DEVELOPMENT OF A TUBULAR PERIODATE ELECTRODE FOR FLOW-INJECTION DETERMINATION OF GLYCEROL

Periodate electrodes without inner reference solution based on tetraoc tylammonium periodate plus solvent mediator (dibutyl phthalate or 2-ni trophenyl octylether) were constructed. Linear dynamic range, practica l detection limit, slope, stability, selectivity coefficients, pH depe ndence, response time and lifetime were evaluated. A tubular version w as further developed and coupled to a flow-injection system for glycer ol determination in samples relevant to the industrial production of s oaps, detergents and similar. The method involves glycerol oxidation b y periodate with potentiometric evaluation of its consumption. The inf luence of oxidizing agent concentration (10(-5)-10(-2)M NaIO4), ionic strength (0.0-1.0M Na2SO4) and mean resident time were investigated an d the feasibility of using a single-line manifold was discussed. The p roposed system handles about 40 samples/hr, is very stable and suitabl e to industrial control. Results within the 1000 and 5000 mg/l range g lycerol are precise (r.s.d. <0.005) and in fair agreement with convent ional procedures. Baseline drift or noise is not observed and a thermo stat water bath is not required. A noteworthy feature is the almost li near relationship between glycerol concentration and recorded peak hei ght which is a consequence of combined effects of reaction kinetics an d electrode Nernstian response.