To obtain good sensitivity, the absorption spectrum obtained
under optimized condition was investigated and showed that the
maximum and characteristic absorption wavelength of the studied
components was 223 and 290 nm for HQ, 217 and 270 nm for PO,
228 nm and 274 nm for BA, 256 nm for SA and the four parabens.
Considering the absorptions of the eight components, 280 nm was
selected.