A modified phenylfluorone method for determining organotin compounds in the ppb and sub-ppb range.

The phenylfluorone method for tin analysis has been modified to be specific for organotin samples in the ppb and sub-ppb range (4-.1 micrograms of tin). Two extractions of an aqueous solution containing bis (tri-n-butyltin) oxide (TBTO) and tin sulfate yield results which are quantitative for TBTO without interference from the tin sulfate. The extracts are wet oxidized with hydrogen peroxide and sulfuric acid. The tin is determined from its lambda max near 530 nm through its complex with 2,6,7-trihydroxy-9-phenylisoxanthane-3-one (phenylfluorone) in the presence of cetyltrimethylammonium bromide. A Beer Lambert plot is obtained in the range of 0.1 to 7.0 micrograms of tin/sample with slope of 0.0344 with a correlation coefficient of greater than 0.990. The method has been successfully used to analyze over 400 environmental samples.