fluid was removed for analysis. The method of additions (Perkin- 
Elmer 1977) was used to minimize matrix interference. 
Water samples (100 ml, not filtered) were adjusted to pH 2. 
A 15.0-ml quantity was then extracted with 10 ml of 15 percent 
(wt/vol) ammonium pyrrolidine dithiocarbamic acid (APDC) in dis¬ 
tilled water. The APDC solution was prepared by dissolving APDC 
in distilled deionized water which had been adjusted to pH 7 
with NaOH. The APDC solution was then extracted three times with 
CCI 4 to remove impurities. The water sample, containing APDC, 
was stirred for 10 min. It was then extracted with a minimum 
volume of methyl isobutyl ketone (MIBK). The mixture was agita¬ 
ted for 1 min and then allowed to separate for 10 min. The MIBK 
phase was analyzed for tin. 
Organic tin-- 
The organic acid solution from bioflasks was analyzed di¬ 
rectly for tin content. 
Medium from Hungate tubes was extracted in such a way that 
inorganic tin compounds remained behind while organotin com¬ 
pounds were extracted. Extensive preliminary experiments showed 
that this extraction was effective. Medium was centrifuged at 
3000 x g for 10 min to remove cells and sediment. The super¬ 
natant medium was then extracted with 2.0 ml of dichloromethane: 
chloroform (9:1, vol/vol). The extraction was conducted over a 
period of 1 hr, with periodic agitation. The mixture was then 
centrifuged at 1,000 x g for 10 min to sediment remaining in¬ 
organic tin precipitate. The lower, organic phase was removed 
and evaporated by dryness under a stream of nitrogen. The re¬ 
sidue was dissolved in MIBK and analyzed for tin. Evaporation of 
the organic phase under nitrogen may have removed some organotin 
material, since organotins are volatile. Thus, results from Hun¬ 
gate tubes are qualitative, not quantitative. 
Atomic absorption spectrophotometry— 
Tin was analyzed with the aid of an HC-2200 graphite furnace 
with ramp accessory on a Perkin-Elmer model 503 AA unit using D 2 
background correction (to minimize interference from "smoke" and 
nonatomic absorption) and an Sn electrodeless discharge lamp 
(EDL). Argon was the sheath gas. 
Mineral acid solutions from sediment samples and organic 
acid solutions from bioflasks were analyzed with the EDL set at 
286.3 nm. Samples were dried at 105 C for 40 sec (10 sec ramp), 
charred at 800 C for 40 sec (10 sec ramp) , followed by atomiza 
tion using maximum power at 2700 C for 8 sec with a 3-sec stop 
of gas. 
MIBK from water samples and from biotubes was analyzed with 
the EDL set at 224.5 nm. Samples were dried at HOC for 40 sec 
90 
