Highly sensitive spectrophotometric determination of cationic surfactants in ground waters as their Cu(II)-TPPS aggregates preceded by solid-phase fractionation

摘要

A highly sensitive spectrophotometric determination of cationic surfactants in ground waters was established by forming their Cu(II)-TPPS aggregates, preceded by solid-phase extraction with all SCX cartridge. Cationic surfactants (CSs) were quantitatively trapped and isolated by the SCX solid phase The use of. Cu(II)-TPPS anionic chromophore could reduce the interference by unintentional metal ions coexisting in Surrounding waters. The method was very sensitive in the determination of CSs less than 10(-5) M levels with acceptable recovery and calibration data. The colorimetric sensitivity was very dependent oil the alkyl-chain length of the surfactants, and a CS having 23 carbon atoms gave the highest sensitivity. Overall recoveries were 95-97% with R.S.Ds. less than 3% in the cases over 10(-6) M levels. In the cases in 10(-7) M levels, however, a portion of the analyte would be adsorbed by reservoir walls, which could seriously affect the trace determination. The preliminary addition of 4,4'-bipyridyl into the sample solution was effective in decreasing such unintentional analyte losses, leading up to 73% recovery. The developed method was applied to the analysis of river water at ppb levels of CSs with a fractional concentration through a SCX solid phase subjected by 500-mL aliquots of sample. (C) 2008 Elsevier B.V. All rights reserved.