product of any known metabolic pathway. Tetrabutyltin has been observed 

 only in locations close to where boats are being painted. Tetrabutyltin 

 is even more hydrophobic and lipophilic than tributyltin and apparently 

 does not disperse into the environment as TBT does. According to Ludgate 

 (1987) [of International Paint, Incorporated] , the TBIO purchased by paint 

 manufacturers typically contains about 1% tetrabutyltin and 1% of other 

 impurities from the manufacturing process. Tributylmethyltin and 

 dibutyldimethyltin have been identified in sea water samples (Michel, 

 1987) . The toxicological properties of these chemical species are unknown 

 at present. 



The ability to detect a single TBT molecule in 1 x 10 9 other molecules 

 is a challenge to technology. Early work on methodology was developed 

 independently by Hodge (1979) and Braman (1979) for methyltins. Currently 

 the most sensitive procedure for detecting and measuring butyltin 

 concentrations is the protocol developed by NOSC (Valkirs et al., 1985). 

 This method represents a completely independent technique from Huggett at 

 VIMS and the original method developed by NBS (Olson et al., 1985; 

 Matthias et al., 1986). It employs an automated hydride generator to 

 strip the butyltins from the seawater sample, a teflon chromatography 

 column in the form of a U-shaped, partially filled with chromatographic 

 packing and immersed in liquid nitrogen. The butyltin hydrides are 

 trapped in the U column at low temperatures. Subsequently, liquid 

 nitrogen is removed and the column is progressively heated by electric 

 resistance wires to selectively evaporate the butyltin hydrides. Helium 

 is used as a carrier gas. Hydrogen and oxygen are added downstream of the 

 chromatography column to produce the flame for the flame photometric 

 detector. Modifications have been made to this system to prevent 

 deterioration of the column packing by adding monomethyl glycol to the 

 samples and by using teflon lined glass to the column to prevent catalytic 

 decomposition of the TBT hydride on the hot glass surface. The apparatus 

 and technique appear to be suitable to test for the presence and 

 concentrations of TBT in water. The NOSC method uses AA which is less 

 sensitive than flame emission (which NBS uses) but is more specific. Each 

 of the four butyltin chemical species can be determined by this method 

 down to a detection limit of 5 ng/1. The differences of the two methods 

 have been qualified by Valkirs (Analyst - January, 1987) . Tbe NOAA/NMPPO 

 Workshop Proceedings (Iandy et al., 1986) also have compared analytical 

 methods for organotin. Further work is needed to develop a comparable 

 technique for sediment and tissue. Interlaboratory comparability has been 

 attempted, but examination of efficiency of recovery suffers from a lack 

 of certified reference standards. 



4.8 COMPARISON OF REPORTED UNITS IN THE LITERATURE 



There is a lack of standardization of the units employed in reporting 

 tributyltin concentrations in the literature. Table 4.21 presents the 

 units which have appeared in the literature concerning butyltin in the 

 environment and the interrelationships of these. In most of the papers 

 published in the OCEANS '86 and '87 Organotin Symposium Proceed in gs, the 



IV-49 



