The determination of titratable acid and ammonium ions in picomole amounts

A methodological system mainly designed for the use on intratubular urine samples is described, which permits the determination of titratable acid and ammonium ions in samples of a few nanoliters. The pH measurements were performed by means of antimony micro electrodes, the construction of which are described in detail. The hydroxyl ions were added to the samples from a second antimony electrode system, by an electric current. The amount of hydroxyl ions liberated was equivalent to the amount of current used.The ammonium determinations were based upon the fact that hydrogen ions were liberated from the ammonium ions by formaldehyde. The hydrogen ions were titrated in the same manner as the titratable acid.The use of two electrode systems simultaneously inserted in the droplet permitted recordings of the titration curves. The magnitude of methodological errors of these ultramicro methods are the same as those of corresponding methods using milliliter volumes.