Application of Fourier transform infrared spectroscopy (FTIR) techniques in the mid-IR (MIR) and near-IR (NIR) spectroscopy to determine n-alkane and long-chain alcohol contents in plant species and faecal samples

•Wax epicuticular compounds are used to assess herbivores’ grazing behaviour.•FTIR technology was used to predict n-alkane and long-chain alcohol concentrations.•Biomarkers in plant species samples were better estimated in NIR intervals.•The performance of MIR and NIR techniques varied with the matrices used.•Technique to be used may depend on the homogeneity of the matrix.