Solid state systems for the potentiometric determination of CO(2).

In a survey of solid state systems for the potentiometric determination of CO(2) their different fundamentals, possibilities and problems are demonstrated. Experimental results are given, obtained from sensors in which Na(2)CO(3) reacts electrochemically with an oxide forming the sodium salt thermodynamically stable in contact with it. Sensors with Na(2)YZr(PO(4)) as solid electrolyte and MoO(3) or SiO(2) did not yield long-term stable signals, probably mainly because of chemical reactions between the oxides and the solid electrolyte. Satisfactory results were obtained with galvanic cells represented by the symbol. Their standard cell tensions U* (= -emf*) determined with different test gases are in relatively good agreement with values thermodynamically calculated.

[Detection and determination of acetone using semiconductor sensors]. / Untersuchungen zum Nachweis und zur Bestimmung von Aceton mit Halbleitersensoren.

Investigations to examine not only the factors of influence on evaluation of acetone by self-prepared semiconductor gas sensors, but also to prove analytical properties, were carried out using different tools. A sensor temperature of 600 degrees C and a carrier gas flow-rate of 5 l/h were found to be suitable conditions for the measurement of flow-injection apparatus. The determination of 1 microliter-samples of aqueous solutions containing 1-700 g of acetone/l yielded deviations of 4 to 33%. Using a head space method, the working temperature of 370 degrees C led to a maximum sensor response, the detection limit ranged from 37.5 to 50 mg of acetone/l. After quantifying 5 microliters-sample solutions of 40-600 mg/l, results with an accuracy of 1 to 36% were obtained. The method showed the possibility of distinguishing concentrations of acetone below and above 40 mg/l according to physiological and pathological urinary values. The tests carried out on 100 human urine samples provide a good agreement with the Legal reference method for samples containing physiological or strong pathological amounts of ketone bodies, but not for those including traces and small amounts. False-positive results might be caused by a possible presence of ethanol in urine.