Fig. 1.

(a) Reference attenuated total reflection (ATR) spectra of Penicillin V (10 g L⁻¹) and phenoxyacetic acid (3 g L⁻¹) in 20 mM phosphate buffer adjusted to pH = 6.5. Pure phosphate buffer was used as a background. Spectral similarities of the two analytes are obvious, however some differences, especially around 1350 cm⁻¹ and 1750 cm⁻¹, are present. (b) Offline ATR spectrum of a typical fermentation broth sample. Between 1200 and 1350 cm⁻¹ typical features of POX and PenV can be seen (black box), their absorbances are however very low compared to other components, e.g. (SO₄²⁻) which absorbs around 1100 cm⁻¹.