DEVELOPMENT OF A POLARIZATION FLUOROIMMUNOASSAY FOR LINEAR ALKYLBENZENESULFONATES (LAS)

ABSTRACT

A polarization fluoroimmunoassay (PFIA) based on rabbit polyclonal antibodies was developed and optimized for the detection and quantification of linear alkylbenzene sulfonates (LAS). Hapten mimics with different lengths of the alkyl radical and positions of the phenyl ring were synthesized to prepare fluorescent conjugates (tracers) for PFIA. Structures of target compounds, LAS derivatives and tracers were confirmed by nuclear magnetic resonance and mass spectrometry. Fluorescent tracers in combination with antibodies raised against different LAS immunogens were used for the development of class-selective PFIAs based on different structural combinations of the aliphatic chain moiety. The most sensitive assay was found for the homologous antibody-tracer combination based on the 3-(p-sulfophenyl)butyric acid hapten mimic. The PFIA has a limit of detection of 0.5 mg/L, calibration curve midpoint of 9 mg/L and a dynamic range of 3 to 85 mg/L. Cross-reactivity studies demonstrated the assay is specific towards the sulfophenyl moiety of anionic surfactants while the recognition of aliphatic alkylsulfonates was not significant (cross-reactivity<5%). Total assay time for 10 samples was 7 min, thus allowing fast and reliable detection of LAS in the low mg/L range.

Keywords:

• Anionic surfactants
• Polarization fluoroimmunoassay
• Linear alkylbenzene sulfonates
• Cross-reactivity

ACKNOWLEDGMENTS

This work was supported by INCO Copernicus grant ERBIC15-CT98-0910 (BIOTOOLS). The authors thank Dr. Emilio Benfenati (Mario Negri Institute of Pharmacological Research, Milan, Italy) for his valuable help with APCI-MS spectra. We are very grateful to Dr. David Smith (St. Bartholomew's Hospital, London, UK) for a careful reading of the manuscript and helpful suggestions.