Селенат-селективные электроды на основе высших четвертичных аммониевых солей со стерически доступным обменным центром

Abstract

A new film selenate selective electrode was developed. The electrode membrane contains 3,4,5-tris(dodecyloxy)-benzyltetroxyethyltrimethylammonium chloride (5 wt.%) as an electroactive component; polyvinylchloride is a polymer matrix (33 wt.%), 1-bromonaphthalene serves as a plasticizer (42 wt.%), p-trifluoroacetylbenzoic acid heptyl ester is a solvating additive (20 wt.%). The electrode shows a wide linear range of 210-6-10-2 mol L-1 Na2SeO4; the slope of the electrode function is 26.0± 0.3 mV decade-1; the lower detection limit is 110-6 mol L-1 Na2SeO4; the working pH range is 2.15-6.3; the potential drift is 0.9 mV h-1; the response time is from 15 to 90 s (depending on the concentration (activity) of SeO4 2- ions). The electrode shows selectivity towards SeO4 2- ions in the presence of chloride, bromide, sulfate and other ions; its lifetime is 1 month. The developed electrode was tested in model solutions using both the «introduced-found» method in a variant of the calibration graph and the method of limiting solutions. The electrode was also used to determine selenium in Brazil nuts. The determination of selenate ions by capillary electrophoresis was used as a reference method.