686 Titroprocessor: the “Oil Titrator”

The TAN and TBN determination in oils according to DIN/ASTM is an abstraction, even at times an anathema, as far as many analysts are concerned owing to its slow and sluggish course. The same is true of the diazotization of aromatic amines, the coupling titration of, for example, phenols as well as the titanometric determinations of organic nitro compounds in dyestuff chemistry. The content determinations of these species are mostly associated with problems involving the potentiometric acquisition of the equivalence point. The highly sensitive, modern titrators such as the METROHM Titroprocessors allow the evaluation of extremely small and flat equivalence points. Although this feature is welcome in principle, it is, however, now always desirable with many arkward redox titrations. In cases of slow adjustment of the equilibrium at the electrodes, additional, undesirable “ghost end points” are often found. The new software of the 686 Titroprocessor from METROHM thus incorporates, with immediate effect, the MET method (Monotonic Equivalence point Titration, i.e. addition of the titrant in fixed volume steps, programmable between 0.01 and 9.99ml). Under kinetically difficult conditions and/or with inhibited reactions, this allows transfer of the measured value after a fixed waiting time or in accordance with a drift criterion set in advance. The monotonic reagent addition alone justifies the new software yet thanks to the reduced sensitivity towards changes in the fine structure of the curve, improved results are found in the equivalence point calculation of titrations suffering equilibrium disturbance. The evaluation is performed using a “FORTUIN” procedure modified by METROHM.