The performance of a biotrickling filter for treatment of concentrated waste gases was investigated. The macrokinetics of methylmethacrylate degradation in the biotrickling filter is studied by measuring the degradation product methacrylic acid in the drain of the filter. The drain was analysed using isotachophoresis (ITP) and capillary zone electrophoresis (CZE). The CZE analyses were carried out in an I.D. 75 µm capillary at 20 kV (negative inlet polarity) using a 0.01 M Tris–acetate buffer of pH 4.45. The electroosmotic flow (EOF) was suppressed by addition of CTA and PVA to the buffer. Detection was at 214 nm. After filtration through a 0.45-µm filter, samples were directly injected. The calibration graph was linear between 10 and 800 mg/l methacrylic acid, with an analysis time under 2 min.