37 New Technology for Personal Sampling of NO
2
and NO in the Workplace x
R. McMAHON and T. KLINGNER MDA Scientific, Incorporated, 1815 Elmdale Avenue, Glenview, IL 60025 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.ch037
B. FERBER and G. SCHNAKENBERG U.S. Bureau of Mines, P.O. Box 18070, Pittsburgh, PA 15236
Employee health problems, such as respiratory effects of exposure to nitrogen dioxide (NO ) and nitric oxide (NO), have prompted the development of new technology for personal monitoring of toxic gases. Prevalent in underground mines where diesel equipment is used, NO and NO levels can be analyzed by chemilumenescence, detector tubes, impingers or area monitors. These analytical methods, however, do not reflect individual employee exposures during an eight-hour workshift, expressed as Time Weighted Average (TWA) measurements. To obtain accurate and complete employee histories of exposure to toxic gases, personal monitoring techniques are required. For the detection of NO and NO (NO ) in mining and other applications, such techniques must be easily implemented, readily portable and must differentiate NO exposures from NO exposures. Combining the principles of a passive diffusion personal sampler and the technology of a dedicated colorimeter, a monitoring system has been developed which meets the above parameters and which is the subject of this report. 2
2
2
x
2
N0 /N0 2
X
Passive Sampler
Based on the research of Dr. E. D. Palmes (1) at New York U n i v e r s i t y s I n s t i t u t e o f Environmental Medicine and on a d d i t i o n a l study supported by a contract from the United States Bureau of Mines, a unique personal sampler has been designed to p a s s i v e l y c o l l e c t N0 . This i s accomplished by way o f molecular d i f f u s i o n and subsequent trapping o f the molecules onto a matrix coated with triethanolamine (TEA) at the closed end o f the sampler. Constructed o f polypropylene, the tubular sampler shown i n Figure 1 i s small, l i g h t w e i g h t , unbreakable and can be e a s i l y worn i n the breathing zone of the employee whose exposure i s to be monitored. No pumping mechanism i s r e q u i r e d . The components o f N0 d i f f u s e a t constant, known rates towards the sealed end o f 1
X
X
0097-6156/81/0149-05 87$05.00/0 © 1981 American Chemical Society
In Chemical Hazards in the Workplace; Choudhary, G.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
588
CHEMICAL
HAZARDS
IN
T H E
WORKPLACE
t h e s a m p l e r and a r e e f f i c i e n t l y c o l l e c t e d o n t o t h e TEA c o a t e d medium. (2^) These r a t e s h a v e b e e n c a l c u l a t e d u s i n g F i c k ' s f i r s t law o f d i f f u s i o n , t h e e s t i m a t i o n o f c o e f f i c i e n t s o f d i f f u s i o n o f g a s e s i n a i r , t h e e f f e c t s o f t e m p e r a t u r e and p r e s s u r e on d i f f u s i o n , as w e l l as t h e d i m e n s i o n s o f t h e s a m p l i n g t u b e . The d e v e l o p m e n t o f a p a s s i v e s a m p l i n g d e v i c e d e s i g n e d f o r t h i s a p p l i c a t i o n i s b a s e d on P a l m e s ' (3) work as g i v e n b e l o w .
D e r i v e d from F i c k ' s f i r s t law, the e q u a t i o n f o r u n i d i r e c t i o n a l , i s o t h e r m a l d i f f u s i o n o f gas 1 (N0 ) t h r o u g h a c o n s t a n t p r e s s u r e m i x t u r e o f gas 1 and gas 2 (air) i s :
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.ch037
2
J
l
=
D
l 2l
d
C
l
E
l
n
2
ppm-hr N O , - 2 , 3 ^
3Z Display ppnrvhr N 0 until removal of cuvette & insertion of next cuvette 2
Figure 5.
Figure 6.
N0 /NO 2
x
Colorimeter functions
field
kit: passive samplers and colorimeter
In Chemical Hazards in the Workplace; Choudhary, G.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
37.
McMAHON E T A L .
Personal Sampling
of NO* and NO
x
or c r o s s - s e c t i o n a l area o f the sampler tube. Examination o f Eqn. 2 shows that the d i f f u s i o n rate i s i n v e r s e l y p r o p o r t i o n a l to the sampler s i z e and could be manipulated by a l t e r i n g the length to area r a t i o of the sampling tube. A longer tube, f o r instance, would c o l l e c t l e s s N 0 per u n i t time and would e f f e c t i v e l y extend the range of N0 d e t e c t i o n . By combining passive samplers and a designated colorimeter i n t o a v e r s a t i l e f i e l d k i t , employee exposures to t o x i c gases can be more e f f i c i e n t l y and a c c u r a t e l y examined than i s p o s s i b l e with other methods r e q u i r i n g s k i l l e d personnel and cumbersome equipment. The c o s t / b e n e f i t r a t i o of maintaining worker h e a l t h i s improved, as i s the q u a l i t y of such maintenance. With the current advances being made i n i n d u s t r i a l hygiene research, i t i s hoped that t h i s new system of personal exposure monitoring can soon be expanded to include other gaseous contaminants a f f e c t i n g worker s a f e t y . X
X
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597
Literature Cited 1.
Palmes, E. D.; Gunnison, A. F. Am. Ind. Hyg. Assoc. J., 1973, 34, 78. 2. Blacker, J. H. Am. Ind. Hyg. Assoc. J., 1973, 34, 390. 3. Palmes, E. D.; Gunnison, A. F.; DiMattio, J.; Tomczyk, C. Am. Ind. Hyg. Assoc. J., 1976, 37, 570. 4. Palmes, E. D.; Tomczyk, C. Am. Ind. Hyg. Assoc. J., 1979, 40, 588. 5. NIOSH Analytical Methods, 1977, 1, 108, DHEW NIOSH Publication No. 78-175. RECEIVED
October 27, 1980.
In Chemical Hazards in the Workplace; Choudhary, G.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
