of α-naphthol i n sample (V) i s somewhat u n c e r t a i n since i t was found t h a t the absorbance r a t i o s were not independent o f the c o n c e n t r a t i o n f o r t h i s sub stance. In g e n e r a l , few peaks could be seen on chromatographing a l l the samples and the same simple p a t t e r n showed up w i t h s e v e r a l dyes. As regards the q u a n t i t a t i v e determination i t remains t o be i n v e s t i g a t e d to what extent inhomogeneity i n the sample tubes i n fluences the r e s u l t . Batch t o batch v a r i a t i o n s from the manufac t u r e may a l s o occur. Conclusions A simple and r a p i d method f o r the a n a l y s i s o f h a i r dyes has been developed. Owing t o low wavelength UV-detection high s e n s i t i v i t y i s achieved w i t h d e t e c t i o n l i m i t s w e l l below 10 ng and at the same time f a t s and detergents i n the dyes do not i n t e r f e r e w i t h the d e t e c t i o n . The simple d i s s o l u t i o n procedure p o s s i b l e together w i t h the chromatographic system used i s an advantage i n comparison w i t h lengthy and u n c e r t a i n e x t r a c t i o n s . I d e n t i f i c a t i o n i s c o n s i d e r a b l y improved by the use o f m u l t i wavelength d e t e c t i o n and absorbance r a t i o i n g . I t was p o s s i b l e t o analyse some commercial h a i r dyes w i t h the method d e s c r i b e d here. However, s e v e r a l substances were found t h a t c o u l d not be i d e n t i f i e d w i t h the present standard substances. Recent r e s u l t s i n t h i s l a b o r a t o r y make a p o s s i b l e improvement o f the chromatography pro bable. Future work w i l l consider t h i s aspect and an increased number o f standard substances (17) w i l l be examined. Acknowledgment s This work was

supported by the Swedish Work Environment Fund.


25.

JOHANSSON E T A L .

Aromatic

Diamines

in Hair

Dyes

411

Literature Cited 1. 2.


3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

Ames, N.B.; Kammen, H.O.; Yamasaki, E. Proc. Nat. Acad. S c i . U . S . , 1975, 72, 2423. NIOSH - Current Intelligence Bulletin 19 US Department of Health Education and Welfare Public Health Service. Rockville MD, January, 1978. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man, Vol. 16, IARC, Lyon, 1977; p. 25. I b i d . , p. 83. Kotteman, C. J. Assoc. Offic. Anal. Chem., 1966, 49, 954. Macke, G.F. J. Chromatogr., 1968, 36, 537. Glinsukon, T . ; Benjamin, T . ; Grantham, P . ; Weisburger, E.; Roller, P. Xenobiotica, 1975, 5, 475. Glinsukon, T . ; Benjamin, T . ; Grantham, P . ; Lewis, N . ; Weisburger, E. Biochem. Pharmacol., 1976, 25., 95. Waring, R . H . ; Pheasant, A . E . Xenobiotica, 1976, 6, 257. Boufford, C.E. J. Gas Chromatogr., 1968, 6, 438. Brydia, L.E.; Willeboordse, F. Anal. Chem., 1968, 40, 110. Willeboordse, F . ; Quick, Q.; Bishop, E . T . Anal. Chem., 1968, 40, 1455. Guthrie, J.L.; McKinney, R.W. Anal. Chem., 1977, 49, 1676. Unger, P.D.; Friedman, N.A. J . Chromatogr., 1979, 174, 379. Turchetto, L.; Cuozzo, V . ; Terracciano, M . ; Papetti, P . ; Percaccio, G . ; Quercia, V. Boll.Chim.Farm., 1978, 117, 475. Choudhary, G. J. Chromatogr., 1980, 193, 277. Johansson, K . ; Lindberg, W. to be published.

RECEIVED November 18,

1980.


Determination of Aromatic Diamines and Other Compounds in Hair

Recommend Documents