2.5. Method validation
2.5.1.Recovery study
The recovery of the method was estimated by comparing the measured concentration of SCFA from non-spiked and spiked biogas digester liquid sample. A liquid sample from a biogas digester was spiked with a mixture of SCFA solution containing 5 mmol/L of each SCFA. Both spiked and non-spiked samples were prepared in triplicate and were further subjected to the sample preparation procedure described above prior to the GC/MS analysis. The peak areas of the SCFA from the spiked and non-spiked sample were used to calculate the concentration of each SCFA.