The aim of the work was to present and compare the basic statistical parameters of titrimetric and HPLC methods of determination of oxalic acid concentration in fermentation liquid after A. niger cultivation on medium with sucrose as a carbon source. Both methods were tested with oxalic, citric and gluconic acids standards. Moreover, the HPLC analysis was done in order to determine the constitution of the fermentation liquid after biomass removing before and after calcium oxalate precipitation. Presented results show that both methods are linear, precise and accurate in the tested range. The reaction of oxalic acid with calcium chloride effects in over 99.8% precipitation of the oxalate in the fermentation broth sample, but the co-precipitation of citrate and gluconate in maximum amount of 3.4 g⋅dm^-3 occurs. Despite that the titrimetric method is reliable and still used to determine the concentration of oxalic acid in liquids.

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