Determination of Respirable Quartz by Infrared Spectroscopy with a

4 Determination of Respirable Quartz by Infrared Spectroscopy with a Multiple Internal Reflectance Accessory RUSSELL BROXTERMAN

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Kansas Department of Health and Environment, Office of Laboratories and Research, Forbes Building 740, Topeka, KS 66620 Subsequent to the passage of the Occupational Safety and Health Act, there has been an increasing awareness among both employers and employees of occupational health hazards in the workplace environment. Correspondingly, there has also been an increase in the demand placed upon our agency and others to evaluate worksites for the presence of occupational health hazards and to recommend control measures when appropriate. In order to provide the analytical support necessary to accommodate an increasing number of requests for evaluations relating specifically to the hazard resulting from exposure to quartz in airborne dusts of respirable size, i t became readily apparent that an analytical procedure would have to be developed. In considering the three most prominent analytical techniques for quartz, i.e. colorimetric, infrared (IR) and x-ray diffraction, it was possible to immediately exclude the x-ray diffraction procedure for use because the instrument was not available and the cost of purchasing such a unit was considered to be prohibitive in view of the relatively small number of samples anticipated. The Talvite (1) colorimetric procedure has previously been employed without particular success. This method was generally considered to be unacceptably tedious, time-consuming and of questionable accuracy. For these reasons and because the infrared instrumentation was available, it was decided to focus our preliminary efforts on the development of an infrared procedure. Although there are certain shortcomings involved in the use of any infrared technique, similar shortcomings exist in the use of colorimetric and x-ray procedures as well. For an overall review of the probelms of major analytical techniques for quartz one is referred to a critical literature review by Anderson (2). He indicated two of the major problems in the use of an IR procedure is the "effects of particle size" and "mutual line interferences". Generally the 800 cm band of quartz is used for infrared analysis because of its sensitivity and because this segment of the IR spectra is relatively free of the common interferences expected from other mineral components of dust samples. The use of the 0-8412-0539-6/80/47-120-067$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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800 cm band does not t o t a l l y e l i m i n a t e the problem of mutual l i n e i n t e r f e r r e n c e s , t h e r e f o r e , some knowledge of the mineral content of dust samples i s necessary to assure the absence of i n t e r f e r i n g components. The s e n s i t i v i t y of t h i s band, however, i s a f f e c t e d by p a r t i c l e s i z e as has been demonstrated by Tuddenham and Lyon (3) and others. Gade and Reisner (4) i n t h e i r demons t r a t i o n of t h i s e f f e c t , have a l s o shown that a determination of the p a r t i c l e s i z e of an unknown can be made by using the r e l a t i o n ship between p a r t i c l e s i z e and the quotients formed of the o p t i c a l d e n s i t y of each of the^two maxima and the minimum of the quartz doublet a t 800/780 cm" . The e f f e c t of p a r t i c l e s i z e can then be negated by using standards w i t h approximately the same p a r t i c l e s i z e as that of an unknown. To achieve the s e n s i t i v i t y necessary to analyze the s m a l l q u a n t i t i e s of quartz c o l l e c t e d on f i l t e r s by personal r e s p i r a b l e dust sampling the use of M u l t i p l e I n t e r n a l R e f l e c t a n c e (MIR) Spectroscopy was considered. According to G i l b y , C a s s e l s and Wilks (5), i n t e r n a l r e f l e c t a n c e spectroscopy "depends f o r i t s e x i s t e n c e on the very small p e n e t r a t i o n of a l i g h t wave beyond a t o t a l l y i n t e r n a l r e f l e c t i n g i n t e r f a c e . I f a sample i s placed i n contact with t h i s s u r f a c e , the r e f l e c t e d beam i s attenuated a t the chara c t e r i s t i c a b s o r p t i o n frequencies of the sample". For a d e t a i l e d d i s c u s s i o n of the theory of i n t e r n a l r e f l e c t i o n spectroscopy r e ference number s i x (6) should be c o n s u l t e d . They f u r t h e r i n d i c a t e d that MIR spectroscopy was a s e n s i t i v e micro sampling technique and lends i t s e l f to the a n a l y s i s of s o l i d samples such as dust on membrane f i l t e r s but cautioned that hard p a r t i c l e s should be ground so as to prevent damage to the c r y s t a l . Hannah and Dwyer (7) concluded that membrane f i l t e r s , because of t h e i r s u r f a c e r e t e n t i o n a b i l i t y , not only accomplish a s e p a r a t i o n of p a r t i c u l a t e m a t e r i a l from a f l u i d media but a l s o permitted a n e a r l y i d e a l p r e s e n t a t i o n of the sample to an Attenuated T o t a l R e f l e c t i o n c r y s t a l . Using the background i n f o r m a t i o n summarized above, a procedure was developed i n which the r e s p i r a b l e dust samples were ashed, taken up i n a suspension and redeposited on a membrane filter. The redeposited membrane f i l t e r was used to present the sample to the MIR c y r s t a l . The cyclone sampler used f o r c o l l e c t ing r e s p i r a b l e dust s e l e c t i v e l y c o l l e c t s p a r t i c l e s l e s s than 10 microns i n diameter and no e f f e c t was made to g r i n d the p a r t i c l e s as no problem i n damaging the c r y s t a l was encountered. Experimental Apparatus. A Perkin-Elmer Model 467 i n f r a r e d spectrophotometer was used under the a n a l y t i c a l c o n d i t i o n s s t a t e d i n Table I . A M u t i p l e I n t e r n a l R e f l e c t i o n Accessory f o r use w i t h Perkin-Elmer i n f r a r e d spectrophotometers was used to introduce the sample to the IR beam. To c o r r e c t f o r l o s s e s i n energy transmittance through the sample beam r e s u l t i n g from the use of the MIR Accessory, a comb-type r e f e r e n c e beam attenuator was employed. A LFE Corpora-

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

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t i o n Model LTA 302 Low temperature r a d i o frequency asher was used to ash samples. Table I INSTRUMENTAL OPERATING CONDITIONS FOR QUARTZ


Instrument: Scan Mode: Time Constant: Slit: Scan Range: Readout: MIR S e t t i n g :

Perkin-Elmer-Model 467 Slow (50 cm /min) 2 (Pen Response.Time 2 . 0 ) , Normal (1.7 cm" @ 800 cm ) 900 to 700 cm (11.0 to 14.0 micro meters) Absorbance (On chart paper) 30° angle

Reagents. Standards were prepared w i t h 15 micron M i n - U - S i l quartz. The h y d r o c h l o r i c a c i d and isopropanol were a n a l y t i c a l r e agent grade. A 0.5% A e r o s o l OT s o l u t i o n was prepared by d i l u t i n g a commercially prepared 25% A e r o s o l OT s o l u t i o n . Water was dei o n i z e d and g l a s s d i s t i l l e d . F i l t e r s used f o r r e d e p o s i t i o n were MSA, 0.5 micron, 37mm, p o l y v i n y l c h l o r i d e (PVC), membrane f i l t e r s . The i n t e r n a l r e f l e c t i n g p l a t e ( c r y s t a l ) was a Wilks and Barnes KRS-5 c r y s t a l , 52.5 χ 20 χ 2mm, w i t h 45° ends. Procedures. Standards are prepared by f i l t e r i n g suspensions of known amounts o f quartz onto a membrane f i l t e r . The d e s i r e d amount of quartz i s weighed on a micro e l e c t r o b a l a n c e and t r a n s f e r r e d to a one l i t e r pyrex reagent b o t t l e to which 500 mis of d i s t i l l e d water i s added. The suspension i s shaken v i g o r o u s l y and placed i n an u l t r a s o n i c bath f o r 15 minutes. P r i o r to p i p e t t i n g ; the suspension i s shaken v i g o r o u s l y f o r 30 seconds, placed on counter and 10 mis of the suspension i s immediately pipeted w i t h a blow-out s e r o l o g i c a l pipet onto a membrane f i l t e r . The pipet i s r i n s e d w e l l w i t h a forced stream of 0.5% A e r o s o l OT s o l u t i o n from from a p l a s t i c washbottle. A blank i s a l s o prepared using d i s t i l l e d water. The f i l t e r i s placed i n a 47mm M i l l i p o r e p e t r i s l i d e and allowed to dry. Drying time can be f a c i l i t a t e d by p l a c i n g on top of an oven or warm place a t about 40 C. Samples from the f i e l d a r e redeposited on membrane f i l t e r s by f i l t e r i n g a suspension o f ashed sample. To ash f i e l d samples, the f i l t e r i s placed dust s i d e down i n a 50 ml pyrex beakers and placed i n a low-temperature r a d i o frequency asher. The asher used has two chambers and w i l l accommodate eight beakers a t one time. The oxygen flow i s s e t a t 15 sec per minute. Samples a r e i n i t i a l l y ashed f o r 15 minutes a t a RF wattage of 100 watts to prevent the f i l t e r from c u r l i n g due to high heat. The RF wattage i s then i n creased to 250 watts and the sample i s allowed to ash f o r an a d d i t i o n a l 30-45 minutes to e l i m i n a t e any carbonaceous m a t e r i a l . The ash i s t r e a t e d with one m i l l i l i t e r of h y d r o c h l o r i c a c i d to e l i m i -



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nate i r o n oxide; d i l u t e d to the 10 m i l l i l i t e r mark with d i s t i l l e d water and placed i n a sonic bath f o r 30 minutes. (Dust samples c o n t a i n i n g i r o n oxide can r e s u l t i n an excessive l o s s o f c r y s t a l reflectivity. The a c i d d i s s o l u t i o n step may a l s o reduce other contaminant i n t e r f e r e n c e s , but t h i s e f f e c t has not been p o s i t i v e l y demonstrated.) The suspension i s s w i r l e d and f i l t e r e d through a membrane f i l t e r . The beaker i s i n i t i a l l y r i n s e d with d i s t i l l e d water, followed by r i n s i n g with 0.5% A e r o s o l OT s o l u t i o n . The f i l t e r i s allowed to dry. A simple f i l t r a t i o n device was made with the bottom p o r t i o n and center r i n g of a three piece M i l l i p o r e , 37mm, c a s s e t t e f i l t e r holder. A M i l l i p o r e f i l t e r support pad and a MSA, 37mm, 0.5 micron, PVC, membrane f i l t e r i s placed, smooth s i d e up, i n the bottom p o r t i o n and the center r i n g i s pressed on. The f i l t e r i s wetted with 5 mis o f 0.5% A e r o s o l OT s o l u t i o n , vacumn i s a p p l i e d , and pressure i s a p p l i e d to the center r i n g to assure the assembly i s tight. S e v e r a l f i l t r a t i o n devices can be made up to save time d i s assembling and reassembling before each f i l t r a t i o n . I t was found that the f i l t r a t i o n device would f i t f i r m l y on a number 7 rubber stopper with a hole d r i l l e d i n i t . The rubber stopper was then placed i n a 250 ml f i l t r a t i o n f l a s k with the c a s s e t t e on top. I t i s important that the sample be evenly deposited onto the filter. The center w e l l of the f i l t r a t i o n device w i l l hold approximately f i v e m i l l i t e r s ; t h e r e f o r e , to assure even d e p o s i t i o n , f i l t r a t i o n i s done as f o l l o w s : the center w e l l i s f i l l e d ; s l i g h t vacumn i s a p p l i e d then r e l e a s e d ; the center w e l l i s f i l l e d again being sure not to d i s t u r b the deposit on the f i l t e r ; again vacumn i s a p p l i e d and r e l e a s e d . T h i s i s continued u n t i l a l l o f the standard or sample suspensions and t h e i r r i n s i n g s a r e f i l t e r e d . The MIR sampler holder i s assembled e s s e n t i a l l y according to the manufacturers i n s t r u c t i o n f o r use with s o l i d samples with a few a d d i t i o n a l steps. The clamping p l a t e i s placed on a t a b l e so that the cut-out f o r l i q u i d s i s against the t a b l e top and the l i q u i d sample ports a r e f a c i n g to the l e f t . A p i e c e of aluminum f o i l , cut the width of one of pressure pads and long enough to overlap the ends, i s placed on one of the pressure pads. ( I f pad i s not covered with f o i l , l o s s of c r y s t a l r e f l e c t i v i t y w i l l occur when the pad comes i n contact with the c r y s t a l . ) The pad, with f o i l , i s placed on the p l a t e centered under the c r y s t a l with the f o i l face up. To assure even pressure of the f i l t e r against the c r y s t a l , h a l f of a 37mm M i l l i p o r e support pad i s placed on the f o i l covered pad with the curve part of the support pad f a c i n g r i g h t . One h a l f o f a membrane f i l t e r i s placed on the support pad with the smooth s i d e (dust-side) f a c i n g up. The c r y s t a l holder and c r y s t a l are placed down on the p l a t e so that the holes i n the c r y s t a l holder are centered over the holes i n the p l a t e . (Sample and pad should be centered under c r y s t a l . ) The other h a l f of the membrane f i l t e r i s placed (dust-side down) through the cut-out of the c r y s t a l holder against the c r y s t a l . For easy alignment of the f i l t e r on the c r y s t a l ; s i g h t down the l e f t s i d e of the cut-out i n



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c r y s t a l holder and a l i g n s t r a i g h t p o r t i o n of membrane f i l t e r d i r e c t l y under the edge. The other h a l f of the support pad i s placed on the membrane f i l t e r . A small p o r t i o n of the curved s i d e of the support pad w i l l have to be cut o f f to f i t through the cut-out of the c r y s t a l holder. T h i s i s not necessary f o r the membrane f i l t e r as i t i s f l e x i b l e enough to place through the cut-out. A p i e c e of aluminum f o i l cut s l i g h t l y l e s s than the width and l e n g t h of the cut-out i s placed on the support pad. The other pressure pad i s placed on the f o i l through the cut-out. A l i g n the clamping block so that the holes i n the block a r e centered above the holes i n the c r y s t a l holder. I n s e r t the screws and t i g h t e n each a small amount as uniformly as p o s s i b l e . When f i n g e r t i g h t , apply as much f o r c e as can be exerted on each screw. T h i s w i l l a i d i n applying good even pressure on the f i l t e r s to assure a good c r y s t a l i n t e r face contact. Care should be taken when assembling f i l t e r s i n sample holder so that they a r e placed on the same areas of the c r y s t a l each time. For i n f r a r e d a n a l y s i s , each standard quartz f i l t e r or redeposi t e d sample f i l t e r i s cut i n h a l f with s u r g i c a l s c i s s o r s and placed on the 30 or d e s i r e d angle s e t t i n g of the MIR_£ccessory base. The IR i s adjusted to a scan s e t t i n g of 750 cm and the r e f e r e n c e beam attenuator i s used to b r i n g the transmittance l e v e l to 90-1 (j)0%. The f i l t e r i s then scanned i n d u p l i c a t e from 900 to 700 cm . _ p i e spectrum i s recorded on absorbance chart paper. The 800 cm peak of the 800/780 cm quartz doublet i s used f o r measurement by the b a s e l i n e method. A f t e r each f i l t e r i s scanned the c r y s t a l may r e q u i r e c l e a n i n g . Due to the t o x i c i t y of the KRS-5 c r y s t a l , i t i s l e f t i n the c r y s t a l holder a t a l l times so as to avoid unnecessary handling as w e l l as, s c r a t c h i n g or damaging the c r y s t a l . The c r y s t a l , i n i t s holder, i s f l u s h e d with a forced stream of anhydrous isopropanol from a p l a s t i c wash b o t t l e . A c o t t o n swab, soaked i n isopropanol,, can be used to remove d e p o s i t s on the c r y s t a l . T h i s should be done with very l i g h t rubbing as the KRS-5 c r y s t a l scratches very easily. Results-Discussion In F i g u r e 1, the i n f r a r e d absorbance spectrum of a blank MSA f i l t e r , a, i s compared d i r e c t l y with that of a prepared standard f i l t e r , b, with 100 micrograms of 15 micron Min-U-Sil quarjz dep o s i t e d on i t . To determine the absorbance of the 800 cm peak i t i s necessary to approximate a b a s e l i n e as i n d i c a t e d by the dotted l i n e of spectrum _ ^ · As an i n d i c a t i o n of s e n s i t i v i t y the absorption of the 800 cm peak i s 0.19 Absorbance u n i t s . In F i g u r e 2, the i n f r a r e d absorbance spectrum of a redeposited blank f i l t e r , a, i s compared d i r e c t l y with that of a redeposited f i e l d sample f i l t e r , b, which has a c a l c u l a t e d 59 micrograms of quartz on i t . The o r i g i n a l f i l t e r from a foundry had 0.222 m i l l i grams of r e s p i r a b l e dust on i t . F i g u r e 3 i s the i n f r a r e d absorb!




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ance spectrum of a redeposited f i l t e r which had a c a l c u l a t e d quartz content of 169 micrograms. The o r i g i n a l f i l t e r from a foundry had 1.103 m i l l i g r a m s of r e s p i r a b l e dust on i t . The spec trum, b, o f F i g u r e 2 provides a good b a s e l i n e f o r a b s o r p t i o n meas urements of the 800 cm peak. However, as the amount of dust i n creases j broad band s p e c t r a l i n t e r f e r e n c e s began to show i n the 850 cm r e g i o n as shown_jn F i g u r e 3. With l a r g e r amounts of dust on the f i l t e r the 800 cm peak w i l l e v e n t u a l l y be masked by these i n t e r f e r e n c e s . Although an adequate b a s e l i n e l i n e can be estab l i s h e d from the spectrum shown i n F i g u r e 3; keeping the amount o f dust c o l l e c t e d from 0.5 to 1 m i l l i g r a m w i l l l e s s e n t h i s type of i n t e r f e r e n c e . I n the event the amount of dust on the f i e l d samples i s considered excessive, the "sample" f i l t e r can be cut i n h a l f or a p p r o p r i a t e s e c t i o n s and analysed s e p a r a t e l y . F i g u r e 4 i s a spectrum of a f i l t e r from the P r o f i c i e n c y Ana l y t i c a l T e s t i n g Program (PAT) conducted by the N a t i o n a l I n s t i t u t e of Occupational Safety and Health (NIOSH) which contained 103 mi crograms as determined by t h i s l a b . PAT f i l t e r s a r e prepared w i t h 2 mg of sodium s i l i c a t e as a contaminant. A b a s e l i n e approximation as d e s c r i b e d f o j F i g u r e 1 i s not p o s s i b l e due to the i n t e r f e r i n g peak a t 845 cm . When a spectrum of t h i s type i s encountered, a l i n e i s drawn from the two minimums on e i t h e r s i d e of the quartz doublet peak as i l l u s t r a t e d by the dotted l i n e i n F i g u r e 4. When a n a l y z i n g PAT f i l t e r s i t was observed that the quartz and sodium s i l i c a t e remained on the f i l t e r . T h i s was determined by a n a l y z i n g the c r y s t a l a f t e r a n a l y z i n g a PAT f i l t e r . No quartz peak or contaminant peaks were noted. This was a t t r i b u t e d to the ase of a wetting agent, A e r o s o l OT, i n the p r e p a r a t i o n of Standard Reference F i l t e r s (8). Apparently the A e r o s o l OT imparts a cohe s i v e q u a l i t y r e s u l t i n g i n the s i l i c a and dust s t a y i n g on the f i l ter. To demonstrate t h i s , a s i n g l e PAT f i l t e r c o n t a i n i n g 0.168 m i l l i g r a m s of quartz was subjected to s i x separate scans. Between each scan the MIR sample holder was disassembled, and the c r y s t a l cleaned and reassembled. The r e s u l t s a r e shown i n Table I I . No s i g n i f i c a n t d i f f e r e n c e was detected between f i r s t and l a s t scan. Table I I Standard Run Number

Stability Absorbance @ 800 cm

1 2 3 4 5 6 From the p l o t Α

x

0.337 0.340 0.338 0.345 0.327 0.337 β η η

(max)/A

7Qn

(min) versus p a r t i c l e s i z e from



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Figure 3. Absorbance spectra of redeposited respirable dust on filter

Figure 4.

Absorbance spectra of PAT filter



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the work reported by Gade and Reisner (4), the p a r t i c l e s i z e of the 15 micron Min-U-Sil quartz i n F i g u r e 1 i s approximately 3.3 microns. For F i g u r e s 2 and 3 the p a r t i c l e s i z e of the quartz i s approximately 2.3 and 2.7 microns r e s p e c t i v e l y . T y p i c a l l y quartz from f i e l d samples analysed by t h i s lab are g e n e r a l l y i n the 2-3 micron p a r t i c l e s i z e range. Tuddenham and Lyon (3), i n t h e i r study to a s c e r t a i n whether r e p r o d u c i b l e r e s u l t s could be obtained using the 800 cm quartz a b s o r p t i o n , found that the absorbance v a r i e d with p a r t i c l e s i z e . From t h e i r p l o t of absorbance versus average p a r t i c l e s i z e , the absorbance i s about the same i n the 2-4.5 micron p a r t i c l e s i z e range. Consequently, the 15 micron M i n - U - S i l quartz with an average p a r t i c l e s i z e of 3.3 microns can be used as a standard f o r samples which c o n t a i n quartz of a p a r t i c l e s i z e i n the range of 2-4.5 microns. The l i n e a r i t y of a c a l i b r a t i o n curve i s demonstrated by a typi c a l c a l i b r a t i o n p l o t , F i g u r e 5, of standard f i l t e r s c o n t a i n i n g 10, 50, 100, 150, and 200 micrograms of quartz. A d e t e c t a b l e peak (2:1 peak height to noise r a t i o ) was obtained f o r the 10 microgram standard and i s considered to be the minimum d e t e c t a b l e l i m i t . A f i l t e r can be standardized against a c a l i b r a t i o n curve and subsequently used as a s i n g l e standard to determine quartz content of other f i l t e r s ; provided appropriate q u a l i t y c o n t r o l measures are taken, i . e . the c r y s t a l should be checked a f t e r a n a l y z i n g the standard f i l t e r to determine i f quartz was dislodged from f i l t e r and a p r e v i o u s l y run sample should be included as a q u a l i t y cont r o l sample. The above technique i s used f o r a n a l y z i n g samples r o u t i n e l y i n t h i s l a b o r a t o r y . G e n e r a l l y a f i l t e r with a c o n c e n t r a t i o n i n the range of 80 to 120 micrograms i s used as a standardized f i l t e r . The quantity of quartz on a sample f i l t e r i s determined by m u l t i p l y i n g the quantity of quartz on a standardized f i l t e r by the absorbance of the 800 cm_^ peak of a sample f i l t e r d i v i d e d by the absorbance of the 800 cm peak of the standardized f i l t e r . This technique has been used to analyze 53 PAT f i l t e r s and the r e s u l t s are shown i n Table I I I . Redeposition was not done due the s i m i l a r d e p o s i t i o n technique used to prepare the Standard Reference F i l t e r s i n the PAT Program (8). The f i r s t fourteen samples i n Table I I I were f i l t e r s that had been r e t a i n e d by the lab from previous PAT Rounds. The a c t u a l r e s u l t s on the r e s t were submitted i n the PAT Program to NIOSH. (PAT F i l t e r Number S-35-2 has not been i n c l u d e d because h a l f of the f i l t e r was i n i t i a l l y analyzed backwards i n the MIR sample holder r e s u l t i n g i n a quartz l o s s on the support pad.) The % recovery was c a l c u l a t e d based upon the PAT Geometric Mean. An o v e r a l l average percent recovery of 103.2% with a standard d e v i a t i o n of 17.5% was obtained.


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CHEMISTRY


OCCUPATIONAL H E A L T H

Quartz Figure 5.

(ug)

Calibration curve of 15-μ Min-U-Sil quartz


4. BROXTERMAN

Determination

of Respirable

Quartz

77

Table I I I S i l i c a R e s u l t s on PAT


PAT F i l t e r Number S-30-2 S-30-3 S-30-4 S-32-1 S-32-2 S-32-3 S-32-4 S-33-1 S-33-2 S-33-3 S-33-4 S-34-2 S-34-3 S-34-4 S-35-1 S-35-3 S-35-4 S-36-1 S-36-2 S-36-3 S-36-4 S-37-1 S-37-2 S-37-3 S-37-4 S-38-1 S-38-2 S-38-3 S-38-4

PAT Geometric Mean, mg .039 .163 .052 .088 .165 .058 .105 .152 .074 .089 .121 .158 .049 .135 .119 .073 .055 .038 .091 .063 .106 .085 .131 .106 .059 .092 .050 .112 .073

Filters

MIR-IR R e s u l t , mg .022 .159 .046 .090 .168 .041 .113 .155 .068 .092 .139 .155 .039 .128 .133 .088 .053 .038 .101 .075 .109 .086 .158 .117 .057 .123 .050 .126 .079

% Recovery 56.4 97.5 88.5 102.3 101.8 70.7 107.6 102.0 91.9 103.4 114.9 98.1 79.6 94.8 111.8 120.5 96.4 100.0 111.0 119.0 102.8 101.2 120.6 110.4 96.6 139.1 100.0 112.5 108.2

continued



Table I I I S i l i c a Results on PAT F i l t e r s


PAT F i l t e r Number S-39-1 S-39-2 S-39-3 S-39-4 S-40-1 S-40-2 S-40-3 S-40-4 S-41-1 S-41-2 S-41-3 S-41-4 S-42-1 S-42-2 S-42-3 S-42-4 S-43-1 S-43-2 S-43-3 S-43-4 S-44-1 S-44-2 S-44-3 S-44-4

PAT Geometric Mean, mg .110 .055 .032 .084 .133 .115 .082 .054 .105 .077 .112 .064 .082 .085 .127 .065 .116 .065 .093 .113 .115 .081 .084 .113

(cont.)

MIR-IR R e s u l t , mg .129 .064 .031 .080 .121 .087 .051 .039 .091 .084 .096 .056 .093 .103 .121 .073 .132 .073 .131 .133 .159 .084 .100 .142 Average Standard D e v i a t i o n

% Recovery 117.3 116.4 96.9 95.2 91.0 75.7 62.2 72.2 86.7 109.1 85.7 87.5 113.4 121.2 95.3 112.3 113.8 112.3 140.9 117.7 138.3 103.7 119.0 125.7 103.2 17.5


4. BROXTERMAN

Determination

of Respirable

Quartz

79


Conclusions Experimental work has shown that the a n a l y s i s of quartz i n r e s p i r a b l e dust by I n f r a r e d spectroscopy using a M u l t i p l e I n t e r n a l R e f l e c t a n c e Accessory i s a v i a b l e technique that i s s e n s i t i v e , accurate and simple to perform. L i n e a r i t y of a c a l i b r a t i o n curve from 0 to 200 micrograms has been demonstrated. A detection limit of approximately ten micrograms of quartz was obtained. An accu racy of + 35% at a 95% confidence l e v e l was demonstrated by data obtained from p a r t i c i p a t i o n i n the NIOSH PAT Program. Suggested improvements i n the procedure have a l s o been recog n i z e d . The use of a second MTR Accessory i n the r e f e r e n c e beam with a blank membrane f i l t e r i n p l a c e w i l l provide a compensated spectrum and may improve the approximation of the b a s e l i n e . Greater s e n s i t i v i t y might have been achieved had the area of con t a c t between the sample and the c r y s t a l face been i n c r e a s e d . While the e n t i r e procedure appears q u i t e promising, c o l l a b o r a t i v e s t u d i e s are needed to p o s i t i v e l y confirm the r e l i a b i l i t y of the method when used f o r the a n a l y s i s of v a r i e d f i e l d samples.

LITERATURE CITED 1

Talvite, Ν. Α., J. Am. Ind. Hyg. Assoc., (1964), 25, 169.

2

Anderson, P. L., J. Am. Ind. Hyg. Assoc., (1975), 36, 767.

3

Tuddenham, W. Μ., and Lyon, R. J., Anal. Chem., (1960), 32, 1630.

4

Gade, M. and Reisner, Μ., Pneumoconiosis Proc. Internatl. Conference, (1969), 3, 636.

5

Gilby, A. C., Cassels, J., and Wilks, P. Α., Jr., Appl. Spectrosc., (1970), 24, 539.

6

Harrick, N. J., "Internal Reflection Spectroscopy", Interscience Publishers (1967).

7

Hannah, R. W. and Dwyer, J. L., Anal. Chem., (1964), 36, 2341.

8

Generation of Standard Reference Silica Filter Samples for Analysis by Colorimetric Methods, Method Number CRL-001, Chemical Reference Laboratory, NIOSH, Issued 2-5-74.

RECEIVED October 15, 1979.


Determination of Respirable Quartz by Infrared Spectroscopy with a

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