Determining higher fatty acid levels in plant materials 1

The higher fatty acids (HFA) are important plant constituents that are implicated in the grass tetany hazard in livestock. A method is given whereby a technician can analyze 12 forage samples daily for HFA content.

The method consists of saponifying the plant material in ethanol and KOH and extracting the subsequently acidified HFA with petroleum ether. The petroleum ether phase is evaporated and the HFA residue is dissolved in ethanol and then titrated with standardized isobutanolic KOH in the absence of O₂ by using a N₂ atmosphere. A standard plant sample, analyzed over a 37‐day period, had a mean of 136 mmol H⁺ /kg ±4.5, where a 0.1 mmol H⁺ / l palmitic standard was determined with an accuracy of 99 ± 1.9%.