Analytical Techniques in Occupational Health ... - ACS Publications

6 Analysis of Aromatic Amines by High Performance Liquid Chromatography JOHN O. FROHLIGER, KARROLL S. BOOTH , and NANCY KOTSKO 1

Downloaded by UNIV OF ARIZONA on January 13, 2013 | http://pubs.acs.org Publication Date: April 22, 1980 | doi: 10.1021/bk-1980-0120.ch006

Department of Industrial Environmental Health Sciences, Graduate School of Public Health, University of Pittsburgh, PA 15261 Aromatic amines are used in the manufacture of rubber chemicals, drugs, dyes, isocyanates, and many other miscellaneous chemical products. The toxicity of aromatic amines has been known and studied for many years.(1) They all penetrate the skin and all produce methemoglobinemia.(2) Recently, the Occupational Safety and Health Administration (OSHA) established exposure limits for 14 human carcinogens, several of which are aromatic amines.(3) There is a need for Industrial Hygienists to measure concentrations of aromatic amines in the working environment. Most Industrial Hygienists prefer to use impingers containing water or a weak acid as the absorber solution since they are readily available, are not flammable, and are less likely to evaporate in comparison to organic solvents. The collection of amines in aqueous acid solutions suggests that a ion exchange chromatographic method of analysis would reduce the need for extensive sample preparation. The liquid chromatograph used in this study consisted of a Cheminert Model CMP-2K (Laboratory Data Control, Riviera Beach, Fl.) which is capable of a maximum flow rate of 2 ml/min at a maximum pressure of 500 PSI. This pump has all liquid contact parts limited to glass, teflon or KEL-F materials to reduce corrosion to a minimum. The injection valve is a Laboratory Data Control Model SU 8031 slider valve with a 0.5 ml sample loop. The injection valve is located at the top of the column to minimize dead volume. The separating column is a Laboratory Data Control type MB glass column, 30 cm long with a 2 mm bore capable of a maximum pressure of 500 PSI. The column is packed with surface sulfonated cation exchanger resin prepared in this laboratory in the following manner. Concentrated sulfuric acid is heated to 100°C on a water bath. Styrene-Divinyl Benzene-2x (Dow Chemical Company, Midland, MI) 200-400 mesh is added to the acid so that the final mixture is 1 yg copolymer per ml of acid. The mixture was maintained at 100°C and stirred with a glass stirring rod for 15 minutes. The 1

C u r r e n t Address:

Mobay Chemical Corporation, Pgh, PA 15205 0-8412-0539-6/80/47-120-115$05.00/0 © 1980 American Chemical Society

In Analytical Techniques in Occupational Health Chemistry; Dollberg, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.


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OCCUPATIONAL H E A L T H CHEMISTRY

r e a c t i o n was q u e n c h e d by p o u r i n g t h e m i x t u r e i n t o 500 ml o f w a t e r f o r e a c h 10 ml o f a c i d . The m a t e r i a l was a l l o w e d t o s e t t l e f o r 20 m i n u t e s and t h e f i n e s d e c a n t e d o f f . The r e s i n was washed and d e c a n t e d t h r e e t i m e s t o remove t h e e x c e s s a c i d and t h e f i n e s . The r e s i n was f i l t e r e d t h r o u g h a B u c h n e r f u n n e l and a i r d r i e d . The r e s i n w i l l have a c a p a c i t y o f 0.03 meq/gm. The r e s i n i s s l u r r y p a c k e d o n t o t h e c o l u m n . T h e s e c o l u m n s u s u a l l y have a back p r e s s u r e o f 200-300 PSI w h i c h i s w e l l w i t h i n t h e r a n g e o f t h e s y s t e m . The o u t l e t o f t h e c o l u m n i s c o n n e c t e d t o a W a t e r s A s s o c i a t e s , Model 440 U.V. D e t e c t o r ( W a t e r s A s s o c i a t e s , M i l f o r d , MA). The w a v e l e n g t h o f t h e d e t e c t o r i s 254 nm. The o u t p u t o f t h e d e t e c t o r i s o b t a i n e d on a 10 m.v. s t r i p c h a r t r e c o r d e r . The c h r o m a t o g r a p h i c s y s t e m i s shown i n F i g u r e 1. A c i d e l u e n t s serve a dual f u n c t i o n . F i r s t , the a c i d w i l l p r o t o n a t e t h e amine so t h a t t h e amine w i l l i n t e r a c t w i t h t h e r e s i n and t h e h y d r o g e n i o n w i l l s e r v e as t h e e x c h a n g e i o n i n t h e c h r o m a t o g r a p h i c p r o c e s s . The e l u e n t s u i t a b l e f o r t h e s e p a r a t i o n o f a r o m a t i c a m i n e s i s an a q u e o u s p e r c h l o r i c a c i d s o l u t i o n . O t h e r m i n e r a l a c i d s c a n a l s o be u s e d b u t may f o r m c o m p l e x e s w i t h m e t a l s i n t h e s a m p l e o r t h e c h r o m a t o g r a p h o r o x i d i z e components o f t h e sample. ~ E a c h amine was d i s s o l v e d i n d i l u t e ( 1 x 1 0 " M HC1). The w o r k i n g s o l u t i o n u s e d i n t h i s s t u d y was 50 ug/ml amine. T h i s i s high c o n c e n t r a t i o n f o r the d e t e c t o r but a s s i s t s i n d e t e r m i n i n g t h e e f f e c t o f e l u e n t c o n c e n t r a t i o n on r e t e n t i o n t i m e . The w o r k i n g s o l u t i o n s were p r o t e c t e d f r o m t h e l i g h t and f r e s h s o l u t i o n s were p r e p a r e d w e e k l y . A s e r i e s o f p e r c h l o r i c a c i d s o l u t i o n s were p r e p a r e d as t h e e l u e n t . Each e l u e n t was f l u s h e d t h r o u g h t h e c h r o m a t o g r a p h u n t i l a s t a b l e b a s e l i n e was o b t a i n e d . E a c h i n d i v i d u a l amine was i n j e c t e d o n t o t h e c o l u m n u s i n g t h e 0.5 ml s a m p l e l o o p . The a m i n e was a l l o w e d t o e l u t e i f p o s s i b l e . I f a f t e r s i x t y m i n u t e s t h e amine had n o t e l u t e d , t h e s y s t e m was f l u s h e d w i t h 1 Μ H C 1 0 t o remove t h e compound. The o r d e r o f e l u t i o n o f t h e a m i n e and t h e e f f e c t o f e l u e n t c o n c e n t r a t i o n on t h e r e t e n t i o n t i m e were d e t e r m i n e d . The r e t e n t i o n v o l u m e was p l o t t e d a g a i n s t t h e e l u e n t c o n c e n t r a t i o n s t o d e t e r m i n e t h e optimum c o n c e n t r a t i o n o f e l u e n t t o o b t a i n the desired separation. Figure 2 i s the p l o t of the r e t e n t i o n volumes o f f o u r amines v e r s u s e l u e n t c o n c e n t r a t i o n s . The g r a p h shows t h a t 2 - m e t h y l a n i l i n e c a n n o t be s e p a r a t e d f r o m 3 - m e t h y l a n i l i n e and t h a t a n i l i n e can be s e p a r a t e d f r o m t h e m e t h y l a n i l i n e i s o m e r s u s i n g an e l u e n t c o n c e n t r a t i o n o f 5 χ 1 0 ~ [ H ] . The s e p a r a t i o n o f 2 - n a p h t h y l a m i n e f r o m 1 - n a p h t h y l amine can be c a r r i e d o u t a t 8 χ 1 0 ~ [ H ] i n l e s s t h a n 20 m i n u t e s . The s e p a r a t i o n o f a n i l i n e and 2 - m e t h y l a n i l i n e u s i n g 5 χ 1 0 ~ [H ] i s shown i n F i g u r e 3. The c o n c e n t r a t i o n o f a n i l i n e i s 5 ppm w h i l e t h e 2 - m e t h y l a n i l i n e i s 10 ppm F i g u r e 4 shows t h e s e p a r a t i o n o f 1 and 2 - n a p h t h y l a m i n e s u s i n g 8 χ 1 0 ~ [ H ] . The 1 - n a p h t h y l a m i n e i s 5 ppm w h i l e t h e 2 - n a p h t h y l a m i n e i s 10 ppm. 4

3

+

3

+

3

d

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6.

Analysis of Aromatic

FROHLiGER E T A L .

PRESSURE GAUGE

117

Amines

— Q

I

SAMPLE I S E C T I O N V A L V E

S E P A R A T I N G COLUMN


To

ΰ

_

RESERVOIR

«1

S

PUMP

Figure 1.

45.0

WASTE

U.V. DETECTOR

RECORDER

Schematic of the liquid chromatograph

r

E L U E N T CONCENTRATION, ft

Figure 2. Effect of low eluent concentration on retention volumes: (X) aniline, (O) 2-methylaniline, 3-methylaniline, (A) 1-naphthylamine, (Φ) 2-naphthyl amine.




118

I N T E N T I O N VOLUME, M L

Figure 3. Liquid chromatogram of aniline and 2-methylaniline: flow rate, 90 mL/hr; eluent, 0.005M HCIO^; (a) 5 ppm aniline, (b) 10 ppm 2-methylaniline.

Β

J

0

1

3

1 6

I

I

9

]2

RETENTION

I

I

15

18

L

21

VOLUME, ML

Figure 4. Liquid chromatogram of 1-naphthylamine and 2-naphthylamine: flow rate, 90 mL/hr; eluent, 0.080M Η CIO 4; (a) impurity, (b) 10 ppm 1-naphthylamine, (c)5 ppm 2-naphthylamine.


6.

FHOHLiGER ET AL.

Analysis

of Aromatic

119

Amines


37.5h

ELUENT CONCENTRATION, fl Figure 5. Effect of high eluent concentration on retention volumes: (X) 2,4 diaminotoluene, (O) 4 4 diaminodiphenylmethane, ( Q ) 4,4' diaminodiphenylether, (A) 2-aminofluorene. y

f

Β

-j Ο

ι 12

1 24

ΐ36

I N T E N T I O N VOLUME, M L

Figure 6. Liquid chromatogram of 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenylether: flow rate, 90 mL/hr; eluent, 0.25M HCIO4, (a) impurity, (b) 4,4' diaminodiphenylmethane, (c) 4,4' diaminodiphenylether.



120

A n o t h e r g r o u p o f a m i n e s c a n be e l u t e d i n a r e a s o n a b l e t i m e u s i n g h i g h e r c o n c e n t r a t i o n s o f e l u e n t . The e f f e c t o f e l u e n t c o n c e n t r a t i o n on r e t e n t i o n v o l u m e i s shown i n F i g u r e 5. E x c e p t f o r t h e 2 - a m i n o f l u o r e n e , t h e s e compounds a r e a l l d i a m i n e s . The r e t e n t i o n v o l u m e s o f 4 , 4 ' - D i a m i n o d i p h e n y l m e t h a n e a n d 4,4'-diaminodiphenylether show a r a p i d s h i f t w i t h d e c r e a s i n g e l u e n t c o n c e n t r a t i o n s . From F i g u r e 5, one c a n p r e d i c e t h a t 4 , 4 ' - d i a m i n o d i p h e n y l m e t h a n e c a n be s e p a r a t e d f r o m 4 , 4 ' - d i a m i n o d i p h e n y l e t h e r u s i n g a n e l u e n t c o n c e n t r a t i o n o f 0.25 [ H ] . F i g u r e 6 shows t h i s s e p a r a t i o n . The m a j o r d i s a d v a n t a g e t o t h e method i s t h a t some a m i n e s o f i n t e r e s t r e q u i r e a c i d c o n c e n t r a t i o n s a p p r o a c h i n g 1 M. I n a n e f f o r t t o avoid using high concentrations o f strong mineral acids as t h e e l u e n t , t e t r a m e t h y l a m m o n i u m c h l o r i d e i n 1 χ 1 0 " M HCL was i n v e s t i g a t e d . T h i s e l u e n t w o u l d e l u t e t h e a m i n e s b u t t h e c o l u m n l i f e was g r e a t l y r e d u c e d m a k i n g t h e u s e o f t h i s e l u e n t impractical. The c o n c e n t r a t i o n s o f t h e a m i n e s a r e p r o p o r t i o n a l t o t h e areas under t h e peaks i n t h e chromatograms. The s e n s i t i v i t y o f e a c h amine d e p e n d s upon t h e a b s o r b t i v i t y o f t h e compound a t 254 nm., t h e w a v e l e n g t h o f t h e U.V. d e t e c t o r . F o r optimum s e n s i t i v i t y o f a l l t h e a m i n e s a v a r i a b l e w a v e l e n g t h d e t e c t o r w o u l d be r e q u i r e d . U s i n g t h e 254 nm w a v e l e n g t h a n d a f u l l s c a l e d e t e c t o r r a n g e o f 0.01 a b s o r b a n c e u n i t s , t h e l i m i t o f d e t e c t i o n f o r a n i l i n e was f o u n d t o be 1 y g . T h i s s e n s i t i v i t y i s more t h a n a d e q u a t e for i n d u s t r i a l hygiene sampling. F o r e x a m p l e , i f an a i r s a m p l e i s c o l l e c t e d f o r 8 hours a t one l i t e r p e r minute through a midget i m p i n g e r c o n t a i n i n g 10 ml o f a b s o r b i n g s o l u t i o n a n d 0.5 ml i s i n j e c t e d on t h e c h r o m a t o g r a p h , t h e l i m i t o f d e t e c t i o n o f a n i l i n e i n t l ^ a i r s a m p l e i s 0.01 ppm ( y l / 1 ) . T h e TLV f o r a n i l i n e i s


+

3

The u s e o f l o w c a p a c i t y s u r f a c e s u l f o n a t e d c a t i o n e x c h a n g e r e s i n f o r t h e l i q u i d chromatographic separation o f aromatic amines p r o v i d e s a r a p i d a n a l y t i c a l technique f o r i n d u s t r i a l h y g i e n e s u r v e y s . A w i d e v a r i e t y o f a m i n e s c a n be a n a l y z e d by t h e same t e c h n i q u e w i t h good s e n s i t i v i t y . T h i s work was s u p p o r t e d by a g r a n t f r o m t h e E n v i r o n m e n t a l P r o t e c t i o n Agency (R80-5298010).

L i t e r a t u r e Cited. 1. T. S. Scott, "Carcinogenic and Chronic Toxic Hazards of Aro matic Amines", E l s e v i e r Publishing Co., New York, 1962. 2. F. A. Patty, "Industrial Hygiene and Toxicology", Interscience Publishers, New York, 1967. 3. Federal Register, Volume 39, No. 125, 3756, 1974. 4. "Threshold Limit Values f o r Chemical Substances and Physical Agents i n the Work Environment with Intended Changes f o r 1977". American Conference of Governmental Industrial Hygienists, C i n c i n n a t i , OH, 1977. RECEIVED

November 16, 1979. In Analytical Techniques in Occupational Health Chemistry; Dollberg, D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Analytical Techniques in Occupational Health ... - ACS Publications

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