Immunochemical methods, especially enzyme-linked immunosorbent
assay (ELISA), provide simple, sensitive, specific and
inexpensive tools for analysis of various targeted analytes [27].
However, ELISA is a heterogeneous method which involves
repeated washing and a certain degree of reaction time (1–2 h).
Fluorescence polarization immunoassay (FPIA) is a homogeneous
technique (no separation or washing), which is an excellent
screening tool in food and environmental analysis because of its
rapidity, reliability and ease of use [28]. It bases on the different
fluorescence polarization between antibody bound tracer (fluorescein-labeled
analyte) and the nonbound form. If the sample
contains free (unlabeled) analyte, it will compete with the tracer
for antibody-binding sites, which will cause a decrease of the
polarization signal. To our knowledge, development of FPIA for
sodium benzoate or benzoic acid in real samples has not been
reported yet. In this study, the polyclonal antibody against sodium
benzoate was prepared by the well-designed immunogen. Based
on that, an FPIA for sodium benzoate was developed and the
accuracy, specificity and sensitivity of the method were studied.