The direct complexometric determination of metals in unused lubricating oils and additives by automatic non-aqueous potentiometric titration

ANALYSTANALYST Pub Date: DOI: 10.1039/AN9739800042

Abstract

Methods are described for the determination of calcium, barium, zinc and magnesium in any combination in additive concentrates and unused lubricating oils. The samples are dissolved in a mixed aqueous-organic solvent and titrated directly with 1,2-bis(2-aminoethoxy)ethane-NNN′N′-tetraacetic acid [ethylene glycol bis(2-aminoethyl)tetraacetic acid; EGTA] or 1,2-diaminocyclohexane-NNN′N′-tetraacetic acid (DCTA), the end-points being indicated by metal ion sensitive electrodes. By use of a masking agent and the appropriate buffer solutions the individual metals in any combination can be determined following a maximum of three titrations.

The results are compared with those obtained by established procedures. The accuracy of the complexometric methods is comparable with that of established wet-chemical methods, but the former are up to ten times faster and are therefore suitable for blending control.

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