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ANALYTICAL CHEMISTRY, VOL. 51, NO. 8,JULY 1979
Determination of Tin(1V) and Organotin Compounds in Natural Waters, Coastal Sediments and Macro Algae by Atomic Absorption Spectrometry Vernon
F. Hodge," Sharon L. Seidel,
and Edward D. Goldberg
Geological Research Division, Scripps Institution of Oceanography, La Jolla, California 92093
A method is described for the measurement of nanogram or subnanogram amounts of Sn(IV) and the halides of methyltin, dimethyltin, trimethyltin, diethyltin, triethyltin, n-butyltin, din-butyltin, tri-n-butyltin, and phenyltin. These compounds in aqueous solution react with NaBH, to produce volatile hydrides which are detected by atomic absorption spectrometry. The hydrides are separated on the basis of their differing boiling points. Detection limits range from 0.4 ng for Sn(IV) to 2 ng for tri-n-butyltin chloride. Compounds yielding dimethyltin dihydride are found in San Diego Bay seawater at levels of 15 to 45 ng/L, usually exceeding the concentrations of methyltin and inorganic tin. Compounds yielding n-butyltin trihydride and di-n-butyltin dihydride are found in Lake Michigan water at 10-1600 ng/L, also generally higher than the methyl species or inorganic tin. Tin( I V ) concentrations are reported for seawater, lake water, marine algae, and sediments from Narragansett Bay.
Organotin compounds rank fourth in the industrial production of organometallics b u t little is known about their presence in environmental waters, including the ocean, aquatic organisms, and sediments. Most of the organic compounds of tin are used in plastics and as biocides such as algicides, fungicides, bactericides, and molluscicides ( I ) . Since most of these uses are dispersive, t h e possible entry of these toxic compounds into natural waters, sediments and the biota must be assessed. Moreover, determination of inorganic tin in these same systems will provide insights into the natural behavior of tin in aqueous environments. Mono-, di-, and tributyltin species in water have been assayed by extraction with a n organic solvent, conversion to t h e corresponding butylmethyltin compounds and detection of these tetrasubstituted tins by combination gas chromatography-mass spectrometry (2). However, no environmental samples were studied. T h e fact that Sn(1V) and many tin compounds form volatile or reasonably volatile and thermally stable hydrides, is often the basis for their determination. For example, another recent report concerned with the environmental cycle of the agricultural fungicide triphenyltin hydroxide, describes t h e measurement of Sn(1V) and the phenyl derivatives of Sn(1V) in water (3). T h e organotins are extracted from water with dichloromethane, reduced to t h e hydrides with lithium aluminum hydride and identified by electron-capture gasliquid chromatography. T h e inorganic Sn(1V) is assayed by a colorimetric method after evaporation of the water to dryness. Unfortunately, the concentrations of the tin species in environmental waters are not reported. T h e atomic absorption detection of nanogram quantities of stannane, SnH, (bp -52 "C ( 4 ) ) ,generated by the reaction of aqueous solutions of Sn(1V) with NaHB4 ( 5 ) ,attracted us t o t h e use of this procedure not only for the determination of Sn(1V) but its potential use for the determination of several 0003-2700/79/0351-1256$01 .OO/O
of t h e volatile organotin hydrides, for example, methyltin trihydride, CH3SnH, (bp 1.4 "C (4)). Nine organotin hydrides, produced by the reaction of NaBH, with the corresponding organotin halides in aqueous solution, could be separated on the basis of their boiling points and nanogram quantities determined by atomic absorption spectrometry. These organotin hydrides have boiling points ranging from 1.4 "C (CH3SnH3) to about 280 "C ((nC4H9)3SnH).Four organotins were observed in the natural waters assayed. Methyltin trihydride and dimethyltin dihydride were produced by the reaction of NaBH, with some seawater samples from San Diego Bay. In addition to the methyltin hydrides, n-butyl and di-n-butyltin hydrides evolved from waters taken from Lake Michigan. Inorganic tin, Sn(IV), was determined in all of t h e environmental samples-water, algae, and marine sediments. In many cases where the seawater had too little Sn(IV) for direct measurement,
