ACCUMULATION OF DIALKYLPHOSPHORUS ANIONS FROM WATER BY ION-EXCHANGE ON MODIFIED XAD-4 RESIN

The efficiency of accumulation from water of dialkyl phosphates, phosphorothioates, and phosphorodithioates is investigated by using an anion exchanger column prepared from XAD-4 resin. Methanol and diethyl ether acidified with hydrogen chloride gas (0.15 M) are used as eluents. Dialkyl phosphates are accumulated from 100-mL water samples, at concentrations ranging from 5 to 100 μg/L, with recoveries over 90%. The acidified methanol is a more efficient eluent than the acidified diethyl ether. Under the same experimental conditions the inorganic phosphates, which can interfere with the determination of dialkyl phosphates, are efficiently removed from water samples. The recoveries of dialkyl phosphorothioates are 50-70%, but not always repeatable, and those of dialkyl phosphorodithioates are poor. A partial or total conversion of sulfur-containing dialkylphosphorus anions to corresponding dialkyl phosphates in the acidic eluent is established. The procedure can be efficiently and reliably applied only for the accumulation of dialkyl phosphates from aqueous samples not containing dialkyl phosphorothioates and phosphorodithioates.