ANALYTICAL CHEMISTRY, VOL. 50, NO. 11, SEPTEMBER 1978
1435
Determination of Triphenyltin Hydroxide and Its Degradation Products in Water Charles J. Soderquist' and Donald G. Crosby' Department of Environmental Toxicology, University of California, Davis, California 956 16
An analytical method has been developed for the simultaneous determination of triphenyltin hydroxide and its possible degradation products tetraphenyitin, diphenyitin oxide, benrenestannoic acid, and inorganic tin in water. The method Is rapid (one sample set per hour), sensitive to less than 0.01 wg/mL for most of the tin species, exhibits no cross-interferences between the phenyltins, and requires no elaborate equipment. The phenyltins are detected by electron-capture gas-liquid chromatography after conversion to their hydride derivatives, while inorganic tin is determined by a procedure which responds to tin(1V) oxide as well as aqueous tin(1V) cation, a procedure not previously described in the literature.
Triphenyltin hydroxide (Duter) is a member of the organotin class of agricultural chemicals which also includes tricyclohexyltin hydroxide (Plictran) and triphenyltin acetate (Brestan), and is currently registered under a experimental-use permit in California as a fungicide in rice culture. As part of a study of the chemicals used in rice culture ( I , Z),we are examining the environmental fate of Duter ( 3 ) . In order t o obtain information necessary to establish the fate of triphenyltin h y d r o x i d e f o r example, photodegradation products and hydrolytic stability-it was essential to have an analytical method that (a) was capable of differentiating the parent compound and its degradation products, (b) was sensitive to sub-pg/mL levels in water, and (c) utilized readily available instrumentation. None of the over 140 methods concerning organotin analysis listed in a 1970 bibliography ( 4 ) or those in the more recent literature (5) adequately met these criteria. For example, the colorimetric procedures of Corbin (6, 7) were sensitive and utilized simple instrumentation but lacked specificity; the anodic stripping voltammetry method of Booth and Fleet (8) was specific for triphenyltin but required elaborate equipment; and t h e gas-liquid chromatography (GLC) procedure of Gauer et al. (9), while specific for various cyclohexyltin bromides, was not adaptable to the phenyltin analogues because of the low volatility of the phenyltin bromide derivatives. From previous studies on other organotin compounds ( I O , I I ) , it appeared that diphenyltin oxide (Ph2Sn0, where P h = phenyl), benzenestannoic acid (PhSnOzH), and inorganic tin would be likely degradation products of triphenyltin hydroxide (Ph3SnOH). (Current Chemical Abstracts nomenclature as follows: PhSnOzH, hydroxyoxophenyl stannane; PhzSnO, oxodiphenyl stannane; Ph,SnOH, hydroxytriphenyl stannane.) None of these compounds responded well to GLC, primarily because of their nonvolatile nature, and attempts to overcome this difficulty by conversion of the phenyltins to their corresponding halide, acetate, or methylether derivatives were unsuccessful. However, preparation of the hydride series, which are the most volatile and least ionic phenyltins possible, resulted in derivatives with excellent 'Present address, California Analytical Labs, Sacramento, Calif. 95814.
Scheme I Ph,Sn
$2
t aq
4
PhzSn
oq
-
PhSn
t3 Oq
. -.'f' /2
Possible Degradation
SnQ2 o q
0
Ph3SnH, P$Sn H2,PhSnH3
0
Sn-PCV complex
C o I o r imetr y
E C -GLC
Analysis
GLC properties, high response to electron-capture (EC) detection, and none of the attendant column stability problems encountered elsewhere with other derivatives (9). T h e inorganic tin species were quantitated by a n adaptation of a sensitized pyrocatechol-violet method (6),modified to account for any tin(1V) oxide present in solution or suspension. The determination of tin(1V) oxide (hydrated tin oxide, metastannic acid, or SnOJ was based on a previously unpublished method provided to us by M&T Chemicals (12). The basis for the proposed method thus involves extraction of the phenyltin species from water followed by their quantitation as phenyltin hydrides by EC-GLC and analysis of the remaining aqueous phase for inorganic tin (Sn4+plus SnO,) by colorimetry.
EXPERIMENTAL Apparatus and Chromatography. Photometric measurements were made with a Bausch and Lomb Spectronic 20 spectrophotometer. Gas-liquid chromatography was performed on a dual column/dual detector Varian Model 2400 instrument equipped, on one side, with a flame-ionization detector (FID) and a 0.7 m by 2 mm (id.)glass column containing 3% OV-17 on 60/80 mesh Gas Chrom Q. Column, injector, and detector temperatures were 265, 275, and 300 "C, respectively; carrier gas (nitrogen) flow rate was 25 mL/min. Ph4Sn eluted within 8 min under those conditions. The second side of the chromatograph was equipped with a tritium EC detector and a 1.1m by 2 mm (id.) glass column containing 4% SE-30 on 60/80 mesh Gas Chrom Q. The injector and detector temperatures were 210 "C, the carrier gas (nitrogen) flow rate was 20 mL/min, and column temperatures which eluted the following compounds within 6 min were: Ph3SnH, 190 "C; Ph2SnH2,135 "C; PhSnH3, 45 "C. Combined gas-liquid chromatography/mass spectrometry (GC-MS) was performed on a Finnigan Model 1015 utilizing a 1.0 m by 2 mm (id.) glass column containing 3% OV-17 on 60/80 mesh Gas Chrom Q. Infrared (IR) spectra were obtained in hexane solution with a Perkin-Elmer Model 337 spectrometer. Reagents. Unless otherwise noted, water was distilled and passed through a column of Amberlite XAD-4 resin (Rohm and Haas) before use. Hexane and dichloroniethane were Nanograde quality (Mallinckrodt) or equivalent. All other commercial chemicals were used as received. All glassware was cleaned by soaking in 2.0 M hydrochloric acid followed by rinsing with copious volumes of water. Lithium Aluminum Hydride Solution. Lithium tetrahydridoaluminate (Ventron) (100 f 10 mg) was added to 25 mL of dry, reagent grade diethyl ether in a glass-stoppered flask, the mixture shaken for 2 min, and the gray precipitate allowed to settle before use. The solution was prepared fresh daily. Sensitized PCV Solution. Pyrocatechol violet (Eastman Organic Chemicals) (12 mg) and 11 mg of cetyltrimethyl-
0003-2700/78/0350-1435$01.00/0C 1978 American Chemical Society
1436
ANALYTICAL CHEMISTRY, VOL. 50, NO. 11, SEPTEMBER 1978
ammonium bromide were added to 100 mL of water. The solution was prepared fresh daily. Ascorbic Acid Solution. Ascorbic acid (2.5 g) was added to 50 mL of water. The solution was prepared fresh daily. Acetate Buffer. Sodium acetate trihydrate (68 g) and 28 mL of glacial acetic acid were combined and diluted to 500 mL with water. This procedure yielded a 2.0 M, pH 4.7 buffer. Citric Acid Solution. Citric acid monohydrate (10 g) was added to 100 mL of water. Sulfuric/Citric Acid Solution. Analytical reagent grade sulfuric acid (25 g) and 13 g of citric acid monohydrate were combined and diluted to 500 mL with water. Standard Compounds. Triphenyltin Hydride (Ph,SnH). A solution of triphenyltin chloride (Ventron) (3.9 g, 10 mmol) in 50 mL of dry diethyl ether was added dropwise under a nitrogen atmosphere to a stirred mixture of lithium aluminum hydride 10.80 g, 20 mmol) and 100 mL of dry diethyl ether. After stirring for 1 h, water was slowly added until the excess lithium aluminum hydride decomposed. The ether layer was decanted and evaporated under vacuum. The residue was dissolved in 50 mL of hexane, any insoluble material discarded, and the hexane concentrated under a gentle stream of nitrogen at less than 40 "C. The resulting 2.2 g (63% yield) of colorless, viscous liquid [lit. mp 29 "C (13)] had the following physical characteristics: nDZo 1.6306 [lit. nDZ51.634 ( I 3 ) ]IR ; 1860 cm-' (Sn-H) [lit. 1843 cm ( 1 4 ) ] ;GC-MS m / e 351 (Ph,Sn), 274 (PhzSn),197 (PhSn), 120 (Sn) with the observed isotope clusters surrounding each major fragment in agreement ( & l o % ) with the known isotopic distribution of tin. The product was homogeneous to FID-GLC and was stored under nitrogen at -10 "C. Working standards were prepared in hexane when convenient. PhsSnH is now commercially available (Ventron). Diphenyltin Dihydride (PhzSnHz). Using the procedure described above, reaction of 3.4 g of diphenyltin dichloride (Research Chem.) and 1.1g of lithium aluminum hydride gave 2.1 g (75% yield) of a clear liquid [lit. bp 89-93 "C/0.3 Torr (1311 with the following physical characteristics: TID" 1.6127 [lit. 1.595 ( 1 3 ) ] ;IR: 1865 cm-I (Sn-H) [lit. 1857 cm-l ( 1 4 ) ] ;GC-MS: m / e 274 (Ph,Sn), 197 (PhSn), 120 (Sn) with the expected isotope clusters. The product was over 95% pure by FID-GLC and was stored under nitrogen at -10 "C. A pg/pL solution in hexane was prepared and quickly diluted to a 1.0 ng/pL working standard. Phenyltin Trihydride (PhSnH,). Again using the above procedure, reaction of 1.0 g of phenyltin trichloride (Research Chem.) and 0.60 g of lithium aluminum hydride provided a hexane solution which was concentrated under nitrogen to a liquid [bp 35 "C at 2.5 Torr (13)].A portion was quickly weighed, dissolved in hexane a t the ,ug/pL level, and immediately diluted to a 1.0 ng/pL working standard. The neat product rapidly decomposed to a colored, insoluble material; however, the pg/pL hexane solution gave (GC-MS) a single peak with m / e 197 (PhSn) and 120 (Sn) with correct isotopic distributions and an IR spectrum with Sn-H at 1892 cm" [lit. 1880 cm-' ( 1 4 ) l . Fortification Standards. For convenience, calculations of recoveries were based on the phenyltin moiety regardless of the accompanying anion (e.g., chloride, acetate, hydroxide, or hydride). A mixed standard was prepared by dissolving about 20 mg of each phenyltin chloride and tetraphenyltin in separate 10-mL volumetric flasks. Aliquots of each were combined, in dichloromethane, to yield PhrSn, Ph3Snt, PhZSnzt,and PhSn3+at 0.20 pg/kL each. The inorganic tin (Sn4+)standard was prepared by dissolving 0.250 g of pure tin in 150 mL of concd. hydrochloric acid and diluting to 500 mL with water. A 5.0 pg/mL working standard was prepared by dilution with sulfuric/citric acid solution. Procedure (Figure 1). Organotim. The 200-mL sample in a 250-mL. separatory funnel was mixed with 5 mL of acetate buffer, the mixture extracted with two 15-mL portions of dichloromethane, and the pooled extract divided into three equal portions, each of which was concentrated to about 0.1 mL in a screw-capped test tube at less than 40 "C under a gentle stream of nitrogen. T o one of the concentrates (EX-1, Figure 1) was added 5 m L of hexane followed by 0.5 mL of lithium aluminum hydride solution. After 2-3 min, the mixture was diluted with hexane, about 0.5 mL of water carefully added, the phases were mixed, and the hexane phase was analyzed by EC-GLC for Ph3SnH,
WATER S A M P L E
7--adjust pH B x t r o c t with CH2Cl2
I
i AQUEOUS PHASE
CH2Cl2 E X T R A C T ~
EX-I
I, cancontrot0
1
divide
. .
1 EX-2
I conctntrote
,'
H2S04,hQat colorimetry
EX-3
1 concentrate 1 Florist1 column
1
FID-GLC
r~
dlVldQ
1-- ,
A0.i
'
concenlmte K H S 0 4 fusion
A0.2
i concenmte ,colorimetry
colorimetry
I
Figure 1. Flow diagram for analytical procedure
PhzSnHz,and PhSnH,. A standard curve was prepared for each of the hydrides with the ng/pL hexane standard solutions, generally in the 0.2- to 2.0-ng range. Quantitation was done by comparison of sample peak heights to the standard curve. To the second dichloromethane concentrate (EX-2) was added 0.50 mL of sulfuric acid and the dichloromethane removed from the mixture with a vigorous stream of nitrogen. The tube was sealed and heated at 100 "C in a water bath for 20 min. After cooling, 4.0 mL of citric acid solution was added and the sample treated as described below under Color Development. To the third dichloromethane concentrate (EX-3) was added 1 mL of hexane, the contents were concentrated under nitrogen to about 0.1 mL, and then diluted back to 1.0 mL with hexane. The sample was transferred to a Florisil micro-column (prepared by packing a disposable Pasteur pipet with 0.35 g of 60/lOO mesh Florisil held with a small glass wool plug and rinsing with two 5-mL portions of hexane before use) and eluted with hexane. The first 2.5 mL of eluate was collected, concentrated to 0.1-0.5 mL, and analyzed by FID-GLC for Ph,Sn. Quantitation was accomplished by comparison of sample peak heights to the Ph4Sn standard curve in the 10-50 ng range. Inorganic Tin. The extracted aqueous sample was divided equally between two 125-mL Erlenmeyer flasks and the samples were concentrated by boiling just to dryness on a hot plate. To one of the dry aqueous concentrates (AQ-1, Figure 1) was added 2.0 g potassium hydrogensulfate and the flask heated at 300-350 "C for 30 min. After cooling, 4.0 mI, of citric acid solution was added and the solids were dissolved with gentle heating if necessary. Any insoluble particulate matter which would interfere with subsequent colorimetric measurements was removed at this point by filtering through tightly packed glass wool. To the second aqueous concentrate (A$-2) was added 4.0 mL of sulfuric acid/citric acid solution. Both samples were then treated as described below under Color Development. Color Deuelopment. The hydrolyzed dichloromethane extract (EX-2) and the two aqueous samples (A$-1 and AQ-2) were analyzed for tin as follows: ascorbic acid solution (2.0 mL) and 4.0 mL of sensitized PCV solution were added and, after 30 min, the absorbance was read a t 660 nm. Developed samples with absorbance values exceeding those of the standard curve were diluted with water. Tin concentrations were obtained from standard curves prepared in a manner consistent with the individual sample workup. That is, a curve for the aqueous tin subsamples (AQ-1 and AQ-2) was prepared by the addition of 0, 1.0, 3.0, and 5.0 pg of Sn to 3.5 mL of sulfuriclcitric acid solution followed by 2.0 mL of ascorbic acid solution, 4.0 mL of sensitized PCV solution, and enough water to give 11 5 mL total volume. A separate standard curve for the hydrolyzed dichloromethane extracts was prepared when the final sample volume, after color development, was less than about 15 mL; in these cases, addition of the same tin standards was to 0.5 mL of sulfuric acid plus 4.0 mL of citric acid, again followed by the usual amounts of ascorbic acid and sensitized PCV.
RESULTS AND DISCUSSION Procedure. Many of the steps in this procedure were subjected to a parametric analysis. For example, it was anticipated that in the initial extraction step the choice of tin
4NALYTICAL CHEMISTRY, VOL. 50, NO. 11, SEPTEMBER 1978
I TIN-PCV 0.30-
A,C B
D E
-
F
COLORIMETRY
PhgSn
z
P CrJ K W
>
z
0
50 I-
k z a
WITH 5 m L HEXANE
A.
5 0 g 0.20W 0
I
A
usual procedure (see t e x t ) 2.09 K H S 0 4 added 2.5mL a c e t a t e b u f f e r added 2.09 KHSO t 2.5mL a c e t a t e buffer oddod EX-2 procedure
1437
t
-\
'.
'WITHOUT HEXANE
z W V
K
-
W
m LL
0 g 0.10-
I
400
a
REACTION T I M E
I
1200
(SEC)
Figure 3. Conversion of phenyltin chlorides to their hydride derivatives
-
I
0
a00
I
I
0.20
I
0.40
pg S n / m L Figure 2. Tin response to the sensitized-PCV procedure under various conditions
species counterion (e.g., C1- in Ph3SnCl), the sample pH, and the extraction solvent and volume would affect extraction efficiency. Recoveries of Ph3Sn+,Ph2Sn2+,and PhSn3+from p H 5.0 water were compared when 0.1 M KN03, KOAc, KCl, KBr, KF, KI, or KC103 was present. This experiment indicated t h a t chloride and acetate consistently provided the highest recoveries. In a second experiment, recovery data for the same phenyltin compounds in 0.1 M KOAc or KCl were compared a t various p H values from 2.0 through 10.0 and indicated t h a t the acetate ion and a p H near 4.5 provided maximum yields. Use of an acetate buffer conveniently met both the counterion and p H requirements. As extraction solvent, dichloromethane offered the proper polarity, readily evaporated, and was more dense than water (thus allowing removal from a separatory funnel without sample transfer). Recoveries were not increased by additional extractions greater in volume or number than those indicated in the procedure. Decomposition of Ph3SnOH, (Ph3Sn)20,and Ph3SnC1while undergoing FID-GLC resulted in a small peak a t the retention time of Ph,Sn; this potential interference was removed by separation of PhlSn from triphenyltin with the Florisil column. The procedure of Corbin (6) was followed for the inorganic tin analyses with some modifications. For example, concentration of the aqueous samples was done without any additional reagents (e.g., sulfuric acid), and it was not found necessary to separate the tin by distillation (7) or extraction. Color development was carried out with smaller volumes of reagents which allowed a lower limit of detectability but did cause some increased variability. T h e response of 0-5 fig of tin to the sensitized PCV method was essentially the same (an average deviation in tin concentration of 4.5% a t 0.20 absorbance unit) whether or not the sample contained added acetate or was fused with potassium hydrogen sulfate. However, the excessive amounts of sulfuric acid required for the hydrolysis of the sub-samples EX-2 caused a consistently lower response (about 28% at 0.20 absorbance unit, Figure 2 ) in samples which had final volumes of 15 mL of less. When greater accuracy for these samples was needed, a separate standard curve was prepared as described in the Procedure. T h e bisulfate fusion step allows determination of tin(1V) oxide which was unresponsive to the usual colorimetric
procedure. When the total inorganic tin level was desired, the entire aqueous sample was extracted, concentrated, and analyzed with the bisulfate fusion procedure. Alternately, when a differentiation of soluble inorganic tin from tin(1V) oxide was necessary, the dual procedure was used. Hydride Derivatives. The phenyltin hydrides, either neat or in solution, should not be brought into contact with readily reducible materials. For example, the usual procedure for decomposing excess lithium aluminum hydride utilizing ethyl acetate (15) should be avoided. Conversion of microgram amounts of the phenyltins to their hydrides was instantaneous and appeared to be quantitative as long as lithium aluminum hydride was present in excess of other reducible materials (e.g., water). When the derivatization proceeded in the presence of only residual dichloromethane and added reagent, the yields of the hydrides decreased with time, particularly for the monoand diphenyl compounds. Dilution with hexane before the addition of lithium aluminum hydride reagent alleviated this difficulty (Figure 3), perhaps because of the increased stability of the products in dilute hexane solution. I n fact, dilute solutions (ng/pL) of the synthetic hydride standards were stable indefinitely in hexane. Gram quantities of Ph,SnH2 and PhSnH3 were more difficult to handle because of their high reducing power and rapid disproportionation. If the purity of the synthetic standards is questionable, the following is suggested: use the (impure) ng/pL standards to obtain retention time and the detector linear range. Then, during the analysis, add the appropriate phenyltin chloride directly to a test tube and derivatize with lithium aluminum hydride, eliminating the usual extraction and concentration steps. Since the conversion occurs quantitatively, peak heights from these derivatization standards can be used to construct a standard curve. T h e procedure calls for concentration of the dichloromethane extracts below 40 "C to a volume no less than about 0.1 mL in order to prevent the evaporative loss of the phenyltins. The small amount of residual dichloromethane did not interfere with the EC-GLC analyses. Since chloride ion can interfere with the colorimetric procedure ( 6 ) ,residual dichloromethane was removed from the sulfuric acid in procedure EX-2 prior to digestion. Likewise, in order to avoid altering the polarity of the eluting solvent during the Florisil separation of Ph& (EX-3),the dichloromethane was removed from the sample as described. The hydride derivatives differ widely in volatility and could not be simultaneously detected with any GLC columns examined. Since chromatography a t different temperatures was required, it was found most efficient to analyze all of a series
1438
ANALYTICAL CHEMISTRY, VOL. 50, NO. 11, SEPTEMBER 1978
Table I. Recovery of Monophenyltin from Water PhSn" added, pg 400a 200a 100a 4 Oa 2l a 14a 7. ga 2O b
PhSn)' recovered
Ph,SnH
Ph,SnH,
PhSnH,
I9O"column 8X attenuation
135°column 8 X attenuotion
51°column 16X attenuation
percent
Mg
117 67 19
29 34
10
3.1 2.0
0.87 16.1 + 0.7
19 25 15 14 11 81
0.4 n g
I
i
a Data are from duplicate 200-mL samples analyzed as described in Procedure except that all the dichloromethane extract was subjected to the hydride procedure (EX-1). Triplicate direct conversions to PhSnH, with lithium aluminum hydride reagent.
of derivatized samples, blanks, and standards for one of the hydrides before equilibration of the chromatograph at a new temperature. Typical chromatograms of the hydride standards near the limit of detectability are shown in Figure 4. A recent report by Aue and Flinn (16) describes a photometric tin detector which could allow the limit of detectability to be lowered by several orders of magnitude. Tin Species. T h e chemistry of phenyltin compounds is dominated by the lability of the bond associated with the accompanying anionic group as compared to the relative stability of the carbon-tin bond. For example, both Ph,SnCl and (Ph3Sn),0 exist in water as Ph3SnOH, which, in the presence of excess acetate, partitions into dichloromethane as Ph3SnOAc. Ph3SnC1, Ph3SnOH, and (Ph3Sn)20 gave identical recoveries using the described procedure. T h e true identity and behavior of the diphenyltin(1V) compounds is less clear. It is expected that neutral aqueous solutions of Ph2SnC1, rapidly produce Ph2Sn(OH), or the corresponding hydrated oxide Ph2SnO-H,0. While recoveries of Ph,SnO equaled those for Ph2SnC1,, solutions of Ph,SnO in dichloromethane containing 5% acetic acid, prepared as fortification standards, always decomposed within a day to yield an unidentified material unresponsive to lithium aluminum hydride. This may be a polymeric diphenyltin species t o which there are frequent references in the literature (e.g., 17). T h e significance of the formation and degradation of these polymeric materials in an aqueous environment has not been assessed. T h e monophenyltin compounds are the least well characterized and the most difficult to study. While solutions of PhSnCl, in dichloromethane were stable, pure PhSnCI, fumed upon exposure to moist air and presumably exists in aqueous solution as PhSn(OH), (or the hydrated benzenestannoic acid, PhSnO,H.H,O). In spite of the quantitative conversion (Figure 3) of microgram amounts of PhSnC1, (or PhSn02H) to PhSnH3, fortification of samples a t equivalent levels re-
0.4ng
U L 4 8 RETENTION TIME ( M I N )
Figure 4.
Typical chromatograms of the hydride derivatives
sulted in consistently low recoveries. Even at relatively high levels (1-2 kg/mL), less than 35% of the PhSn3+ was recovered. Further experiments indicated that the rapid initial loss was independent of sample pH, volume or nature of extractant, or level of fortification (Table I). As with the diphenyl tin species, the possibility of formation of a nonextractable polymeric material seems reasonable. The '$aging" of monophenyltin has been previously observed (18). While the mode of this rapid loss of PhSn3+ in aqueous solution under mild laboratory conditions remains unexplained, it is surely indicative of the transitory existence which this compound must have under environmental conditions. Tin(1V) oxide is extremely inert. While there have been reports alluding to its solubility [e.g., in concentrated alkali (19)],it was insoluble (less than 0.1%) in all the solvent systems we examined. Further, no chemical system (20) other than the bisulfate fusion method was found which would solubilize milligram amounts of SnO,. Aqueous tin solutions must be kept acidic and at a high level of a complexing ligand such as chloride or sulfate to prevent conversion to the insoluble tin(1V) hydroxide species and, presumably, further to SnOz. Recovery Studies. Four distilled water samples (200 mL) were spiked with 50 WLof the fortification standard to give the organotins and inorganic tin a t 0.050 kg/mL each; an unfortified (blank) sample also was analyzed. All the organotins except PhSn3+were successfully recovered (Table 11). Analysis for total extractable organotin, on a mole basis, resulted in slightly more tin than the sum of the specific hydride analyses and in the absence of any intentionally-added inorganic tin, some inorganic tin still was found (parenthetic values in Table 11); both observations support the notion that PhSn"' is unstable in water. There was no cross-interference
Table 11. Recovery of Tin Species from Water species
procedurea
pg/mL added
fortified samples pg/mL found
blank sample, gg/mL found
Ph4Sn EX-3 0.050 0.035 t 0.002b i 0.003 Ph,Sn'+ EX-1 0.050 0.054 t O.OOlb
