This document specifies a method for the determination of organic acids in animal feeding stuffs by Ion Chromatography with conductivity detection (IC-CD).
The method is intended to be used for the determination of formic acid, lactic acid, propionic acid, citric acid, fumaric acid and malic acid as active substances in feed additives, premixtures, feed materials, compound feed and water and for acetic acid in a limited manner in the same matrices. This method determines the total extractable concentration of the above mentioned organic acids and their salts.
It is advisable that the user of this standard determines the working range of the method for each organic acid. The lower limit of the working range depends on the matrix and the interferences encountered. It is advisable that a working range between 10 mg/l and 100 mg/l is achievable.
The method was successfully tested in an inter-laboratory study in concentrations between 0,02 % up to 27 % of the above mentioned organic acids.
NOTE Limitation occurs during simultaneous determination of high concentration of lactic acid and low concentration of acetic acid. If the ratio of concentration of lactic acid to acetic acid exceeds factor 20, the determination of acetic acid is not guaranteed.
On the basis of the referred working range, sample weight and extraction volume, limits of quantification (LOQ), as calculated (Table 1) can be achievable.