Sampling Methods for Airborne Pesticides - ACS Symposium Series

19

Sampling Methods for Airborne Pesticides

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.ch019

ELLEN C. GUNDERSON SRI International, Menlo Park, CA 94025 Airborne pesticides have been collected by a variety of techniques using filters, impingers, bubblers, solid sorbents, polyurethane foams, and combinations thereof. Sampling for pesticides in air is complicated because specific pesticides may be present as particulate or as a vapor or both, depending on the concentration of the pesticide in the atmosphere, the equilibrium vapor concentration, and the temperature (1-6). Personal sampling is often used to determine pesticide exposure in the workplace environment. Thus, the convenience of the sampling method becomes a major factor in selection of the best sampling medium or media. Impingers and bubblers containing a liquid absorbing solution may perform well, but they are very cumbersome to the worker and the industrial hygienist. Also, shipping regulations prohibit the mailing of most organic solvents. Filters have been shown to efficiently collect some pesticide vapors, but this has not been consistently demonstrated. In general, personal sampling for pesticides is best done by collecting pesticide aerosols on filters, vapors on solid sorbents, and aerosol/vapor mixtures with filter/sorbent sampling trains. A universal sampler applicable to the majority of pesticides would be an ideal sampling device. In this study, personal sampling and analytical methods were developed and validated in the laboratory for determining workplace exposure to several pesticides. The major objectives of the study were to standardize on specific sampling media and to develop and validate methods using filter/ sorbent sampling trains. Sampling Device Criteria The following criteria were used to define a good sampling device: (1) The sampling medium or media must be compatible with the analytical method. For example, the sampling media should not dissolve in the most appropriate solvent for analysis and the media should not interfere in obtaining optimum detection of the pesticide. 0097-6156/81/0149-0301 $05.00/0 © 1981 American Chemical Society

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


302

CHEMICAL HAZARDS IN THE

WORKPLACE

(2)

Greater than 90% of the p e s t i c i d e should be recovered from the sampling device.

(3)

The sampler should c o l l e c t the sample e f f i c i e n t l y and have adequate c a p a c i t y .

(4)

C o l l e c t e d samples should be s t a b l e on the device f o r at l e a s t seven days b e f o r e a n a l y s i s .

(5)

The sampling media should not i n t e r f e r e w i t h good p r e c i s i o n and accuracy of the o v e r a l l method.

To meet the c r i t e r i a f o r a good sampling device as w e l l as a good o v e r a l l sampling a n a l y t i c a l method, each method was t e s t e d e x t e n s i v e l y w i t h the p e s t i c i d e of i n t e r e s t . The t e s t i n g procedure i n v o l v e d the f o l l o w i n g : (1)

An a n a l y t i c a l method was developed. Optimum c o n d i t i o n s were e s t a b l i s h e d f o r maximum s e n s i t i v i t y and s e l e c t i v i t y .

(2)

The p o t e n t i a l sampling medium (or media) was s e l e c t e d based on the p a r t i c u l a r chemical p r o p e r t i e s of the p e s t i c i d e , i t s expected p h y s i c a l s t a t e , and the a n a l y t i c a l method to be used, keeping i n mind t h a t we wanted to s t a n d a r d i z e on the m a t e r i a l s used.

(3)

Recovery of the p e s t i c i d e from the sampling media was d e t e r mined w i t h s p i k e d samples; g r e a t e r than 90% recovery was d e s i r e d . For f i l t e r / s o r b e n t methods we have found that the sample l o s s e s due to v o l a t i l i z a t i o n are minimized i f the f i l t e r and sorbent are combined a f t e r sampling. The combined sample i s then analyzed. This r e q u i r e s t h a t the r e c o v e r i e s from f i l t e r and sorbent be s t a t i s t i c a l l y the same.

(4)

Test atmospheres of known c o n c e n t r a t i o n of the p e s t i c i d e i n a i r were dynamically generated at l e v e l s o f t w i c e , o n e - h a l f , and a t the OSHA standard f o r the s p e c i f i c p e s t i c i d e .

(5)

The c o l l e c t i o n e f f i c i e n c y o f a f i l t e r sampler was demonstrated by sampling t e s t atmospheres w i t h a backup c o l l e c t o r a t the proposed sampling r a t e and time, and a n a l y z i n g the c o l l e c t e d samples. For sorbents or f i l t e r / s o r b e n t sampling t r a i n s , the breakthrough volume was determined (to demonstrate c a p a c i t y ) at 80% r e l a t i v e humidity.

(6)

Storage s t a b i l i t y was demonstrated by c o l l e c t i n g a set of samp l e s of a t e s t atmosphere at a known c o n c e n t r a t i o n and a n a l y z i n g


19.

303

Airborne Pesticides

GUNDERSON

h a l f of the samples immediately and the other h a l f a f t e r seven days storage at room temperature. A d i f f e r e n c e of no more than 10% between the r e s u l t s was acceptable. (7)

The p r e c i s i o n and accuracy of the o v e r a l l method was assessed by c o l l e c t i n g and a n a l y z i n g three sets of samples from t e s t atmospheres o f known concentration. An o v e r a l l c o e f f i c i e n t of v a r i a t i o n of 10% f o r a l l a n a l y t i c a l data and accuracy of ±10% was required f o r method v a l i d a t i o n .


Sampling Methods The methods developed and v a l i d a t e d i n our s t u d i e s can be c l a s s i f i e d f o r d i s c u s s i o n i n t o three c a t e g o r i e s — f i l t e r , sorbent, and f i l t e r / s o r b e n t methods. These methods should not be considered absolute s i n c e they were v a l i d a t e d over the c o n c e n t r a t i o n range of one-half to two times the OSHA standard f o r each p e s t i c i d e and a t o r near room temperature. However, many may be a p p l i c a b l e f o r a wide concentration and temperature range with some a d d i t i o n a l t e s t i n g or knowledge of vapor pressure data. For example, a f i l t e r method f o r an a e r o s o l may be inadequate i f a h i g h temperature and/ or low concentration of the m a t e r i a l r e s u l t s i n a s i g n i f i c a n t f r a c t i o n of the m a t e r i a l being present as vapor. The method would then r e q u i r e a backup c o l l e c t o r f o r vapor. The problem of sampling f o r c o e x i s t i n g p a r t i c u l a t e and vaporous forms of a t o x i c substance, as discussed by T a y l o r et a l . Ç7), becomes important when the OSHA environmental l i m i t f o r vapor-producing p a r t i c u l a t e s i s low compared to the substance s vapor pressure. To determine i f a mixture may be present i n workplace a i r , a comparison of the e q u i l i b r i u m vapor c o n c e n t r a t i o n (EVC) with the OSHA standard i s h e l p f u l . For a s p e c i f i c compound the EVC i s c a l c u l a t e d as f o l l o w s : 1

6

EVC =

(VP)(MW)10 (760)(24.47)

3

mg/m at 25°C

where VP = vapor pressure i n mm Hg a t 25°C. MW = molecular weight. I f the r a t i o EVC/std i s i n the range 0.05 to 100-300, then a mixture of p a r t i c u l a t e and vapor may be present ( 7 ) . A r a t i o above t h i s range i n d i c a t e s the presence o f vapor alone and below the range, p a r t i c u l a t e . The r e l i a b i l i t y of t h i s determination depends on the accuracy o f vapor pressure data. In method development and v a l i d a t i o n s t u d i e s , i t i s o f t e n necessary to perform s p e c i a l t e s t s with generated t e s t atmospheres at d i f f e r e n t temperatures and conc e n t r a t i o n s to demonstrate the p h y s i c a l form of the substance. F i l t e r Methods. The f i l t e r s most commonly used were mixedc e l l u l o s e e s t e r (MCE), g l a s s f i b e r (GF), and p o l y t e t r a f l u o r o e t h y l ene (PTFE). Glass f i b e r and PTFE f i l t e r s were used almost



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e x c l u s i v e l y i n the a e r o s o l methods because high-performance l i q u i d chromatography (HPLC) was chosen as the best a n a l y t i c a l method. C l e a r l y , the sampling device must be compatible w i t h the a n a l y t i c a l method. The most commonly used mobile phases i n HPLC analyses were methanol-water and a c e t o n i t r i l e - w a t e r . To avoid adding i n t e r f e r i n g substances to the sample, we l i m i t e d the e x t r a c t i o n s o l v e n t s f o r the f i l t e r samples to those used i n the HPLC mobile phase or we used the mobile phase i t s e l f . Since MCE f i l t e r s d i s s o l v e i n many of these organic s o l v e n t s , MCE f i l t e r s were not acceptable f o r use w i t h the exception of ethylene g l y c o l . Table I summarizes the compounds f o r which methods were d e v e l oped and v a l i d a t e d using f i l t e r s as a c o l l e c t i o n medium. Each method was t e s t e d over the c o n c e n t r a t i o n range l i s t e d . A l l methods demonstrated good recovery (>95%) of the a n a l y t e from the f i l t e r s , e x c e l l e n t c o l l e c t i o n e f f i c i e n c y , and good storage a b i l i t y . P r e c i s i o n of the method i s i n d i c a t e d by the t o t a l c o e f f i c i e n t of v a r i a t i o n (CV ) f o r the t o t a l (sampling and a n a l y t i c a l ) method. The d e t a i l e d sampling and a n a l y t i c a l methods f o r the s p e c i f i c compounds are p u b l i s h e d i n the "NIOSH Manual of A n a l y t i c a l Methods" (8,90 under the compound's method number (as l i s t e d i n Table I ) . Supp o r t i n g experimental data obtained i n the v a l i d a t i o n e f f o r t f o r each method are i n c l u d e d i n the method's "Backup Data Report" (10). In g e n e r a l , a i r samples are c o l l e c t e d from the worker's b r e a t h i n g zone w i t h 37-mm diameter f i l t e r s contained i n c a s s e t t e f i l t e r h o l d ers. A c a l i b r a t e d personal sampling pump draws a i r through the f i l t e r at a flow r a t e of 1 to 2 l i t e r s / m i n to o b t a i n a p r e s c r i b e d sample volume. A f t e r sampling i s completed, the f i l t e r holder i s sealed and prepared f o r storage or s h i p p i n g to the a n a l y t i c a l l a b o r a t o r y . In the l a b o r a t o r y , the compound of i n t e r e s t i s e x t r a c t e d from the f i l t e r w i t h the a p p r o p r i a t e s o l v e n t , and the r e s u l t i n g s o l u t i o n i s analyzed by the p r e s c r i b e d a n a l y t i c a l method. The use of g l a s s f i b e r and PTFE f i l t e r s i s not interchangeable. Besides the p o s s i b i l i t y of i n t r o d u c i n g f i b e r s i n t o the HPLC system (which cannot be t o l e r a t e d ) and thus having to f i l t e r samples c a r e f u l l y , a s i g n i f i c a n t recovery problem w i t h g l a s s f i b e r f i l t e r s could occur. This was demonstrated f o r ANTU (alpha-napthy1-thiorea) and thiram. Reduced r e c o v e r i e s were noted when samples were s t o r e d f o r very s h o r t periods of time. We f e l t t h i s may have been due to decomposition of the sample on the f i l t e r s u r f a c e — p o s s i b l y because i t i s s l i g h t l y a l k a l i n e (pH 8.5-9). In a d d i t i o n , a background of i n t e r f e r i n g peaks was noted from the g l a s s f i b e r f i l t e r s i n the rotenone method. In these cases, the PTFE f i l t e r s were s a t i s f a c t o r y — t h e i r i n e r t s u r f a c e and f i b e r - f r e e property j u s t i f i e d t h e i r use. The method developed f o r sodium f l u o r o a c e t a t e i s based on c o l l e c t i o n of the sample w i t h c e l l u l o s e e s t e r f i l t e r s e s p e c i a l l y low i n e x t r a c t a b l e s (Toyo-cel c e l l u l o s i c e s t e r membrane f i l t e r s from Nuclepore were used). The samples were e x t r a c t e d w i t h water and analyzed by i o n chromatography. Other MCE f i l t e r s contained h i g h l e v e l s of e x t r a c t a b l e s (from w e t t i n g agents, s u r f a c t a n t s ) that T



Substance

ANTU

Paraquat

Pentachloro-

S294

5297

MCE

0.5

S301

Sodium f l o r o acetate

PTFE

PTFE

GF

GF

Methanol

Acetonitrile

Methanol

Methanol

Mobile phase ( i o n p a i r i n g reagent i n acetonitrile/water)

Acetonitrile

Acetonitrile

0.054-0.24

3.0-12.2

4.9-21.4

5.1-20.3

0.073-0.34

1.16-11.1

1.41-8.5

0.265-1.13

0.256-1.03

0.128-0.76

0.05

MCE (Toyo-cel)

Water

3

Range (mg/m )

0.020-0.137

Ion c h r o m a t o g r a p h y / e l e c t r o l y t i c c o n d u c t i v i t y d e t e c t i o n

5

0.1

Thiram

Warfarin

S256

10

2,4,5-T

S303

P&CAM 313

10

2,4-D

S279

GF

0.15

Strychine

S302

PTFE

5

Rotenone

S300

GF

5

Ethylene g l y c o l

Water

PTFE

0.5

E x t r a c t i o n Solvent

Methanol

Pyrethrum

A n a l y t i c a l Method

Filter Collection Medium

FILTER SAMPLING METHODS

PTFE

0.3

5298

phenol

3

OSHA S t d . (mg/m )

HPLC/UV d e t e c t i o n

S276

A n a l y t i c a l Method:

Method No.

TABLE I .


0.060

0.056

0.055

0.053

0.051

0.059

0.079

0.070

0.072

0.088

0.054

T

Total Coefficient of V a r i a t i o n (CV )


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WORKPLACE

produced i n t e r f e r e n c e s . PTFE f i l t e r s were not acceptable because they are not wettable w i t h water. Another f a c t o r r e g a r d i n g recovery of the sample i s t h a t the complete sampling device should be t e s t e d , not j u s t the f i l t e r i t s e l f . Generation o f t e s t atmospheres may be necessary to perform these t e s t s . This became most apparent i n the work on thiram where the f i l t e r c a s s e t t e top c o l l e c t e d thiram to some degree. The amount v a r i e d from 1% to 12% of the t o t a l sample. F o r t u n a t e l y , the thiram on the c a s s e t t e was s t a b l e so t h a t c a s s e t t e s c o n t a i n i n g f i l ter samples could be stoppered and shipped f o r a n a l y s i s . In l a b o r a t o r y a n a l y s i s , a separate " c a s s e t t e - r i n s e " was analyzed based on a 5-ml wash of the c a s s e t t e top w i t h a c e t o n i t r i l e . Sorbent Methods. The sorbent methods developed i n t h i s program are l i s t e d i n Table I I . These methods are s t r i c t l y f o r vapors of the l i s t e d p e s t i c i d e s . Complete methods are p u b l i s h e d i n the "NISOH Manual of A n a l y t i c a l Methods" (9,11). Samples are c o l l e c t e d w i t h e s p e c i a l l y prepared sorbent tubes. A g l a s s tube (6-mm I.D. by 8-mm O.D. by 3-cm long) i s packed w i t h approximately 100 mg of sorbent i n a f r o n t s e c t i o n and 50 mg i n a backup s e c t i o n , each separated by g l a s s wool plugs. Sorbents of coarse mesh s i z e (^20/40) are used to minimize the pressure drop across the tube. A c a l i b r a t e d p e r s o n a l sampling pump draws a i r through the sorbent tube a t a flow r a t e o f up to 1 l i t e r / m i n . Capped sorbent tubes c o n t a i n i n g the sample are shipped to the anal y t i c a l l a b o r a t o r y , where the p e s t i c i d e i s desorbed from the s o r bent w i t h toluene and the s o l u t i o n i s analyzed by gas chromatography. The s e l e c t i o n of a s o l i d sorbent f o r p e r s o n a l sampling of pest i c i d e s was based on the f a c t o r s of good recovery of the sample, adequate c a p a c i t y and storage s t a b i l i t y , and c o n t r i b u t i o n to overa l l p r e c i s i o n and accuracy of the method as d i s c u s s e d e a r l i e r . The sorbent should a l s o be i n e r t and f r e e of background i n t e r f e r e n c e s . Prewashing the sorbents before use by Soxhlet e x t r a c t i o n w i t h a methanol/acetone s o l u t i o n and d r y i n g was done to remove r e s i d u a l monomers, i m p u r i t i e s , and any s o l v e n t s . The sorbents, Chromosorb 102 and XAD-2, which are s t y r e n e d i v i n y l benzene c r o s s - l i n k e d porous polymers, proved to be most usef u l i n our s t u d i e s . Capacity of the sorbent sampling tubes was not a problem w i t h the p e s t i c i d e s we s t u d i e d s i n c e most were not extremely v o l a t i l e . Sampling humid atmospheres of the p e s t i c i d e s a l s o d i d not a f f e c t the sorbent c a p a c i t y s i n c e these porous p o l y mers are hydrophobic. We attempted to s t a n d a r d i z e on Chromosorb 102 f o r c o l l e c t i o n and on d e s o r p t i o n of the sample w i t h toluene f o r a l l p e s t i c i d e s amenable to a n a l y s i s by gas chromatography. In a few cases, Chromosorb 102 was not a c c e p t a b l e , u s u a l l y because of reduced r e c o v e r i e s ; i n these cases, XAD-2 was used. The reason f o r reduced r e c o v e r i e s was not apparent. The d i f f e r e n c e i n behavior between Chromosorb 102 (Johns-Manville Corp.) and XAD-2 (Rohm and Haas) remains to be



Toluene Toluene Toluene Toluene

Chrom 102 Chrom 102 Chrom 102 XAD-2

0.5

0.1

0.05

Heptachlor

Phosdrin

TEPP

Dichlorvos (DDVP)

S287

S296

P&CAM 315

P&CAM 295

3

Sorbent

=

GC/FPD-P =

GC/EC

GC/FPD-P

GC/FPD-P

GC/FPD-P

GC/EC

Analytical Method

0.38-1.71

0.025-0.124

0.027-0.145

0.23-1.0

3

fog/* )

Range

gas chromatography/flame photometric detector-phosphorus mode

gas chromatography/electron capture d e t e c t o r

Substance

Method No.

Desorption Solvent

SORBENT METHODS


TABLE I I .


0.054

0.086

0.069

0.066

T

Total Coefficient of V a r i a t i o n (CV )


308

CHEMICAL HAZARDS IN THE WORKPLACE

determined. One would expect that both sorbents should e x h i b i t s i m i l a r o r i d e n t i c a l p r o p e r t i e s s i n c e Chromosorb 102 i s prepared commercially from XAD-2 (12). In s t u d y i n g heptachlor i t was i n i t i a l l y thought, based on v a por pressure data, that a f i l t e r / s o r b e n t sampling t r a i n would be necessary to c o l l e c t both vapor and a e r o s o l components. A breakthrough t e s t was performed by sampling a t e s t atmosphere a t 80% r e l a t i v e humidity o f h e p t a c h l o r a t twice the OSHA standard. Severa l sampling d e v i c e s , each c o n s i s t i n g o f an MCE f i l t e r f o l l o w e d by a Chromosorb 102 sorbent tube, were connected to the sampling chamber. The t e s t a i r was sampled a t the proposed f l o w r a t e , 1 l i t e r / m i n , and samplers were removed a t i n t e r v a l s throughout the t e s t ; the i n d i v i d u a l p a r t s o f the samplers were analyzed s e p a r a t e l y . The h e p t a c h l o r breakthrough t e s t , i l l u s t r a t e d i n F i g u r e 1, shows an i n t e r e s t i n g r e s u l t . The amounts o f h e p t a c h l o r found on the f i l t e r and sorbent and the t o t a l a r e p l o t t e d versus the time of sampling. The amount of m a t e r i a l c o l l e c t e d on the f i l t e r appears to r i s e and l e v e l o f f t o a constant amount a f t e r extended sampling. I t was apparent t h a t the f i l t e r s were absorbing h e p t a c h l o r vapor up to a s a t u r a t i o n p o i n t and then a l l o w i n g the remainder to pass through t o the sorbent. Based on these r e s u l t s , i t was decided that only h e p t a c h l o r vapor was present and that a sorbent tube alone would be the most a p p r o p r i a t e sampler. A second t e s t , performed w i t h sorbent tubes o n l y , demonstrated t h a t the sorbent had s u f f i c i e n t capacity. F i l t e r / S o r b e n t Methods. The methods developed u s i n g f i l t e r / sorbent sampling t r a i n s are l i s t e d i n Table I I I . The sampling t r a i n c o n s i s t s o f a 37-mm diameter f i l t e r contained i n a c a s s e t t e f i l t e r h o l d e r f o l l o w e d by a sorbent tube as d e s c r i b e d above. Samples a r e c o l l e c t e d a t 1 l i t e r / m i n t o o b t a i n the p r e s c r i b e d sample volume. A f t e r sampling i s completed, the f i l t e r i s removed from the f i l t e r h o l d e r and placed i n a g l a s s v i a l w i t h the f r o n t sorbent s e c t i o n and capped. The combined sample i s e x t r a c t e d w i t h toluene and the r e s u l t i n g s o l u t i o n i s analyzed by gas chromatography. Again, we t r i e d to s t a n d a r d i z e on sampling media and sample treatment, u s i n g MCE f i l t e r s f o l l o w e d by Chromosorb 102 sorbent tubes and e x t r a c t i o n o f the sample from the c o l l e c t i o n media w i t h toluene. I n the case of demeton, poor r e c o v e r i e s were noted from Chromosorb 102; t h i s was a l s o found by other i n v e s t i g a t o r s (13). XAD-2 was demonstrated to be s a t i s f a c t o r y . The breakthrough t e s t r e s u l t s f o r these compounds g i v e the best i l l u s t r a t i o n o f the p a r t i t i o n i n g o f m a t e r i a l on the sampling t r a i n . These t e s t s were performed w i t h t e s t atmospheres a t twice the OSHA standard f o r each p e s t i c i d e , 80% r e l a t i v e humidity, and a t or near room temperature. Figures 2 through 4 a r e g r a p h i c a l r e p r e s e n t a t i o n s o f the t e s t s performed on the f i l t e r / s o r b e n t sampling t r a i n s t o t e s t f o r sorbent c a p a c i t y o r breakthrough, and t o best determine aerosol/vapor partitioning.



19. GUNDERSON

Airborne Pesticides

TIME (min)

Figure 2. Chlordane breakthrough test


309


=

GC/FPD-P =

GC/EC

gas chromatography/flame photometric detector-phosphorus mode

0.080 2.82-17.1

GC/FPD-P

Toluene

MCE/Chrom 102

gas chromatography/electron c a p t u r e d e t e c t o r

10

Ronnel

S299

0.071 0.06-0.31

GC/EC

Toluene

MCE/Chrom 102

0.1

Endrin

S284

0.080 0.06-0.33

GC/FPD-P

Toluene

MCE/XAD-2

0.1

Demeton

S280

0.070

3

0.156-0.17

Toluene

MCE/Chrom 102

0.5

Chlordane

S278

Analytical Method GC/EC

Solvent

Filter/Sorbent

Substance

3


Method No.

Total Coefficient of V a r i a t i o n (CVT)

FILTER/SORBENT METHODS

Range (mg/m )

TABLE I I I .



GUNDERSON

Airborne

Pesticides

TIME (min)

Figure 3.

70

Ronnel breakthrough test

ι

1

1

0

40

80

r

120

160

200

240

TIME (min)

Figure 4.

Endrin breakthrough test




312

WORKPLACE

The f i r s t of the set i s chlordane (Figure 2 ) . In t h i s case chlordane was c o l l e c t e d p r i m a r i l y on the m i x e d - c e l l u l o s e e s t e r f i l t e r w i t h about 10% c o l l e c t e d on the sorbent. I f the sampling dev i c e was only t e s t e d over the proposed sampling p e r i o d , one hour i n t h i s case, vapor c o l l e c t e d on the sorbent may not have been det e c t e d . Hence, extended sampling periods are necessary to r e a l i s t i c a l l y t e s t c o l l e c t i o n e f f i c i e n c y of the i n d i v i d u a l sampling media i n the t r a i n . A l s o , a t h i g h e r temperatures and lower chlordane c o n c e n t r a t i o n , the f r a c t i o n c o l l e c t e d on the sorbent may be subs t a n t i a l l y increased. The r o n n e l t e s t (Figure 3) was s i m i l a r to the chlordane t e s t , w i t h about 5% of the t o t a l c o l l e c t e d sample found on the sorbent. The e n d r i n t e s t , i l l u s t r a t e d i n F i g u r e 4, a l s o showed that the m a j o r i t y of m a t e r i a l was c o l l e c t e d on the f i l t e r . This was another case i n which a f r a c t i o n of the t o t a l sample was c o l l e c t e d on the f i l t e r h o l d e r c a s s e t t e p a r t s . This amount of m a t e r i a l was equival e n t to the amount c o l l e c t e d on the sorbent. In a s h o r t sampling p e r i o d these amounts may be undetected; however, at the longer samp l i n g p e r i o d , they were about 7% f o r each f r a c t i o n . Again, a t higher temperatures and/or lower c o n c e n t r a t i o n s , the sorbent f r a c t i o n may be much g r e a t e r . Demeton, or Systox, was one of the most i n t e r e s t i n g and c h a l l e n g i n g p e s t i c i d e s s t u d i e d . Demeton c o n s i s t s o f two isomers, Demeton-S and Demeton-0. The vapor pressures of both isomers are reported to be n e a r l y the same. When gas chromatographed, the i s o mers are completely r e s o l v e d and e a s i l y q u a n t i t a t e d s e p a r a t e l y . Our t e s t s l e d us to d i s b e l i e v e the reported vapor pressure data. The r e s u l t s f o r the S-isomer are shown i n F i g u r e 5. The S-isomer was p r i m a r i l y found on the f i l t e r w i t h a s m a l l f r a c t i o n on the XAD-2 sorbent. F i g u r e 6 shows the 0-isomer r e s u l t s . The XAD-2 sorbent c o l l e c t e d the m a j o r i t y of t h i s isomer. I t a l s o appeared t h a t the m a t e r i a l c o l l e c t e d on the f i l t e r may be vapor s i n c e the curve l e v e l s out as i n the heptachlor t e s t . Thus, Demeton-0 probably has a h i g h e r vapor pressure than Demeton-S and t h i s r e s u l t i s c o n s i s t e n t w i t h GC r e t e n t i o n time data. These r e s u l t s demonstrate the value of t e s t i n g proposed sampling devices w i t h t e s t atmospheres i n d e t a i l and over extended sampling p e r i o d s . Conclusions As a r e s u l t of developing and v a l i d a t i n g f i l t e r / s o r b e n t samp l i n g methods, some a d d i t i o n a l c r i t e r i a f o r t e s t i n g were formulated and added to the o r i g i n a l method t e s t i n g c r i t e r i a f o r these samp l i n g t r a i n s . These are summarized below: (1)

Recovery of the sample must be g r e a t e r than 90% from a l l i n d i v i d u a l p a r t s of the sampling t r a i n . Because the f i l t e r and sorbent should be combined f o r a n a l y s i s , the r e c o v e r i e s from each must be q u a n t i t a t i v e . I f >90% recovery i s obtained, no recovery c o r r e c t i o n should be r e q u i r e d .



GUNDERSON

31

Airborne Pesticides

0

2

4

6

8

10

12

T I M E (hours)

Figure 5.

Breakthrough test—Demeton-S; MCEF/XAD-2: (A) total Dem-S, Ο MCE, (Ο) XAD-2

T I M E (hours)

Figure 6.

Breakthrough test—Demeton-O; MCEF/XAD-2: (A) total Dem-S, Ο MCE, (Ο) XAD-2


314

CHEMICAL HAZARDS IN THE WORKPLACE

(2) The sampling device should be tested over an extended concentration range. That is, i f l i t t l e vapor contribution is expected, the recovery of the analyte from the sorbent should be tested at low levels. In addition, i f extreme temperatures are anticipated in the workplace, the sampler should be tested in such an environment.


(3) After sample collection, the filter and sorbent should be combined by transferring them to a glass vial. This ensures against the possible loss of a sample that may volatilize from the filter when being stored or shipped. (4) All parts of the sampling device should be checked for sample adsorption, especially filter holder cassettes. If material collects on the cassette, complete recovery and storage stability must be demonstrated. In summary, i t should be said that these methods may be applicable to other air sampling situations, not just workplaces, and the principles and problems involved in aerosol/vapor sampling are not in any way exclusive to pesticide sampling. Acknowledgments The author wishes to thank the National Institute for Occupational Safety and Health for supporting this work, and especially Dr. Laurence Doemeny, the project officer. Staff members of the Analytical and Inorganic Chemistry Department at SRI International are acknowledged for their work on this project. Special thanks are given to Dr. Dale M. Coulson and C. Clarine Anderson for their help. Also, the staff at Arthur D. Little, Inc., which was a subcontractor on this work, is greatly appreciated. They performed work on about half of the pesticides. Abstract Air sampling and analytical methods have been developed and validated for determining workplace exposure to a number of pesticides. The methods incorporate the use of filters and solid sorbents independently and in combination as filter/sorbent sampling trains. Filters composed of glass fiber, mixed-cellulose ester, and polytetrafluoroethylene materials were studied, in addition to XAD-2 and Chromosorb 102 solid sorbents. Sampling devices were chosen based on compatibility with the analytical methods and the specific substances' physical and chemical properties. The methods developed were tested for analytical recovery, collection efficiency, breakthrough volume, storage stability of collected samples, and precision and accuracy. Samples were collected from dynamically generated test atmospheres of each pesticide over a known


19.

GUNDERSON

Airborne Pesticides

315

concentration range and analyzed to test the overall methods. Criteria were developed for testing pesticides that have significant vapor and particulate contribution at workplace concentrations.


Literature Cited 1.

Van Dyk, L. P.; Visweswariak, K. Residue Reviews, 1975, 55, 91.

2.

Miles, J. W.; Fetzer, L. E.; Pearce, G. W. Environ. Sci. Technol., 1970, 4, 420.

3.

Thomas, T. C.; Seiber, J. N. Bull. Environ. Contam. Toxicol., 1974, 12, 17.

4.

Farwell, S. O.; Bowes, F. W.; Adams, D. F. J. Environ. Sci. Health, 1977, B12, 71.

5.

Turner, B. C.; Glotfelty, D. E. Anal. Chem., 1977, 49, 7.

6.

Melcher, R. G.; Garner, W. L.; Severs, L. W.; Vaccaro, J. R. Anal. Chem., 1978, 50, 251.

7.

Taylor D. G.; Doemeny, L. J.; Heitbrink. W. A. "Developing and Validating Methods for the Sampling and Analysis of Vapor-Particulate Mixtures," presented at the 18th Annual American Industrial Hygiene Conference, Los Angeles, CA, 1978.

8.

Taylor, D. G. (Manual Coordinator) "NIOSH Manual of Analytical Methods," 2nd ed., Vol. 4, DHEW(NIOSH) Publication No. 78-175, Cincinnati, Ohio, 1978.

9.

Taylor, D. G. (Manual Coordinator) "NIOSH Manual of Analytical Methods," 2nd ed., Vol. 5, DHEW(NIOSH) Publication No. 79-141, Cincinnati, Ohio, 1979.

10. Available through National Technical Information Service by Method No. 11. Taylor, D. G. (Manual Coordinator) "NIOSH Manual of Analtyical Methods," 2nd ed., Vol. 6, DHEW(NISOH) Publication (to be published). 12. Private communication with S. Dave (Johns-Manville Corp.). 13. H i l l , R. H.; Arnold, J. E. "A Personal Air Sampler for Pesticides" (to be published). RECEIVED October 27, 1980.


Sampling Methods for Airborne Pesticides - ACS Symposium Series

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