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Distribution of silicones in water, sediment and fish in Japanese rivers
The Science of the Total Environment, 73 (1988) 1 9 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
1
D I S T R I B U T I O N OF SILICONES IN W A T E R , S E D I M E N T A N D FISH IN J A P A N E S E RIVERS
NORITO WATANABE Gifu Prefectural Research Institute for Environmental Pollution, 58-2, Yabuta 8 chome, Gifu-shi, 500 (Japan)
HISAMITSU NAGASE and YOUKI OSE Gifu Pharmaceutical University, Department of Environmental Hygiene, 5-6-1 Mitahorahigashi, Gifu-shi, 502 (Japan)
ABSTRACT A new analytical method for assaying polyorganosiloxanes (silicones) in environmental samples is presented. The method utilizes petroleum for solvent extraction of the sample (water, sediment, biological tissue) together with inductively coupled plasma detection of the extracted organic silicones. The detection limit for silicones in the final methyl isobutyl ketone sample] extract is ~ 0.01 ppm, and the method is applied to samples from various Japanese rivers to quantify silicones in several environmental materials. Silicones are reported from river waters (up to ~ 50 ppb), riverine sediments (up to 6 ppm), and as an extractable component of fish tissue (up to 0.9 ppm).
INTRODUCTION Silicone fluids possess m a n y desirable properties, s u c h as low surface tension, w a t e r repellency, t h e r m a l a n d c h e m i c a l stability, r e s i s t a n c e to ult r a v i o l e t r a d i a t i o n and p r e s u m e d biological inertness. These desirable p r o p e r t i e s h a v e led to t h e i r extensive use in i n d u s t r i a l a n d domestic applications, i n c l u d i n g use as a n t i - f o a m i n g a n d release agents, polishes for automobiles and as cosmetic additives. The w i d e s p r e a d use of silicones suggests t h a t t h e y m a y be released into the e n v i r o n m e n t , a n d m a y r e s u l t in environm e n t a l c o n t a m i n a t i o n , w h i c h deserves special c o n s i d e r a t i o n b e c a u s e of t h e i r e x c e p t i o n a l persistence. I n J a p a n , i n v e s t i g a t i o n s on the d i s t r i b u t i o n of silicones were c o n d u c t e d u s i n g a t o m i c a b s o r p t i o n s p e c t r o m e t r y (AAS) in o r d e r to e s t i m a t e t h e i r b e h a v i o u r in the e n v i r o n m e n t ( J a p a n EPA, 1981), b u t this m e t h o d is n o t a l w a y s sufficiently sensitive to d e t e r m i n e t r a c e a m o u n t s of silicones in e n v i r o n m e n t a l samples. In this report, a simple a n d rapid m e t h o d is p r e s e n t e d for the s e p a r a t i o n and d e t e r m i n a t i o n of silicones in e n v i r o n m e n t a l samples u s i n g i n d u c t i v e l y coupled p l a s m a emission s p e c t r o m e t r y (ICP), and the o c c u r r e n c e of siIicones in some
0048-9697/88/$03.50
© 1988 Elsevier Science Publishers B.V.
2.0 -
2.0
1.9 1.8 I I I J J 1.2 1.4 1.6 Plasma support gas, l/min
1.8
16 18 20 Coolant gas, ]/min
Fig. 1. Effect of p l a s m a s u p p o r t g a s flow r a t e o n silicone r e s p o n s e . C o o l a n t g a s flow rate, 201 m i n - l ; c a r r i e r g a s flow rate, 0.81 m i n -1 . Fig. 2. Effect of c o o l a n t g a s flow r a t e on silicone r e s p o n s e . P l a s m a s u p p o r t g a s flow rate, 1.21 m i n - 1; c a r r i e r g a s flow rate, 0.81 m i n - 1 .
Japanese river waters, industrial effluents, aquatic sediments, sludges and fish is reviewed. ESTABLISHMENT OF ANALYTICAL METHOD
Optimisation of ICP operating conditions When determining trace amounts of silicones in methyl isobutyl ketone (MIBK), the strict control of three argon gas flow rates (coolant, plasma support, carrier) and the plasma height above the induction coil are considered to be important. The effect of variation of the plasma support gas flow rate on the silicone response is shown in Fig. 1, with the plasma height fixed at 9.7mm above the induction coil. The change in response is small when the plasma support gas flow rate is varied, with the coolant gas flow rate (201 min -1) and carrier gas flow rate (0.81 min -1) held constant. Below a flow rate of 1.21 min-1, measurement becomes impossible because of extinction of the plasma torch. The effect of variation of coolant gas flow rate on the silicone response is shown in Fig. 2, with the plasma height fixed at 9.7 mm above the induction coil. Sensitivity increases as the coolant gas flow rate increases from 161 min -1 to a maximum level, with the plasma support gas flow rate (1.21 min-1) and carrier gas flow rate (0.81 min-1) held constant. The effect of variation of carrier gas flow rate on the silicone response is shown in Fig. 3, with the plasma height fixed at 9.7 ram above the induction coil. Maximum emission occurred for a flow rate of between 0.7 and 0.81 min-1, with the plasma support gas flow rate (1.21min -1) and coolant gas flow rate (201min 1) held constant. In Fig. 4 the effect of variation of plasma height on silicon response is shown
2.0 :
1.8
-p
1.4
B
1.6
1.0
1.2
0
0.6 I
l
I
l
I
I
0.5 0.7 0.9 Carrier gas flow-rate, I/min
2.0 6.0 I0 Height above induction coil,mm
Fig. 3. Effect of carrier gas flow r a t e on silicone response. P l a s m a support gas flow rate, 1.21 m i n - 1; coolant gas flow rate, 2 0 1 m i n - L Fig. 4. Effect of plasma h e i g h t on silicone response. Carrier gas flow rate, 0.81min-~; plasma support gas flow rate, 1.21min-1; coolant gas flow rate, 2 0 1 m i n - L
at three selected gas flow rates. Emission intensity varies markedly with small changes in plasma height; the best compromise position is between 7 and 10 mm. The ICP operating conditions for the determination of trace amount of silicones in MIBK are listed in Table 1.
Analytical procedure Liquid samples Five hundred to four thousand millilitres of the sample was placed in a separating funnel and extracted twice with two aliquots (2 x 100ml) of petroleum ether by shaking vigorously for 10 min. Combined petroleum ether TABLE 1 Operating conditions for Shimadzu ICPQ-100 emission spectrometer Oscillator frequency Incident power Reflection power P l a s m a h e i g h t above i n d u c t i o n coil Coolant gas flow rate P l a s m a support gas flow rate Carrier gas flow rate Sample i n t r o d u c t i o n r a t e P r e b u r n time I n t e g r a t i o n time Wavelength
27.12 MHz 1.8 W < 5W 9.7 m m Ar, 201rain -1 Ar, 1.21rain -1 Ar, 0.81 min-1 2.5 ml m i n -1 45 s 2s 2516.1 n m
extracts were dehydrated with anhydrous sodium sulfate, then rotary evaporated to dryness. The residue was dissolved in 5 ml MIBK. The silicone concentration was obtained by reference to a linear working curve prepared from octaphenylcyclotetrasiloxane.
Sediment and fish tissue Solid samples (5-10g) were placed in a 200ml Erlenmeyer flask with a ground-glass stopper, then allowed to stand overnight after addition of 100 ml petroleum ether. The samples were extracted ultrasonically for 15min, dehydrated with anhydrous sodium sulfate and then rotary evaporated to dryness; the residue was taken up in 5 ml MIBK. The silicone concentration was determined as for liquid samples.
Detectability The calibration curve of silicone in MIBK gives a straight line; a wide working range of 0-200 #g of silicone per 10 ml of MIBK is obtained. The detection limit of silicone in MIBK is 0.01 ppm, provided it is defined as the concentration of silicone in ppm t h a t produces an emission intensity twice the background. The detection limit of ICP is more than two orders of magnitude lower t h a n that of AAS.
Recovery and precision The recovery of silicone by the proposed method was evaluated by processing distilled water, river sediment and fish tissue spiked with known quantities of polydimethylsiloxane (PDMS) (Table 2). PDMS was recovered with yields of 69.0% for water, 57.7% for river sediment and 48.9% for fish tissue. The recovery from solid samples by the proposed method was interTABLE 2 Recovery of PDMS a from water, s e d i m e n t and fish samples Sample
A m o u n t of sample
PDMS added (pg)
PDMS found (#g)
Recovery (%)
Distilled w a t e r
1000 ml 1000 ml 10 g 10 g 10 g 10 g 10 g 10 g
20 200 0 20 200 0 20 200
13.5 141 12.6 24.5 124.4 1.3 10.3 107
67.5 70.5
69.0
59.5 55.9
57.7
45.0 52.8
48.9
River s e d i m e n t
F i s h tissue
a P D M S = p o l y d i m e t h y l s i l o x a n e (Toray silicone fluid SH-200).
TABLE 3 Extractable silicone in environmental samples (Japan EPA, 1981) Sample
Tokyo Bay
IseBay
Osaka Bay
Water Sediment Fish
0/21 17/21 12/15
0/21 9/21 21/21
0/15 7/15 6/6
Denominator and numerator denote the number of analyzed samples and positive number, respectively. Detection limit is 2.5 ppb for water samples and 1ppm for sediment and fish samples. mediate between the recovery by Soxhlet ext ract i on (Pellenbarg, 1979) and by Dean Stark ext r a c t i on (Tsuchitani et al., 1978). In a test of precision, four environmental samples, river water, river sediment, sewage sludge and fish tissue were examined. The coefficient of v ar iatio n was 4.7% for river water, 10.8% for river sediment, 1.2% for sewage sludge and 13.3% for fish tissue. The proposed method gives good precision and is acceptable for the determination of trace levels of silicone in environmental samples. GENERAL SITUATION ON DISTRIBUTIONOF SILICONE IN JAPAN J a p a n EPA has surveyed the concentrations of various chemicals in water, sediment and biota since 1976, and found silicones in some sediment and fish samples. Silicone c o n c e n t r a t i o n s in 120 samples from major rivers and bays in J a p a n were less t ha n the detection limit (2.5 ppb), while some sediment samples from Tokyo Bay and fish samples from the River N agara contained > 10 ppm. As a general rule, silicone was detected mostly in samples from industrialized and overpopulated districts, as shown in Table 3. DISTRIBUTION OF SILICONE IN THE NAGARA RIVER WATERSHED The J a p a n EPA studies showing silicone pollution of an aquatic environment stimulated us to investigate the distribution of silicones in the River Nag ar a watershed. The River Nagara, located in mid-Japan, flows southeasterly for 160 km t h r o u g h Gifu Prefecture and then discharges into Ise Bay; the catch men t area is ~ 2050 km 2, and the flow rate is > 50 m 3s 1. Municipal and industrial effluents from five t r i b u t a r y rivers enter the N agara River in the middle reach. The dyeing industry is very prosperous in the Nagara River watershed. Water quality and extractable silicone cont ent of the river water and sediment samples from the N a ga r a River watershed are shown in Table 4. Silicones were not detected in the water samples from N agara River, but water samples from t r i b u t a r y rivers contained a detectable, but low, silicone content, similar to those for Chesapeake Bay and Delaware Bay (Pellenbarg, 1979);
6 TABLE 4 W a t e r q u a l i t y a n d e x t r a c t a b l e silicones in w a t e r and sediment samples Sampling
BOD ~
COD e
SS a
Silicone in
Silicone in
station
(ppm)
(ppm)
(ppm)
waterb( p p b )
sedimenff (ppm)
Nagarabashi
1.4
2.0
9
ND
ND
Nagaraohashi Nannouohashi Tokaiohashi Takebashi Suimonbashi Sakaigawabashi Matuyama (near junction) Koyabu (near junction)
1.2 1.5 1.5 2.9 6.1 6.1 9.3
2.2 2.8 2.8 4.3 7.5 11 13
5 7 9 24 43 26 14
ND ND ND 2.8 2.0 7.9 54.2
ND ND ND ND 5.8 ND 0.3
3.4
6.4
15
2.0
ND
a A v e r a g e of 12 data in FY1981. b Based on 69% recovery in w a t e r samples. CBased on 57.7% r e c o v e r y in sediment samples. Silicones are 37.9% silicon; ND = not detected.
silicone c o n t e n t s r a n g e d f r o m 2.0 to 54.2ppb, w i t h the h i g h e r levels u s u a l l y o c c u r r i n g in the w a t e r s a m p l e s s h o w i n g the h i g h e r BOD or COD. This r e l a t i o n ship s e e m s to c o r r o b o r a t e the c o n c l u s i o n t h a t silicones o r g i n a t e f r o m ant h r o p o g e n i c sources. S e d i m e n t s a m p l e s h a v i n g t h e h i g h e s t i g n i t i o n loss also c o n t a i n e d t h e h i g h e s t silicone levels. T h e c o n c e n t r a t i o n of silicone in t h e S u i m o n b a s h i a n d M a t u y a m a w a s 5.8 a n d 0.3 ppm, r e s p e c t i v e l y . T h e e x t r a c t a b l e silicones in fish c a u g h t in t h e N a g a r a R i v e r a r e s h o w n in T a b l e 5. A v e r a g e e x t r a c t a b l e silicones in fish m u s c l e of d e e p b o d i e d c r u c i a n carp, steed b a r b e l a n d J a p a n e s e d a c e r a n g e d f r o m 0.36 to 0.89ppm. Silicone levels in this s t u d y w e r e a b o u t one o r d e r of m a g n i t u d e l o w e r t h a n t h o s e r e p o r t e d by J a p a n E P A . M e a s u r a b l e silicones w e r e d e t e c t e d in t h e t r i b u t a r y r i v e r s r e c e i v i n g a cons i d e r a b l e v o l u m e of effluents f r o m s e w a g e t r e a t m e n t p l a n t s a n d / o r d y e i n g f a c t o r i e s i a n d it m i g h t be p l a u s i b l e to a s s u m e t h a t s e w a g e t r e a t m e n t p l a n t s a n d d y e i n g f a c t o r i e s s e r v e as o n e of t h e s o u r c e s of silicone c o n t a m i n a t i o n . A n a l y s i s of d o m e s t i c w a s t e w a t e r , i n d u s t r i a l effluents a n d t h e i r sludges w e r e also c a r r i e d o u t to clarify the s o u r c e of silicone. T h e e x t r a c t a b l e silicones in effluents a n d sludges a r e s h o w n in T a b l e 6. T h e silicone levels w e r e v e r y v a r i a b l e . R e l a t i v e l y h i g h levels w e r e f o u n d in b o t h effluents a n d sludges, w i t h one e x c e p t i o n b e i n g t h e effluent f r o m a d y e i n g f a c t o r y . Sludges w i t h t h e h i g h e r silicone c o n t e n t s w e r e f r o m the d y e i n g factories. T h u s , silicone c o n t a m i n a t i o n of t h e a q u a t i c e n v i r o n m e n t m a y be derived f r o m a n t i f o a m i n g a g e n t s p r e s e n t in w a s t e w a t e r s a n d sludges.
TABLE 5 Extractable silicones in fish muscle Fish
No. of samples
Siliconesa (ppm)
Body length (cm)
Body weight (g)
Deepbodied crucian carp
6
0.69 (0.204.47) 0.36 (0.2(~0.85) 0.40 (0.284).59) 0.89 (0.81=0.98)
23 (21.5-24.5) 18.2 (16-20) 30.4 (3(~32) 26.9 (26-28)
287 (245-360) 110 (75-145) 276 (27(~296) 214 (20(~245)
(Carassius cuvieri) Deepbodied crucian carp
6
(Carassius cuvieri) Steed barbel
6
(Hemibarbus labeo) Japanese dace
(Leuciscus hakonensis)
4
Based on 48.9% recovery in fish muscle. Silicones are 37.9% silicon.
IDENTIFICATION OF SILICONES IN ENVIRONMENTAL SAMPLES
Gel chromatography with Sephadex LH-60 was combined with ICP for selective detection and determination of molecular weights of silicones in environmental samples. The gel filtration chromatogram of silicones having different molecular weights is shown in Fig. 5. Relatively good separation was obtained within the molecular weight range from 162 to 25000. A good linear relationship between the logarithm of molecular weight and the elution volume was also found, as shown in Fig. 6. The gel chromatograms of silicones in environmental samples are shown in Fig. 7. The environmental samples were sludge from a night soil treatment plant, sediment from an urban river receiving the effluents of dyeing factories, TABLE 6 Extractable silicones in industrial effluents and sludges Type of industry
Effluentsa (ppb)
Sludge b (ppm)
Dyeing factory A B C D Sewage treatment plant Night soil treatment plant Domestic waste water A B
ND
41.0 49.4 629O 3350 144 34.4
2.6 1150 13.1 10.2 3.0 2.4 4.9
a Based on 69% recovery in water samples. b Based on 57.7% recovery in solid samples. Silicones are 37.9% silicon. ND, not detected. Not measured.
2.o
~
: (4)
(~
4
~
e 0 I0
20
30
Fraction number
'~ 40
2
,
(
4
)
. . . . . . . . . . . . . . I00 150 200 Elution volume (ml)
Fig. 5, Gel chromatogram of silicones by Sephadex LH-60. The sample volume was 3 ml. The column (20mmi.d. × 79.0cm) was eluted with M I B K - m e t h a n o l (10:3, v/v) at 0.7mlmin 1. Each fraction was collected in 5 ml. (1) PDMS MW 25000; (2) MW 6000; (3) MW 1200; (4) MW 162. Fig. 6, Relationship between average molecular weight and elution volume. Numbers correspond to those given in Fig. 5,
and ash from a municipal incineration plant. The molecular weight of silicones extracted from sludge and sediment was ~ 6000. The silicones in ash from an incineration plant exhibited a broad molecular weight distribution, although they consisted mostly of high molecular weight compounds. Infrared spectra of silicones fractionized by Sephadex LH-60 are shown in Fig. 8. The characteristic Si CH3 bands at 1260 and 790cm -1 appear in the spectra from the silicone standard and sludge, and the strong Si-O frequencies around 1080 cm-~ are sharp in both spectra. The Si-CH3 and Si-O absorption bands in the spectrum from incineration ash are much less intense than those of the silicone standard and sludge. The organosilicon compounds in sludge and incineration ash were ascertained to be polydimethylsiloxane. CONCLUSION
A simple and rapid method is presented for the separation and determination of silicones in water, sediment and fish samples, using inductively coupled plasma emission spectrometry. Silicones extracted with petroleum ether are evaporated to dryness. The damp residue is dissolved in methyl isobutyl ketone, and aspirated into the plasma. The silicone concentration of 120 water samples from main rivers and bays in J a p a n was < 2.5 ppb, while some sediment and fish samples contained > 10 ppm. As a general rule, silicones were detected mostly in industrialized and overpopulated areas. Higher levels of silicones were found in effluents from dyeing factories and sewage treatment plants and in their sludges. Silicones in environmental samples are ascertained to be poly-
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•
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i
i
,
l
15
l
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,
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•
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Wavenumber, 102 (cm - I )
Fig. 7. Gel chromatogram of silicones from sludge (upper panel), river sediment (middle panel) and incineration ash (lower panel) using Sephadex LH-60. Analytical conditions correspond to those given in Fig. 5. Fig. 8. Infrared spectra of fraction obtained by Sephadex LH-60. The upper, middle and lower panels indicate silicone standard, sludge and incineration ash, respectively. d i m e t h y l s i l o x a n e , a n d s i l i c o n e s u s e d as a n t i f o a m i n g a n d d i s p e r s i n g a g e n t s i n t h e d y e i n g i n d u s t r y a r e i d e n t i f i e d as t h e s o u r c e o f s i l i c o n e c o n t a m i n a t i o n i n t h e aquatic environment. REFERENCES Japan EPA, 1981. Chemicals in the Environment. No. 7, p. 70. Pellenbarg, R., 1979. Environmental poly(organosiloxane) (silicones). Environ. Sci. Technol., 13: 565-569. Tsuchitani, Y., K. Harada, K. Saito, N. Muramatsu and K. Uematsu, 1978. Determination of organosilicone in sewage sludge by atomic absorption spectrometry. Bunseki Kagaku, 27: 343-347.
1
D I S T R I B U T I O N OF SILICONES IN W A T E R , S E D I M E N T A N D FISH IN J A P A N E S E RIVERS
NORITO WATANABE Gifu Prefectural Research Institute for Environmental Pollution, 58-2, Yabuta 8 chome, Gifu-shi, 500 (Japan)
HISAMITSU NAGASE and YOUKI OSE Gifu Pharmaceutical University, Department of Environmental Hygiene, 5-6-1 Mitahorahigashi, Gifu-shi, 502 (Japan)
ABSTRACT A new analytical method for assaying polyorganosiloxanes (silicones) in environmental samples is presented. The method utilizes petroleum for solvent extraction of the sample (water, sediment, biological tissue) together with inductively coupled plasma detection of the extracted organic silicones. The detection limit for silicones in the final methyl isobutyl ketone sample] extract is ~ 0.01 ppm, and the method is applied to samples from various Japanese rivers to quantify silicones in several environmental materials. Silicones are reported from river waters (up to ~ 50 ppb), riverine sediments (up to 6 ppm), and as an extractable component of fish tissue (up to 0.9 ppm).
INTRODUCTION Silicone fluids possess m a n y desirable properties, s u c h as low surface tension, w a t e r repellency, t h e r m a l a n d c h e m i c a l stability, r e s i s t a n c e to ult r a v i o l e t r a d i a t i o n and p r e s u m e d biological inertness. These desirable p r o p e r t i e s h a v e led to t h e i r extensive use in i n d u s t r i a l a n d domestic applications, i n c l u d i n g use as a n t i - f o a m i n g a n d release agents, polishes for automobiles and as cosmetic additives. The w i d e s p r e a d use of silicones suggests t h a t t h e y m a y be released into the e n v i r o n m e n t , a n d m a y r e s u l t in environm e n t a l c o n t a m i n a t i o n , w h i c h deserves special c o n s i d e r a t i o n b e c a u s e of t h e i r e x c e p t i o n a l persistence. I n J a p a n , i n v e s t i g a t i o n s on the d i s t r i b u t i o n of silicones were c o n d u c t e d u s i n g a t o m i c a b s o r p t i o n s p e c t r o m e t r y (AAS) in o r d e r to e s t i m a t e t h e i r b e h a v i o u r in the e n v i r o n m e n t ( J a p a n EPA, 1981), b u t this m e t h o d is n o t a l w a y s sufficiently sensitive to d e t e r m i n e t r a c e a m o u n t s of silicones in e n v i r o n m e n t a l samples. In this report, a simple a n d rapid m e t h o d is p r e s e n t e d for the s e p a r a t i o n and d e t e r m i n a t i o n of silicones in e n v i r o n m e n t a l samples u s i n g i n d u c t i v e l y coupled p l a s m a emission s p e c t r o m e t r y (ICP), and the o c c u r r e n c e of siIicones in some
0048-9697/88/$03.50
© 1988 Elsevier Science Publishers B.V.
2.0 -
2.0
1.9 1.8 I I I J J 1.2 1.4 1.6 Plasma support gas, l/min
1.8
16 18 20 Coolant gas, ]/min
Fig. 1. Effect of p l a s m a s u p p o r t g a s flow r a t e o n silicone r e s p o n s e . C o o l a n t g a s flow rate, 201 m i n - l ; c a r r i e r g a s flow rate, 0.81 m i n -1 . Fig. 2. Effect of c o o l a n t g a s flow r a t e on silicone r e s p o n s e . P l a s m a s u p p o r t g a s flow rate, 1.21 m i n - 1; c a r r i e r g a s flow rate, 0.81 m i n - 1 .
Japanese river waters, industrial effluents, aquatic sediments, sludges and fish is reviewed. ESTABLISHMENT OF ANALYTICAL METHOD
Optimisation of ICP operating conditions When determining trace amounts of silicones in methyl isobutyl ketone (MIBK), the strict control of three argon gas flow rates (coolant, plasma support, carrier) and the plasma height above the induction coil are considered to be important. The effect of variation of the plasma support gas flow rate on the silicone response is shown in Fig. 1, with the plasma height fixed at 9.7mm above the induction coil. The change in response is small when the plasma support gas flow rate is varied, with the coolant gas flow rate (201 min -1) and carrier gas flow rate (0.81 min -1) held constant. Below a flow rate of 1.21 min-1, measurement becomes impossible because of extinction of the plasma torch. The effect of variation of coolant gas flow rate on the silicone response is shown in Fig. 2, with the plasma height fixed at 9.7 mm above the induction coil. Sensitivity increases as the coolant gas flow rate increases from 161 min -1 to a maximum level, with the plasma support gas flow rate (1.21 min-1) and carrier gas flow rate (0.81 min-1) held constant. The effect of variation of carrier gas flow rate on the silicone response is shown in Fig. 3, with the plasma height fixed at 9.7 ram above the induction coil. Maximum emission occurred for a flow rate of between 0.7 and 0.81 min-1, with the plasma support gas flow rate (1.21min -1) and coolant gas flow rate (201min 1) held constant. In Fig. 4 the effect of variation of plasma height on silicon response is shown
2.0 :
1.8
-p
1.4
B
1.6
1.0
1.2
0
0.6 I
l
I
l
I
I
0.5 0.7 0.9 Carrier gas flow-rate, I/min
2.0 6.0 I0 Height above induction coil,mm
Fig. 3. Effect of carrier gas flow r a t e on silicone response. P l a s m a support gas flow rate, 1.21 m i n - 1; coolant gas flow rate, 2 0 1 m i n - L Fig. 4. Effect of plasma h e i g h t on silicone response. Carrier gas flow rate, 0.81min-~; plasma support gas flow rate, 1.21min-1; coolant gas flow rate, 2 0 1 m i n - L
at three selected gas flow rates. Emission intensity varies markedly with small changes in plasma height; the best compromise position is between 7 and 10 mm. The ICP operating conditions for the determination of trace amount of silicones in MIBK are listed in Table 1.
Analytical procedure Liquid samples Five hundred to four thousand millilitres of the sample was placed in a separating funnel and extracted twice with two aliquots (2 x 100ml) of petroleum ether by shaking vigorously for 10 min. Combined petroleum ether TABLE 1 Operating conditions for Shimadzu ICPQ-100 emission spectrometer Oscillator frequency Incident power Reflection power P l a s m a h e i g h t above i n d u c t i o n coil Coolant gas flow rate P l a s m a support gas flow rate Carrier gas flow rate Sample i n t r o d u c t i o n r a t e P r e b u r n time I n t e g r a t i o n time Wavelength
27.12 MHz 1.8 W < 5W 9.7 m m Ar, 201rain -1 Ar, 1.21rain -1 Ar, 0.81 min-1 2.5 ml m i n -1 45 s 2s 2516.1 n m
extracts were dehydrated with anhydrous sodium sulfate, then rotary evaporated to dryness. The residue was dissolved in 5 ml MIBK. The silicone concentration was obtained by reference to a linear working curve prepared from octaphenylcyclotetrasiloxane.
Sediment and fish tissue Solid samples (5-10g) were placed in a 200ml Erlenmeyer flask with a ground-glass stopper, then allowed to stand overnight after addition of 100 ml petroleum ether. The samples were extracted ultrasonically for 15min, dehydrated with anhydrous sodium sulfate and then rotary evaporated to dryness; the residue was taken up in 5 ml MIBK. The silicone concentration was determined as for liquid samples.
Detectability The calibration curve of silicone in MIBK gives a straight line; a wide working range of 0-200 #g of silicone per 10 ml of MIBK is obtained. The detection limit of silicone in MIBK is 0.01 ppm, provided it is defined as the concentration of silicone in ppm t h a t produces an emission intensity twice the background. The detection limit of ICP is more than two orders of magnitude lower t h a n that of AAS.
Recovery and precision The recovery of silicone by the proposed method was evaluated by processing distilled water, river sediment and fish tissue spiked with known quantities of polydimethylsiloxane (PDMS) (Table 2). PDMS was recovered with yields of 69.0% for water, 57.7% for river sediment and 48.9% for fish tissue. The recovery from solid samples by the proposed method was interTABLE 2 Recovery of PDMS a from water, s e d i m e n t and fish samples Sample
A m o u n t of sample
PDMS added (pg)
PDMS found (#g)
Recovery (%)
Distilled w a t e r
1000 ml 1000 ml 10 g 10 g 10 g 10 g 10 g 10 g
20 200 0 20 200 0 20 200
13.5 141 12.6 24.5 124.4 1.3 10.3 107
67.5 70.5
69.0
59.5 55.9
57.7
45.0 52.8
48.9
River s e d i m e n t
F i s h tissue
a P D M S = p o l y d i m e t h y l s i l o x a n e (Toray silicone fluid SH-200).
TABLE 3 Extractable silicone in environmental samples (Japan EPA, 1981) Sample
Tokyo Bay
IseBay
Osaka Bay
Water Sediment Fish
0/21 17/21 12/15
0/21 9/21 21/21
0/15 7/15 6/6
Denominator and numerator denote the number of analyzed samples and positive number, respectively. Detection limit is 2.5 ppb for water samples and 1ppm for sediment and fish samples. mediate between the recovery by Soxhlet ext ract i on (Pellenbarg, 1979) and by Dean Stark ext r a c t i on (Tsuchitani et al., 1978). In a test of precision, four environmental samples, river water, river sediment, sewage sludge and fish tissue were examined. The coefficient of v ar iatio n was 4.7% for river water, 10.8% for river sediment, 1.2% for sewage sludge and 13.3% for fish tissue. The proposed method gives good precision and is acceptable for the determination of trace levels of silicone in environmental samples. GENERAL SITUATION ON DISTRIBUTIONOF SILICONE IN JAPAN J a p a n EPA has surveyed the concentrations of various chemicals in water, sediment and biota since 1976, and found silicones in some sediment and fish samples. Silicone c o n c e n t r a t i o n s in 120 samples from major rivers and bays in J a p a n were less t ha n the detection limit (2.5 ppb), while some sediment samples from Tokyo Bay and fish samples from the River N agara contained > 10 ppm. As a general rule, silicone was detected mostly in samples from industrialized and overpopulated districts, as shown in Table 3. DISTRIBUTION OF SILICONE IN THE NAGARA RIVER WATERSHED The J a p a n EPA studies showing silicone pollution of an aquatic environment stimulated us to investigate the distribution of silicones in the River Nag ar a watershed. The River Nagara, located in mid-Japan, flows southeasterly for 160 km t h r o u g h Gifu Prefecture and then discharges into Ise Bay; the catch men t area is ~ 2050 km 2, and the flow rate is > 50 m 3s 1. Municipal and industrial effluents from five t r i b u t a r y rivers enter the N agara River in the middle reach. The dyeing industry is very prosperous in the Nagara River watershed. Water quality and extractable silicone cont ent of the river water and sediment samples from the N a ga r a River watershed are shown in Table 4. Silicones were not detected in the water samples from N agara River, but water samples from t r i b u t a r y rivers contained a detectable, but low, silicone content, similar to those for Chesapeake Bay and Delaware Bay (Pellenbarg, 1979);
6 TABLE 4 W a t e r q u a l i t y a n d e x t r a c t a b l e silicones in w a t e r and sediment samples Sampling
BOD ~
COD e
SS a
Silicone in
Silicone in
station
(ppm)
(ppm)
(ppm)
waterb( p p b )
sedimenff (ppm)
Nagarabashi
1.4
2.0
9
ND
ND
Nagaraohashi Nannouohashi Tokaiohashi Takebashi Suimonbashi Sakaigawabashi Matuyama (near junction) Koyabu (near junction)
1.2 1.5 1.5 2.9 6.1 6.1 9.3
2.2 2.8 2.8 4.3 7.5 11 13
5 7 9 24 43 26 14
ND ND ND 2.8 2.0 7.9 54.2
ND ND ND ND 5.8 ND 0.3
3.4
6.4
15
2.0
ND
a A v e r a g e of 12 data in FY1981. b Based on 69% recovery in w a t e r samples. CBased on 57.7% r e c o v e r y in sediment samples. Silicones are 37.9% silicon; ND = not detected.
silicone c o n t e n t s r a n g e d f r o m 2.0 to 54.2ppb, w i t h the h i g h e r levels u s u a l l y o c c u r r i n g in the w a t e r s a m p l e s s h o w i n g the h i g h e r BOD or COD. This r e l a t i o n ship s e e m s to c o r r o b o r a t e the c o n c l u s i o n t h a t silicones o r g i n a t e f r o m ant h r o p o g e n i c sources. S e d i m e n t s a m p l e s h a v i n g t h e h i g h e s t i g n i t i o n loss also c o n t a i n e d t h e h i g h e s t silicone levels. T h e c o n c e n t r a t i o n of silicone in t h e S u i m o n b a s h i a n d M a t u y a m a w a s 5.8 a n d 0.3 ppm, r e s p e c t i v e l y . T h e e x t r a c t a b l e silicones in fish c a u g h t in t h e N a g a r a R i v e r a r e s h o w n in T a b l e 5. A v e r a g e e x t r a c t a b l e silicones in fish m u s c l e of d e e p b o d i e d c r u c i a n carp, steed b a r b e l a n d J a p a n e s e d a c e r a n g e d f r o m 0.36 to 0.89ppm. Silicone levels in this s t u d y w e r e a b o u t one o r d e r of m a g n i t u d e l o w e r t h a n t h o s e r e p o r t e d by J a p a n E P A . M e a s u r a b l e silicones w e r e d e t e c t e d in t h e t r i b u t a r y r i v e r s r e c e i v i n g a cons i d e r a b l e v o l u m e of effluents f r o m s e w a g e t r e a t m e n t p l a n t s a n d / o r d y e i n g f a c t o r i e s i a n d it m i g h t be p l a u s i b l e to a s s u m e t h a t s e w a g e t r e a t m e n t p l a n t s a n d d y e i n g f a c t o r i e s s e r v e as o n e of t h e s o u r c e s of silicone c o n t a m i n a t i o n . A n a l y s i s of d o m e s t i c w a s t e w a t e r , i n d u s t r i a l effluents a n d t h e i r sludges w e r e also c a r r i e d o u t to clarify the s o u r c e of silicone. T h e e x t r a c t a b l e silicones in effluents a n d sludges a r e s h o w n in T a b l e 6. T h e silicone levels w e r e v e r y v a r i a b l e . R e l a t i v e l y h i g h levels w e r e f o u n d in b o t h effluents a n d sludges, w i t h one e x c e p t i o n b e i n g t h e effluent f r o m a d y e i n g f a c t o r y . Sludges w i t h t h e h i g h e r silicone c o n t e n t s w e r e f r o m the d y e i n g factories. T h u s , silicone c o n t a m i n a t i o n of t h e a q u a t i c e n v i r o n m e n t m a y be derived f r o m a n t i f o a m i n g a g e n t s p r e s e n t in w a s t e w a t e r s a n d sludges.
TABLE 5 Extractable silicones in fish muscle Fish
No. of samples
Siliconesa (ppm)
Body length (cm)
Body weight (g)
Deepbodied crucian carp
6
0.69 (0.204.47) 0.36 (0.2(~0.85) 0.40 (0.284).59) 0.89 (0.81=0.98)
23 (21.5-24.5) 18.2 (16-20) 30.4 (3(~32) 26.9 (26-28)
287 (245-360) 110 (75-145) 276 (27(~296) 214 (20(~245)
(Carassius cuvieri) Deepbodied crucian carp
6
(Carassius cuvieri) Steed barbel
6
(Hemibarbus labeo) Japanese dace
(Leuciscus hakonensis)
4
Based on 48.9% recovery in fish muscle. Silicones are 37.9% silicon.
IDENTIFICATION OF SILICONES IN ENVIRONMENTAL SAMPLES
Gel chromatography with Sephadex LH-60 was combined with ICP for selective detection and determination of molecular weights of silicones in environmental samples. The gel filtration chromatogram of silicones having different molecular weights is shown in Fig. 5. Relatively good separation was obtained within the molecular weight range from 162 to 25000. A good linear relationship between the logarithm of molecular weight and the elution volume was also found, as shown in Fig. 6. The gel chromatograms of silicones in environmental samples are shown in Fig. 7. The environmental samples were sludge from a night soil treatment plant, sediment from an urban river receiving the effluents of dyeing factories, TABLE 6 Extractable silicones in industrial effluents and sludges Type of industry
Effluentsa (ppb)
Sludge b (ppm)
Dyeing factory A B C D Sewage treatment plant Night soil treatment plant Domestic waste water A B
ND
41.0 49.4 629O 3350 144 34.4
2.6 1150 13.1 10.2 3.0 2.4 4.9
a Based on 69% recovery in water samples. b Based on 57.7% recovery in solid samples. Silicones are 37.9% silicon. ND, not detected. Not measured.
2.o
~
: (4)
(~
4
~
e 0 I0
20
30
Fraction number
'~ 40
2
,
(
4
)
. . . . . . . . . . . . . . I00 150 200 Elution volume (ml)
Fig. 5, Gel chromatogram of silicones by Sephadex LH-60. The sample volume was 3 ml. The column (20mmi.d. × 79.0cm) was eluted with M I B K - m e t h a n o l (10:3, v/v) at 0.7mlmin 1. Each fraction was collected in 5 ml. (1) PDMS MW 25000; (2) MW 6000; (3) MW 1200; (4) MW 162. Fig. 6, Relationship between average molecular weight and elution volume. Numbers correspond to those given in Fig. 5,
and ash from a municipal incineration plant. The molecular weight of silicones extracted from sludge and sediment was ~ 6000. The silicones in ash from an incineration plant exhibited a broad molecular weight distribution, although they consisted mostly of high molecular weight compounds. Infrared spectra of silicones fractionized by Sephadex LH-60 are shown in Fig. 8. The characteristic Si CH3 bands at 1260 and 790cm -1 appear in the spectra from the silicone standard and sludge, and the strong Si-O frequencies around 1080 cm-~ are sharp in both spectra. The Si-CH3 and Si-O absorption bands in the spectrum from incineration ash are much less intense than those of the silicone standard and sludge. The organosilicon compounds in sludge and incineration ash were ascertained to be polydimethylsiloxane. CONCLUSION
A simple and rapid method is presented for the separation and determination of silicones in water, sediment and fish samples, using inductively coupled plasma emission spectrometry. Silicones extracted with petroleum ether are evaporated to dryness. The damp residue is dissolved in methyl isobutyl ketone, and aspirated into the plasma. The silicone concentration of 120 water samples from main rivers and bays in J a p a n was < 2.5 ppb, while some sediment and fish samples contained > 10 ppm. As a general rule, silicones were detected mostly in industrialized and overpopulated areas. Higher levels of silicones were found in effluents from dyeing factories and sewage treatment plants and in their sludges. Silicones in environmental samples are ascertained to be poly-
°.3,I
II I\ i
1
i
,
1
|
i
i
1
I
I
I
I
r,r-
~3.o g .~ 2.o
g
g 1.o L
o.4
g
o.2, O, ....~ I0
,_ ~20 30 40 Fraction number
•
20
i
i
,
l
15
l
J
,
J
l
,
•
•
I0
•
6
Wavenumber, 102 (cm - I )
Fig. 7. Gel chromatogram of silicones from sludge (upper panel), river sediment (middle panel) and incineration ash (lower panel) using Sephadex LH-60. Analytical conditions correspond to those given in Fig. 5. Fig. 8. Infrared spectra of fraction obtained by Sephadex LH-60. The upper, middle and lower panels indicate silicone standard, sludge and incineration ash, respectively. d i m e t h y l s i l o x a n e , a n d s i l i c o n e s u s e d as a n t i f o a m i n g a n d d i s p e r s i n g a g e n t s i n t h e d y e i n g i n d u s t r y a r e i d e n t i f i e d as t h e s o u r c e o f s i l i c o n e c o n t a m i n a t i o n i n t h e aquatic environment. REFERENCES Japan EPA, 1981. Chemicals in the Environment. No. 7, p. 70. Pellenbarg, R., 1979. Environmental poly(organosiloxane) (silicones). Environ. Sci. Technol., 13: 565-569. Tsuchitani, Y., K. Harada, K. Saito, N. Muramatsu and K. Uematsu, 1978. Determination of organosilicone in sewage sludge by atomic absorption spectrometry. Bunseki Kagaku, 27: 343-347.