Abstract: Gas-selective electrodes in liquid analyzing devices have a characteristic curve K with a linear portion L and a non-linear portion NL. In the non-linear portion NL, the characteristic previously could only be estimated so that determinations of the concentration were rather inexact. According to the present application, the electrode is rinsed with an acid and the zero point voltage UN at the electrode is determined during the rinsing. Using the zero point voltage UN, the non-linear portion NL of the characteristic K is determined with high precision so that even low concentrations c can be determined with great accuracy.

Abstract: A method for automatically determining the concentration of nitrite in a liquid sample includes: determination of the extinction of the liquid sample at a wavelength ? of 150-250 nm, addition of a nitrite reducing agent to the liquid sample, determination of the extinction of the reduced liquid sample at a wavelength ? of 150-250 nm, and determination of the nitrite concentration from the difference between the concentration values obtained from the extinctions of the non-reduced and the reduced liquid samples.

Abstract: The invention relates to a waste water immersion probe (10) comprising a liquid-tight housing (11), a sensor (18) which is disposed in the housing (11) and a sensor window (20) formed on the housing (11). A wiper element (22) for cleaning the sensor window (20) is arranged on the outside of the sensor window (20), and the wiper element (22) is driven by a drive motor (24) which is arranged essentially in the housing (11). The housing is devoid of openings. A magnetic element (36, 37) is associated with the drive motor (24) and a magnetic element (34, 35) is associated with the wiper element (22) in such a manner that the magnetic drive motor element (36, 37) produces a magnetic field which transverses the housing wall and transmits a drive torque to the wiper element (22) without a shaft.

Abstract: The present invention relates to a method for determining the organically bound carbon (TOC) in an apparatus which has at least one reaction zone (2) and at least one detection zone (3), a) the sample being placed into the reaction zone (2) of the apparatus (1), b) the apparatus being sealed, c) the organically bound carbon being converted into gaseous carbon dioxide by means of physical, chemical, biochemical or microbiological methods, d) the gaseous carbon dioxide being transferred to the detection vessel (3, 3a) and e) the carbon dioxide content being determined by means of measurement methods known per se on the basis of the colour change of the indicator, after step a), the inorganic carbon being converted into carbon dioxide and expelled.